Post on 20-May-2018
Final Design Report
Brian DeKock
Brenton Eelkema
Jacqueline Kirkman
Nathan Meyer
Brandon Vonk
May 12, 2011
Calvin College; Grand Rapids, MI
Engineering 340: Senior Design Engineering Capstone
©2011 Calvin College and
Brian DeKock, Brenton Eelkema, Nathan Meyer, Jacqueline Kirkman, Brandon Vonk
Food production, distribution and consumption have become a growing concern due to the
movement of populations into more urban settings. It is predicted that there will be a need to increase
overall agricultural production by 70% before the year 2050. One way to mitigate the increase in costs for
food production and decrease the amount of energy expended on food production is to grow food locally.
The HydroTower design was developed as a means to decrease the cost of food production, decrease the
number of miles necessary for producing shipments and increase the number of people with access to
fresh produce.
Executive Summary
The HydroTower design is based on the principles of hydroponics. The main goal of the
HydroTower team was to create a modular and stackable design that was could be used to grow various
fruits and vegetables year-round and indoors. The HydroTower was developed with a focus in four main
areas: structure, nutrient control, lighting and user interface. The exterior structure focused on providing a
safe and visually appealing design for the user. The interior structural design focused on providing the
optimal arrangement of equipment and plants for the fastest possible growing times. The nutrient control
system of the HydroTower focused on research and implementation of various nutrient control systems.
Auto-replenishment of the seven nutrients in solution was chosen as the optimal solution however
currently a three part General Hydroponics solution is being used and replenished on a monthly basis.
Lighting design focused on an energy efficient and optimal implementation that would be both beneficial
to the user and plants. A red and blue LED array was chosen to light the HydroTower. Lastly, the user
interface and touchscreen was created to provide an interactive way for people to understand and adjust
the functions of the HydroTower.
The HydroTower is currently a working prototype that is currently growing tomatoes, lettuce,
spinach, peppers and radishes. The estimated cost of the HydroTower is approximately $200 with a sale
price of approximately $750.
i
Table of Contents
Table of Acronyms and Terms ................................................................................................................. iv
List of Tables ............................................................................................................................................... v
List of Figures ............................................................................................................................................. vi
1. Introduction ......................................................................................................................................... 1
1.1. Project .......................................................................................................................................... 1
1.2. HydroTower Team ...................................................................................................................... 1
1.3. Structure of Design Report ........................................................................................................ 2
2. Requirements ....................................................................................................................................... 3
2.1.1. Functional Requirements ................................................................................................... 3
2.1.2. Performance Requirements ............................................................................................... 6
2.1.3. Interface Requirements ...................................................................................................... 6
2.1.4. Environmental Requirements ............................................................................................ 7
2.1.5. User Requirements .............................................................................................................. 8
2.1.6. Manufacturing Requirements ............................................................................................ 8
2.1.7. Delivery Requirements ....................................................................................................... 9
3. Design Norms .................................................................................................................................... 10
3.1. Transparency ............................................................................................................................. 10
3.2. Stewardship ............................................................................................................................... 10
3.3. Trust ........................................................................................................................................... 10
4. System Architecture .......................................................................................................................... 11
5. Nutrient Regulation and Control ..................................................................................................... 13
5.1 Background and Requirements ........................................................................................... 13
5.2 Feasibility .......................................................................................................................... 14
5.3 Function ............................................................................................................................. 16
5.4 Safety Considerations ........................................................................................................ 16
5.5 Design Procedure ............................................................................................................... 17
5.6 Assembly and Prototype .................................................................................................... 18
5.6.1 Nutrient Uptake Model .............................................................................................. 18
ii
5.6.2 Electroconductivity Sensor ........................................................................................ 21
5.6.3 pH Sensor ................................................................................................................... 24
5.6.4 Water Filtration ......................................................................................................... 27
5.6.5 Solenoid Valves .......................................................................................................... 27
6. Structure ............................................................................................................................................ 28
6.1. Requirements ............................................................................................................................. 28
6.2. Function ..................................................................................................................................... 29
6.3. Design Procedure ...................................................................................................................... 31
6.4. Safety Considerations ............................................................................................................... 31
6.5. Assembly and Prototype ........................................................................................................... 32
6.6. Final Design for Production ..................................................................................................... 35
7. Electrical and Control Systems ........................................................................................................ 36
7.1 Requirements ..................................................................................................................... 36
7.2 Function ............................................................................................................................. 36
7.3 Design Procedure ............................................................................................................... 37
7.3.1 User Interface (UI) ..................................................................................................... 37
7.3.2 Data Management and Processing ............................................................................. 39
7.3.3 Software Model .......................................................................................................... 39
7.4 Automatic Control Circuitry ............................................................................................. 42
7.4.1 Relay Circuitry ........................................................................................................... 42
7.4.2 Valve and Pump Control Circuitry ............................................................................ 43
7.5 Power Supply ..................................................................................................................... 44
7.6 Safety Considerations ........................................................................................................ 45
7.7 Final Design for Production .............................................................................................. 45
8. Lighting System ................................................................................................................................. 46
8.1. Requirements ............................................................................................................................. 46
8.2. Function ..................................................................................................................................... 47
8.3. Design Procedure ...................................................................................................................... 47
8.3.1. Lighting type considerations and decision ...................................................................... 47
8.3.2. LED Frequency and Power Design ................................................................................. 47
8.3.3. Heat Sink Design ............................................................................................................... 56
8.4. Safety Considerations ............................................................................................................... 56
iii
8.5. Assembly and Prototype ........................................................................................................... 56
8.6. Final Design for Production ..................................................................................................... 60
9. Mechanical Systems .......................................................................................................................... 61
9.1. Requirements ............................................................................................................................. 61
9.2. Function ..................................................................................................................................... 61
9.3. Design Procedure ...................................................................................................................... 61
9.3.1. Valves ..................................................................................................................................... 62
9.3.2. Pump ...................................................................................................................................... 66
9.3.3. Ventilation Fans .................................................................................................................... 67
9.3.4. Water Reservoir .................................................................................................................... 67
9.3.5. Water Reservoir Mixer ......................................................................................................... 69
9.4. Safety Considerations ............................................................................................................... 70
9.5. Assembly and Prototype ........................................................................................................... 70
9.6. Testing and Calculations .......................................................................................................... 72
9.6.1. Drainage and Drainage Testing: ...................................................................................... 72
9.6.2. Full Mechanical System Integration Testing: ................................................................. 75
9.7. Addition Considerations and Final Design for Production ................................................... 77
10. Manufacturing ............................................................................................................................... 81
10.1. Requirements ......................................................................................................................... 81
10.2. Safety Considerations ........................................................................................................... 81
10.3. Manufacturing Process Considerations .............................................................................. 81
11. Business Plan ................................................................................................................................. 82
12. Organization and Management ................................................................................................. 108
13. Appendices ................................................................................................................................... 109
13.1. WBS and final hour summary ........................................................................................... 109
13.2. Mechanical Calculations and Tests ................................................................................... 109
14.2.1 Psychrometric Calculations .......................................................................................... 110
14.2.2 Drainage Testing, Interior Grow Level Spacing and Water Reservoir Calculations ... 115
14.2.3 Nutrient Container Calculations................................................................................... 125
14.2.4:Water Reservoir Deflection Calculations ..................................................................... 128
14.3 Lighting System Heat Sink Calculations ............................................................................. 132
14.4 Financials ............................................................................................................................ 140
iv
Table of Acronyms and Terms
Base unit The lower most modularized structure of the
HydroTower product as a whole
cfm Cubic feet per minute
CPU Central Processing Unit
EC Electro Conductivity
gph Gallons per hour
gpm Gallons per minute
HydroTower ©HydroTower: Gardening Solutions
LCD Liquid Crystal Display
LED Light Emitting Diode
MS Microsoft
PCB Printed Circuit Board
PPFS Project Proposal and Feasibility Study
SWOT Strengths, Weaknesses, Opportunities, Threats
UI User Interface
WBS Work Breakdown Structure
v
List of Tables
Table 1: Nutrient Control System Decision Matrix .................................................................................... 14Table 2: Different options for touch-screen devices ................................................................................... 38Table 3: Lighting Type Summary ............................................................................................................... 47Table 4: Purchased Valves for Water System ............................................................................................. 66Table 5: Submersible Pumps Purchased ..................................................................................................... 67Table 6: Volume of Grow Levels Based on Flow Rate Experimentation ................................................... 67Table 7: Volume of Grow Levels Based on Geometries ............................................................................ 67Table 8: Dimensions for Cuts on Water Reservoir ..................................................................................... 69Table 9: Volume of Grow Levels Based on Elevated Flow Rate Experimentation .................................... 72Table 10: Volume of Grow Levels Based on Geometries .......................................................................... 72Table 11: Volume of Grow Levels Based on Flow Rate Change (initial test) ........................................... 74Table 12: Summary of Wick Humidifier Design For Fan Usage ............................................................... 80
vi
List of Figures
Figure 1.2: HydroTower: Gardening Solutions (Engr 339/340 Team 2)………………………………… 1Figure 2. Electrical Sub-Systems Flowchart ............................................................................................... 11Figure 3. Mechanical Sub-Systems Flowchart ........................................................................................... 12Figure 4. Nutrient Uptake. P. Adams, 2002 Nutritional Control in Hydroponics. Pg. 223. ....................... 15Figure 5. Nutrient Control Design Procedure. ............................................................................................ 17Figure 6. Nutrient Control Flow Chart. ....................................................................................................... 18Figure 7. D. Savvas Basic Auto Replenishment Flow Chart. ..................................................................... 19Figure 8. Nutrient Uptake for Young Tomato Plants .................................................................................. 20Figure 9. Plant Nutrient Availiability. Source: scienceinhydroponics.com ................................................ 20Figure 10. HydroTower Nutrient Control Flow Chart. ............................................................................... 21Figure 11. EC Sensor Schematic. ................................................................................................................ 22Figure 12. Final EC sensor on vector board. ............................................................................................... 22Figure 13. Finished EC probe. .................................................................................................................... 23Figure 14. Initial Results EC Sensor. Water and NaCl Solution. ............................................................... 23Figure 15. Smoothed EC Sensor Results. Water and NaCl Solution. ......................................................... 24Figure 16. Initial EC Results. Nutrient Solution and Water. ...................................................................... 24Figure 17. pH Sensor Schematic. ................................................................................................................ 25Figure 18. Final pH sensor on vector board. ............................................................................................... 25Figure 19. Raw pH data. Measuring water and nutrient solution. .............................................................. 26Figure 20. Smoothed pH sensor data. Water and Nutrient Solution. .......................................................... 26Figure 21: HydroTower Structure ............................................................................................................... 29Figure 22: (L to R) First HydroTower prototype (Circular), Second HydroTower prototype (Square) .... 32Figure 23: (L to R) HydroTower Prototypes .............................................................................................. 34Figure 24: HydroTower Spring Break Prototype ........................................................................................ 35Figure 25: Overview of the Control System ............................................................................................... 36Figure 26: Microcontroller Automation Program ....................................................................................... 40Figure 27: Growth Cycle Program .............................................................................................................. 41Figure 28: Main UI ..................................................................................................................................... 42Figure 29: Relay Control Circuit ................................................................................................................ 43Figure 30: Valve Control Circuitry ............................................................................................................. 44Figure 31: Pump Control and Water Sensor Circuit ................................................................................... 44Figure 32: HydroTower Power System ...................................................................................................... 45Figure 33: LI-COR Quantum Line Sensor Action Spectrum ...................................................................... 48Figure 34: Photosynthetic Action Spectrum ............................................................................................... 49Figure 35: Absorption spectrum of Chlorophyll a and b ............................................................................ 49Figure 36: Sun's Irradiance as a function of wavelength ............................................................................ 51Figure 37: Integration Area of Sun's Irradiance Curve ............................................................................... 52Figure 38: Spectral emission of Blue LEDs Figure 39: Spectral emission of Red LEDs ......................... 52Figure 40: Total Einstein Calculation for Line Sensor ............................................................................... 54Figure 41: LED density measurements and number calculations ............................................................... 55Figure 42: LED support angle calculations ................................................................................................. 57Figure 43: LED Mounting Diagram ............................................................................................................ 58
vii
Figure 44: 1st Level Lighting Array ........................................................................................................... 59Figure 45: LED Power Draw Calculation ................................................................................................... 59Figure 46: Circuit Diagram for Red and Blue LED Arrays ........................................................................ 60Figure 47: P&ID of Water System with Valves ......................................................................................... 62Figure 48: Actual Prototype Pictures of Water System .............................................................................. 62Figure 49: Basic Results of Differential Equation Calculations on Drainage and Volume ........................ 65Figure 50: FEA Analysis Results for Reservoir Bottom of 1/8th inch thick Polycarbonate ....................... 68Figure 51: Example of how router was used to create ledges ..................................................................... 69Figure 52: "Splitter" Valves ........................................................................................................................ 71Figure 53: MathCad Screen Shot for Differential Drainage Calculations .................................................. 73Figure 54: Flow Rate Change During Initial Drainage Test ....................................................................... 74Figure 55: Flow Rate Change During Elevated Drainage Test ................................................................... 75Figure 56: "Splitter" Solenoid Valve with Algae Clogged Filter ................................................................ 76Figure 57: Mounted Drainage Valves ......................................................................................................... 77Figure 58: Disassembled Drainage Valve ................................................................................................... 77Figure 59: Team HydroTower .................................................................................................................... 84Figure 60: Advantages to hydroponic growth of plants .............................................................................. 88Figure 61: (L to R): Survey results ............................................................................................................ 92Figure 62: (L to R): RotoGro 240, Desktop Hydroponic Stystem, AeroGarden Pro 200 ........................... 93
HydroTower: Gardening Solutions 2011 1
1. Introduction
1.1. Project
The HydroTower idea is based on the rapidly growing need to create a more sustainable source of
food production as the world population continues to grow. By creating a small and stackable hydroponic
system, HydroTower has the ability to be used year round in urban homes, schools and restaurants to
produce high quality fruits and vegetables.
Food production, distribution and consumption have become a growing concern due to the
movement of populations into more urban settings. It is widely believed that there will be an overall
increase of 70% in agricultural production by the year 2050 (J.A. Burney, “Greenhouse gas mitigation by
agricultural intensification”, National Academy of Sciences 2010). Increasing food production and
maintaining sustainability is necessary in the twenty first century. A growing trend in sustainable
agriculture is the idea that agricultural production should take place in small and localized areas. Local
food production provides a more sustainable means for consumption of produce without requiring
consumers to decrease the amount of fresh produce purchased. Sustainability increases as the produce
travel distance is reduced. In addition, freshness increases as foods are locally grown. The HydroTower
design has been developed as a means to deliver the freshest possible fruits, vegetables and herbs at the
most local level, in a home.
1.2. HydroTower Team
Figure 1.2: HydroTower: Gardening Solutions (Engr 339/340 Team 2). Back Row (Left to Right): Jacqueline Kirkman (ME), Brandon Vonk (EE). Front Row (Left to Right): Brian DeKock (ME), Nathan Meyer (EE), Brenton Eelkema (EE)
HydroTower: Gardening Solutions 2011 2
Brenton Eelkema will graduate with a BSE with an electrical concentration and is from Irvine,
California. Nathan Meyer grew up in Elmhurst, Illinois and is studying Electrical and Computer
Engineering and is getting a minor in Physics and he currently has an internship with DornerWorks in
Grand Rapids. Brandon Vonk is originally from Hamilton, Ontario, Canada, is an Electrical Engineering
Major with a Physics Minor at Calvin College. Brandon has also had an internship with Johnson Controls,
Inc. Brian DeKock grew up in Salt Lake City, Utah and is pursuing a BS in Mechanical Engineering.
Brian currently has an internship with Temper in Rockford and is also seeking a full time position after
graduation. Jacqueline Kirkman will graduate in May 2011 with a BSE with a mechanical concentration
and a minor in International Relations. Jacqueline has interned at Westinghouse Electric Co in Pittsburgh,
Pennsylvania and has accepted a full time position with Cargill Meat Solutions in Schuyler, NE.
1.3. Structure of Design Report
This final report for Calvin College Engineering Senior Design is organized in a manner that subdivides
each of the main components of the HydroTower project into general, electrical and mechanical sections.
Furthermore, the main components of the report being the electrical and mechanical sections are
subdivided into the following:
• Nutrient Control
• Structure
• Electrical and Computer Systems
• Lighting
• Mechanical Systems
• Power Supply
• Manufacturing
Each subdivided section addresses the design, analysis, problems and outlook for future work or
production for each of the above systems. The general sections of the report refer to those which were
addressed by the team as a whole and include such sections as the requirements and business plan.
Overall, this report summarizes the work completed by Team HydroTower throughout the 2010-2011
school year for the Senior Design Capstone.
HydroTower: Gardening Solutions 2011 3
2. Requirements
The following design requirements are assumed to be System-Level Design.1
2.1.1. Functional Requirements
These requirements
have an established concept development and have been implemented in a detailed design and prototype.
The following design requirements represent the current design direction and specification for
HydroTower. Requirements headings are not ranked in order of importance, however sub headings are
ranked by the currently foreseen importance to overall success and design of the product. The
HydroTower will function according the requirements stated as follows:
a. The HydroTower is designated for specific use as a hydroponic grower capable of growing
plants, vegetables and herbs hydroponically. Hydroponics is defined as the growth of plants
using only water.
b. The HydroTower shall be a moveable structure when not operating. Therefore the
HydroTower shall consist of one base unit and on additional stackable unit.
c. Growing Ability: HydroTower shall allow the growth of any plant, vegetable, or herb that is
height permitting to less than 27”.
d. Autonomous Ability: HydroTower shall have the ability to function in an autonomous mode
capable of running without human intervention for fourteen consecutive days. Any significant
system failure within HydroTower will trigger a fail-safe automatic shutdown of the system
which must be reset by a human operator.
e. Location: HydroTower shall be designed primarily for use in an indoor environment. In
addition HydroTower shall be capable of handling moderate outdoor temperatures for
summertime growing. HydroTower will be able to operate in conditions between 100o F and
32o F outdoors. In an indoor environment HydroTower will be designed to operate at indoor
temperatures of between 40o and 85o.
f. Overall Size: HydroTower shall be suitable for indoor use. Therefore the product must fit
through doorways and stand upright in a room without touching the ceiling. HydroTower
must be lower than 8 feet in height and less than 34 inches wide.
1 Karl T. Ulrich and Steven D. Eppinger. Product Design and Development. McGraw-Hill, New York, 1995. Print.
HydroTower: Gardening Solutions 2011 4
g. Overall Weight Unloaded: HydroTower base station shall be able to be carried by an
average adult person regardless of gender capable of carrying 50 lbs. The maximum weight
for the base station without growing media or water will be less than 30 lbs. Each additional
stackable unit should weigh less than 20 lbs. when not filled with growing media or water.
The total weight of an unloaded HydroTower will be no greater than 80 lbs.
h. Overall Weight Loaded: HydroTower fully loaded should not be able to be pushed over or
toppled by a child under the height of 3 feet. The fully loaded base station should weigh
approximately 50 lbs. Each additional stackable unit should weigh no more than 30 lbs.
Therefore a HydroTower with base unit and two additional stackable units should weigh
approximately 110 lbs fully loaded.
i. Structure Supports: The structure of HydroTower shall be supported by four rectangular
supports capable of supporting the weight and torque forces applied to HydroTower from
standard usage as claimed by the HydroTower user manual.
j. Power Consumption: The HydroTower shall not consume power greater than what is
available in a conventional 120 VAC outlet. Power on and shutoff switch will be easily
accessible and labeled near the user interface. Attachment Plugs and Receptacles along with
Fuses will be in accordance with UL standards. 2
k. Light Emitting Diodes: LEDs shall be shielded by the outer shell of the HydroTower in
order to prevent retina damage from bright LEDs to users outside of the HydroTower.
Warning label will be placed on the inside of the HydroTower.
3
l. Strength: HydroTower shall be able to endure the climbing and pulling of a small child or
animal no more than 3 feet tall and 30 lbs. HydroTower structural design shall be first and
foremost focused on the supports holding together the base unit and additional stackable
units. Secondly, HydroTower structural design shall be focus on building a strong
containment reservoir to ensure water does not escape HydroTower. In addition, the outer
shell of HydroTower shall be able to endure a moderate amount of force exerted by accidents
and normal wear.
2 "Ul-498.14." UL StandardsInfoNet. N.p., 16 Nov. 2007. Web. 05 Dec. 2010.
<http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0498.html>. 3 "UL | Additional Resources." N.p., n.d. Web. 05 Dec. 2010.
<http://www.ul.com/global/eng/pages/offerings/industries/lighting/lightingindustryservices/articles/>.
HydroTower: Gardening Solutions 2011 5
m. Durability: HydroTower shall be designed to last in an indoor environment for 10 years.
Additional use of HydroTower in an outdoor environment during moderate summer
conditions may increase wear and reduce the operational life of HydroTower.
n. Water Reservoir and Usage: The reservoir shall be capable of holding at least 50 liters of
nutrient solution. HydroTower shall be designed to operate using soft water. The prototype
will not have the ability to process hard water.
o. Water Pump: The water pump shall be submerged in the water reservoir and shall be
capable of pumping water to the top growing level of HydroTower. The pumping rate shall
be a minimum of 150 gallons per hour to ensure
p. Water Level Sensor: Each level of the HydroTower shall have a single water level sensor
that is connected to the microcontroller. This will function as the shutoff for the pump on
each level.
q. Grow Level Dimensions: The dimensions of each grow box shall provide at least a 4” by”
4” by 4” grow space for each plant to meet the goal of feeding a family of 4 people.
r. Plant Diseases and Insects: One of the main advantages of hydroponic growing is that
diseases and insects that live in soil are not present. Over 80% of all plant diseases come from
soil. The inside of the container will be closed to prevent insects from entering and escaping
should any insects enter HydroTower via plants or users.
s. Corrosion Resistance: HydroTower shall use materials that are corrosion resistant.
Corrosion resistance will first focus on any areas in HydroTower where electrical connections
and water are near each other. Secondary focus areas will include water piping and the outer
shell of HydroTower.
t. Water Resistance: Water resistance will be an utmost issue when dealing with almost all
major components of HydroTower. Water resistance will be assumed using the water criteria
set out in the earlier section titled, Water Reservoir and Usage. Water overflow will be
considered and overflow channels will exist on each level to ensure that water does not exit
HydroTower during standard operation.
HydroTower: Gardening Solutions 2011 6
2.1.2. Performance Requirements
a. Quality: HydroTower must produce quality plants capable of delivering fruits,
vegetable and herbs that are comparable to produce found in local supermarkets. This
quality should be replicated through multiple plant cycles.
b. Growing Time: HydroTower shall be able to grow plants between 25-50% faster than
conventional soil grown plants. This growth speed will ensure that produce can be
planted and harvested in a timely manner in order to supply a family of 4 people.
c. Growing Ability: HydroTower shall be limited to plants that meet height and width
requirements of the product. The HydroTower team will recommend a wide variety of
plants that can be grown successfully in HydroTower, but will not specify a listing of
plants as stated in Growing Ability above.
d. LED Usage: The LEDs on each level of HydroTower shall have a minimum operating
life of 17,520 hours. This number accounts for 16 hours of light per day for a 3 year
period.
e. Air Temperature: The air temperature of HydroTower shall be based on the Location
requirements specified in the previous section Functional Requirements. Any
temperature for a sustained period that cannot support plant growth in HydroTower will
issue a shutoff command that stops all operation in HydroTower. Any sudden
temperature increase or decrease in HydroTower will issue a warning to the user. The
prototype of the HydroTower will assume a room temperature of approximately 67o F.
No temperature adjustments will be made within the current prototype.
f. Water Temperature: Water Temperature will follow the same guidelines set out in
the previous subsection titled, Air Temperature.
2.1.3. Interface Requirements
a. User Interface (General): The interface and interaction requirements for HydroTower
shall assume a rugged design that is capable of usage with wet and dirty hands.
Emergency shutoff features and signals will be intuitive to the user without an
HydroTower: Gardening Solutions 2011 7
instruction manual. All controls for HydroTower shall be located in the base unit.
Instructions on operation will not be included for the user interface on HydroTower.
These instructions will be provided separately in the user manual.
b. User Interface (Control Systems Interface): The user interface for the control system
of the project shall feature a touchscreen controller that is capable of displaying
information related to growth time, chemical concentration, water usage, and
temperature controls. On the touchscreen, the size of the choice selection buttons shall
be a minimum of one square inch.
c. User Interface (Power Options/Water and Nutrient Insertion): HydroTower shall
feature intuitive buttons to turn on and off both the entire HydroTower and individual
systems. In addition, an emergency shutoff switch will be prominently accessible.
Water and nutrient insertion points will be labeled and normally closed to prevent
accidents, tampering, or contamination from other users, children, or pets.
d. Nutrient Cycle Time: The nutrient cycle time shall be performed in less than 10
minutes per level. Cycle time is defined as time taken to pump water to fill one level of
HydroTower and then cycle back into the reservoir.
2.1.4. Environmental Requirements
a. Visual: HydroTower shall have a uniform outer shell made of plastic that will be a
neutral color. An effort will be made to contain the LED light from HydroTower to
prevent the light from being a large distraction in the room
b. Sound: HydroTower shall not produce any sustained noise that is greater than 60 dB.
c. Smell: HydroTower shall not contaminate its immediate location with any smell from
inside the unit. An air purification system will not be included in the current HydroTower
prototype.
d. Humidity: The humidity of HydroTower shall be optimized to a relative humidity of
between 50-80%. Measurement and control of humidity will be taken care of by the
HydroTower: Gardening Solutions 2011 8
control system. Humidity controls will not be included in the current HydroTower
prototype.
e. Recycling: All attempts shall be made to ensure that HydroTower is as environmentally
friendly as possible. This means further developing the already excellent environmental
achievements of hydroponic growing. Specific efforts shall be made in ensuring that
recycled or recyclable materials are used in the creation of HydroTower.
f. Water and Nutrient Disposal: Leftover water at the end of a growing cycle will have
little nutrients and will be discarded. Waste water shall be limited to, at most, two gallons
of leftover nutrient solution per cycle. Each cycle will be approximately three weeks
long.
2.1.5. User Requirements
a. Ergonomics: Defined as the efficiency and the usability of HydroTower:
i. Maintenance: Standard maintenance on HydroTower shall be limited to
cleaning after plant cycles and possibly changing filters. This maintenance plan
will take no longer than one hour to complete for each plant cycle.
ii. Cleaning: All parts of HydroTower that need to be cleaned shall be easily
accessible and removable when possible.
b. Assembly: HydroTower shall be able to be completely assembled and disassembled in
less than one day by a select user of HydroTower. A select user is defined as someone
capable of
2.1.6. Manufacturing Requirements
a. Development Time: The HydroTower prototype shall be completed by May 7, 2011.
b. Project Development Cost: HydroTower development cost shall be less than $2,000.
HydroTower: Gardening Solutions 2011 9
c. Development Capability: HydroTower shall be mass produced based on the
documentation of the HydroTower team. This documentation will be specified in the
Delivery Requirements section.
d. Product Quality: The quality of HydroTower shall be based on the design norms
chosen by HydroTower team and specified in these requirements.
e. Product Cost: HydroTower shall cost less than $250 to produce.
f. Sale Price: HydroTower shall sell for less than $700.
g. Sellable Unit: A sellable unit of HydroTower shall include two versions: the base unit
and stacking unit. Included in the base unit are all components of HydroTower in
addition starting seed packages and a user’s manual. The stacking unit shall include a
brief instruction guide on how to attach to the base unit. The stacking unit shall not
include any seed packages or an additional user’s manual.
2.1.7. Delivery Requirements
a. Team Website: The team website was created by November 25, 2011 and updated
monthly.
b. PPFS: The PPFS was completed by December 16, 2010.
c. Working Prototype: The working prototype will be created by May 7, 2011.
d. Final Report: The Final Report shall be completed by May 11, 2011.
HydroTower: Gardening Solutions 2011 10
3. Design Norms
The requirements of HydroTower are influenced by the selected design norms of transparency,
stewardship and trust. Design norms are expectations that discussed in the context of Christian
engineering ethics.
3.1. Transparency
Transparency to Team HydroTower is a reflection of the openness and intuitive nature of the
product. The Team wants to be open and genuine with customers such that customers both understand
how HydroTower functions and secondly understand the benefits of HydroTower and hydroponics. If
potential customers do not understand the benefits of HydroTower or feel as though HydroTower is an
unsafe product for their families HydroTower units will not sell. Furthermore, Team HydroTower
emphasizes the unique aspect that HydroTower is a fully automated system, and while such systems can
intimidate customers HydroTower is also being designed to be user friendly and intuitive. An added
feature of HydroTower would be to educate many people on the benefits and applications of hydroponics
in regards to overall health, fossil fuels and basic plant knowledge.
3.2. Stewardship
Team HydroTower also wants to be good stewards of God’s creation by eliminating many of the
fossil fuels and costs used in transportation and other current food processes. Many resources are used in
the current distribution of produce. Reduction in the distance food travels before reaching market would
decrease the amount of fossil fuels being used. Furthermore, as stated earlier, hydroponics are very
beneficial in regards to using less water, nutrients and land. The norm of stewardship is also directly
linked to the transparency aspect of having users understand the benefits of hydroponics.
3.3. Trust
The third design norm is trust which is vital in any relationship between a company and a
customer. Team HydroTower wants customers to trust that families can be fed with an efficient and
reliable system especially given some of the incorrect perceptions of hydroponic gardening. The trust
issue plays a role in the educational outlook for HydroTower in sharing the benefits of hydroponics while
simultaneously addressing the issues of malnutrition, obesity and lack of produce in diets. Customers of
HydroTower should never feel as though the product is unreliable or that the designers were not honest
and clear in the function of HydroTower.
HydroTower: Gardening Solutions 2011 11
4. System Architecture
The system architecture of the HydroTower was divided into electrical and mechanical system
designs. Given the makeup of the team it served as the easiest way to divide up the necessary systems.
The system architecture breakdowns for the electrical and mechanical systems are shown below.
Figure 2. Electrical Sub-Systems Flowchart
The HydroTower team began designing the electrical systems by starting with the LED lighting
system followed by control systems for the both the lights and pumps. Completion of these systems was
followed by a customized power supply design and nutrient control system. Lastly, the user interface was
created to integrate information from the HydroTower with the manual modes of HydroTower operations.
Additional research into hydroponic growing and plant biology was designated as part of the nutrient
control system.
HydroTower: Gardening Solutions 2011 12
Figure 3. Mechanical Sub-Systems Flowchart
The mechanical systems of the HydroTower began with considering the air flow and heat
dissipation through the HydroTower when the LED lighting system was operational. The structure of the
HydroTower was considered first to creating a base station and then focused on designing and supporting
additional levels. Implementation of the structural system involved considering the water flow through the
HydroTower in order to minimize excess pumping and the leakage of nutrient solution. Lastly, the
chemical distribution system for the HydroTower was created in conjunction with the electrical portion of
the nutrient control system.
HydroTower: Gardening Solutions 2011 13
5. Nutrient Regulation and Control
The nutrient control system of the HydroTower is a vital system to ensuring that plants are fed the
correct amount of nutrients. The HydroTower team undertook a thorough amount of research to look at
different types of nutrient control before attempting to design an auto-replenishment system that would
replace individual nutrients based on the pH and EC (electroconductivity) of the nutrient solution.
5.1 Background and Requirements
Plants in a hydroponic environment require a nutrient solution to replace the nutrients that are
traditionally gathered from the soil. This is accomplished by mixing a nutrient solution with water to feed
to plants daily at a regular time intervals. In 1933 a nutrient solution called Hoagland’s solution was
developed that addressed the widest range of plant nutrient needs. The tables below describe this nutrient
solution.
Hoagland’s Nutrient Solution
Element Symbol PPM Nitrogen N 210 Potassium K 235 Calcium Ca 200 Sulfur S 64 Phosphorus P 31 Magnesium Mg 48 Boron B 0.5 Iron Fe 5 Manganese Mn 0.5 Zinc Zn 0.05 Copper Cu 0.02 Molybdenum Mo 0.01
Major Elements
Minor Elements
Element PPM
Element PPM Nitrogen 210
Sulfur 64
Potassium 235
Magnesium 48 Calcium 200
Phosphorus 31
HydroTower: Gardening Solutions 2011 14
This nutrient solution adequately provides everything that a plant needs to survive. The nutrients are
added to water through seven different chemical compounds. The major compounds are, KNO3, Ca(NO3)2
Iron Chelate, MgSO4, NH4NO3. The minor compounds which are combined into one solution are H3BO3,
MnCl2, ZnSO4, CuSO4, H3MoO4, Na2MoO4, KH2PO4. These chemical compounds are stored separately to
prevent a precipitate from forming. The solution may need to be adjusted for different plants and different
plant stages of growth.
There is currently nothing on the commercial market with a system exactly like the one that is needed by
the HydroTower. All current nutrient control systems are either larger or smaller than the proposed
nutrient control system. On the larger side, nutrient control systems exist for hydroponic farms which use
thousands of gallons of water and rely on advanced chemical measurements to make adjustments to the
solution. On the smaller side, various nutrient control systems do exist however they do not have the
capability to last autonomously for up to two weeks at a time and cannot support a variety of plants. In
addition these smaller control systems almost always cost more than the entire HydroTower design.
The requirements for the nutrient control system are as follows:
a. Function autonomously without human intervention for 14 days
b. Cost less than $50
c. Carry enough supply nutrients for up to six months of growing time
d. Measure and adjust pH and EC.
5.2 Feasibility Table 1: Nutrient Control System Decision Matrix
Nutrient Control System Decision Matrix
Cost Implementation Patent
Waste Water
Nutrient Supply Customer Total
1.Electrode Analysis 2 0 3 8 4 9 4.55 Total 2.Spectrophotometry 1 2 3 8 4 9 4.55 3. Autoreplenishment 7 4 7 7 4 8 6.65 4.MacroReplenishment 6 5 7 5 7 7 6.1 5.General Hydroponics 6 7 1 2 8 4 4.65 6.No replenishment 10 9 0 2 10 2 5.65
Weight 30% 15% 10% 15% 5% 25% 100%
Note: 10 indicates favorable rating / 0 indicates unfavorable rating
HydroTower: Gardening Solutions 2011 15
The initial design for the nutrient control system was strongly based on two assumptions. The first was
that the nutrient uptake of various plants could be simply modeled. The second assumption was that
nutrients could be measured through a variety of techniques in order to give an up to date composition of
the nutrient solution.
Result of Assumption 1:
The HydroTower team began project by looking into what it would take to build a simple model of
nutrient uptake for plants. Initially there was debate over what it would take to model the nutrient uptake
of one plant. It was quickly clear that the most optimal plant growth could not be achieved without
advanced measurement equipment that cost thousands of dollars. Reading through biology research and
textbooks it became clear that a simple and optimized nutrient uptake model is not possible in the
timeframe of our project. The first reason is that the nutrient uptake for different type of plants covers a
wide range as shown below.
Figure 4. Nutrient Uptake. P. Adams, 2002 Nutritional Control in Hydroponics. Pg. 223.
The difference between the nutrient uptake of, for example, tomatoes and peppers is quite different. A
much more complex nutrient model would be required for a tomato plant compared to a head of lettuce.
This is somewhat obvious when looking at one tomato and one leaf of lettuce. The second reason is that
the uptake on individual plants is not uniform and the uptake of individual nutrients affects other
HydroTower: Gardening Solutions 2011 16
nutrients. Our biology research showed that the shortage of one individual nutrient leads to the reduced
consumption of another nutrient while increasing the consumption of the third nutrient.
Result of Assumption 2:
The second assumption that HydroTower team made was the nutrients could be measured in real
time for a low cost. Even though we have not fully ruled out a low cost way to measure nutrients in real
time it will not be as easy as we intended.
Electrode Anaylsis:
The second alternative for the flood and drain system with the electrode analysis would be to
research solutions for analyzing individual ions in the water nutrient system. The premise behind the
second design alternative is based upon knowledge that when compounds are in solution, ions dissociate
and are thus individual elements. For example, NH3 is a compound in Hoagland’s Solution, but in theory,
the second alternative would use an electrode which measures for N elements. Electrodes for N, Mg, Ca,
K and possibly Fe would be used in research to measure the conductivity of the water solution and
analyze for specific algorithms to add the makeup nutrients. Professor Doug VanderGriend assisted team
HydroTower in researching possible ways to isolate the dissociated elements in solution using electrodes
much like the initial design intended. Electrode analysis did not prove to be a feasible solution given the
amount of ions in the solution and due to the high cost of electrodes.
5.3 Function The HydroTower nutrient control system uses an Arduino microcontroller. Solenoid valves (12
VDC) will control the nutrient storage tanks. A mixer and filtration system will circulate the water. pH
and EC sensors will measure nutrient reservoir for processing on Arduino.
5.4 Safety Considerations The nutrient control system of the HydroTower consists of safety considerations for both users on
the outside and plants on the inside. The first safety consideration was to make sure that none of the
nutrients leak out of their respective containers. None of the nutrients are unsafe for humans or animals to
touch however leaking nutrients can damage both the interior of the HydroTower and the surrounding
environment. Unmixed nutrients leaking out of designated areas also poses a risk that nutrients will
precipitate when they are unintentionally mixed together. Solenoid control was also key to the growth of
the plants within the HydroTower. An overconcentration of the nutrient solution will ruin plants within 24
HydroTower: Gardening Solutions 2011 17
hours. The nutrient solution will also need to be disposed of as waste water. The nutrient control system
of the HydroTower will attempt to minimized the disposal of all leftover nutrient solution within the
HydroTower.
5.5 Design Procedure The design procedure of the nutrient control system based both on the need for quality research
and then application. The nutrient control system of the HydroTower represents the largest part of new
innovation on our project. The HydroTower nutrient control system attempts to find a balance between
large scale nutrient control systems and basic nutrient control systems such as that found in the
Aerogarden. Innovative design is needed to create the most advanced system possible to manage the
nutrient uptakes of many different types of plants. However at the same time cost must be minimized both
in terms of the equipment required to measure the nutrients and the nutrients and water used in the
process. There is currently no system on the market that is comparable to the system that we are trying to
create. This meant that the existing research would only serve as a basis for our project. Research by the
HydroTower team would need to be completed and applications would need to be iterated in order to
ensure a functional prototype system for the HydroTower.
Figure 5. Nutrient Control Design Procedure.
Initial research began by looking at current hydroponic nutrient control systems on the market.
Our research indicated that there are currently many industrial control systems in operation. Furthermore
small scale control systems existed on the market which proved that some sort of nutrient control system
was possible. Our initial research also involved reading about basic biology concepts related to nutrient
uptake and the mixing of chemical compounds. The next step in our research was to look at the academic
research from the last decade in hydroponics and nutrient uptake. The HydroTower team located
HydroTower: Gardening Solutions 2011 18
advanced articles in both hydroponic nutrient control system and tomato nutrient uptake. Research then
turned online to applications for the pH and EC sensors that would be needed. After confirming the
difficulties of our initial design we began working on applications for the nutrient control system.
5.6 Assembly and Prototype
Figure 6. Nutrient Control Flow Chart.
5.6.1 Nutrient Uptake Model
The attempted solution at a nutrient uptake model for the HydroTower proved to be far beyond
the knowledge of anything in mechanical or electrical engineering. After completing the PPFS a nutrient
uptake model was found that would provide auto replenishment. This academic paper, Automated
Replenishment of Recycled Greenhouse Effluents with Individual Nutrients in Hydroponics by Means of
Two Alternative Models, by D. Savvas in the Agricultural Technology department of the Technological
Educational Institute of Epirus, Greece. The basis of the design uses pH and EC sensors to measure the
drainage and nutrient solutions and calculate nutrient replenishment based on the output of various
nutrient control algorithms. The knowledge required to translate many of the biology and chemistry
equations into computer algorithms was beyond the level of anything that could be accomplished in nine
months. In addition a redesign of the system would be required in order to accommodate the additional
sensor data needed along with the freshwater intake that is specified by the Automated Replenishment
paper. The flow chart below only briefly summarized fourteen pages of equations and explanations for an
automated nutrient control system.
HydroTower: Gardening Solutions 2011 19
Figure 7. D. Savvas Basic Auto Replenishment Flow Chart.
The auto replenishment system presents results that show a sustained nutrient solution for more
than 100 days. However this nutrient solution was only used on one type of chrysanthemums. Further
research and testing would need to be conducted to see if this design could be implemented with multiple
types of edible crops.
In addition the HydroTower team considered the use of a macronutrient uptake model to model
the basic nutrients that are required for tomato plants to grow. Time constraints did not allows us to
complete the design since the research was found later than anticipated. However macronutrient control
represents a possibility to decrease the complexity of the nutrient control system while at the same time
reducing waste water and measuring some nutrients.
HydroTower: Gardening Solutions 2011 20
Figure 8. Nutrient Uptake for Young Tomato Plants. P. Adams, 2002. Nutritional Control in Hydroponics. Pg. 223
A basic nutrient control system was implemented which adjusted the pH based on the readings
that were output from the pH sensor. Based on reading of the pH sensor the solenoid values would insert
a pH buffer solution which would raise or lower the pH. The monitoring the pH level of the nutrient
solution in the HydroTower is one of the largest indicators of the plant growth rates. The nutrient
availability chart below shows how important a balance pH is for nutrient uptake.
Figure 9. Plant Nutrient Availiability. Source: scienceinhydroponics.com
HydroTower: Gardening Solutions 2011 21
With the previous graph in mind the HydroTower team created a short piece of code on the
Arduino that monitored the pH of our nutrient solution and adjusted accordingly. The average was
calculated to prevent momentary spikes in the sensor data from allowing the program to inadvertently
raise or lower the pH based on single data inputs.
Figure 10. HydroTower Nutrient Control Flow Chart.
5.6.2 Electroconductivity Sensor
The electroconductivity (EC) sensor within HydroTower allow users to see when plants are
receiving the correct or incorrect amount of nutrients. The base design for the EC sensor was taken from
the online resource, octiva.net.4
4 http://www.octiva.net/projects/ppm/
The EC sensor operates by using an oscillator, gain loop, and DC
converter. Electroconductivity is measured using an AC signal in order to not disturb the molecules
within a liquid. This AC signal is converted into a DC signal which is used to measure
electroconductivity at the output. The figure below shows the full schemtic for the EC sensor.
HydroTower: Gardening Solutions 2011 22
Figure 11. EC Sensor Schematic.
Figure 12. Final EC sensor on vector board.
Beginning on the left of the schematic, a Wein bridge oscillator was used to create an AC sine
wave to measure the EC. The frequency of the oscillator is given by the equation f = 1
2𝜋𝜋𝜋𝜋𝜋𝜋 . Give the
values of C and R as .015 µF and 1k Ω respectively, the frequency of the oscillation is approximately 10
kHz. The components through the oscillator continue through resistor R6. The middle part of the circuit
functions as a gain loop for the probe. The EC probe was created by taking two small pieces of copper
tubing and hot gluing them to the inside of a small plastic tube. See figure below for probe design.
HydroTower: Gardening Solutions 2011 23
Figure 13. Finished EC probe.
The third and fourth op amps within the circuit function as an AC to DC converter. These op
amps also include controls for the range and offset of the final output value. The graphical outputs below
were plotted in MATLAB using data collected every second from Arduino output. The raw data below
shows oscillation and change between measuring the EC of drinking water and the addition of salt to the
water. It was not possible to carry out any substantial tests on the EC sensor due to time constraints
however the EC sensor was calibrated to output 4 volts for a high strength nutrient solution and 0 volts for
a low concentration nutrient solution.
Figure 14. Initial Results EC Sensor. Water and NaCl Solution.
The following graphs show the RMS output value of the EC sensor. Sensor values are known for
small and large spikes in the output due to distortions within the solution. By taking the RMS value of the
output it is possible to smooth out the data to give a more consistent output. Future work on the EC sensor
would add more analog and digital filtering to cut out some of the disturbances. In addition a more precise
voltage offset would need to be created to create a consistent output that would not need to be tune daily.
HydroTower: Gardening Solutions 2011 24
Figure 15. Smoothed EC Sensor Results. Water and NaCl Solution.
Figure 16. Initial EC Results. Nutrient Solution and Water.
5.6.3 pH Sensor
The pH sensor was based off of the online resource, pHduino.5
5 http://code.google.com/p/phduino/
The pH sensor operates using a
JFET amplifier and basic filtering stage to output an analog voltage which represents the pH. By taking
the RMS voltage of the output gives the pH of the nutrient solution in Volts. pH is typically measured on
a scale from 0 to 14. The typical pH for plants is between 5.5 and 6. The figure below shows the full
schematic for the pH sensor.
HydroTower: Gardening Solutions 2011 25
Figure 17. pH Sensor Schematic.
Figure 18. Final pH sensor on vector board.
The pH sensor shown above features a gain and filtering stage using a JFET operational amplifier
in addition to offset adjustments for calibrating the pH. A TL072 JFET operational amplifier was used
because it has a high input impedance and low harmonic distortion that makes it ideal for high fidelity
applications. The first stage of the sensor features an impedance adjustor, basic filtering and gain. The
second states of the sensor feature more filtering and an offset adjustment. In future versions this offset
will need to be more advanced to ensure that the value of the sensor output remains constant. Any
disturbance in the sensor output will lead the nutrient control system to correct the nutrient solution base
on incorrect sensor values.
The graphs below shows the output values of the pH sensor plotted in MATLAB every second. A
voltage reference was used to adjust the voltage output readings into integers from 0 to 1,400. A standard
HydroTower: Gardening Solutions 2011 26
pH probe was plugged into the circuit to measure the amount of hydrogen ions. The first graph below
shows the raw data from the pH sensor when switching between water and nutrient solution. In initial
value of the pH of drinking water shows approximately 725 or a pH of 7.25. Moving the probe into an
unused sample of nutrient solution shows a pH of approximately 6.25. The voltage spikes in the data are
typical for a sensor such as this. To solve this problem the RMS value was taken. The pH data shown
further down uses the RMS data to calculate the pH. This second graph is not distorted by voltage spikes
like the first graph.
Figure 19. Raw pH data. Measuring water and nutrient solution.
Figure 20. Smoothed pH sensor data. Water and Nutrient Solution.
HydroTower: Gardening Solutions 2011 27
5.6.4 Water Filtration
Consideration was taken when looking the need for water filtration within HydroTower.
Numerous sources show that large commercial hydroponic systems have UV or sand water filtration
systems. It is currently unknown if water filtration is necessary for HydroTower since water is not
recycled for long periods of time ( >3 weeks). Further biology and chemistry research are necessary to
determine how the nutrient solution would be affected by water filtration. UV filtration for the
HydroTower is feasible given the power and size requirements. The current cost of a UV filter made it
unfeasible to place in the current HydroTower design. Sand filtration is feasible in cost but no in the size
requirements for the HydroTower.
The final prototype of the HydroTower will use a basic aquarium filter to keep large particles
from the grow levels out of the pump. This will not filter any pathogens that may enter the water. The
current recycling of the nutrient solution as specified by the requirements section should prevent any
pathogens from entering the water.
5.6.5 Solenoid Valves
Gravity fed solenoid valves were chose since the nutrient could be dispensed from above the
reservoir. Using the pressure of gravity of dispense the nutrient saved the HydroTower team the hassles of
creating a pressurized systems. Solenoid valves are further classified and discussed in the mechanical
systems section of the report.
HydroTower: Gardening Solutions 2011 28
6. Structure
The structure of the HydroTower unit define many of the functions and capabilities of HydroTower. More
specifically, the frame and structure are the actual load-bearing components of HydroTower which
provide the shape and support. The structure is known as the main legs, in the prototype the 2-by-4s and
the plywood bases and tops and also provides more of the rigidity such as the side walls and steel frame
in the base unit. The overall dimensions determine the amount of produce grown as well as dictate the
possibilities of where customers may place HydroTower within a residential dwelling. Throughout the
project, the outlook of HydroTower as both a prototype and as a product were considered in the frame and
structure design.
6.1. Requirements
Overall Size: HydroTower shall be suitable for indoor use. Therefore the product must fit
through doorways and stand upright in a room without touching the ceiling.
Overall Weight Unloaded: HydroTower base station shall be able to be carried by an average
adult person regardless of gender capable of carrying 50 lbs. The maximum weight for the base
station without growing media or water will be less than 30 lbs. Each additional stackable unit
should weigh less than 20 lbs. when not filled with growing media or water. The total weight of
an unloaded HydroTower will be no greater than 80 lbs.
Overall Weight Loaded: HydroTower fully loaded should not be able to be pushed over or
toppled by a child under the height of 3 feet. The fully loaded base station should weigh
approximately 50 lbs. Each additional stackable unit should weigh no more than 30 lbs. Therefore
a HydroTower with base unit and two additional stackable units should weigh approximately 110
lbs fully loaded.
Structure Supports: The structure of HydroTower shall be supported by four rectangular
supports capable of supporting the weight and torque forces applied to HydroTower from
standard usage.
Strength: HydroTower shall be able to endure the climbing and pulling of a small child or animal
no more than 3 feet tall and 30 lbs. HydroTower structural design shall be first and foremost
focus on the supports holding together the base unit and additional stackable units. Secondly,
HydroTower structural design shall be focus on building a strong containment reservoir to ensure
HydroTower: Gardening Solutions 2011 29
water does not escape HydroTower. In addition, the outer shell of HydroTower shall be able to
endure a moderate amount of force exerted by accidents and normal wear.
6.2. Function
The structure functions by providing the stability to secure all the components and working features of
HydroTower. The frame consists of the base unit and grow levels. Due to the modular nature of the
design, HydroTower has the ability to include either one or two grow levels depending on the user’s
desires. Thus, HydroTower was designed to be modular with the second grow level easy to attach and
program into the overall HyrdoTower product.
Figure 21: HydroTower Structure
The base unit functions to house electrical components such as the power supply and mechanical relays
with their supporting circuitry. The base unit also contains mechanical components such as the water
reservoir, nutrient distribution system, valves, piping system and pump. The base unit is an enclosed
space, but has three “easy access” panels such that users may easily refill the nutrients and the water when
necessary. Furthermore, the base unit has two other access panels should maintenance by the user prove
necessary. The concept behind the base unit was to have HydroTower capable of having hidden
Second Grow Level (optional for users)
First Grow Level
Base Unit
HydroTower: Gardening Solutions 2011 30
components since user’s would not care to see the raw working materials of HydroTower on a daily basis.
However, as a design norm of transparency Team HydroTower wanted to emphasize the ease of use and
maintenance for HydroTower operations.
Analysis of the base unit was performed using Finite Element Analysis and subsequently Algor. The base
unit structure was analyzed for deflections possible from the hydrostatic loading of the water in each grow
level. The analysis results were also used to verify that the plywood structure would not deflect or fail
under normal daily operations. The Algor simulation showed that a 3/8th inch thick plywood could be
used in the HydroTower prototype and that the loading from a worst case scenario of 27 US gallons
would not cause structural failure. The 27 US gallons was the maximum each grow level could be filled
without flooding. Furthermore, the 27 US gallons in actual prototyping was decreased by the use of
Styrofoam blocks to conserve water and thus less than 15 US gallons was used in HydroTower. The
reduction in water decreased the weight loading by about 100 lbs. Thus, the weight reduction from water
provided more safety for the system.
Each grow level functions to hold the plants in a controlled and optimized environment. Controls for the
grow levels include watering (with nutrients) lights, air circulation and protection from the environment
outside HydroTower. Grow levels were also installed with a drainage slope to allow for proper drainage
and minimal pooling of water after the feeding of plants. The drainage slope was first assumed to have an
increased height of 0.5 inch from the corner opposite the drainage bulkhead. Ball bearings were used to
test the drainage slope since the rolling action of ball bearings was considered similar to water and the
grow level was not yet water proofed. However, after initial testing of rolling ball bearings down the
slope, it was determined that a larger incline was necessary due to friction and impedances to the water
flow. Thus, the final drainage height was 1 inch to increase the flow rate of the drainage and decrease the
drainage time.
LED were mounted in a Fresnel lens application designed by Nathan Meyer and Brandon Vonk. More
specific information regarding the lighting system is found later in this report. The LEDs were mounted
on wood slots and were cut to the specified angles from Brandon and Nathan in order to give the LEDs
direction and focus more light towards the center of each HydroTower grow level.
Overall, the function of the structure was to allow the plants and all components of HydroTower. Further
consideration for the structure was given for the safety of users and bystanders during normal operation
and normal. Lastly, the structure was designed to be safe for some misuse such as children or small pets
climbing on HydroTower.
HydroTower: Gardening Solutions 2011 31
6.3. Design Procedure
Initial requirements for the HydroTower unit were for circular designs based on the knowledge of circular
objects having more visual appeal to customers. However, the circular design was considered not as
feasible since manufacturing of circular components is less efficient and more difficult. Lastly, the
circular design was changed because the interior dimensions of the growing space were not as conducive
as a rectangular growing unit.
The grow levels were designed as 2 feet high and 32inches by 32inches such that the overall structure of
the HydroTower is about the size of a refrigerator. The HydroTower prototype was maximized in space to
allow for the most growing space possible while still meeting the US standard dimension of fitting
through a standard door that is 34 inches wide. The US standard door widths are being used since
HydroTower is being developed in the US though international standards may need to be used if future
applications of HydroTower involve other countries. The height of 2 feet on each of the grow levels was
due to clearances necessary for growing plants such as tomatoes.
6.4. Safety Considerations
Ensuring the HydroTower unit is sound in structure and design was a large factor in building and
prototyping. Since HydroTower has the potential to be used in numerous applications, HydroTower was
designed in a way to incorporate adaptability and modularization to provide the user with options while
also ensuring the safety of users in any and all applications. Specifically, safety was considered in a
manner to account for the misuse of HydroTower. Should HydroTower be placed in a home or public
arena the likelihood of people leaning on the HydroTower or even children or pets crawling on the
HydroTower exterior could be possible. Thus, the sturdiness of HydroTower was a crucial issue.
The base unit in HydroTower was the most significant in facilitating a sound structure that would not be
apt to topple if people leaned on it or if HydroTower had a sudden force applied to it, for example,
someone falling into it. The base unit was also important for structural rigidity since HydroTower is a
vertically integrated unit with either one or two grow levels. Since the base unit was the beginning
structural component of HydroTower the finite element analysis helped to show how the design should
occur to provide stability for vertical integration of the grow levels.
Alternative safety considerations for the structure were in design for how to layout and build the water
piping system and run electrical wires. Since the HydroTower has nutrients in the water, the ions in the
HydroTower: Gardening Solutions 2011 32
water add some safety concern. Valves were chosen on not only the function (size, operation, installation
methods) but also were considered for the power necessary. Housing units were designed for the base unit
to keep electrical components and water/mechanical components separate. For those components such as
pumps or valves, the units were mounted in a manner easily maintained by users and also in a manner to
be structurally sound such that components were not at risk of falling into the water reservoir. The
electronic housing unit was designed by Brenton Eelkema and had a lid to cover and protect the power
supply and other circuitry from exposure to water.
6.5. Assembly and Prototype
Prototyping of HydroTower began very early in the design stages. Initial point designs for the structure
were created in late October and November 6, 2010 was the first initial hand sketch of the new square
prototype though the square prototype was not built until February 2011. SolidWorks drawings are shown
below for both the circular and square prototype design. Building of the first prototype was selected to be
made of wood due to cost but final production designs would be made of polycarbonate or a cast resin as
discussed below.
Figure 22: (L to R) First HydroTower prototype (Circular), Second HydroTower prototype (Square)
HydroTower: Gardening Solutions 2011 33
Based upon the objectives and goals for HydroTower, the unit size was developed to fit within a
residential dwelling. Thus, some design specifications were made such that HydroTower accommodates a
range of users from third world countries in villages to apartment dwellers in the United States or
classrooms in schools. Specifically, HydroTower is designed with a 2.5 foot diameter and is no more than
6 foot tall. While the first built prototype was circular and had a 2.5 foot diameter, the Team decided to
change the HydroTower structure design to a rectangular module with a short end length of 32 inches.6
Prototyping began early due to the ability of the team to test designs as the project proceeded as opposed
to waiting until the end of the project design cycle to test. Furthermore, the nature of the project was such
that plants were grown to test different growing methods and styles. Plants needed a place to live, and
thus the mechanical students (Brian and Jacqueline) built a functioning prototype to provide a place for
plants to live and grow. As the project continued, more of the prototyping occurred to reach the main
objective of a fully functioning prototype by Senior Design Night (May 7, 2011). Pictured below are the
series of two HydroTowers where the circular prototype was the earliest version and the rectangular
version was built then modified into the final prototype design.
A
rectangular structure was chosen for several reasons. First, while circular shapes are assumed to be more
aesthetically pleasing, a rectangular shape is more functional when placed in a room. The HydroTower
Team rationalized that most likely, the placement of a HydroTower unit would be in a corner of a room,
thus making rectangular a more feasible option. Secondly, in regards to manufacturing of HydroTower,
square and rectangular components are made faster and more easily. The dimension of 32 inches for the
short end was based on standard widths of doors in houses as described in the requirements section above.
Team HydroTower assumed that a HydroTower unit would be situated in a living room or den area in a
house and/or in a corner of an apartment or other building. Standard widths for door frames are 34 inches,
but Team HydroTower took into account extra clearances.
6 http://www.access-board.gov/adaag/html/adaag.htm#4.13
HydroTower: Gardening Solutions 2011 34
Figure 23: (L to R) HydroTower Prototypes
The most difficult portion of the installation of the grow level prototype was the water proofing shower
liner, however in production the water proofing step would be unnecessary with the material chosen
instead of the PVC shower liner. The manufacturing section has some further analysis for the type of
material used in full scale production, but overall it would be recommended to mold HydroTower out of a
two part resin plastic.
One of the most significant prototyping feats was the automation of the pump, fans, lights, and drainage
valve before spring break began (March 18-27, 2011). As the team members left for the ten day break,
HydroTower still needed to function to feed plants and provide a growing environment such that the
plants started in December would not die. From the frame and structure standpoint, the prototype was
completed minus the added features of doors/ sides of the grow level and base unit and the fact that no
pipes or valves were directly mounted to the structure. The spring break prototype is shown below.
HydroTower: Gardening Solutions 2011 35
Figure 24: HydroTower Spring Break Prototype
6.6. Final Design for Production
While the initial and final project prototypes were constructed mainly from wood, the production design
would use a plastic possibly with metal such as angle iron to increase strength and rigidity. Most likely,
similar mechanical fasteners for hinges and door handles would be used, as well as the pump, valves, and
lighting structure. However, the wood and thus screws and water proofing shower liner would not be
necessary in the production structure. Further production descriptions are contained in the manufacturing
section.
HydroTower: Gardening Solutions 2011 36
7. Electrical and Control Systems
7.1 Requirements
In order to satisfy the requirements as established by the HydroTower team (see Requirements section),
the following section details both the design decisions and methods for the electrical and computer
system.
7.2 Function
The function of the electrical and computer system is to process and relay commands to various modules
of the HydroTower. This includes the lighting, nutrient and pump controls inside of the HydroTower. A
microprocessor will serve as the central control unit that receives the inputs from the user and sensors and
sends output signals to the control circuitry in the form of transistors and relays. These relays are
designed to control the larger power components of the HydroTower, such as the light arrays, pump, and
valves for each level. Figure 25 shows the control system block diagram that describes the
interconnections between each component found in the system.
Figure 25: Overview of the Control System
HydroTower: Gardening Solutions 2011 37
The function of the automatic controls will be regulated by the microprocessor but customizable by the
user. This is done with a user interface to the microprocessor that allows the user to set variables such as
when the lights turn on and off and the current date and time. The user interface will also display data
generated by the HydroTower. This data consists of a history of past watering cycles and sensor readings.
7.3 Design Procedure
The prototype will be designed using prebuilt development boards. The user interface and higher level
control systems are implemented in software that runs on prebuilt hardware. Other systems, such as the
automated control systems, lighting, and nutrient controls will be custom designed for implementation in
HydroTower. The decision to purchase rather than design the digital hardware was made because such
design work would not contribute to the operation of HydroTower inside the scope of the initial
prototype. That is, the objective for Engr 340 is to build a working prototype capable of growing plants
and demonstrating an automated nutrient distribution system along with a control system and user
interface. For the production model, the team will design a
7.3.1 User Interface (UI)
The user needs a way to operate HydroTower that is simple and efficient. The UI needs two features, a
method for the user to input commands to the HydroTower and a display for conveying information to the
user. HydroTower will require input from the user to perform initial setup, letting the system know when
plants are added or removed. Furthermore, alerting the user to routine maintenance, such as cleaning the
filter, replenishing the water reservoir, and replacing nutrient concentrates will be a needed output from
the UI.
The first solution for the HydroTower’s UI is a character LCD and an array of buttons. A character LCD
could satisfy the needs of the display because a character LCD will allow the HydroTower to display
basic text information to the user with little formatting. To allow input, a series of labeled buttons will
control the system functions. A character LCD is the basic solution and would be the least expensive to
the overall system to implement. However, the character LCD is not the best solution for accomplishing
the overall design goals of making the system aesthetically pleasing and simple to use.
The second solution to providing a UI is to implement an LCD touch screen. This is a more expensive
solution than a character LCD, but an LCD touch screen offers more options to the overall functioning of
HydroTower. A touch screen LCD is able to provide a dynamic interface to the user where context menus
are simple and intuitive, allowing a user to navigate the program and operate basic functions of the
HydroTower even if the instruction manual was not read by the user.
HydroTower: Gardening Solutions 2011 38
HydroTower will use a touch screen interface for the UI because it better addresses the goal of making the
HydroTower more aesthetically pleasing and the requirement of being easy to use. The next decision to
make is on which specific touch screen LCD to implement because all requirements must be met. Hence,
cost is a large factor in selection of a touch screen LCD. Since it was decided that the HydroTower will
use an Arduino microcontroller (discussed in the Data Management and Processing section) to run the
higher level automation and UI program code, the touch screen chosen needs to be compatible with this
platform. The table below outlines three alternatives that will satisfy the needs of the touch screen device.
Table 2: Different options for touch-screen devices
Device/
Manufacturer
Screen
Size Resolution Support Price Availability
Nuelectronics7 2.8” QVGA Datasheets $57 Available
BL-
TFT240320PLUS8 3.2”
QVGA Datasheets $60 Sold Out
TouchShield Slide9 3.2” QVGA Datasheets, Larger
user community $175 Available
When comparing these alternatives, it is not hard to see a clear choice that is superior to the rest. The
TouchShield Slide would prove to be a more powerful option but is also the most expensive, costing
almost three times more than the competition. The TouchShield Slide device does, however, include a
dedicated processor for handling the graphical display and provides the clearest documentation, providing
sample code, and support to make development easier. The BL-TFT240320PLUS is also a possible
option because the the BL-TFT240320PLUS has the same 3.2-inch screen as the TouchShield Slide but
has a lower price. Unfortunately, the BL-TFT240320PLUS overall is a less feasible option since it is 7 "2.8 TFT Color LCD,touch Screen Shield V1.2 for Arduino 168/328 - £29.00 : Nuelectronics.com, Arduino Freeduino
Projects." Nuelectronics.com. N.p., n.d. Web. 12 May. 2011. <http://www.nuelectronics.com/estore/index.php?main_ page=product_info&cPath=1&products_id=19>. 8 "BL-TFT240320PLUS V2." Circuit Ides Design. N.p., n.d. Web. 05 Dec. 2010. <http://www.circuitidea.com/dev-board/BL-
TFT240320PLUS-V2.html>. 9 "Liquidware : TouchShield Slide." Liquidware : Open Source Electronics. N.p., n.d. Web. 05 Dec. 2010.
<http://www.liquidware.com/shop/show/TSL/TouchShield Slide>.
HydroTower: Gardening Solutions 2011 39
more difficult to acquire. This shield only has one listed supplier, www.thaieasyelec.net10
, who lists the
product as sold out as of November 30, 2010. Nuelectronics’ touch screen is also available, but the lack
of a dedicated processor would provide for a rougher user experience. Due to these factors, the
HydroTower will include the TouchShield Slide as its UI.
7.3.2 Data Management and Processing
The Altera DE2 development kit with a NIOS II processor and ARM based processors were considered as
possible solutions. The ARM based development kits cost on average $100, whereas the Altera DE2
board may be borrowed from the Calvin College Engineering department for the prototype. In the final
design the Arduino microcontroller is used. This platform is very flexible and easy to program. There are
many different expansion “shields” for Arduino boards. These shields contain extra hardware in a form
factor that directly plugs into the standard I/O pin interface of the Arduino. This allows us to use I/O ports
for controlling external systems such as the lighting control, pump system, and the nutrient control
systems. Also the Arduino has touchscreen shields that will easily allow development of a clean and
sleek UI. The Arduino board solution is far less expensive, costing about $25, and adequately flexible
option and therefore is the main data storage and processing unit of HydroTower.
7.3.3 Software Model
Below is the software breakdown for the different actions of the HydroTower. The first-run program is
shown in Figure 26 and will require basic information from the user as inputs along with verifying the
system reservoirs are properly setup. The next program function will be the general function that will
handle the water pumping and nutrient replenishment in the system. This is shown in Figure 27.
10 Arduino - 3.2 Inch TFT Touch Screen with Arduino Interface V2." ThaiEasyElec.net. N.p., n.d. Web. 05 Dec. 2010. <http://www.thaieasyelec.net/index.php/Arduino/3-2-inch-TFT-Touch-Screen-with-Arduino-Interface-V2/p_68.html>.
HydroTower: Gardening Solutions 2011 40
Welcome
Set Date/Time
Check NutrientAnd Water Levels
Prompt to Address
Reservoir Levels
Low Levels
Levels OK
Prompt to Start Plant Cycle
Yes Begin Growth Cycle
Program
Enter Sleep Mode
NoDelay 4 hours
Figure 26: Microcontroller Automation Program
HydroTower: Gardening Solutions 2011 41
Flood Level X
Wait while Roots Soak
Drain Level X
Check Nutrient Concentrations
Calculate and Inject Make-up
Nutrients
All Levels Watered?
End
Yes
Low Nutrients
OK
Increment X
No
End
BeginX=1
Check Light State Toggle Lights
Should beONToggle Lights
ON
Should be OFF
Figure 27: Growth Cycle Program
The User Interface on the touch screen will need to give several options and controls over the
HydroTower system. The high level view of this menu is shown in Figure 28. From here the user can
control the lighting and pumping schedule of the HydroTower. Also, the user can let the system know that
they have added or removed plants from the system. Another menu provides the user a way to read and
address maintenance alerts.
HydroTower: Gardening Solutions 2011 42
Figure 28: Main UI
7.4 Automatic Control Circuitry
The output of the microcontroller provides enough power to carry a signal, but not enough to drive the
larger components of the HydroTower. The control circuitry is necessary to convert the 5V low current
signals into larger voltages and currents so systems such as the pumps, lights, and valves can function
properly. Another challenge the control circuitry was designed to overcome was the lower amount of I/O
pins on the microcontroller. These designs are illustrated in the section below.
7.4.1 Relay Circuitry
The bulk of the control circuitry consists of relays that switch power on and off to larger components.
There are five sets of relays the microcontroller controls as is shown in the control system overview of
Figure 25. Each set of relays consist of only on relay, except for the lighting set, which requires three
relays to control sets of LEDs at different voltages as is described in the Lighting section of this report.
Figure 29 shows the design of this circuit. The control signal is hooked up to the base of a Darlington
NPN transistor. When the signal is high, I biases the transistor which and allows the current to flow
through the coil of the relay. The relay will then close and the higher voltage is then allowed to flow
through the load. Likewise, a low signal will shut off the transistor and in turn the relay.
HydroTower: Gardening Solutions 2011 43
7.4.2 Valve and Pump Control Circuitry
The valve control circuitry design has the purpose of driving multiple valves with fewer control lines.
The logic used simplifies it so that four related signals can be driven using only two outputs from the
microcontroller. Figure 30 shows the design of this circuit. Two and gates are used to drive the outputs
to the relays. A Valve Enable signal from the microcontroller provides on input to the and gates. The
second signal is a Level Select signal. A low value on this line will be inverted to turn on the first level
valves and the non-inverted signal will turn on the second level valves when it is high.
To control the pump so the water always reaches a certain height, a water level sensor is implemented in
each grow level. This design consists of two wire leads, one grounded and one at +5V, which will drive a
signal low when water comes into contact with them. The signal then combines with the pump signal
from the microcontroller in an and gate whose output controls the relay of the pump. Figure 31 shows
this water level sensor and circuit.
7.5
Figure 29: Relay Control Circuit
HydroTower: Gardening Solutions 2011 44
7.6 Power Supply
The HydroTower power supply consists of a single 520W computer power supply donated from Chris
Vonk, Calvin Alum. Its power supply is a standard 120-240VAC wall outlet. The HydroTower runs
strictly off of the 12V and 5V supply lines. A block diagram, including voltage, current, and power draw
for each system and subsystem is depicted in the figure below. The typical power draw for normal daily
operation is less than 160W. The microcontroller, control relays, splitter valves, pump, drainage valves,
fan, red LEDs, and the nutrient valves are all powered from the 12V supply line. The 5V line powers the
blue LEDs, along with the semiconductors, and control circuitry.
Figure 30: Valve Control Circuitry
Figure 31: Pump Control and Water Sensor Circuit
HydroTower: Gardening Solutions 2011 45
7.7 Safety Considerations
Several safety considerations were designed into HydroTower. The automatic shut-off of the pump will
activate before either grow level has a chance to overflow. Also the power supply used in the prototype
has built in safety features to shut down when operating conditions become unfavorable.
7.8 Final Design for Production
The final design of HydroTower will have many modifications from the prototype design. Certain parts
of the system will require much redesign. The microcontroller will no longer use a development board
and get its own custom solution. This will allow it to use only the features necessary for the HydroTower
while giving the opportunity to expand certain areas, such as the amount of I/O. Another system to be
redesigned is the power system. Having a custom power supply will allow the HydroTower to be more
efficient with the power it creates and consumes.
Figure 32: HydroTower Power System
HydroTower: Gardening Solutions 2011 46
8. Lighting System
The HydroTower Lighting system consisted of Light Emitting Diodes (LEDs) which were mounted on
the ceiling levels of the HydroTower to provide optimal light to the plants. Given the calculation in the
LED Frequency and Power Design section, 30 2W red, and 15 3W blue LEDs were used. All LEDs used
in the HydroTower were donated by SoundOff Signal Inc. The acquired LEDs needed heat sinks to be
designed in order to run them at their required power of 1.82W for red, and 2.80W for blue. To run them
at these powers, the red and blue LED heat sinks were designed. Using copper, heat sinks cut into squares
(notches cut for leads as in datasheets11, 12
8.1. Requirements
) were used and required a side length of 5 centimeters for red
and 7 centimeters for blue.
Light is to be distributed to the plants in each grow level in such a way as to provide optimal
photosynthesis so that the speed of plant growth will not be limited by the amount of light
received.
The lighting system provides light while requiring less than two hundred watts of power during
typical operation.
The lighting system provides light to the plants that is as efficient as possible, allowing for quick
user financial payback time.
The electrical wiring of the lighting system does not interact with any liquid components of the
HydroTower mechanical systems, being routed separately from the piping system.
The lighting system is designed as to limit the amount of wires traversing grow levels. No more
than four wires connect the lighting system to the base station.
The lighting system is designed as to limit the maintenance required for the HydroTower.
Moreover, the lights will be designed to function for three years of normal operation maintenance
free. This amounts to a lighting system life cycle of at least 20,000 hours.
11 "LR W5SM." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010. <http://catalog.osram-
os.com/catalogue/catalogue.do?favOid=000000000003f86200020023&act=showBookmark>. 12 "LD W5SN." OSRAM Opto Semiconductors - Product Catalog. N.p., n.d. Web. 05 Dec. 2010. <http://catalog.osram-
os.com/catalogue/catalogue.do?favOid=000000030002a14801f30023&act=showBookmark>.
HydroTower: Gardening Solutions 2011 47
8.2. Function
Lighting system would function in accordance with the software controlling systems to meet the above
requirements. The microcontroller controls the on/off status of the lighting system to provide optimized
growing conditions for the plants within HydroTower via a relay switch in the lighting circuit.
8.3. Design Procedure
Several lighting types were considered. The lighting system used red and blue LEDs designed for optimal
plant growth. Research was conducted on the frequency of LEDs needed and their resulting power
requirements. Heat sinks were then designed for proper heat dissipation in the HydroTower.
8.3.1. Lighting type considerations and decision
Several types of lighting systems were considered including High Pressure Sodium lamps (HPS), Metal
Halide lamps (MHs), Compact Fluorescent Lamps (CFLs), Low Pressure Sodium, and Light Emitting
Diodes (LEDs). However, the final decision to use LEDs stemmed from our efficiency requirement,
power draw requirement of under 200W, life cycle greater than 20,000 hours, and their natural small size.
This is summarized in the table below: Table 3: Lighting Type Summary
8.3.2. LED Frequency and Power Design
Since LEDs were the design decision for the lighting system, Research and calculations were done to find
the specific needed frequencies. To fulfill the efficiency and power requirements, research was conducted
on two fronts. The first was focused on the goal of finding the most efficient wavelength of light that
provides optimal lighting. The second was focused on finding the amount of that light needed to make the
plants grow as fast as possible.
A LI-COR Quantum line sensor, obtained from the biology department was used to measure light
irradiance. This sensor measures the number of micro-moles of photosynthetically active photons per
HydroTower: Gardening Solutions 2011 48
square meter per second13
(micro-Einsteins, µE) and reports them in 𝝁𝝁𝝁𝝁𝝁𝝁𝝁𝝁𝝁𝝁𝟐𝟐𝒔𝒔
= 𝝁𝝁𝝁𝝁. However, this sensor
has an active sensing spectrum across the entire visible range as shown in the figure below:
Figure 33: LI-COR Quantum Line Sensor Action Spectrum
This type of sensor then measures the irradiance of photosynthetically active radiation (PAR14
More than just PAR was examined during research. A plot of “photosynthetic activity
). That is, it
measures the amount of light that strikes a surface in terms of radiation that is generally absorbed by
plants.
15” as a function of
the “wavelengths of light absorbed16
13 "LI-191 Line Quantum Sensor." LICOR Biosciences. N.p., n.d. Web. 12 May 2011. <http://www.licor.com/>.
” was obtained from Winona State University, and is depicted below.
14Cerny, Jim. "Understanding the microEinstein Measurement Unit." University of NH, 10 May 2000. Web. <http://www.preterhuman.net/>. 15 "Chapter 15: Photosynthesis." Winona State University. N.p., n.d. Web. <http://course1.winona.edu/sberg/308s10/Lec-note/Photosynthesis.htm>. 16 "Chapter 15: Photosynthesis." Winona State University. N.p., n.d. Web. <http://course1.winona.edu/sberg/308s10/Lec-note/Photosynthesis.htm>.
HydroTower: Gardening Solutions 2011 49
Figure 34: Photosynthetic Action Spectrum17
This plot covers the entirety of what drives the photosynthetic reaction in plants, and not just that of
chlorophyll production, which was also studied and is depicted below
18
.
Figure 35: Absorption spectrum of Chlorophyll a and b
Therefore, to produce the right amount of light for the plants, LED’s were selected in the frequency that
drives the most reaction.
17 "Chapter 15: Photosynthesis." Winona State University. N.p., n.d. Web. <http://course1.winona.edu/sberg/ ILLUST/act-spec.jpg >. 18"Chapter 15: Photosynthesis." Winona State University. N.p., n.d. Web. <http://course1.winona.edu/sberg/ ILLUST/act-spec.jpg >.
HydroTower: Gardening Solutions 2011 50
Since the above plots indicate a range of frequencies that all drive the same reaction, frequencies could be
selected that could produce the total amount of photosynthetically active photons needed for
photosynthesis. This means that regardless of the chosen frequencies, the power could be adjusted to
produce the right amount of photons that drive the photosynthetic reaction. This could be done by finding
the total area under the action spectrum curve that drives the reaction, and using power calculations to
give the plant all of the reaction active photons needed.
Finding data that could give the area under this curve proved less than satisfactory. Therefore a different
avenue for power normalization was used.
Insolation19
The raw data
data was received from the National Renewable Energy Laboratory’s Renewable Resource
Data Center (RReDC). A normalized integration under the sun’s spectral irradiance curve in the red and
blue visible wavelength regions that drive photosynthesis as gleaned from figure 37 was used as a
multiplication factor to find the total amount of power needed by including it with the optimal irradiance
of the sun for plant growth as received from Putra University in Malaysia.
20
19 "Insolation." Wikipedia. N.p., n.d. Web. <http://en.wikipedia.org/wiki/Insolation>.
received from the RReDC contains the electromagnetic irradiance spectrum as measured
on the Earth’s surface. It was graphed using LoggerPro and is shown in figure 36 below:
20 "Reference Solar Spectral Irradiance: ASTM G-173." Renewable Resource Data Center. N.p., n.d. Web. 12 May 2011. <http://rredc.nrel.gov/solar/spectra/am1.5/ASTMG173/ASTMG173.html>.
HydroTower: Gardening Solutions 2011 51
Figure 36: Sun's Irradiance as a function of wavelength
Gleaning approximate numbers for the wavelength limits of the photosynthetic action spectrum in figure
two gave wavelength ranges of 400nm-510nm, and 620nm to 700nm. The curve in figure 36 was
normalized to have a total area of 1000 units. Integrating under the aforementioned wavelength ranges
gave areas of 154.5 units and 109.8 units as shown in figure 37 below. Dividing these numbers by the
total area gives a multiplication ratio. Therefore, finding the total sun irradiance that is optimal for plants
could give the power needed for LED’s in that frequency.
HydroTower: Gardening Solutions 2011 52
Figure 37: Integration Area of Sun's Irradiance Curve
Red and Blue LEDs were donated by SoundOff Signal at 465nm, and 635nm. The datasheets give the
approximate wavelength spread of the blue and red LEDs are shown below in the curves centered on
465nm and 635nm respectively, in figures 38 and 39 respectively:
Figure 38: Spectral emission of Blue LEDs Figure 39: Spectral emission of Red LEDs
HydroTower: Gardening Solutions 2011 53
Research found that the value for the sun’s total irradiance that proved most optimal for plant growth was
14.7MJ*m^-2*day^-1.21 That is, 14.7MJ of light energy would hit one square meter area over the course
of one day. This value was confirmed through another source22
21 Ismail, Mohd R., and Zainab Ali. Effects of Low Irradiance on Growth, Water Uptake and Yield of Tomatoes Grown by the Nutrient Film Technique. Putra University, Malaysia: n.p., 1994. Web.
and was settled on as the number to
continue through the calculations. This number was converted to W/m^2, and multiplied by our
multiplication factors received from the RReDC data to give 23.247W/m^2 and 16.521W/m^2 for blue
and red respectively. Frequency and Power become blurred in the conversion to PAR, as the energy of a
photon is inversely proportional to the wavelength of the light. After making this calculation, the numbers
found were 90.364µE, and 64.22µE. This process is shown in the calculations below as figure 40:
22J. Benton Jones Jr. HydroPonics. <http://books.google.com/books?id=3uqIHH4dpAkC&pg=PA202&lpg=PA202&dq=tomato+optimum+irradiance&source=bl&ots=4UO5pKvbmn&sig=t88GlHMinCNTrNGkT_UJj_tcZpE&hl=en&ei=oRhkTdmXEIeglAeRtcinDA&sa=X&oi=book_result&ct=result&resnum=10&ved=0CFEQ6AEwCQ#v=onepage&q=tomato%20optimum%20irradiance&f=false>
HydroTower: Gardening Solutions 2011 54
Figure 40: Total Einstein Calculation for Line Sensor
These PAR values then gave us the ability to take data with the LICOR Quantum Line Sensor. The sensor
was one meter long and effectively averages all light received over its length. To take more accurate data,
a black foam covering was used to cover a fraction of the sensor, and the resulting measurement was
multiplied by that fraction to achieve the total irradiance.
HydroTower: Gardening Solutions 2011 55
This data was entered into a MathCAD file and values were allowed to cascade down through
calculations to tell us the number of LEDs needed at the measured PAR irradiance levels from the LEDs.
The MathCAD calculations are shown in figure 41 below:
Figure 41: LED density measurements and number calculations
The calculations show that with 27.25 red and 12.5 blue LEDs in the lighting array, the plants would
receive the optimal amount of photosynthetically active photons needed for producing photosynthesis.
These values were rounded up to 30 red and 15 blue LEDs due to the average spread angle of 120 degrees
HydroTower: Gardening Solutions 2011 56
for our surface mount LEDs. More than that, the LEDs were angled to point to the plant canopy area as
added angle spread compensation to ensure efficiency of lighting just the plants and not the surrounding
environment. Calculations and design of this angled array is described in section 8.5 Assembly and
Prototype below.
8.3.3. Heat Sink Design
The LEDs were operated at 0.7A, 2.6V and 4V for an operating power of 1.82W and 2.80W for red and
blue respectively. These power ratings mean that heat sinks needed to be designed as to avoid
overheating. The heat sink calculations are shown in Appendix 14.3. The values found showed a side
length of 3.664cm and 5.684cm for red and blue respectively. The heat sinks were cut and mounted via
heat paste and solder.
8.4. Safety Considerations
Overheating and Thermal runaway was a consideration with the lighting system. As a final decision, the
heat sinks were designed for extra dissipation. The final heat sinks were cut to a side length of 5cm and
7cm for red and blue respectively. Temperature data was also taken of the LEDs after implementation to
make sure the operating junction temperature was under on hundred degrees Celsius, far below the
maximum values.
Shorting of wires and LEDs was also a consideration with the lighting system. As a final decision, the
wires were cleaned and waterproofed with electrical tape. In addition, the wires were routed separately
from any piping.
Also, four wires were used to carry power to the LED’s. These 12 gauge wires were more than adequate
to handle the current passing through them.
The LEDs and Heat sinks were suspended via screws in the mounting array and a fan was added for
proper thermal dissipation as calculated by Brian.
8.5. Assembly and Prototype
In total, 45 LEDs were used; 30 2W red LEDs and 15 4W blue LEDs were mounted to the heat sinks and
angled array. The angled array was created to narrow down the 120 degree LED lighting spread to the
immediate plant leaf canopy located approximately ten inches below the lighting array.
HydroTower: Gardening Solutions 2011 57
To calculate how the LEDs needed to be positioned, simple geometry was used. The LEDs were spaced
equally apart across 24 inches (12 inches from the center), in two directions parallel to the plant canopy.
The center LED was positioned at an angle of 90 degrees (straight down) the angles of the individual
LED mountings surfaces were calculated by taking the inverse tangent of the focal height divided by the
distance from the center line, and are shown below. The height of the LED’s to the focal point (the
bottom of the HydroTower level) was 20 inches. The calculations are shown below as figure 42:
Figure 42: LED support angle calculations
These calculations showed that angles of 79, 68, and 59 degrees for positions of L, 2L/3, and 1L/3 from
the center where L is the length of the support would be adequate. These angles were produced in seven
different supports, with notches cut for the individual angles as shown in the diagram of figure 43:
HydroTower: Gardening Solutions 2011 58
Figure 43: LED Mounting Diagram
The supports were cut and screwed into the ceiling of the HydroTower. The LEDs were attached to the
heat sinks via thermal compound and solder. The heat sinks had two holes drilled into them and were
suspended close to the mounting array via screws to allow for backside separation from the mounting
array and proper heat dissipation. The LEDs were wired into their arrays, and routed to a corner of the
ceiling of the HydroTower’s first level. The wires were secured with electrical tape, and mounting screws
and the ceiling was screwed onto the corner supports. Wires were routed and connected to their relay
circuits for power control by the microcontroller. The entire prototype was successful and the mounting
process is depicted below in figure 44:
HydroTower: Gardening Solutions 2011 59
Figure 44: 1st Level Lighting Array
The LEDs were designed to be powered by 12VDC and 5VDC lines from the power supply. Using ohms
law, the 12V line supplied seven parallel sets of four series red LEDs followed by a 2Ω, 2W resistor. This
covered 28 of the 30 red LEDs. The remaining two were placed in series with a blue LED coming from
the 12V line followed by a 4Ω, 2W resistor. The remaining 14 blue LED arrays consisted of 14 parallel
sets of a single blue LED in series with a 2Ω, 2W resistor. This gave a current of 0.68A through all
LED’s. The total power draw from the entire LED array then is calculated to be just under 115W as
shown in figure 45 below:
Figure 45: LED Power Draw Calculation
Models of the red and blue LEDs were made in MATLAB’s Simulink, and the circuit diagram was drawn
up as shown in figure 46 below:
HydroTower: Gardening Solutions 2011 60
Figure 46: Circuit Diagram for Red and Blue LED Arrays
8.6. Final Design for Production
The final design of the lighting system implemented for wide-scale production would be very different
from the current prototype. The LEDs would not be mounted on angled arrays but would be mounted on a
flat printed circuit board with PCB copper performing the heat dissipation. In essence all LEDs would be
attached to one large heat sink there would be focusing lenses placed on the LED to narrow the angular
spread for directionality. All LEDs would run off of the same supply line, and a small yet dedicated LED
power supply would be placed in the array. The array would be housed in a narrow rectangular box of
molded plastic for perfect water proofing, protecting the entire lighting system. Two wires would connect
the LED array, rather than four and the heat sink would be designed so no fan is needed. More
experiments would be conducted while growing full plants to find the best optimal light power and
frequencies for the plants. LEDs would still be used as they are the most efficient solution to lighting.
HydroTower: Gardening Solutions 2011 61
9. Mechanical Systems
The mechanical systems for HydroTower include the water piping network and the nutrient distribution
system. Another component for mechanical design was the air ventilation and ensuring the electrical
wiring and electrical components were housed safely.
9.1. Requirements
The water is to be distributed to each grow level in a modular fashion such that users may purchase and
install an additional unit and install the unit with minimal hassle. Furthermore, the second grow level
shall be independent of the first such that users have the ability to purchase only one grow level with no
loss of overall function.
Drainage of the HydroTower had to occur such that the water would be recycled to align with the design
norm of stewardship wherein water and resources are not wasted. The nutrients are also regulated through
the measurements of pH and EC sensors which serve as inputs to the micro-controlled nutrient program.
Water and air kept at 70°F provides an optimal growing temperature for plants, though measurement and
regulation of each was not incorporated into the final prototype design since it was assumed the
HydroTower would function in a home dwelling and thus operate at room temperature. Furthermore, it
was determined that no heater for the air or water would be used in the HydroTower prototype though one
could be included in the production model. The final production design could incorporate heaters and
sensors to monitor and control water and air temperature as discussed below.
The electrical wiring must not come into contact with any water piping.
9.2. Function
The mechanical systems are controlled by the Arduino microcontroller to meet the above requirements.
The HydroTower must function to properly flood and drain the grow levels along with creating the
controlled and optimized growing conditions for the plants within HydroTower.
9.3. Design Procedure
Several possible methods existed for each of the mechanical systems and design decisions were based on
overall function, alignment with the overall project goals and objectives and finally with budget.
HydroTower: Gardening Solutions 2011 62
9.3.1. Valves
Valves were one of the most costly purchases for the entire prototype to achieve the required functionality
of the HydroTower prototype specifically for the water system which fed the plants. The higher cost was
several reasons, firstly, multiple types of valves are used in HydroTower and secondly the valves are used
in different capacities as shown below.
Figure 47: P&ID of Water System with Valves
Figure 48: Actual Prototype Pictures of Water System
HydroTower: Gardening Solutions 2011 63
The water system works by feeding each of the two different grow levels which are controlled by the
microcontroller. Again, a user can purchase HydroTower with one grow level or two grow levels. Thus,
to conserve on space and the amount of water necessary to feed plants, one single water reservoir and
pump were chosen thus requiring the water stream to be split to properly direct water flow to the grow
levels.
Thus in order to split the water flow, two normally open solenoid valves were purchased. Two valves
were selected such that each HydroTower grow level would operate independently. The splitter as it was
called functioned much like a manual y-splitter like those used for garden hoses. However, since
HydroTower is to run autonomously, the splitter used solenoid valves off of a PVC tee. Specifically, the
solenoid valves chosen ran on 12VDC and 450mA and were normally closed diaphragm valves that were
servo operated. While it was considered having the inner diameter (ID) of the solenoid valves the same as
the pump outlet tube (3/8th in ID), the ½ in ID was selected to yield a greater flow rate and thus decrease
the amount of time necessary to run through a feed cycle. Furthermore, the 3/8th ID valves only had
barbed connection which would have not made it ideal for splitting the water flow through a tee or other
plumbing device other than tubes which could more easily leak as hose and barb clamps would be the
method of connection.
Other options included purchasing two pumps or flooding both grow levels at the same time. However,
having two pumps was excessive for space within the water reservoir and was also wasteful in terms of
components since the pumps are more extraneous when compared to valves. Pumping both levels at the
same time was not feasible since that would require users to purchase two grow levels and would further
not allow each grow level to operate independently of the other. Another consideration was that one
drainage valve would function by the second grow level draining via a bulkhead and pipe to the first grow
level then to the water reservoir. However, such an operation would mean the first grow level would be
flooded before the second grow level was drained which was not a desired outcome since the flooding of
the first grow level would not be regulated in that situation. Thus, each HydroTower unit will be equipped
with two drainage valves and should the second grow level be purchased the user would only need to
connect the drainage pipes as well as the feed water pipes and tell the user interface a second grow level
would be in use.
The drainage valves were selected to be normally open solenoid valves to allow for drainage at all times
despite being three times the cost. Normally closed valves would require the drainage time to be known
and calculated, which was not accurate since rather complex differential equations were necessary and the
factors such as the change in area due to the drainage slope and the impact of friction from the perlite
HydroTower: Gardening Solutions 2011 64
made the differential equations very different from the actual application. Professor Heun of the
engineering department was contacted for assistance with the modification of the differential equations,
yet in the end the equations proved too complex and inaccurate for use to control a normally closed
solenoid valve. Furthermore, while the drainage time of water from each grow level could be measured,
the problem is the perlite adding friction and impeding the water flow such that normally closed solenoid
drainage valves would need to be powered for a longer amount of time to allow for water flow to occur
and return water to the reservoir. The differential equations were based on experimentation measuring the
volumetric flow rate to eventually calculate the interior volume of the grow level. The basic results of the
differential equations are located below. Overall, without any perlite but with the Styrofoam spacers in
place, the drainage time was just over 5.5 min while drainage with the perlite was timed to be about 7 min
with a continuous dripping/draining occurring as more water came from the perlite. As shown in the
below calculations, the measured dimensions resulted in an interior volume of 18.3 US gallons when no
perlite or Styrofoam spacers are present while the differential equations resulted in 5.8 US gallons.
HydroTower: Gardening Solutions 2011 65
Figure 49: Basic Results of Differential Equation Calculations on Drainage and Volume
Nutrient distribution valves were selected at 0.25 inch diameter gravity fed solenoid valves since the
amount of nutrients added is a small volumetric amount in comparison to the water reservoir. The nutrient
valves are mounted below the nutrient container and connected to pipes which lead to the water reservoir.
Six nutrient valves were purchased due to the six different nutrients added separately to the water
reservoir to create the desired Hoagland’s solution. The nutrient valves are all 12 VDC and 500mA.
All of the purchased valves were selected to run on 12 VDC to best accommodate the power supply in
HydroTower.
HydroTower: Gardening Solutions 2011 66
Table 4: Purchased Valves for Water System
Description Qty Unit Price
Total Cost
1/2" Electric Solenoid Valve 12-V DC NORMALLY OPEN B21N
2 $44.95 $89.90
1/4" Electric Solenoid Valve 12-volt Air, Water... BBTF
6 $15.99 $95.94
1/2" straight pipe Electric Solenoid Valve - Water etc. (DDT-
CS-12VDC)
2 $13.99 $27.98
shipping/handling 1 $4.95 $4.95 Total $218.77
9.3.2. Pump
An initial submersible pump for early prototype production was purchased in November by Brandon from
Horizen Hydroponics, and had a max of 4 foot of head and 158 gph. While such a pump was suitable for
feeding the plants early in prototyping, the second grow level of HydroTower was over 4 foot high, thus
requiring a more powerful pump. The main considerations in pump selection were the maximum head and
the power required to run the pump. Submersible pumps were selected to conserve space within the base
unit furthermore, submersible pumps were advantageous since they did not require mounting other than
using a pipe hanger to secure the tubing that went to the splitter. The larger submersible pump purchased
was from Grianger and had 25 feet of max head and had a maximum of 3.3 gpm (200gph). Furthermore,
then new pump was specified at 12VDC and 2.8A. The 12VDC was advantageous since that meant the
pump could also be incorporated into the power supply. The 25 foot max head was chosen since
HydroTower would require a max pumping of about 5.5 feet and with the added splitter (loss of head) the
25 foot max head pump was the smallest option in a submersible bilge pump that would be able to handle
exposure to the ion water as well as filtering the perlite that ends up in the water reservoir. While a 15
foot max head fountain pump would have worked for HydroTower, the added benefits of the relatively
low cost of the bilge pump (compared to alternative pumps) made the Grainger pump the best option for
the HydroTower prototype.
HydroTower: Gardening Solutions 2011 67
Table 5: Submersible Pumps Purchased
Description Qty Unit Price
Total Cost
Max 4 foot head
1 $14.27 $14.27
Max 25 foot head
1 $27.81 $27.81
Total
$42.08
9.3.3. Ventilation Fans
The ventilation fans were selected off the cfm rating and the overall size. Two 12 cfm (maximum) fans
were selected based on psychrometrics calculations performed. While the psychrometrics calculations (as
found in the appendices in section 14.2.1) showed that about 6 cfm would be adequate to keep the
HydroTower air at 70°F, the electrical engineering students in charge of the LED lighting system
communicated their concern that the LEDs may burn out if the heat sinks did not have air flow. Thus,
thermal calculations were performed and are described in the lighting section. Overall, the 12 cfm fans
were installed, one on each grow level to ensure the LEDs would not overheat and the plants would have
airflow. However, in actual production, a baffling system would be considered to cool the LEDs and
decrease the total airflow in the grow levels since it was observed that plants closer the fan would wilt
throughout the day due to too much air flow which subsequently caused the stomata to close.
9.3.4. Water Reservoir
During the design of the water reservoir for HydroTower, the dimensions were based on the design
calculations that one grow level holds about 13gallons of water with the Styrofoam blocks in place as
seen below by experimentation and volume calculations. Calculation results are shown below and full
calculations are available in the appendices in section 14.2.2
Table 6: Volume of Grow Levels Based on Flow Rate Experimentation
Without Styrofoam Spacers 18.49 US gal With Styrofoam Spacers 12.87 US gal
Table 7: Volume of Grow Levels Based on Geometries
Without Styrofoam Spacers 18.36 US gal With Styrofoam Spacers 13.30 US gal
HydroTower: Gardening Solutions 2011 68
A contingency of water volume was added during the design to allow for ample water supply for the grow
levels and also to allow for some capacity of water under filling by the user and evaporation/water
consumption overtime. Thus, the final design of the water reservoir was increased to hold a volume of
15gallons. Other constraints on the water reservoir design were the lengthwise dimensions of the
HydroTower base unit. The longest side of the water reservoir would be a maximum of 25in since that is
the largest dimension possible with the current HydroTower base unit constrained by the widths and
thicknesses of the 2-by-4s used in construction. However, since design also considered the
implementation of drawer slides to allow the user to pull out the nutrient container, the longest side was
made to be 22in to incorporate the necessary steel frame and drawer slides.
The water reservoir was made out of 0.5in (for the bottom) and 0.25in (for the sides) thick polycarbonate
since those building materials were available in the Calvin wood/metal shop. Deflection calculations
given in section 14.2.4 if the appendices show the deflection is negligible for the uniform loading
provided by the 15gal requirement and thus no cross bracing was necessary below the bottom plate of the
water reservoir. In the deflection calculations, the bottom 0.5in thick polycarbonate sheet was treated like
a simply supported beam with a uniform load applied. The uniform load was a surface load from the
weight of the 15gal of water. Bowing on the side polycarbonate (0.25in thickness) plates was a concern
and so an aluminum frame was made to be placed over the edges of the water reservoir. The major FEA
analysis results from the water reservoir base are shown below.
Figure 50: FEA Analysis Results for Reservoir Bottom of 1/8th inch thick Polycarbonate
HydroTower: Gardening Solutions 2011 69
A 0.25in ledge was used on the bottom (0.5in thick) polycarbonate plate to allow for two surfaces of
contact to join the bottom to the sides. The height of the reservoir was constrained by the amount of
0.25in thick polycarbonate, which was one sheet 48in by 43in. Thus, the water reservoir was made a
height of 12in, giving just under 15gal when filled to the brim with water and considering the 0.25in
ledge on all sides of the base made by a router.
Figure 51: Example of how router was used to create ledges
One major change to the overall HydroTower base unit was that the height was increased from 12in to
18in to allow for the 12in height on the water reservoir and also allowing in turn for more time between
filling up the water reservoir so the submersible pump would not run dry and for the inclusion of the
nutrient container on the drawer slide. Furthermore, more height on the water reservoir allows for more
coverage of the submersible pump and also allows for a shorter-side of the water reservoir which
subsequently increases the amount of room left for electrical components. Lastly, the height of
HydroTower was increased to allow for more room to implement piping and the nutrient container into
the base unit above the water reservoir. The table below shows the final dimensions of the HydroTower
water reservoir for cuts to be made from the polycarbonate.
Table 8: Dimensions for Cuts on Water Reservoir
Height 12 in Width 22 in Length 14 in
9.3.5. Water Reservoir Mixer
The water reservoir mixer was created off of a car window motor and then had a polycarbonate tube and
propeller. The car window motor was an available resource from Calvin and was tested at both available
HydroTower: Gardening Solutions 2011 70
power supply lines (12 VDC and 5 VDC) from the power supply in HydroTower. The 5VDC power
supply showed the mixer would mix the water reservoir and the 12VDC power supply created “sloshing”
in the water reservoir. The mixer functions after nutrients are distributed into the water reservoir to ensure
proper mixing occurs before the plants are fed. For the production of HydroTower as a product, and DC
motor with a propeller would be used, if possible the motor and propeller would all be made from plastic
such that rusting and other material degradation would not occur from exposure to water evaporation and
possibly condensation.
9.4. Safety Considerations
The main safety objective for the mechanical systems was to prevent the HydroTower grow levels from
over flow and such that if the HydroTower units malfunction or fail it would be in a fail-safe manner. For
example, the valves were selected to be fail-safe during operation and backup sensors were installed to
prevent the pump from continually pumping.
Furthermore, other safety systems included in the base unit and subsequently other areas of HydroTower
were in the selection of normally open solenoid valves as drainage valves. In a fail-safe logic, normally
open valves need power supplied to close. Thus, the only time power is supplied to the drainage valves is
when flooding (or feeding) of the plants in the grow levels occur. All other times of operation have the
drainage valve open such that water may return to the water reservoir.
Despite the addition of the normally open solenoid valve, another safety feature was to turn off the pump
should the water level rise too high where a water sensor would turn off the pump. The water sensor was
built by Nathan Meyer to detect when water crossed the two probes of the device and turn off the pump
through an independent circuit. Furthermore, the water sensor served as a safety feature through two
purposes. Firstly, having the sensor on a separate circuit would ensure that if the microcontroller failed
the safety sensor would be independent and provide the necessary redundancy. Secondly, the sensor
would ensure that the water level would not rise above the perlite to not flood the plants, grow algae from
too much water and not flood HydroTower. Preventing the algae growth was an added benefit since the
overarching safety feature. More information on specific design of the water level sensor can be found in
the computer and electrical section.
9.5. Assembly and Prototype
The water was distributed via a 200 gph submersible pump as discussed above. The pump was able to
distribute to both grow levels through the utilization of the “splitter” valves. Thus, in order to pump to the
HydroTower: Gardening Solutions 2011 71
first grow level, the pipe/valve that led water to the second level remained closed while the first grow
level valve was powered open. The pump is controlled by the Arduino microcontroller and programmed
to run for four minutes based on the programming capabilities of the Arduino coupled with the time
necessary to fill one HydroTower grow level. The pump runs for four minutes unless the water sensor is
tripped meaning the maximum desired water level was reached, for more information on the water sensor
see the section on automation and the microcontroller.
Both the drainage valves and the water piping valves operate in a similar manner to the nutrient valves as
they are controlled by the Arduino. Furthermore, all the valves are integrated into the base unit such that
the nutrient valves are mounted below the nutrient container but above the water reservoir. The drainage
valves are both mounted above the water reservoir and are connected via mechanical fasteners to the steel
structure/frame within the base unit. Specific wooden frames were built to hold the drainage valves at a
45º to allow for proper drainage since through experience of operating the valves they functioned best at
45º up to 90º (or inline flow with the drainage bulk head). However, 45º was selected since 90º was not a
feasible angle with the given space in the base unit and the pipe bends that would have been necessary.
Furthermore, 45º was much more easily produced in the wood shop and thus also easier for
manufacturing/production. Lastly, the “splitter” valves and corresponding plumbing are mounted via pipe
hangers to the wooden permanent side in the base unit. The valves and PVC tees and PVC barbs are all
light weight (under 0.5 lb combined) and are thus supported by two pipe hangers (one on each side of the
tee) as pictured below, please note that the brass 90º elbows were replaced by PVC 90º elbows once they
came in Lowes since all PVC made for lighter weight overall and also leads to better water sealing
possibilities for the plumbing.
Figure 52: "Splitter" Valves
HydroTower: Gardening Solutions 2011 72
The fans are connected to the interior top of the HydroTower grow levels and are directed at
approximately 45° angles to create a cross ventilation over the installed LEDs.
The piping and electrical wiring are grouped in two locations, one in the corner with the water feed and
the pump (the supply) and the other nearest the drain (the return). Though the piping and electrical wiring
run together for ease of installation and maintenance, the electrical wires are still secured independently
from the water pipes such that safety is maintained.
9.6. Testing and Calculations
9.6.1. Drainage and Drainage Testing:
Both the flooding and drainage of the HydroTower grow levels required controls from the Arduino. As
stated previously, normally open solenoid valves were selected as drainage valves. During the
construction of HydroTower, different tests were performed on both the water-seals and secondly the
drainage. The drainage of the HydroTower is in accordance with a differential equation due to the
drainage-slope and the change of the water level.
Several different test methods were employed since hand calculations of the volume of the grow level did
not initially align with experimental result. The first experiment took one measurement of fluid flow rate
and assumed that the flow rate remained constant for the entire drainage time in HydroTower. Such an
assumption was not adequate since the flow rate changes as a function of both the height of the water and
the area of the drainage plane. That is, due to the slope of the HydroTower grow level the area changed
during drainage. The second round of experiments took into account the change in flow rate by taking
measurements all throughout the draining process of the grow level. The results of the second set of
experiments correlated well with the geometrical calculations as displayed by the overall volume results
below and are the same as discussed above. The full experimental data can be found in the appendices in
section 14.2.2.
Table 9: Volume of Grow Levels Based on Elevated Flow Rate Experimentation
Without Styrofoam Spacers 18.49 US gal With Styrofoam Spacers 12.87 US gal
Table 10: Volume of Grow Levels Based on Geometries
Without Styrofoam Spacers 18.36 US gal With Styrofoam Spacers 13.30 US gal
HydroTower: Gardening Solutions 2011 73
The final analysis for drainage was in regards to the differential equations and solving for either the
amount of time each grow level would take to drain or the area needed for the drainage pipe. Team
HydroTower considered the options of having a solenoid valve for drainage and also considered having
drainage pipe to a size that would allow the pump to input water at a greater rate than was allowed to
drain. Both options would allow for continuous drainage of water that may be held in the perlite thus
fulfilling the design requirement of fail-safe operation. The final design decision was to install a normally
open valve since the calculations of the drainage pipe diameter/area were heavily dependent upon the
differential equations which were too complex based on both the friction from the added perlite in the
grow level and the changing area from the drainage slope. While the differential equations were
calculated in MathCAD, as shown below, actual results were not modeled realistically enough as shown
by the numerical results below and can be compared to the geometric results above.
Figure 53: MathCad Screen Shot for Differential Drainage Calculations
HydroTower: Gardening Solutions 2011 74
For example, the friction of the perlite was not taken into account for the initial differential equation but
would need to be due to the large effect the perlite had on drainage during testing. Secondly, the
differential equations did not account for the change in the area from the drainage slope (since the area
goes from a square plane to a decreasing square plane). Below are shown the graphs of experimental data
for the drainage tests performed.
Figure 54: Flow Rate Change During Initial Drainage Test
Testing for the initial drainage flow rate change occurred by recording the time it took to fill a 2L beaker
with water then using the flow rate and overall time taken to drain the grow level to solve for the interior
volume to ultimately compare the experimental volume to the geometric volume. Only the first few
(three) data points were consistently measured, which was shown to not be as accurate as subsequent
experiments described below since the volume calculated did not correlate as well with the geometrical
calculations described previously.
Table 11: Volume of Grow Levels Based on Flow Rate Change (initial test)
Without Styrofoam Spacers 13.5 US gal With Styrofoam Spacers 11.7 US gal
HydroTower: Gardening Solutions 2011 75
Figure 55: Flow Rate Change During Elevated Drainage Test
Testing in the elevated experiment occurred by recording the amount of time it took to fill a 1.5L
container in order to observe the change in flow rate. The above results are for the grow level with the
drainage slope installed but no perlite. Furthermore, in order to ensure the test results were not affected by
gravity wherein the drainage tube was curved or twisted the entire HydroTower grow level was placed on
a platform approximately 6 feet above the floor level such that the drainage tube was perpendicular the
ground. The volumes calculated are shown in the figure titled “Volume of Grow Levels Based on
Elevated Flow Rate Experimentation”.
After much discussion with Professor Heun, it was concluded that the normally open valve provided the
best option for complete drainage of the HydroTower grow levels since the differential equations would
not necessarily be worth the time necessary for testing and calculating when the elevated flow rate
experiment results and geometric volume calculations supported and affirmed the results.
9.6.2. Full Mechanical System Integration Testing:
Once all valves were installed and connected to the nutrient program in the microcontroller the entire
system integration was tested with the nutrient valves, pumps and pump valves and drainage valves to test
HydroTower: Gardening Solutions 2011 76
the water tightness of the system along with testing the head of the pump and the flow rate for filling
HydroTower during the feed cycles. During initial testing, the seals on a number of the pipes were not
water tight since crimps were not added in order to allow the system to be taken apart. However, once the
cycles controlled by the Arduino were proven functional, the system was crimped to create water tight
seals on barb fittings. However, the barb fittings on the drainage barbs and on the pump were never
crimped such that if a worst-case scenario occurred HydroTower could be completely disassembled and
moved without having to un-crimp any fittings.
One problem that arose during function was that the “splitter” valves became clogged with algae as
shown below.
Figure 56: "Splitter" Solenoid Valve with Algae Clogged Filter
The filters were removed from one of the valves to test if the algae would still clog the valve without the
filter or if the flow rate through the valve was high enough to prevent clogging. After about two more
weeks of function the valve with the filter left in clogged again but the other valve was clear, this was
discovered as the splitter was disassembled and inspected.
Other problems occurred with the proper drainage of the normally open drainage valves. It was thought
that the drainage valves were either clogged or were being drained at the incorrect angle. Upon
disassembly of the drainage valves it was noted each were clear and not clogged. Then, after testing
numerous angles, it was found the drainage valves operated best at about a 45° angle with the tube into
the water reservoir at a slight gradient as opposed to being bent down abruptly.
HydroTower: Gardening Solutions 2011 77
Figure 57: Mounted Drainage Valves
Figure 58: Disassembled Drainage Valve
9.7. Addition Considerations and Final Design for Production
The production design for HydroTower in regards to the mechanical apects such as the pumps, valves and
fans would have a number of modifications to increase the overall integration of components as well as
increasing the overall functionality and decreasing the cost. This section breifly describes some additions
and modifications that would occur before production.
The ventilation fans would have more sensors to add more control of the air flow within each
HydroTower grow level. For example, thermocouples and hygrometers would be used to control when the
fans would turn on. If the humidity in the HydroTower level rose above 50% relative humidity, both fans
HydroTower: Gardening Solutions 2011 78
would turn on to create the cross ventilation. The environmental conditions for plants are optimal when
relative humidity is about 50% and temperature is 70°F.
From a biological standpoint, if humidity is too high, and condensation forms on plant leaves, the plants
become susceptible to fungus and disease.23
Initially, the mechanical designs for the final production design were going to measure humidity with a
hygrometer and then have the regulation of air flow controlled by fans and a venting system with
mechanical flaps capable of different degrees of opening/closing. However further analysis of alternative
design options showed that a more complex and expensive humidity control system was not necessary to
meet the design requirements. For example, below is a list of the alternative designs for the
humidifiers/dehumidifiers, four humidifying systems researched and then analyzed included the
following.
Thus, the mechanical design of HydroTower includes
compensation for air flow and ventilation to regulate the humidity within the HydroTower growing
structure. Furthermore, if the relative humidity is too low, plants will close their stomatas, which are how
plants intake CO2 and release O2. Should the humidity become too low, a humidifier will turn on via the
control system for psychrometrics and will subsequently add moisture to the air within HydroTower.
1) Steam humidifiers which boil water to release steam into the air
2) Impeller humidifiers which move water through a diffuser to make very fine water
droplets in the air
3) Ultrasonic humidifiers which vibrate at an ultrasonic frequency to create water
droplets which are absorbed into the air.
4) Wick/evaporative humidifier which draws water out of a reservoir and allows water
to evaporate as air passes over the wick via a fan-powered ventilation system
The cost and implementation of each of the four humidifying/dehumidifying systems was considered and a
qualitative analysis of implementation and cost allowed Team HydroTower to eliminate the steam
humidifier and the ultrasonic humidifier as production options based on market research of the
humidification processes. Further research not discussed in the body of this section is located in the
appendices in section 14.2.1. Both of the aforementioned options would require more electrical and
mechanical systems to control the humidity, which would add to the overall cost of HydroTower. 23 Raven, Peter H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants. 6th ed. New York: W.H. Freeman and Worth
Company, 1999.728-730. Print.
HydroTower: Gardening Solutions 2011 79
Furthermore, the components necessary to have either a steam humidifier or an ultrasonic humidifier
would subtract the amount of space usable in the base unit by the electrical control systems and/or the
amount of water held within the base unit. Thus, either the controls box would move outside of the base
unit or the base unit size would need to increase. Overall, Team HydroTower decided to not pursue further
designs of implementing the steam humidifier or the ultrasonic humidifier.
The two other humidification system alternative designs were the impeller and then the wick humidifier.
Due to resources and initial thoughts of Team HydroTower and the tech lead on the psychrometric design,
the wick humidifier was pursued in quantitative analysis for several reasons. First, the wick humidifier
would require forced ventilation, and since Team HydroTower found several CPU fans the cost for
production of a prototype would be low. Furthermore, the wick for the humidifier would be placed in the
water tubing and then in the middle of the forced air flow stream. The wick would be a water-absorbent
cotton rope which could be purchased at a fabric store for under $0.50/foot.24 A filter for the system may
also be necessary, but testing of the implemented wick design would show if a filter is needed for better
functioning. Should a filter on the wick humidifier prove necessary, the cost of the filter would be under
$10.25
The wick humidification system will work well for ensuring that the air within HydroTower remains at
about 50% relative humidity because as the air becomes more humid, the water requires more energy to
evaporate and the same principle applies for dry air (easier to evaporate water when air is less humid).
Thus, the wick humidification system works by natural evaporation of water from the wick. Specific
design of the wick humidifier will occur during spring semester once the final design direction is known.
However, one specific issue with wick humidification to be addressed during the design phase is that wick
humidification will be to ensure that condensation does not occur within the HydroTower. As previously
mentioned, the two fans will be installed on each growing level on either side of HydroTower. The wick
humidifier will have a control system based on readings from a hygrometer. For the control system, if the
humidity is too high the fan furthest to the water input flow (hence, the fan without the wick in front of it)
will turn on. The table below shows a more visual summary of how the fans will turn on and off via the
control system and hygrometer readings.
24 "Cotton Rope | Twisted & Braided 1/4 - 1 Inch Sizes." KnotandRope.com. N.p., n.d. Web. 5 Dec. 2010.
<www.knotandrope.com/store/pc/Cotton-Rope-c6.htm>. 25 "Wick Humidifier - Google Search." Google. N.p., n.d. Web. 05 Dec. 2010. <http://www.google.com/search?q=wick
humidifier...>
HydroTower: Gardening Solutions 2011 80
Table 12: Summary of Wick Humidifier Design For Fan Usage
System Reading Fan with Wick Fan without wick
Humidity too high Off On Humidity too low On Off Extreme ranges high or low On On Fail-safe method for humidity out of range On On
HydroTower: Gardening Solutions 2011 81
10. Manufacturing
Since HydroTower units will be assembled by Team HydroTower during the startup phase, inventory
costs must be kept to a minimum while also not having the manufacturing process take much room or
require equipment that is too specialized. In the long-term outlook of Team HydroTower, large
manufacturing layouts would occur wherein HydroTower would be manufactured most likely via molding
or casting of plastics.
10.1. Requirements
Full scale production of HydroTower units must be efficient and time effective. Manufacturing will occur
on a basis of lean manufacturing and just-in-time. Manufacturing will use as many similar parts as
possible to make assembly easier and less costly. Furthermore, manufacturing will minimize the number
of machine set-ups and changes to decrease the amount of time necessary to manufacture one unit.
10.2. Safety Considerations
The safety of persons in contact with HydroTower during manufacture or after sale must be kept safe
according to OSHA, USDA, FDA and possibly others. Specifically, OSHA has a division for the plastics
industry (Society of the Plastics Industry) which incorporates controlling hazardous energy, requirements
on machines and requirements on personal protective equipment. However, specific safety requirements
for manufacturing would be detailed once full scale production was finalized.
10.3. Manufacturing Process Considerations
The manufacture of HydroTower units is feasible since the design considered methods of manufacturing
as well as ease of assembly. HydroTower units would be mass produced through plastic casting, vacuum
molding or vacuum permanent-mold casting for the low volume applications. For high volume
production, HydroTower units could use injection molding.
HydroTower: Gardening Solutions 2011 82
11. Business Plan
The business plan below is indicated by the left border and was submitted in the Calvin College 2011
BizPlan Competition presented by the Calvin Entrepreneurship Club, the Business Department and the
Engineering department and further sponsored by Soundoff Signal, Inc. and the Kern Foundation. Team
HydroTower placed second overall in the BizPlan competition based on scores from the business plan
presented below as well as judges interpretations of the proposed idea and an oral presentation delivered
to the panel of judges.
The HydroTower is a new and innovative approach to typical gardening applications by
moving the outdoor garden indoors. Team HydroTower is comprised of five engineering seniors
with the simple mission statement of “feed people, more efficiently, through hydroponics”.
Hydroponics refers to plants being grown without soil using only water and nutrients necessary
for plant growth. The HydroTower is hydroponic gardening in a modularized and stackable unit
that can be used in apartments or homes. A stackable design allows a HydroTower owner to
decide how many levels they would like to grow plants
Executive Summary:
As a company HydroTower would distribute products to consumers in urban areas to
decrease the distance produce travels before reaching market. Marketing in urban areas will also
increase the availability of fresh produce to urban families. The target customer of the
HydroTower would be women ages 25-39 years who would most likely be interested in feeding
their families more healthy with fewer trips to the grocer. HydroTower would begin as a small
company serving customers on a basis of filling orders per customer demand. HydroTower units
would be produced by Team HydroTower during the growth phase. Once revenue increases are
consistent, the second phase growth plan would implement more mechanized production
facilities to meet growing demand for the product. A website would be used to facilitate the
orders as well as email and phone communication methods. Currently, Team HydroTower has an
HydroTower: Gardening Solutions 2011 83
established website that is updated by team members on a monthly basis. Later stages of
HydroTower sales would be directed through major distributors such as Meijer and Lowes or
home and garden centers.
HydroTower enhances the design and functionality of current hydroponic designs to
create a new product. The unique feature of HydroTower is the full automation of growing
plants. HydroTower is designed with a friendly and easy-to-use user interface that allows the
owner to select which types of plants will be grown. In addition, HydroTower will regulate and
optimize growing conditions for plants including temperature, water, nutrients, lighting and
ventilation. HydroTower will also be able to notify the users if water or nutrients need to be
replenished. Nutrient replenishment is a marketing point for Team HydroTower since nutrients
can also be sold to customers as a replenishment product. Team HydroTower believes citizens in
urban environments will embrace the idea of hydroponics for fresh produce year round based on
the growth of farmers markets and roof-top gardens. While hydroponics is not a new concept,
few competitors offer a complete hydroponic system. The market for full automation of plant
growth such as HydroTower is open to many new customers.
The initial growth stage would have the five original team members as the only company
employees. Secondary and tertiary growth stages would see the addition of accountants,
marketing personnel and finally a board of directors and trustees. The company would be started
as an LLC and would be managed by Jacqueline Kirkman. In the secondary phase a CEO would
be appointed. The secondary and tertiary stages of growth would also have employees to
assemble and distribute HydroTower units through the company facilities which would be leased
or purchased depending on availability and options.
HydroTower: Gardening Solutions 2011 84
Since HydroTower is currently a prototype focused on proof of concept, research and
development is necessary to transition from a prototype stage to a production stage. Team
HydroTower is participating in the 2011 Bizplan Competition to gain funds for future research
and development while also earning funds towards the production launch. Team HydroTower
would further ask for $100,000(USD) from investors as debt financing and $50,000(USD) as a
bank loan to begin the start-up phase of the company. Team HydroTower would pay all
monetary funds back on a monthly basis with an annual interest rate of 7% within three years of
operation. Should the previously mentioned financial plan fail, Team HydroTower would
employ a “run-dry” method and all assets would be liquidated and distributed according to
contracts signed prior to initial investment.
The HydroTower is a new idea being prototyped by five students from the Calvin College
Engineering program, pictured below. The HydroTower Team has been working on prototyping
the HydroTower design through the Calvin College Engineering Senior Design (SD) Capstone
course .
Company Introduction:
Figure 59: Team HydroTower: Back Row(L to R): Jacqueline Kirkman(ME), Brandon Vonk(EE)
HydroTower: Gardening Solutions 2011 85
Front Row (L to R) Brian DeKock (ME), Nathan Meyer (EE), Brenton Eelkema (EE)
The HydroTower idea is based on the rapidly growing need to create a more sustainable
source of food production as the world population continues to grow. By creating a small and
stackable hydroponic system, HydroTower has the ability to be used year round in urban homes,
schools and restaurants to produce high quality fruits and vegetables.
Food production, distribution and consumption have become a growing concern due to
the movement of populations into more urban settings. It is widely believed that there will be an
overall increase of 70% in agricultural production by the year 2050 (J.A. Burney, “Greenhouse
gas mitigation by agricultural intensification”, National Academy of Sciences 2010). Increasing
food production and maintaining sustainability is necessary in the twenty first century. A
growing trend in sustainable agriculture is the idea that agricultural production should take place
in small and localized areas. Local food production provides a more sustainable means for
consumption of produce without requiring consumers to decrease the amount of fresh produce
purchased. Sustainability increases as the produce travel distance is reduced. In addition,
freshness increases as foods are locally grown. The HydroTower design is being developed as a
means to deliver the freshest possible fruits, vegetables and herbs at the most local level, in a
home.
An important area of innovation for HydroTower is the nutrient control system. Since
hydroponically grown plants cannot take nutrients from the soil a precise nutrient control is
required. Using the open source and inexpensive Arduino microcontroller computer,
HydroTower will have the ability to take measurements and replenish nutrients as they are
consumed by the plants. Additionally, the microcontroller computer will automate the process of
HydroTower: Gardening Solutions 2011 86
controlling features in the HydroTower such that a user is capable of leaving HydroTower alone
for up to two weeks at a time.
Research and development will be carried out due to the possibility of a patentable
product. Initial patent searches showed no current products like HydroTower. The United States
Patent Number (USPN) 5,598,663 Hydroponic nutrient solution control system has been
identified as the closest possible barrier to patent protection for HydroTower. Hydroponic
nutrient solution control system was patented in the United States on February 4, 1997, and has a
claim similar to the current HydroTower objective. While the patent contains similar technology
to analyzing and controlling the nutrients in a hydroponic system, no technology or products
have been patented which contain a fully automated growing system holistically. To ensure
patent and legal safety, Team HydroTower will be working with Michael Harris and the
Enterprise Center at Calvin College for legal advice.
HydroTower: Gardening Solutions (HydroTower) will be legally bound as a limited
liability company (LLC). HydroTower will be a small business and a partnership finance
approach will be beneficial based on the working format of the team during the 9 months of
Calvin Engineering Senior Design. An LLC approach will assist in legal protection should
HydroTower need said protection. From a taxation standpoint, HydroTower will be established
as a partnership LLC wherein all members of Team HydroTower will have equal share of the
profits should they choose to remain members of the team post-graduation from Calvin.
Furthermore, as an LLC, each member of Team HydroTower is able to decide how taxes are
filed on the incomes from HydroTower. HydroTower would be a new product to the market with
a planned release date in early 2012 to maximize research and development in 2011 .
HydroTower: Gardening Solutions 2011 87
HydroTower would launch in Grand Rapids, MI with units being shipped throughout the United
States to customers.
The hydroponic industry is currently experiencing resurgence due to the high quality of
hydroponically grown fruits and vegetables. Over the next five years, the number of tomatoes
grown in hydroponic greenhouses is expected to rise by 50%. Lettuce and herbs are also
increasingly being grown hydroponically with microgreens being introduced as a new and
valuable hydroponic crop. High quality hydroponic and organic hydroponic fruits and vegetables
are selling at more than 15% - 50% higher prices than conventional fruits and vegetables.
Industry Analysis:
26
26 Brentlinger, D.J. 2007. NEW TRENDS IN HYDROPONIC CROP PRODUCTION IN THE U.S. Acta Hort. (ISHS) 742:31-
33. <http://www.actahort.org/books/742/742_3.htm>
Other
advantages for hydroponic growth, such as using less nutrients and water, are shown below in
Figure 2.
HydroTower: Gardening Solutions 2011 88
Figure 60: Advantages to hydroponic growth of plants27
The Standard Industrial Classification Code (SIC) for HydroTower would most likely be
0781-10 for hydroponics supplies and lights for growing. However, HydroTower and hydroponic
products are new to the market within the last decade. Thus, HydroTower could be given a
general classification of 9999-04 for Hydroponics equipment and supplies.
Within the last 9 years, hydroponics as, well as organic products, have been increasing in
popularity not only for local grocers and restaurants but also for medical and pharmaceutical
applications.28 Many consumers have been raising demands for more clean and sustainable
methods of food and medicinal production, thus leading to the market growth of hydroponics.
Specifically, HydroTower would attempt to join the Progressive Gardening Trade Organization
which declares members are “retailers, manufacturers and distributors of the latest earth-friendly
organic and water-wise gardening products”.29
27 CityScape Farms, San Francisco, CA
As a member in such a trade organization,
28 “Quality in Commercial Hydroponics” HydroGarden. March 13, 2011. <http://www.commercial-hydroponics.com/hydro.html> 29 “Membership Information”. Progressive Gardening Trade Organization. March 13, 2011. <http://www.pgta.org/membershipinfo.htm>
HydroTower: Gardening Solutions 2011 89
HydroTower would gain the benefits of networking with other suppliers and retailers as well as
gaining credibility.
One main political issue surrounding HydroTower is the fact that hydroponics have been
accustomed to growing marijuana. While hydroponics provide numerous benefits to growing
produce and brining the availability of fresh produce to more people, Team HydroTower is
prepared to deal with the negative aspect of marijuana growth. HydroTower would add to the
warranties and guarantees information about how the user is responsible for abiding all local,
state and federal laws. Team HydroTower realizes that every new technology has both benefits
and some drawbacks, and in this case Team HydroTower feels the added benefits greatly
outweigh the negatives.
Overall, the industry for hydroponics and organic products in growing rapidly, providing Team
HydroTower with a unique opportunity to launch a new product to claim part of the growing
market of hydroponics.
First and foremost, HydroTower is designed for the individual or family who is looking
for a gardening solution without having a backyard garden. More specifically, HydroTower is for
those persons without outdoor gardening space and looking for a way to grow fresh fruits and
vegetables. HydroTower presents a solution for the consumer who is looking to eat fresh produce
whose quality can be ensured while also reducing the carbon footprint of large scale food
Customers:
HydroTower: Gardening Solutions 2011 90
production. As more people move into cities, garden growing space will become scarcer, making
it necessary for alternative gardening solutions.
The target market for HydroTower is women who have a family at home and need fresh
produce for their children. The table below shows the 2006-2008 statistics from the United States
Census Bureau. These statistics provide a market that is large enough to begin selling the
HydroTower into. Team HydroTower believes that the customer motivation is increasing for
products such as HydroTower due to the increase in the number of food recalls over the past two
years.30
Hydroponic gardening prevents almost all major diseases that can be found on plants
since most diseases are soil based. There is additional customer motivation to buy HydroTower
when comparing the cost of other hydroponic units. HydroTower, on average, costs one-third to
one-half as much as competing products.
Table 1: Census Bureau 2008 population31
30 http://www.huffingtonpost.com/2010/05/06/lettuce-recall-e-coli-pos_n_566956.html 31 http://factfinder.census.gov/servlet/STTable?_bm=y&-geo_id=01000US& qr_name=ACS_2008_3YR_G00_S0101&-
ds_name=ACS_2008_3YR_G00_
HydroTower: Gardening Solutions 2011 91
An ongoing market research survey is being conducted during the writing of this report.
Preliminary results will be available soon. Currently there are 21 responses to the survey with 10
questions, and key results are shown in Figure 3 below. The questions are listed below:
1. How often do you buy fresh produce from the grocery store?
2. How much of the produce that you buy is organic?
3. Would you be more likely to buy produce labeled organic?
4. Do you have a garden at home?
5. Please list what fruits or vegetables you grow in your garden.
6. Would you prefer to grow more of your own food if you had enough space?
7. Are you familiar with hydroponics?
8. How likely would you be to purchase a hydroponic system for growing vegetables?
9. Please list what vegetables you would want to grow most in a hydroponic system?
10. Which of the following would make you more likely to purchase and use a
hydroponic system?
The key market survey results have indicated that HydroTower will need to have an easy-
to-use user interface along with a low maintenance design. Furthermore, the market survey
indicated that many consumers would grow their own food if provided the opportunity. Overall,
the market survey has assisted Team HydroTower in confirming objectives for design and
marketing.
HydroTower: Gardening Solutions 2011 92
Figure 61: (L to R): Survey results on likely aspects for purchasing HydroTower, Results on customers growing their own food
Growth for HydroTower outside of the defined customer basis has potential to increase as
larger questions are raised about the safety for consumers involved with commercial food
production. Additional growth could also be driven by the growing number of people moving
into cities and living in apartments and high rise condominiums. Future customer groups
currently outside the focus of the HydroTower Team include third world applications, schools,
healthcare organizations and high end restaurants.
Market Analysis:
Restaurants in the United States, according to the 2007 census bureau, had an estimated
$190,417 million dollars of sales for full service and $186,326 million for limited service eating
places.32
32 “2007 Annual Trade Retail Survey”. Web. 13 March. 2011. <http://www2.census.gov/retail/releases/historical/arts/2007_ARTS.pdf>
Team HydroTower estimates that initial growth into the restaurant market would begin
in Grand Rapids, Michigan and would ideally expand throughout the United States to provide
food establishments the option of growing their own produce and herbs along with adding to the
revolution of fresh and organic products available on menus. The annual growth rate for the food
HydroTower: Gardening Solutions 2011 93
market coincides with population growth and the number of people moving to urban
environments, which the World Bank estimates that by 2030, 60% of the world populations will
live in cities.33
The market for schools and healthcare has not been estimated since Team HydroTower
would look to partner with community projects to educate people about eating healthfully and to
also educate people about the advantages to hydroponically growing produce. Thus, the
marketing changes for healthcare and schools would be more of a move to establish more
thoroughly and to deepen the brand name of HydroTower.
Competition:
Existing Competitors
33“Urbanization”. YouThink:ReadyToAct. World Bank. Web. March 13, 2011. <http://youthink.worldbank.org/issues/urbanization>
Figure 62: (L to R): RotoGro 240, Desktop Hydroponic Stystem, AeroGarden Pro 200
HydroTower: Gardening Solutions 2011 94
The RotoGro 240 Rotating Garden has an innovative design with timer and rotating
motors. The rotating design is quoted as, “The effect of gravity on the rotation of plants is
amazing”. Its strengths are that the RotoGro is a developed product on the market and it has an
innovative design. The weaknesses of this product are that it costs $5,200 and lacks in visual
appeal.34
The second established competitor is the Desktop Hydroponic System. The Desktop
Hydroponic System is a compact planter that grows small herbs on desk using sunlight or the
artificial light from an office. This product has a strong visual appeal and a low cost of $40. The
weaknesses of the Desktop Hydroponic System are that it has no additional light source and is
not big enough to feed a family. Growing options are limited.
35
The AeroGarden Pro 200 Indoor Tabletop Vegetable Garden is a fully automated system
that is capable of growing multiple types of herbs and vegetables. For $200 the indoor garden
provides everything that is needed to start growing. The weaknesses of this product are that it
lacks growing spaces and still does not have a strong visual appeal.
36
34 "RotoGro 240 Rotating Garden." HHydro.com. N.p., n.d. Web. 5 Dec. 2010. <http://www.hhydro.com/RotoGro-240-Rotating-
Garden.html>. 35 "ThinkGeek :: Power Plant Herb Garden." ThinkGeek. N.p., n.d. Web. 05 Dec. 2010.
<http://www.thinkgeek.com/homeoffice/kitchen/b7d7/?cpg=cj&ref=&CJURL>. 36 "The Indoor Tabletop Vegetable Garden." Hammacher Schlemmer. N.p., n.d. Web. 05 Dec. 2010.
<http://www.hammacher.com/publish/75426.asp#?cm_mmc=CJ-_-2617611-_-3682082-_-Save up to 70% on Electronics>.
HydroTower: Gardening Solutions 2011 95
Potential Competitors
Figure 5: (L to R): Biosphere Home Farming and Nano Garden
“Biosphere home farming concept generates food and cooking gas, while filtering water.
The concept supplements a family’s nutritional needs by generating several hundred calories a
day in the form of fish, root vegetables, grasses, plants and algae. Unlike conventional
hydroponic nurseries this system incorporates a methane digester than produces heat and gas to
power lights, similarly algae produces hydrogen and the root plants produces oxygen, which is
fed back to fish. Carbon Dioxide is pumped into the plants. It is a closed loop interdependent
system. The system uses waste water and non-consumable household matter and delivers food in
return.”37
The Nano Garden is a design concept produced by Hyundai with a strong visual appeal.
“The Nano Garden is a vegetable garden for the apartment kitchen, using hydroponics, so users
don't need to worry about pesticides or fertilizers. Instead of the sunlight, Nano Garden has
The strength of this idea is that it is backed by Phillips which is a large company.
However the system is larger than most needs for a family.
37 "Biosphere Home Farming by Philips." Yanko Design. N.p., n.d. Web. 05 Dec. 2010.
<http://www.yankodesign.com/2009/03/17/the-ultimate-recycle-bin-nourishes-as-well/>.
HydroTower: Gardening Solutions 2011 96
lighting which promotes the growth of plants. The amount of light, water and nutrient supply is
also controllable, so users can decide the growth speed. It lets users know when to provide water
or nutrients to the plants, and Nano Garden functions as a natural air purifier, eliminating
unpleasant smells.”38
SWOT Analysis
Strengths: Expanding market with many new ideas on hydroponic gardening. People are more
likely to try out ideas and product which are showing up multiple places in different forms.
Weaknesses: Quality reference research material lacking in applications of hydroponic systems.
Hydroponic gardening is also not recognized as organic by the Federal Organic Standards.
HydroTower also involves experimenting with untested ideas for automation.
Opportunities: There are many small startup companies in the industry. A growing number of
investors and venture capitalists are looking at agriculture as a large area of investment in the
twenty-first century. The growing number of competitors will also keep Team HydroTower
focused on thinking and working towards the best possible solution.
Threats:
There are currently many corporate research and development labs looking at consumer
hydroponic use. These companies benefit from funding and resources much greater than what
Team HydroTower has available.
38 "Kitchen Nano Garden." Fast Co. Design. N.p., n.d. Web. 5 Dec. 2010. <www.fastcodesign.com/idea-2010/kitchen-nano-
garden>.
HydroTower: Gardening Solutions 2011 97
The sale of HydroTower units over the first year have been projected to be about 5,000
units in the first year with an increasing number of units as popularity increases. The objectives
for sales would be to increase sales steadily to fill 30% of the 30 million person market. While
30% of the market is a large goal, Team HydroTower would like to set objectives high to
continue to push to expand the market. Once a footing in the market hold is established, the
market would be expanded to the other areas such as schools, healthcare organizations and
restaurants.
Marketing/Sales Plan:
Team HydroTower plans to use print media to promote HydroTower at grocery stores
and home and garden supply stores before moving to television commercials or infomercials.
The message will be carefully marketed in order to both educate potential customers about the
benefits of hydroponic gardening and emphasize the low cost and high quality of HydroTower
when compared to other products on the market for hydroponics. However, HydroTower would
first be exhibited at home and garden shows as well as craft fairs and other areas where the target
market could be reached. Having customers see the product would be beneficial since they will
know how the product works and would be able to envision one in their homes for feeding their
families. By the fifth year of business, Team HydroTower would like to have commercials along
with the product on its way to becoming a household brand name.
More specifically, Team HydroTower plans to market products locally before expanding
availability to across the United States. For initial local partnerships, HydroTower will be
distributed though local hydroponic stores such as Horizen Hydroponics located in Grand
Rapids. In the long run, Team HydroTower would like to partner with large home and garden
HydroTower: Gardening Solutions 2011 98
centers to sell units to customers as well as the replacement products. Initial sales, as mentioned,
will occur through phone, email and ordering online. Customers are looking for a product that is
reliable and easy to use, as well as low cost and low maintenance. The market survey conducted
has proven what customers would like in a hydroponic system and Team HydroTower has
designed accordingly. Team HydroTower is focused on a design that contains both utility and
significance to create a unique product that is unavailable anywhere else.
The initial price for HydroTower has been set to $500 or less. A lower product price is
important in order to attract customers to the new idea of hydroponic gardening and show that
hydroponic gardening is worth the cost. HydroTower provides double the growing space and
technology for the cost when compared to similar competitors. Competing products range from
$40 for a product with less than one-fifth of the growing space up to $3,000 for a product with
similar technology and growing space. The anticipated gross profit margin of the HydroTower is
25%. The current HydroTower design is being built based on an $800 budget. Production unit
prices are expected to be about $400, though that price may vary with the amount of material
purchased in bulk.
Team HydroTower has interdisciplinary backgrounds of three electrical engineers and
two mechanical engineers to work on topics including biological, chemical, electrical and
mechanical principles. During the start-up phase of the company Team HydroTower will equally
delegate tasks to be accomplished based on strengths of team members. As the second phase of
company growth occurs between years three and five, Team HydroTower will add financial
Human Resource Plan:
HydroTower: Gardening Solutions 2011 99
advisors to track expenses and revenues. . During the start-up phase Team HydroTower would be
influenced by the initial investors of the investment capital, and a board of directors would be
established during the second growth phase.
The organizational structure of Team HydroTower during the initial start-up phase will
closely resemble the working structure for the Senior Design capstone. Currently in the Senior
Design, Team HydroTower members have equal say in brainstorming and decisions are put to a
vote with final authority resting in the hands of the project manager, Jacqueline Kirkman. As
HydroTower grows, a board of directors and other outside investors will be delegated decision
making authorities in a voting structure. However, the actual formulation of said Board of
Directors or other outside investor groups with decision making authority have yet to be
determined. As HydroTower transitions from a low production volume to a high production
volume, additional personnel will be added in both administrative roles and manufacturing roles.
While no official hiring numbers have been determined, Team HydroTower is forecasting a two
shift manufacturing operation wherein one manufacturing facility will be used for all raw
materials, production and final product distribution. The same facility would also house all
administrative personnel to take orders and continue engineering work.
The human resource budget will be controlled by Brandon Vonk and will be taken from
the revenue generated by HydroTower. Since HydroTower is a start-up company with a new
product Team HydroTower may have to forego compensation for work until actual profits are
made.
HydroTower: Gardening Solutions 2011 100
Daily operations will be managed by the Project Manager (Jacqueline Kirkman) who will
delegate tasks out to the other four members of the team according to individual strengths. Each
team member will be responsible for specific tasks related to the design and development of
HydroTower. Jacqueline will be in charge of all managerial, administrative and legal tasks along
with working in coordination with several team members on specific project tasks. While each
team member is delegated specific non-engineering tasks, engineering design in sub-set groups
will continue in a similar format to Senior Design.
Operations:
As previously stated, product orders will be taken in through the website, emails and
phone. Nathan Meyer will maintain the website and will be accountable for expanding
HydroTower’s customer outreach. Thus, Nathan will be in charge of communicating with
customers and interpreting what specific needs customers will want met such that HydroTower
can continue to impress and develop as market trends change. Nathan will also be held
accountable for orders and the 30 day satisfaction guarantee policy.
Brandon Vonk will be in charge of budgeting and finances for Team HydroTower until
the second phase of growth is reached in which case accountants will be hired. Brandon will
work closely with Nathan to ensure HydroTower is able to meet the growth trends and
successfully reach the breakeven point. Brandon will also work with Jacqueline and Brian to
secure facilities for when full production of HydroTower begins.
Brenton Eelkema will be in charge of market analysis as well as contacting
subcontractors with Jacqueline. Brenton has extensive knowledge of market trends and a strong
HydroTower: Gardening Solutions 2011 101
intuition for changes in the market place. Brenton will also work closely with Brandon and
Nathan for the after-purchase-products such as the grow medium and nutrients.
Brian DeKock will be in charge of the facility layout and production implementation for
HydroTower. Brian will ensure equipment for production is working along with continuing to
make sure the production facility layout is efficient and can make the change from job-shop
production to high volume production. Brian will also work with Jacqueline on quality control
for the production facilities.
Initial research and development (R&D) will be dedicated to completing a production
prototype of HydroTower. The production prototype will take the designs from the Engineering
Senior Design capstone and implement a full working prototype. During the growth and life of
HydroTower, R&D will work towards expanding and developing HydroTower for use in
different applications. While Team HydroTower is strong in the area of brainstorming,
difficulties may arise in the allocation of funds for R&D. Brandon Vonk will track all monetary
assets for HydroTower and will allocate funds accordingly. Team HydroTower has discussed
allocating as much as 40% of revenue towards R&D during forecasted times of growth, which
will be scoped out by Brenton Eelkema. On a normal operation basis, 15% of revenue will be
allocated to R&D.
Research and Development Plan:
HydroTower as a product will further be developed into a product used for education in
conjunction with schools and healthcare programs. HydroTower has the capability to be
HydroTower: Gardening Solutions 2011 102
developed into a community project, and Team HydroTower would work to partner with
different health organizations and schools to expand the marketing potential of HydroTower.
Furthermore, HydroTower could be developed into a product for high end restaurants that could
grow their own produce and herbs. Again, Team HydroTower would work to partner with chefs
and restaurant owners to expand this market. As previously mentioned, more people are moving
into urban environments and HydroTower can assist in feeding people while also decreasing the
amount of resources used to grow, transport and distribute food.
Overall, HydroTower will continue to develop with growing markets and market trends.
While the initial development has been included, many other opportunities may arise, in which
case completely different avenues could be taken to develop more products and expand the
customer base.
The current HydroTower financials for the first 5 years of operation assumes the
following:
Financials:
• 20% of the 30 million person market will be reached in the five years
• Unit sale price of $500 USD, unit production price of $400 USD
• 10% annual interest rate on debt
• MACRS Rates 7 year recovery
• Equipment purchase for first year is $100,000 USD with all other years $20,000
• Contribution margins years 1-3 of 12% and years 4-5 of 20%
HydroTower: Gardening Solutions 2011 103
Team HydroTower is requesting $100,000 (USD) for an initial first year investment
capital as a debt financing from investors and applying for a $50,000 (USD) loan. The
investment money would be used to cover initial variable and fixed costs of materials and
equipment used in the assembly. Furthermore, the initial investment money will go toward
marketing and advertising HydroTower units.
HydroTower will repay all monetary funds to individual investors within three years and
payments will be made on a monthly basis plus an annual interest rate of 7%. In the event that
Team HydroTower is not able to meet the projected growth goals and fails as a company, all
assets within HydroTower will be liquidated and sold at market value. Furthermore, Team
HydroTower will employ a “run-dry” method such that all debts may be repaid in full according
to contractual agreements. However, should the liquidated assets not cover the initial money
invested, Team HydroTower will make other accommodations to repay all debts in full, for
which terms would be negotiated prior to initial investment.
HydroTower is planned to launch in February of 2012 following the initial startup phase to
grow for three years. Should the initial three year projected growth phase objectives not be
reached, Team HydroTower will re-evaluate the objectives and goals to determine if the
aforementioned exit strategy must occur. After a successful initial startup phase, the second
phase of growth would occur from years 3 to 5 and the current business plan would be re-
adjusted to accommodate for further growth goals. After the second growth phase, the tertiary
growth phase would be implemented, though no specifics have been planned for the third phase
of growth.
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Appendix A: Five Year Financial Projections
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Appendix A: Five Year Financial Projections (Cont.)
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Appendix B: Initial Planning/Estimation HydroTower Senior Design Budget
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Appendix C: Current Working HydroTower Senior Design Budget
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12. Organization and Management
Specifically, below is a description of each of the Team member’s responsibilities. While much work is done in teams, the descriptions below explain individual roles of the Team and the specific delegation of work.
• Brian DeKock was placed in charge of the overall structure and manufacturing of prototypes. Thus, Brian was the best fit for each of his task delegations.
• Brenton Eelkema was in charge of developing the business overview and WBS creation. In addition he worked to build and measure preliminary experiments in hydroponics. Brenton was also delegated the task of the nutrient control system after the Team selected to use Ebb and Flow hydroponics with a general hydroponics approach.
• Jacqueline Kirkman was delegated the psychrometrics and the water system. Jacqueline has further acquired the position of Project Manager, thus other tasks are delegated to Jacqueline which fall under team management but are not specifically listed here.
• Nathan Meyer was delegated to manage the software design and implementation for both the microcontroller and the use interface. Nathan was also assigned to maintain the team website and update it as content becomes available.
• Brandon Vonk was delegated the design of the power system and the lighting system for HydroTower. Brandon was also delegated the responsibility of maintaining an updated team budget.
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13. Appendices
13.1. WBS and final hour summary
13.2. Mechanical Calculations and Tests
13.2.1. Psychrometric Calculations
13.2.2. Drainage Testing, Interior Grow Level Spacing and Water Reservoir Calculations
13.2.3. Nutrient Containers
13.2.4. Water Reservoir Deflection Calculations
13.3. Lighting System Heat Sink Calculations
13.4. Financials
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14.2.1 Psychrometric Calculations
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14.2.2 Drainage Testing, Interior Grow Level Spacing and Water Reservoir Calculations
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Method Change: put HydroTower about 7 feet high on elecated platform and drain with valve fully open. Measured in 1.5L increments with alternating pop bottles
Without Styrofoam With StyrofoamRun Time Volume (L) Run Time Volume (L)
1 12 1.5 1 10.76 1.52 9 1.5 2 10.22 1.53 10 1.5 3 9.89 1.54 9 1.5 4 9.84 1.55 9 1.5 5 9.64 1.56 10 1.5 6 9.89 1.57 10 1.5 7 9.4 1.58 9 1.5 8 9.55 1.59 9 1.5 9 9.89 1.5
10 9 1.5 10 9.69 1.511 9 1.5 11 9.59 1.512 10 1.5 12 9.96 1.513 9 1.5 13 9.76 1.514 10 1.5 14 9.82 1.515 10 1.5 15 9.74 1.516 10 1.5 16 9.49 1.517 10 1.5 17 9.63 1.518 10 1.5 18 10.12 1.519 10 1.5 19 9.63 1.520 10 1.5 20 9.9 1.521 10 1.5 21 10.25 1.522 10 1.5 22 10.16 1.523 10 1.5 23 9.58 1.524 10 1.5 24 9.37 1.525 10 1.5 25 10.11 1.526 9 1.5 26 10.14 1.527 10 1.5 27 10.28 1.528 10 1.5 28 9.73 1.529 9 1.5 29 10.35 1.530 9 1.5 30 9.79 1.530 10 1.5 31 10.01 1.530 10 1.5 32 10.39 1.530 10 1.5 33 23 0.7530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 10 1.530 28 1
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Summary of Results/Comparison to Four Different Methods
Conclusion: geometrical volume calculations and improved method of elevated HydroTower with multipleflow rate measurements verify each other. Thus, the assumption that flow rate is constant was proved icorrect (this was known before and led to the application of differential equations). The differential equation method needs to be corrected with the help of Prof. Heun to account for both the change in height and the change in area as HydroTower drains.Overall Results show the volume of HydroTower (when filled to a water height of 5 in) is about 18.5 gal.
Volume Estimation based on data points (test with elevated HydroTower):1 US gallon = 3.785412 L
Without Styrofoam With Styrofoam70 L 48.75 L
18.49204 gal 12.87839 gal
From Wood Testing Spacing Calcs After Test Corrections (geometrical volume calcs)Volume of One Level (No Styrofoam)
Inner 4241.328 in^318.36073 gal
Volume of Styrofoam Spacing:1170 in^3
Volume of Water Not Used due to spacing:5.064935 gal
Total Volume with styrofoam13.29579 gal
Differential Equation (not correct, need to fix with Prof. Heun's input)DVQ: 5.81 galDVQ Sheet Volume: 18.329 gal
From Volume Wood Spacing Test_1 (using flow rates based on initialflow rate, not correct assumption that flow rate is constant)Without Styrofoam2000mL 45 sFlow Rate 44.44444 mL/s 1ml =
0.011741 gal/s 0.000264 US galTotal Vol 1151 s
Volume_Calculated13.51387 gal
With Styrofoam2000mL 33 sFlow Rate 60.60606 mL/s
0.01601 gal/sTotal Vol 733 s
Volume_Calculated11.73564 gal
©HydroTower: Gardening Solutions 2011 120
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35
Tim
e to
Dra
in 1
.5 L
(s)
Trial Number
Flow Rate Change During Drainage (Elevated Test)
Series1
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Trial Two VarianceDiffering the sizingheight 10 inleaves 346.5 in^2
Area Possible Check on Volume1 18.61451 in for square 3465 in^3
15 gal2 16 in from a drawer slide 3465 in^3
21.65625 in 15 gal
3 18 in from a drawer slide 3465 in^319.25 in 15 gal
3 14 in from a drawer slide 3465 in^3 this one may be a tighter fit since 2*4 are24.75 in 15 gal slightly off/not perfectly square
4 22 in from a drawer slide 3465 in^315.75 in 15 gal
5 24 in from a drawer slide 3465 in^314.4375 in 15 gal
Trial Three VarianceDiffering the sizingheight 9 inleaves 385 in^2
Area Possible Check on Volume1 19.62142 in for square 3465 in^3
15 gal1.5 18 in from a drawer slide 3465 in^3
21.38889 in 15 gal
2 16 in from a drawer slide 3465 in^324.0625 in 15 gal
3 14 in from a drawer slide 3850 in^327.5 in 16.66667 gal
4 22 in from a drawer slide 3850 in^317.5 in 16.66667 gal
5 24 in from a drawer slide 3850 in^316.04167 in 16.66667 gal
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Actual Sizing from Placement in HydroTowerThicknesses of Materials, Etc
Only concerned with the constraint from the height and the side withthey 2*4s, then optimize to have the other dimension smallest to resultin highest point of the water so pump has best ease of use.
Possible Thicknesses of materialsAl 0.1875 in 2 thickness and one heightSlides 1 in 2 thicknessBracing ? in height
Constraints from HydroTower Base UnitWidth 25.25 inHeight 11.25 in making this such that it is no longer a
constraint…can change base unit with noDiffering the sizing problemheight 11 in This height is of water….box is going to be 15inleaves 378 in^2 base unit height increased to 18in
gives us 3in to play around with piping and valves
Option Dims Units VolumeCheck1 13.5 in 3192.75 in^3
21.5 in 13.82143 gal
Therefore: say make 13gal of Hoaglands
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Making Hoagland's Solution for Water ReservoirMax (to brim) of Reservoir13.82143 gal
1 US gallon = 3.78541178 LHoaglands we will make
13 gal50.000 L Making Hoaglands in Water Reservoir
13.2086 gal 50.000 L in the reservoir40 mL Added to Reservoir:
8 mL Distilled Water 2000 mL4 mL Distilled Water 4000 ml
2000 mL Distilled Water 2000 mL400 mL Distilled Water 4000 mL200 mL Distilled Water 4000 mL
Distilled Water 2000 mLDistilled Water 4000 mL
Buckets 33 L 1 gal = Distilled Water 2000 mLTotal Made 17.000 L 3.785412 L Distilled Water 4000 mL
4.490925 gal Distilled Water 2000 mL1037.404 in^33.368194 in Ca(NO3)2 2000 mL
KNO3 2000 mLMgSO4 2000 mLKH2PO4 2000 mLFeEDTA 400 mLMicros 200 mL
Distilled Water 2000 mL4000 mL4000 mL2000 mL
Nutrient Volume: 0 mLDistilled Water: 50000 mLTotal: 50600 mL
50.6 L
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14.2.3 Nutrient Container Calculations
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14.2.4:Water Reservoir Deflection Calculations
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14.3 Lighting System Heat Sink Calculations
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14.4 Financials
Final Budget
Delegation of funds Source Expected Received
Calvin College $
500.00 $
500.00 SoundOff N/A 74 LED's
Dorner Works $
300.00 $ -
Competitions:
Elevator Pitch $
300.00 $
300.00
Business Plan $
600.00 $
600.00 Big Idea none none IEEE Presidents… up to 10k
NCIIA Sponsored $ - N/A
TOTAL $
1,700.00 $
1,400.00
Funding Distribution Item Funding Source Total Cost
Already Purchased
Arduino Touch Screen Elevator Pitch $
184.00
Thermal Compound Brandon $
10.59
Plastic Containers/Caulking Brenton $
8.72
Perlite/grow medium Brandon $
23.85
Water pump Brandon $
14.27
Wood,shower liner,piping supplies Brian $
75.92
Growing Seeds Brenton $
19.45
LED Grow Lights Sound Off $ -
Caulking Brenton $
3.00
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Chemicals Calvin Biology Dept $ -
Bulkhead (water dispensing) Brian $
13.49
Wood (2x4's: 3) Brian $
6.49 Valve (nutrient dispensing and on pump splitter) Calvin
$ 95.94
Valve (drainage) Calvin $
89.90
Splitter (Manual) Calvin $ 4.54
Valve (splitter) Calvin $ 27.98
RTC and Crystal Calvin $ 3.96
Water Filter Brenton $17.50 Bulkhead (second level) Jacq $14.17 Pump (improved) Jacq $27.81 1/2 in PVC tee (pumping sys) Jacq $3.43 1/2 in MNPT barb adapter (pump sys) Jacq $1.18
1/2 in tubing Brian $ 5.55
foam tape Brian $ 2.08
test plug Brian $ 0.93
crimp tee Brian $ 2.98
1/2 in male barb elbow Brian $ 0.60
5 hinges Brian $ 5.25
second level building materials Brian $ 127.00
TOTAL $
606.58
Money Left to use $
793.42
Operation Cost Analysis
The operation cost analysis of the HydroTower shows the fixed and variable cost of operating the
HydroTower year round and compares it to the value of the crops created within the HydroTower. Water
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and electricity were assumed to be the variable costs at $1.30 and $60 respectively. Fixed costs were
assume to be nutrients at $45/year, seeds at $10/year and GroCubes at $7 per year. Total operation cost of
the HydroTower stands at $123.30.
The value of fruits and vegetables grown in the HydroTower is shown in the table below. The
expected total value of the crops grown in the HydroTower is estimated at $141.50. These calculation
shows that over a year period the operation cost of the HydroTower is approximately equal to the value
created in the crops grown within the HydroTower.
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Plant Store Cost Harvest Rate Value Head of Lettuce $1.50 13 heads per year $19.50 1 lb of Basil $8 4 harvests per year $32 1 lb of Tomatoes $3 20 lb per plant per year $60 1 pepper $2 10 peppers per year $20 1 lb Parsley $2 5 lbs per year $10
Est. Total Value $141.50