Final Design Report - Calvin College | Grand Rapids, Michigan · · 2011-05-13Final Design Report...

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


8.3.1. Lighting type considerations and decision ...................................................................... 47

8.3.2. LED Frequency and Power Design ................................................................................. 47

8.3.3. Heat Sink Design ............................................................................................................... 56


iii


8.6. Final Design for Production ..................................................................................................... 60

9. Mechanical Systems .......................................................................................................................... 61

9.1. Requirements ............................................................................................................................. 61

9.2. Function ..................................................................................................................................... 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



9.6. 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)


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.


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.


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/>.


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.


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


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


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.


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.


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.


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.


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.


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


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


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


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


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


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.


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.


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


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.


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.


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.


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.


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


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.


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.


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


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


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.


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


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)


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


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.


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.


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


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 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>.


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>.


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


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.


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.


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


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


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


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>.


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.


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


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>.


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 >.


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>.


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.


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


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>


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.


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


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.


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.


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.


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:


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:


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:


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.


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.


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.


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


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


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.


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.


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.


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



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


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


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.


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.


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


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


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


Table 10: Volume of Grow Levels Based on Geometries



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


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)



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


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.


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


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.


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...>


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


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.


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.


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


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.


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)


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


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 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.


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 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:


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_


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.


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


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


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>.


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/>.

http://www.yankodesign.com/images/design_news/2009/03/16/biosphere2.jpg


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>.


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


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:


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.


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


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


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%


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.


Appendix A: Five Year Financial Projections (Cont.)


Appendix B: Initial Planning/Estimation HydroTower Senior Design Budget


Appendix C: Current Working HydroTower Senior Design Budget


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.


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


14.2.1 Psychrometric Calculations


14.2.2 Drainage Testing, Interior Grow Level Spacing and Water Reservoir Calculations


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


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


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


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



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


3 14 in from a drawer slide 3850 in^327.5 in 16.66667 gal




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


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


14.2.3 Nutrient Container Calculations


14.2.4:Water Reservoir Deflection Calculations


14.3 Lighting System Heat Sink Calculations


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


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


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.


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

Final Design Report - Calvin College | Grand Rapids, Michigan · · 2011-05-13Final Design Report...

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Transcript of Final Design Report - Calvin College | Grand Rapids, Michigan · · 2011-05-13Final Design Report...