Engineering Design and Problem Solving CHAPTER4: 3 RD DESIGN PROJECT.

Engineering Design and Problem Solving

CHAPTER4: 3RD DESIGN PROJECT

Copyright © Texas Education Agency 2012. All rights reserved.

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Introduction/Description

The 3rd Design Project will further allow students to apply the engineering design process (EDP), build a Grätzel cell solar system and test it using different colored dyes, and build an intermediate open or closed loop solar water heater system or an advanced feedback control loop system.

You will calculate your home’s electricity usage based on your family’s electrical utility bill, calculate the heat transfer of a solar water heater system, and create a presentation about solar energy systems documenting the steps of the (EDP) for the general public.


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Chapter 4: Outline

1. Solar Energy 2. Solar Heat3. Wind Energy4. Other Renewable Energy

Sources


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Objectives and Results

Objectives Explain how the sun provides Earth with useful energy. Explain how the sun's energy can be used to heat water. Explain how the sun's energy can used to create electricity,

using a Grätzel cell. Explain the difference between temperature and heat. Identify the features of a system. Identify the features of open and closed loop systems. Identify the features of a feedback and control system. Calculate the efficiency of a process. Calculate power used and produced by a system. Calculate the rate of heat transfer. Practice the design process by designing and building a solar

heating or power system.


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Objectives and Results, cont.

Results The students will have demonstrated that they can

apply the engineering design process, their knowledge of solar power and solar water heating systems, and their knowledge of control and feedback systems to design and build a solar heating or power system.

Students will demonstrate their knowledge and skills by presenting their project to the instructor and the class and by completing the quiz and meeting all of the criteria in the 3rd Design Project and presentation rubrics.


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Schedule of Assignments

Class Period(s)

Topic(s) Assignment

1-2 • The Engineering Design Process-Quick Review

• Student Background about Need for Solar Energy

• Vocabulary

#1-Individual; Points to Ponder Handout(Daily), Vocabulary Work

3-4 • Solar Energy Background and History

• Calculate Home Power Usage

#2-Individual; Solar Energy Timeline Reading Packet Handout and Worksheet

5-10 • Grätzel Cell Introduction and Team Project

#3-In teams of 2-3; Apply the engineering design process to the scenario given; complete the “Mini Engineering Notebook” (Daily)

11-30 • Intermediate Open or Closed Loop Solar Water Heating System or Advanced Feedback Control Design System

• Background and Team Project

#4-In teams of 2-3; Apply the engineering design process to the scenario given; complete the communication and presentation of your design following the rubric given (Major); complete the “Mini Engineering Notebook” (Daily)


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Student Project Basics

Individually and in teams, you will calculate your home’s electricity usage based on

your family’s electrical utility bill, build a Grätzel cell solar system and test it using

different colored dyes, calculate the heat transfer of a solar water heater

system, build an intermediate open or closed loop solar

water heater system or an advanced feedback control loop system, and

create a presentation about solar energy systems documenting the steps of the engineering design process (EDP) for the general public.


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Vocabulary

Black Body Radiation Current Diffraction Efficiency Electrical Power Electrolyte Electromagnetic

Radiation

Electromagnetic Spectrum

Frequency Heat Heat Conduction Heat Convection Heat Radiation Kinetic Energy


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Vocabulary, cont.

Particle-Wave Duality Photoelectric Effect Photon Photosensitive Photovoltaic Refraction Solar Cell

Solar Power Solar Water Heater Temperature Thermal Energy Volt meter Voltage Wavelength


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Renewable Energy Background Lack of electricity concerns Supply vs. demand Unreliable energy sources Reliable energy sources


Sun as an Energy Source

The light from the sun heats the Earth and provides energy.

Reasons to support solar energy usage include political and economic climate, dependence on foreign oil, and opportunity for innovation in

solar cell creation.

Solar Energy Timeline

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http://www1.eere.energy.gov/solar/pdfs/solar_timeline.pdf


What is Sunlight?

Sunlight is visible light, but this is only part of the electromagnetic spectrum.

The Sun can be approximated as a black body source of radiation, meaning that it gives off all types of radiation in the electromagnetic spectrum.

The intensity of the radiation and its energy depend on the temperature of the black body source.

Sunlight Interactive

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http://phet.colorado.edu/en/simulation/blackbody-spectrum


Waves and Particles in Sunlight

The wave portion of light has three main properties that are related to each other: Wavelength (λ) Frequency (ν) Speed of light (c)

They are related to each other with the following equation:

c = ν × λ The speed of light is approximately 3×108 m/s. Frequency and wavelength are inversely related to

each other.Particle-Wave Duality

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Light Diffraction

Light diffraction happens when light scatters from a regularly repeating object, such as rain droplets, clouds, or a CD. The different wavelengths of light scatter in slightly different ways, causing the “white” light to separate.

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Light Refraction

Light refraction happens when light travels from one material into another. Differences in the atomic structure of the material cause the light to bend. The different wavelengths of light bend at slightly different angles and cause the “white” light to separate, such as when light passes through a prism.

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Photoelectric Effect

Photoelectric Effect Simulation

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http://phet.colorado.edu/en/simulation/photoelectric


How Photovoltaic Cells Work

Solar Energy

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http://www.youtube.com/watch?v=he_JjrXEfN0


Grätzel Cells18

Grätzel Cell

http://www.youtube.com/watch?v=ncsNMDgngYI



Calculating Power

The electrical power generated by solar cell can be found by using Joule’s Law:

P = Electrical Power = Current × Voltage = I × V

where the current is given in amps (A), the voltage is given in volts (V), and, power is reported in watts (W).

You can use a volt meter to measure the current and voltage produced by the solar cell and the multiply them together to find the power.

For example, a typical Grätzel cell can supply 2 milliamps and 0.5 volts to the circuit. Using Joule’s Law gives us the following equation for the power output of the cell:

P = 2×10-3 × 0.5 = 1 ×10-3 watts

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Efficiency of Solar Cell

The efficiency of a solar cell is the measure of how much electrical power is produced. Engineers use it to compare the performance of different solar cells.

For example, if a solar cell produces a power of 1×10-3 W/cm2 in sunlight, then the efficiency of that cell would be

(1×10-3)/(1×10-1)=1×10-2 .

To change this to percent efficiency, multiply the answer by 100. This solar cell has a 1% efficiency.

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Calculate Power Usage at Home Using your monthly power (electricity) bill and the

worksheet, calculate how much power your household uses in a day. Your energy bill reports your energy use in kilowatt

hours (kWh). To calculate the power, P, in kilowatts (kW), divide the energy used by the time period, t, in hours (hr) that it was used over the billing period (usually 28 days or 672 hours):

P(kW) = E(kWh)/t(hr)

This is how much power your house hold uses in a day.

How does this relate to the typical output from a single silicon solar cell (approximately 2W)?

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Student Scenario

Imagine that you have been relocated to a remote rural area in which you have limited access to electricity on the normal utility grid.

You need to have regular electricity to conduct business, stay in contact with friends and family members, and have a reliable potable and hot water source.

You have to present your idea to a local zoning board and your company in order to get the funding and clearances for your systems, so you don’t have to pay the costs yourself.


Design and Build a Grätzel Cell

Using the Grätzel cell kit materials, construct Grätzel cells with different plant based dyes: chlorophyll, blackberries, and raspberries. Use a volt meter to measure the voltage and current

produced with each dye, when exposed to a broad-spectrum light or sunlight as the light source. Record data for each dye-based cell.

Using the standard sunlight power per unit area of 0.1 W/cm2, calculate the efficiency of each type of dye-based solar cell and determine which dye is the most effective.

How many Grätzel cells would you need to power your house for a day?

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Earth as a Thermodynamic System

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Heat, Thermal Energy, and Temperature

Heat is the transfer of thermal energy from a system with higher thermal energy to one with lower thermal energy.

Thermal energy is the kinetic energy of atoms in a system.

In solids, it is the vibrations of the bonds between the atoms. In liquids and gases, it is the movement of the atoms in space.

Heat is transferred by one energized particle “bumping” into another particle and giving away some of its energy to the second particle. For solids, the “bump” is through the bond connecting the

atoms. For liquids and gases, the “bump” is the atoms colliding.

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Gas Properties Interactive

http://phet.colorado.edu/en/simulation/gas-properties


Rate of Heat Transfer

The rate of heat transfer is how fast thermal energy is transferred into the solar heater system. This can be calculated with the following equation:

Q = h × A × (Tin- Tout)

where h is the heat transfer coefficient (and depends on the material being heated), and A is the internal surface area of the tubing being heated.

Using the sample data set provided in your student handout, calculate the rate of heat transfer for each experiment.

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Solar Water Heating Systems

Solar water heating systems collect the radiant heat from the sun and use it to heat water in your house.

There are two basic types of solar heating systems: Open loop Closed loop

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Open Loop Systems28


Closed Loop Systems29


Feedback and Control Loops30


Feedback and Control Loops, cont.

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Intermediate Open or Closed Loop Using tubing, water, antifreeze, and tubs,

design and build an open or closed loop solar water heater.

Your group should be prepared to present the following to your instructor and your class:1. Problem statement and how you solved your

problem using the engineering design process

2. Original design of your open or closed loop solar water heater system

3. Working model of your system

4. Measurement and analysis of the rate of heat transfer


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Advanced Feedback Control Design In addition to the requirements for the open or

closed loop system, add one of the following feedback and control systems to your design project: Design and develop a solar water heating system

that uses a feedback and control loop to switch between heating water with a solar heater and an electric element, when the temperature drops below a certain temperature.

Design and develop a solar panel system that uses a feedback and control loop to change the angle of the panel, when the power output of the solar cell drops below a level that you determine is too low.


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Credits

ClipArt; http://www.clipart.com/en/

Images; http://commons.wikimedia.org/wiki/Main_Page

Slide 17 Solar Energy video; from YouTube user; EngineeringTimelines; http://www.youtube.com/watch?v=he_JjrXEfN0

http://www.clipart.com/en/

http://commons.wikimedia.org/wiki/Main_Page

http://commons.wikimedia.org/wiki/Main_Page




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Credits, cont.

Slide 18Grätzel cell video; from YouTube user; Polytechpress; http://www.youtube.com/watch?v=ncsNMDgngYI

Slide 24Earth as Thermodynamic System http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Role_of_Clouds.html



http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Role_of_Clouds.html

http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Role_of_Clouds.html

Engineering Design and Problem Solving CHAPTER4: 3 RD DESIGN PROJECT.

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