CHAPTER4:
3RD DESIGN PROJECT
Engineering Design and Problem Solving
Introduction/Description
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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.
Copyright © Texas Education Agency 2012. All rights reserved.
Chapter 4: Outline
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1.
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4.
Solar Energy
Solar Heat
Wind Energy
Other Renewable Energy Sources
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Objectives and Results
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Objectives
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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.
5
Results
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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
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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
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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.
Copyright © Texas Education Agency 2012. All rights reserved.
Vocabulary
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Black Body Radiation
Current
Diffraction
Efficiency
Electrical Power
Electrolyte
Electromagnetic Radiation
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Electromagnetic Spectrum
Frequency
Heat
Heat Conduction
Heat Convection
Heat Radiation
Kinetic Energy
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Vocabulary, cont.
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Particle-Wave Duality
Photoelectric Effect
Photon
Photosensitive
Photovoltaic
Refraction
Solar Cell
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Solar Power
Solar Water Heater
Temperature
Thermal Energy
Volt meter
Voltage
Wavelength
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Renewable Energy Background
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Lack of electricity concerns
Supply vs. demand
Unreliable energy sources
Reliable energy sources
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Sun as an Energy Source
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The light from the sun heats the Earth and provides
energy.
Reasons to support solar energy usage include
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political and economic climate,
dependence on foreign oil, and
opportunity for innovation in
solar cell creation.
Solar Energy Timeline
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What is Sunlight?
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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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Waves and Particles in Sunlight
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The wave portion of light has three main properties that
are related to each other:
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They are related to each other with the following equation:
c=ν×λ
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Wavelength (λ)
Frequency (ν)
Speed of light (c)
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
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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
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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
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Photoelectric Effect Simulation
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How Photovoltaic Cells Work
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Solar Energy
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Grätzel Cells
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Grätzel Cell
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Calculating Power
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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).
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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
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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 .
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To change this to percent efficiency, multiply the answer by 100.
This solar cell has a 1% efficiency.
Copyright © Texas Education Agency 2012. All rights reserved.
Calculate Power Usage at Home
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Using your monthly power (electricity) bill and the worksheet,
calculate how much power your household uses in a day.
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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)
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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)?
Copyright © Texas Education Agency 2012. All rights reserved.
Student Scenario
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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.
Copyright © Texas Education Agency 2012. All rights reserved.
Design and Build a Grätzel Cell
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Using the Grätzel cell kit materials, construct Grätzel
cells with different plant based dyes: chlorophyll,
blackberries, and raspberries.
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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?
Copyright © Texas Education Agency 2012. All rights reserved.
Earth as a Thermodynamic System
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Heat, Thermal Energy, and Temperature
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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.
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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
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Rate of Heat Transfer
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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)
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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
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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:
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Open loop
Closed loop
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Open Loop Systems
28
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Closed Loop Systems
29
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Feedback and Control Loops
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Feedback and Control Loops, cont.
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Intermediate Open or Closed Loop
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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
Copyright © Texas Education Agency 2012. All rights reserved.
Advanced Feedback Control Design
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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:
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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.
Copyright © Texas Education Agency 2012. All rights reserved.
Credits
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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
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Credits, cont.
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Slide 18
Grätzel cell video; from YouTube user; Polytechpress;
http://www.youtube.com/watch?v=ncsNMDgngYI
Slide 24
Earth as Thermodynamic System
http://www.nasa.gov/audience/forstudents/58/features/F_The_Role_of_Clouds.html
Copyright © Texas Education Agency 2012. All rights reserved.