Difference between revisions of "Renewable Energy Competition"

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== Objective ==
== Objective ==
The experimental objective is to study the different types of renewable energy sources and power storage devices including hydrogen fuel cell by going through various setups provided in the lab. Design a renewable energy vehicle using the power sources and power storage devices provided in the lab to compete in a competition within the section.
The experimental objective is to evaluate different sources  of renewable energy and design a renewable energy vehicle using the power sources and power storage devices provided in the lab to compete in a competition in the section.


== Overview ==
== Overview ==
=== Types of Renewable Energy ===
=== Types of Renewable Energy ===
Renewable energy are types of energy that can be harnessed from naturally replenished resources, some examples of this includes sunlight, wind, and water. There are many benefits of using renewable energy such as clean energy sources, and they come from an abundant source that doesn’t become depleted. If we are able to efficiently utilize these renewable resources we can solve the problems with using non-renewable energy sources such as fossil fuels. [1]
Renewable energy sources are types of energy that can be harnessed from naturally replenished resources. Some examples include sunlight, wind, and water. There are many benefits to using renewable energy. They are clean energy sources, and they come from an abundant source that does not become depleted. If these sources can be utilized efficiently, this can solve the problems with using non-renewable energy sources, such as fossil fuels (NextEra Energy Resources, LLC, 2012).  


==== Solar Power ====
==== Solar Power ====
Sunlight, like any other types of light contains energy. Typically when the sunlight hits an object the energy that it contains is converted into heat. However certain materials can convert the energy into electrical current, and in this form we can harness it and store it as energy. Some solar panels are made out of large crystalline structures using the material silicon. The silicon on the solar panels would capture the free electrons from sunlight creating a potential difference between two plates. The silicon can convert a large amount of the sunlight into electrical energy but it was not cost effective because it is expensive to produce solar panels using silicon.[2]
Sunlight, like any other type of light, contains energy. Typically when the sunlight hits an object, the energy it contains is converted into heat. Certain materials can convert the energy into electrical current that can be harnessed  and stored  as energy. Some solar panels are made out of large crystalline structures using the material silicon. The silicon on the solar panels captures the free electrons from sunlight creating a potential difference between two plates. The silicon can convert a large amount of the sunlight into electrical energy, but it is not cost effective because it is expensive to produce solar panels using silicon (Locke, 2012).


Another common material used to create solar panels is the material ''Copper indium gallium (di)selenide'' (CIGS), which has a smaller crystalline structure but are less expensive. CIGS are relatively flexible and can easily be shaped into flexible films. The use of CIGS to make solar panels is referred to as thin-film solar technology because of its flexible nature. However CIGS are not as good at converting the absorbed light into electrical current compared to silicon, but for mass production purposes CIGS solar panels would be the more cost effective approach to produce solar panels for frequent use. [2]
Another common material used to create solar panels is  Copper indium gallium (di)selenide (CIGS), which has a smaller crystalline structure, but is less expensive. CIGS is relatively flexible and can easily be shaped into flexible films. The use of CIGS to make solar panels is referred to as thin-film solar technology because of its flexible nature. CIGS is not as good at converting the absorbed light into electrical current compared to silicon, but for mass production purposes, CIGS solar panels are the more cost effective approach to produce solar panels for frequent use (Locke, 2012).


In a crystal structure, the materials used for solar panels contain covalent bonds where electrons are shared by the atoms within the crystal. When the light is absorbed, electrons within the crystal become excited and move to a higher energy level. When this occurs the electron has more freedom of motion within the crystal. When the electrons move around the crystal structure an electrical current is generated, this in turn gives us electrical energy. The reaction that occurs when sunlight shines onto a solar panel is shown in Figure 1. [2]
The materials used for solar panels contain covalent bonds where electrons are shared by the atoms within the crystal. When the light is absorbed, electrons within the crystal become excited and move to a higher energy level. When this occurs, the electron has more freedom of motion within the crystal. When the electrons move around the crystal structure, an electrical current is generated that produces electrical energy. The reaction that occurs when sunlight shines onto a solar panel is shown in Figure 1 (Locke, 2012).


[[Image:Lab_renewener_01.png|thumb|500px|center|Figure 1: A solar panel made using silicon is shown to have a change of electron flow as photons are being absorbed by the plate.]]<br style="clear: both;" />
[[Image:Lab_renewener_01.png|thumb|500px|center|Figure 1: A solar panel made using silicon shows a change of electron flow as photons are being absorbed by the plate.]]<br style="clear: both;" />


==== Wind-turbine ====
==== Wind-turbine ====


Wind-turbines are used to capture the wind’s energy and convert it into electrical energy, which can later be used to power cities. The structure of the wind-turbines has a heavy influence on its functionality. The blades on the wind-turbine are shaped so that as the wind passes through the blades it creates an uneven pressure on each side, which causes it to spin (similar to the mechanism used to keep planes airborne). As the wind-turbine spins it will cause a low speed shaft (which is connected to a gearbox) inside the blade to spin. The gearbox within the wind-turbine converts the low speed rotation to a high speed rotation through a high speed shaft. The high speed shaft is connected to a brake and then into an electrical generator, which then converts this mechanical energy into electrical energy. [3]
Wind-turbines are used to capture the wind’s energy and convert it into electrical energy that can later be used to power cities. The structure of the wind-turbines influences  its functionality. The blades on the wind-turbine are shaped so that as the wind passes through the blades it creates an uneven pressure on each side that causes it to spin (similar to the mechanism used to keep planes airborne). As the wind-turbine spins, it causes a low speed shaft, which is connected to a gearbox, inside the blade to spin. The gearbox within the wind-turbine converts the low speed rotation to a high speed rotation through a high speed shaft. The high speed shaft is connected to a brake and then to an electrical generator that converts this mechanical energy into electrical energy (Layton, 2012).  


The electrical generator is made up of permanent magnets on each side with a rectangular coil connected to a commutator, a rotary electrical switch. The two permanent magnets on each side have creates a magnetic field. As the rectangular coil spins mechanically between the two poles of permanent magnets as shown in Figure 2, an electrical current is generated. This electrical output is then used as electrical energy. [3]
The electrical generator is made up of permanent magnets on each side with a rectangular coil connected to a commutator, which is a rotary electrical switch. The two permanent magnets on each side create a magnetic field. As the rectangular coil spins between the two poles of permanent magnets, as shown in Figure 2, an electrical current is generated. This electrical output is then used as electrical energy (Layton, 2012).
   
   
[[Image:Lab_renewener_02.png|thumb|500px|center|Figure 2: The internal structure of an electrical generator [3]]]<br style="clear: both;" />
[[Image:Lab_renewener_02.png|thumb|500px|center|Figure 2: The internal structure of an electrical generator (Layton, 2012).]]<br style="clear: both;" />


==== Hydrogen fuel cells ====
==== Hydrogen fuel cells ====
A fuel cell is a power storage device which stores chemical energy and converts it into electrical energy. The fuels uses can range from hydrogen, methane to even gasoline. For the purpose of this lab we will be using hydrogen as a fuel; therefore we are using hydrogen fuel cells. The main components that make up the fuel cell are an electrolyte, an anode chamber, a cathode chamber, and bipolar plates. The electrolyte acts as a separator that keeps the reactions from interacting with each other, by separating the anode and cathode chambers. When the water molecules are broken down, the hydrogen is stored in the anode chamber and oxygen on the cathode chamber. The bipolar plates collect the current generated by the fuel cell when the reaction takes place. Refer to Figure 3 for the internal structure of a fuel cell. [4]
A fuel cell is a power storage device that stores chemical energy and converts it into electrical energy. The fuels used  range from hydrogen, methane to gasoline. For the purpose of this lab, hydrogen will be used as a fuel so these are hydrogen fuel cells. The main components that make up the fuel cell are an electrolyte, an anode chamber, a cathode chamber, and bipolar plates. The electrolyte acts as a separator that keeps the reactions from interacting with each other by separating the anode and cathode chambers. When the water molecules are broken down, the hydrogen is stored in the anode chamber and oxygen in the cathode chamber. The bipolar plates collect the current generated by the fuel cell when the reaction takes place. Figure 3 shows the internal structure of a fuel cell (Tyler, 2012).  


Generally the gas used by the fuel cell is already separated prior to the use with a fuel cell using various methods such as using an electrolyzer, a device that separates distilled water into hydrogen and oxygen. In some cases fuel cells can be used to initiate this reaction, they are called reversible fuel cells. When supplied with water the reversible fuel cell separates the distilled water into hydrogen and oxygen. The stored hydrogen and oxygen can then be supplied to the fuel cell to generate electrical energy. Hydrogen fuel cells can be used to power various utilities such as computers, cars, power plants and even whole cities. However due to the nature of producing and storing the gas required to generate large amounts of electrical energy fuel cells are generally very large. This becomes a problem when being used in vehicles.
Generally, the gas used by a fuel cell is separated prior to use with a fuel cell using various separation methods, such as using an electrolyzer, which is a device that separates distilled water into hydrogen and oxygen. In some cases, fuel cells can be used to initiate this reaction. These fuel cells are called reversible fuel cells. When supplied with water, the reversible fuel cell separates the distilled water into hydrogen and oxygen. The stored hydrogen and oxygen can then be supplied to the fuel cell to generate electrical energy. Hydrogen fuel cells can be used to power computers, cars, power plants, and even whole cities. Due to the nature of producing and storing the gas required to generate large amounts of electrical energy, fuel cells are generally very large. This becomes a problem when used in vehicles.
 
[[Image:Lab_renewener_03.png|thumb|500px|center|Figure 3: This is the internal structure of a fuel cell [4]]]<br style="clear: both;" />
[[Image:Lab_renewener_03.png|thumb|500px|center|Figure 3: This is the internal structure of a fuel cell (Tyler, 2012). ]]<br style="clear: both;" />


=== Electrical Components ===
=== Electrical Components ===
In electrical engineering different electrical components are represented by different symbols. Below a few of them are shown:
In electrical engineering, different electrical components are represented by different symbols. Figures 4a and 4b show two symbols.
   
   
<div><div style="float: left; display: inline;">[[Image:Lab_renewener_04.png|thumb|500px|left|Figure 4a: Cell]]<br style="clear: both;" /></div><div style="float: left; display: inline;">[[Image:Lab_renewener_05.png|thumb|500px|left|Figure 4b: Battery]]<br style="clear: both;" /></div></div><br style="clear: both;" />
<div><div style="float: left; display: inline;">[[Image:Lab_renewener_04.png|thumb|500px|left|Figure 4a: Cell]]<br style="clear: both;" /></div><div style="float: left; display: inline;">[[Image:Lab_renewener_05.png|thumb|500px|left|Figure 4b: Battery]]<br style="clear: both;" /></div></div><br style="clear: both;" />
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A cell is a single unit for the conversion of chemical energy to electrical energy. A battery is comprised of multiple cells linked together.
A cell is a single unit for the conversion of chemical energy to electrical energy. A battery is comprised of multiple cells linked together.


A capacitor is an electrical device used to store charge temporarily. Some capacitors can be used in place of a battery but they operate very differently from one. A capacitor is charged by a voltage source logarithmically, as shown in Figure 5.
A capacitor is an electrical device that is used to store charge temporarily. Some capacitors can be used in place of a battery, but they operate very differently from a battery. A capacitor is charged by a voltage source logarithmically, as shown in Figure 5.
   
   
[[Image:Lab_renewener_06.png|thumb|500px|center|Figure 5: Capacitor Charging Curve]]<br style="clear: both;" />
[[Image:Lab_renewener_06.png|thumb|500px|center|Figure 5: Capacitor charging curve]]<br style="clear: both;" />


Because of their design, these capacitors are sensitive to the polarity of the voltage applied to them. The capacitors used in this lab must be connected with the proper polarity, or they will fail. Therefore, be sure to check the capacitor used to make sure you have the negative sign on the capacitor connected to the negative applied voltage. Failure to do this will cause the capacitors to fail.
Because of their design, capacitors are sensitive to the polarity of the voltage applied to them. The capacitors used in this lab must be connected with the proper polarity or they will fail. Be sure to check the capacitor used to make sure the negative sign on the capacitor is connected to the negative applied voltage. Failure to do this will cause the capacitors to fail.
   
   
[[Image:Lab_renewener_07.png|thumb|500px|center|Figure 6: Polarized laboratory capacitor]]<br style="clear: both;" />
[[Image:Lab_renewener_07.png|thumb|500px|center|Figure 6: Polarized laboratory capacitor]]<br style="clear: both;" />


The total energy a capacitor holds is given by the equation ''E = CV<sup>2</sup> / 2''. Note that the energy that the capacitor holds is proportional to the '''square''' of the voltage.
The total energy a capacitor holds is given by the equation ''E = CV<sup>2</sup> / 2''. Note that the energy holds is proportional to the square of the voltage.


A '''diode''' is a device that allows current to pass through it in only one direction. This means that it has polarity, and will only allow current to pass from its positive side to its negative side. A '''Light Emitting Diode (LED)''' not only passes current, but also lights up when it's passing current.
A diode is a device that allows current to pass through it in only one direction. This means that it has polarity and will only allow current to pass from its positive side to its negative side. A light emitting diode (LED)  passes current and lights up when it is passing current.


Different combinations of electrical components allow engineers to design different devices. Resistors, inductors, and capacitors can be arranged in three different ways. In a series circuit, the element's conductors are connected end to end. The current in a series circuit remains the same in all the electrical elements. In a series circuit, as shown in Figure 7, the sum of the voltages across each element is equal to the voltage of the power source (''V<sub>out</sub> = V<sub>A</sub> + V<sub>B</sub> + V<sub>C</sub>'').  
Different combinations of electrical components allow engineers to design different devices. Resistors, inductors, and capacitors can be arranged in three different ways. In a series circuit, the elements  are connected end to end. The current in a series circuit remains the same in all the electrical elements. In a series circuit, as shown in Figure 7, the sum of the voltages across each element is equal to the voltage of the power source (''V<sub>out</sub> = V<sub>A</sub> + V<sub>B</sub> + V<sub>C</sub>'').  
   
   
[[Image:Lab_renewener_08.png|thumb|500px|center|Figure 7: A series circuit]]<br style="clear: both;" />
[[Image:Lab_renewener_08.png|thumb|500px|center|Figure 7: A series circuit.]]<br style="clear: both;" />


In a parallel circuit, as shown in Figure 8, the element's conductors are connected at opposing ends. The current that is supplied by the voltage source equals the current that flows though elements '''''D''''' and '''''E'''''. The voltage across the elements that are parallel is the same (V<sub>out</sub> = V<sub>D</sub> = V<sub>E</sub>).
In a parallel circuit, as shown in Figure 8, the elements  are connected at opposing ends. The current that is supplied by the voltage source equals the current that flows though elements D and E. The voltage across the elements that are parallel is the same (V<sub>out</sub> = V<sub>D</sub> = V<sub>E</sub>).
   
   
[[Image:Lab_renewener_09.png|thumb|500px|center|Figure 8: A parallel circuit]]<br style="clear: both;" />
[[Image:Lab_renewener_09.png|thumb|500px|center|Figure 8: A parallel circuit.]]<br style="clear: both;" />


The motor provided is a 9V motor that will operate with voltages lower than 9V with reduced torque and speed. A motor with no load draws 9mA; a stalled motor draws well over 350mA. By increasing the voltage provided to the motor you can increase the motor speed. By increasing current you increase the torque.
The motor provided is a 9V motor that will operate with voltages lower than 9V, but with reduced torque and speed. A motor with no load draws 9mA; a stalled motor draws well over 350mA. By increasing the voltage provided to the motor, the motor speed will be increased. By increasing current, the torque is increased.


== Your Assignment ==
== Design Considerations ==
=== Individual Lab Report ===
* Which source yields the most voltage per unit cost?
Follow the lab report guidelines laid out in the page called [[Specifications for Writing Your Lab Reports]] in the Technical Communication section of this manual. As you write, the following discussion points should be addressed in the appropriate section of your lab report:
* Which circuit configuration will provide the most desirable voltage across the load? Parallel or series?
* Describe the rules of the competition in your introduction. What consequences did the rules have for your design decisions? Use the appropriate equations in your answer.
* Which aspects of the competition formula are most advantageous?
* Explain how solar panels and wind turbines work.
* Explain the concepts of the hydrogen fuel cell and capacitors.
* Discuss the advantages and disadvantages of the solar panel and wind-turbine.
* Discuss the advantages and disadvantages of hydrogen fuel cell compared to other storage devices (e.g. capacitors or batteries)
* Describe your renewable energy vehicle design and explain the choices you made in your design.
* Discuss minimal design. Did you use all the materials you purchased? Describe the importance of minimal design and explain how you employed it in your design. (how did you minimize your cost)
* Describe how your design succeeded or failed. What choices could you have made to improve your final standing in the competition?  
* Discuss how you would improve the competition ratio, how was your design compared to the other group’s designs.
 
=== Team PowerPoint Presentation ===
Follow the presentation guidelines laid out in the [[EG1003 Lab Presentation Format]] section of this manual. When you are preparing your presentation, consider the following points:
* Since one term in the competition ratio is cost, present the cost of your vehicle. Use the page [[How to Show Cost Data in Presentations]] for instructions on how to do this.
* How would you improve your renewable energy powered car?


== Materials and Equipment ==
== Materials and Equipment ==
* Horizon Wind-Turbine
=== Materials with Price List ===
* Sunforce 50013 1-Watt Solar Battery Charger
* A Horizon wind-turbine: $5.00 each
* Adjustable Table fan
* Solar battery panels: $10.00 each
* Heat Lamp
* A Horizon hydrogen fuel cell: $12.00 each
* DMM (Digital Multi-meter)
* A 1 Farad 2.5V capacitor: $3.00 each
* Music Voltmeter
* Alligator cable sets: $0.50/pair
* 2V DC Motor
* A standard Lego car chassis plus Lego parts kit: $0, limit one per group
* Horizon Hydrogen Fuel cell
* A Lego to alligator cable clip connector: $0.10 each
* 1 Farad 2.5V Capacitor
* Tape: $0.10/feet
* Mini Electric propeller
=== Equipment Used ===
* LED (Light Emitting Diode)
* A Horizon Wind-Turbine
* A Sunforce 50013 1-Watt solar battery charger
* An adjustable Table fan
* A heat lamp
* A DMM (Digital Multi-meter)
* A Music voltmeter
* A 2V DC motor
* A Horizon hydrogen fuel cell
* A 1 Farad 2.5V capacitor
* A mini electric propeller
* An LED (Light Emitting Diode)
* 3 Alligator cable sets  
* 3 Alligator cable sets  
* Standard Lego Car Chassis plus Lego parts kit  
* A standard Lego car chassis plus Lego parts kit  
* Lego to Alligator Cable Clip Connector
* A Lego to alligator cable clip connector
* Scissors  
* Scissors  
* Tape  
* Tape


== Procedure ==
== Procedure ==
=== Part 1: Testing the Power sources ===
=== Part 1: Testing the power sources ===
==== Wind turbine ====
==== Wind turbine ====
# Connect the Wind turbine to the digital multi-meter using the alligator clips provided. The connection is shown in Figure 9 below. Place the wind turbine in front of the fan and take down the voltage.
# Connect the wind turbine to the mini propeller using the alligator clips provided. Place the wind turbine in front of the fan and measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
# Disconnect the two connections from the digital multi-meter and connect the alligator clips to the Music Voltmeter. Place the wind turbine in front of the fan and observe what happens to the music voltmeter.
#: [[Image:Lab_renewener_19.png|thumb|500px|left|Figure 9: Voltage measurement circuit]]<br style="clear: both;" />
#: [[Image:Lab_renewener_12.png|thumb|500px|left|Figure 9: Music Voltmeter]]<br style="clear: both;" />
#: [[Image:Lab_renewener_20.png|thumb|500px|left|Figure 10: Current measurement circuit.]]<br style="clear: both;" />
# Adjust the position of the turbine to find the highest voltage and current that can be generated.
# Calculate and record the power generated by the turbine.


==== Solar Panel ====
==== Solar panel ====
# Connect the solar panel to the digital multi-meter using the alligator clips (refer to Figure 10 below). Place the solar panel near the window or a heat lamp and record the voltage reading.  
# Connect the solar panel to the mini propeller using the alligator clips provided. Place the solar panel near the heat lamp and measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
# Repeat the process in step two and observe the results from Music Voltmeter.  
# Adjust the position of the solar panel to find the highest voltage and current that can be generated.
#: [[Image:Lab_renewener_10.png|thumb|500px|left|Figure 10: The connections are indicated by connecting the same color cables to each other.]]<br style="clear: both;" />
# Calculate and record the power generated by the solar panel.
#: '''<span style="color: red">Caution!</span> The heat lamps and solar panels may become extremely hot when used for a long duration of time do not touch them immediately after use and turn them off when not in use.'''
#: '''<span style="color: red">Caution!</span> The heat lamps and solar panels may become extremely hot when used for a long duration of time. Do not touch them immediately after use and turn them off when not in use.'''


=== Part 2: Testing the Power storage devices ===
=== Part 2: Testing the power storage devices ===
==== Preparing the Hydrogen Fuel cell ====
==== Preparing the hydrogen fuel cell ====
# Place the 2x4cm (small) length pieces of rubber tube into the bottom right pin on the hydrogen fuel cell (on both sides) and insert a cap (<span style="color: red;">'''red'''</span> for oxygen and '''black''' for hydrogen) into the other end of the tube.
# Place the 2x4cm (small) length pieces of rubber tube into the bottom right pin on the hydrogen fuel cell (on both sides) and insert a cap (<span style="color: red;">red</span> for oxygen and black for hydrogen) into the other end of the tube.
# Insert the two longer tubes into the top left pin of the hydrogen fuel cell.
# Insert the two longer tubes into the top left pin of the hydrogen fuel cell (Figure 11).
#: [[Image:Lab_renewener_13.png|thumb|500px|left|Figure 11]]<br style="clear: both;" />
#: [[Image:Lab_renewener_13.png|thumb|500px|left|Figure 11: Hydrogen side of fuel cell.]]<br style="clear: both;" />
# Take the two cylindrical beakers and place them on top of the stand provided locking it in place, then fill the two beakers with distilled water until the water level reaches zero.
# Take the two cylindrical beakers and place them on top of the stand provided locking it in place then fill the two beakers with distilled water until the water level reaches zero (Figure 12).
#: [[Image:Lab_renewener_14.png|thumb|500px|left|Figure 12]]<br style="clear: both;" />
#: [[Image:Lab_renewener_14.png|thumb|500px|left|Figure 12: Beakers filled with 30ml of distilled water.]]<br style="clear: both;" />
# Place the two inner containers into the cylindrical beakers (make sure the side openings on the inner container is not blocked by the inner ring on the beakers), the distilled water from the beaker will fill out the inner container at this point.
# 1. Place the two inner containers into the cylindrical beakers. Make sure the side openings on the inner container are not blocked by the inner ring on the beakers (Figure 13). The distilled water from the beaker will fill out the inner container at this point.
#: [[Image:Lab_renewener_15.png|thumb|500px|left|Figure 13]]<br style="clear: both;" />
#: [[Image:Lab_renewener_15.png|thumb|500px|left|Figure 13: The cylindrical beaker and inner container.]]<br style="clear: both;" />
# On the oxygen side of the fuel cell connect the syringe to the uncapped tube (first remove the <span style="color: red;">'''red'''</span> cap on the smaller tube). Fill the reversible fuel cell with distilled water using the syringe until all the air is removed from the long tube. Afterwards place the red cap on the smaller tube
# Connect the two longer tubes to the inner container on each of the beakers corresponding to oxygen and hydrogen on the fuel cell. Make sure there is no air in the inner containers.
#: [[Image:Lab_renewener_16.png|thumb|500px|left|Figure 14]]<br style="clear: both;" />
#: [[Image:Lab_renewener_17.png|thumb|500px|left|Figure 14: Oxygen tube inserted into the tip of the inner container.]]<br style="clear: both;" />
#: '''IMPORTANT''': Make sure the connections of the wires to the fuel cell match (<span style="color: red;">'''red'''</span> to <span style="color: red;">'''red'''</span>, '''black''' to '''black''') otherwise it may lead to failure of this part of the experiment and damage to the fuel cell. If this problem occurs the students will have to take full responsibility for replacing the parts.  
# On the oxygen side of the fuel cell (Figure 14), connect the syringe to the uncapped tube (first remove the <span style="color: red;">red</span> cap on the smaller tube). Fill the reversible fuel cell with distilled water using the syringe until all the air is removed from the long tube (Figure 15). Afterwards place the <span style="color: red;">red</span> cap on the smaller tube.
#: [[Image:Lab_renewener_16.png|thumb|500px|left|Figure 15: Oxygen side of fuel cell with a syringe inserted to fill oxygen tubes side with distilled water.]]<br style="clear: both;" />
#: '''IMPORTANT''': Make sure the connections of the wires to the fuel cell match (<span style="color: red;">red</span> to <span style="color: red;">red</span>, black to black) otherwise it may lead to failure of this part of the experiment and damage to the fuel cell. If this problem occurs the students will have to take full responsibility for replacing the parts.  
#: '''Hint: Place the longer tube above the oxygen beaker to hold the water coming out of the longer tube.'''
#: '''Hint: Place the longer tube above the oxygen beaker to hold the water coming out of the longer tube.'''
# Connect the two longer tubes to the inner container on each of the beakers corresponding to oxygen and hydrogen on the fuel cell. (Make sure there is no air in the inner containers.)
#: [[Image:Lab_renewener_17.png|thumb|500px|left|Figure 15]]<br style="clear: both;" />
# Connect the 3V power supply to the positive and negative inputs on the fuel cell and turn on the power supply.  
# Connect the 3V power supply to the positive and negative inputs on the fuel cell and turn on the power supply.  
# Charge until both containers (oxygen and hydrogen) are filled with gas.  
# Charge until the H<sub>2</sub> inner container is filled with gas. The O<sub>2</sub> should be half because the fuel cell is converting H<sub>2</sub>O and the stoichiometric coefficients demand that balance.
# Discharge the charged fuel cell by connecting it to the mini propeller provided.
# Discharge the charged fuel cell by connecting it to the mini propeller provided (Figure 16).
#: [[Image:Lab_renewener_18.png|thumb|500px|left|Figure 16]]<br style="clear: both;" />
# Measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
# Calculate and record the power produced by the hydrogen fuel cell.  
#: [[Image:Lab_renewener_18.png|thumb|500px|left|Figure 16: Mini Propeller and 3V power supply with extended cables.]]<br style="clear: both;" />
 
==== Charging a capacitor ====
==== Charging a capacitor ====
# Connect an alligator clip to each of the cables coming out of the 3V power supply. (<span style="color: red;">'''red'''</span> is positive and '''black''' is negative)  
# Connect an alligator clip to each of the cables coming out of the 3V power supply. (<span style="color: red;">red</span> is positive and black is negative).
# Connect to the one of unconnected alligator clips the ammeter (multimeter setting)  
# Connect one of unconnected alligator clips to the ammeter (multimeter setting).
# Connect the rest of the unconnected cables (one from ammeter and one alligator clip) connect to pins of the capacitor with correspond polarity. (refer to Figure 10)
# Connect the rest of the unconnected cables (one from ammeter and one alligator clip) connect to pins of the capacitor with correspond polarity (Figure 10).
# Charge until the current is zero.  
# Charge until the current is zero.  
# Discharge the charged capacitor by connecting it to the mini propeller provided.
# Discharge the charged capacitor by connecting it to the mini propeller provided.
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[[Image:Lab_renewener_11.png|thumb|500px|left|Figure 17: This is circuitry for charging a capacitor.]]<br style="clear: both;" />
[[Image:Lab_renewener_11.png|thumb|500px|left|Figure 17: This is circuitry for charging a capacitor.]]<br style="clear: both;" />


=== Part 3: Renewable Car competition ===
=== Part 3: Renewable car competition ===
# Assess your materials and consider the data established from Part 1 and Part 2. Choose materials for your car design, keeping in mind the Competition Ratio. Make sure you take notes and make preliminary sketches during this process. (You may choose different combinations of power sources and power storage devices for your design)
# Assess the materials and consider the data produced from Part 1 and Part 2. Choose materials for the car design, keeping in mind the competition ratio. Create preliminary sketches during this process. Different combinations of power sources and power storage devices may be used for the design.
# You will be given a standard chassis for your renewable energy vehicle. Your design must be able to hold the power storage devices on top of it during the trials (you may modify your design to fit the power storage devices as you deem fit). Prepare a price-list for your renewable energy powered vehicle based on the setups and materials you have chosen. Have your TA '''sign''' the sketches and the price-list.  
# The design must be able to hold the power storage devices on top of it during the trials. The design can be modified. Prepare a price-list for the renewable energy-powered vehicle based on the design and materials chosen. Have a TA sign the sketches and the price-list.
# Your TA will provide the materials needed for your design. If you decide to modify your design during the construction of your car, note the changes and describe the reasons for them. If the modifications required more materials to be used, make sure you update your price list and your TA approves it. (Note: You may modify your design between trials)
# A TA will provide the materials needed for the design. If the design is modified during construction, note the changes and describe the reasons for them. If the modifications required more materials, make sure the price list is updated and a TA approves it. Designs may be modified between trials.
Before entering the competition, test if your motor is working. This can be done by using the lighting system from your LabVIEW lab. Attach the red alligator clip to one end of an LED. Attach the black alligator clip to the other end of the LED. Run the LabVIEW program. The motor should run when the LED that connects the motor lights up. If the motor doesn't run, ask your TA for another motor.
 
Before entering the competition, test the motor.


==== Competition ====
==== Competition ====
The renewable energy vehicle must be able to carry the power storage device you choose to use on it (e.g. fuel cell, capacitor). You may only power your capacitor and fuel cell using the power sources provided, violations to these rules will result in a failing grade for the lab report for this lab.
The renewable energy vehicle must be able to carry its power storage device (e.g. fuel cell, capacitor). If a capacitor is used, it may only be powered using the power sources provided. Violations to these rules will result in a failing grade for the lab report for this lab.


When requested by the TA, the student will position the renewable energy car and complete the necessary connections before the trial begins.
When requested by the TA, the renewable energy car will be positioned and the necessary connections will be completed before the trial begins.


The competition will be won by the team that has the highest competition ratio:
The design that has the highest competition ratio will win the competition (Equation 1).
   
   
<math>CR = \frac{distance\left[\text{ft}\right]}{1\left[\text{s}\right] + time\left[\text{s}\right]} \times \frac{100}{Cost\left[$\right]} + distance\left[\text{ft}\right]\,</math>
<math>CR = \frac{distance\left[\text{ft}\right]}{1\left[\text{s}\right] + time\left[\text{s}\right]} \times \frac{100}{Cost\left[$\right]} + distance\left[\text{ft}\right]\,</math>
Equation 1: Competition ratio.


The TA will record the test data after five minutes or when the car stops moving, whichever occurs first. The TA will then calculate the competition ratio. The tabulation for the whole class will be provided.
The TA will record the test data after five minutes or when the car stops moving, whichever occurs first. The TA will then calculate the competition ratio. The tabulation for the whole class will be provided.
== Assignment ==
=== Individual Lab Report ===
Follow the lab report guidelines laid out in  Specifications for Writing  Lab Reports in the Technical Communication section of this manual. The following  points should be addressed in the appropriate section of the lab report:
* Describe the rules of the competition in your introduction. What consequences did the rules have for  design decisions? Use the appropriate equations in the answer
* Explain how solar panels and wind turbines work
* Explain the concepts of the hydrogen fuel cell and capacitors
* Discuss the advantages and disadvantages of the solar panel and wind-turbine
* Discuss the advantages and disadvantages of hydrogen fuel cell compared to other storage devices (e.g. capacitors or batteries)
* Describe the renewable energy vehicle design and explain the design choices
* Discuss minimal design. Were all the materials  purchased used? Describe the importance of minimal design and explain how it was employed  in the design
* Describe how the design succeeded or failed. What choices would  be made to improve its final standing in the competition?
* Discuss how  to improve the competition ratio and compare the ratios
* Describe the power source chosen for the design
* Include spreadsheet with every  designs’ results. Describe the results and talk about other designs in the class
{{Lab notes}}
=== Team PowerPoint Presentation ===
Follow the presentation guidelines laid out in the EG1004 Lab Presentation Format section of this manual. When  preparing the presentation, consider the following points:
* Since one term in the competition ratio is cost, present the cost of the vehicle. Use the page How to Show Cost Data in Presentations for instructions on how to do this
* How can the performance of the renewable energy powered car be improved?


== References ==
== References ==
[1] NextEra Energy Resources, LLC., . "Benefits of Renewable Energy." NextEra Energy Resources. NextEra Energy Resources, 2012. Web. 24 Jul 2012. <http://www.nexteraenergyresources.com/content/environment/benefits.shtml>.
NextEra Energy Resources, LLC., . "Benefits of Renewable Energy." NextEra Energy Resources. NextEra Energy Resources, 2012. Web. 24 Jul 2012. <http://www.nexteraenergyresources.com/content/environment/benefits.shtml>.


[2] Locke, S.. "How does solar power work." Scientific american. Scientific American, 2008. Web. 24 Jul 2012. <http://www.scientificamerican.com/article.cfm?id=how-does-solar-power-work>.
Locke, S.. "How does solar power work." Scientific american. Scientific American, 2008. Web. 24 Jul 2012. <http://www.scientificamerican.com/article.cfm?id=how-does-solar-power-work>.
   
   
[3] Layton, J.. "How Wind Power Works." How stuff works. Discovery, 2011. Web. 24 Jul 2012. <http://science.howstuffworks.com/environmental/green-science/wind-power.htm>.
Layton, J.. "How Wind Power Works." How stuff works. Discovery, 2011. Web. 24 Jul 2012. <http://science.howstuffworks.com/environmental/green-science/wind-power.htm>.


[4] Reg Tyler, . "Types of Fuel Cells." Energy efficeny and renewable energy. U.S. Department of Energy, 2011. Web. 24 Jul 2012. <http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html>.
Reg Tyler, . "Types of Fuel Cells." Energy efficeny and renewable energy. U.S. Department of Energy, 2011. Web. 24 Jul 2012. <http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html>.

Latest revision as of 02:11, 31 August 2022

Objective

The experimental objective is to evaluate different sources of renewable energy and design a renewable energy vehicle using the power sources and power storage devices provided in the lab to compete in a competition in the section.

Overview

Types of Renewable Energy

Renewable energy sources are types of energy that can be harnessed from naturally replenished resources. Some examples include sunlight, wind, and water. There are many benefits to using renewable energy. They are clean energy sources, and they come from an abundant source that does not become depleted. If these sources can be utilized efficiently, this can solve the problems with using non-renewable energy sources, such as fossil fuels (NextEra Energy Resources, LLC, 2012).

Solar Power

Sunlight, like any other type of light, contains energy. Typically when the sunlight hits an object, the energy it contains is converted into heat. Certain materials can convert the energy into electrical current that can be harnessed and stored as energy. Some solar panels are made out of large crystalline structures using the material silicon. The silicon on the solar panels captures the free electrons from sunlight creating a potential difference between two plates. The silicon can convert a large amount of the sunlight into electrical energy, but it is not cost effective because it is expensive to produce solar panels using silicon (Locke, 2012).

Another common material used to create solar panels is  Copper indium gallium (di)selenide (CIGS), which has a smaller crystalline structure, but is less expensive. CIGS is relatively flexible and can easily be shaped into flexible films. The use of CIGS to make solar panels is referred to as thin-film solar technology because of its flexible nature. CIGS is not as good at converting the absorbed light into electrical current compared to silicon, but for mass production purposes, CIGS solar panels are the more cost effective approach to produce solar panels for frequent use (Locke, 2012).

The materials used for solar panels contain covalent bonds where electrons are shared by the atoms within the crystal. When the light is absorbed, electrons within the crystal become excited and move to a higher energy level. When this occurs, the electron has more freedom of motion within the crystal. When the electrons move around the crystal structure, an electrical current is generated that produces electrical energy. The reaction that occurs when sunlight shines onto a solar panel is shown in Figure 1 (Locke, 2012).

Figure 1: A solar panel made using silicon shows a change of electron flow as photons are being absorbed by the plate.


Wind-turbine

Wind-turbines are used to capture the wind’s energy and convert it into electrical energy that can later be used to power cities. The structure of the wind-turbines influences its functionality. The blades on the wind-turbine are shaped so that as the wind passes through the blades it creates an uneven pressure on each side that causes it to spin (similar to the mechanism used to keep planes airborne). As the wind-turbine spins, it causes a low speed shaft, which is connected to a gearbox, inside the blade to spin. The gearbox within the wind-turbine converts the low speed rotation to a high speed rotation through a high speed shaft. The high speed shaft is connected to a brake and then to an electrical generator that converts this mechanical energy into electrical energy (Layton, 2012).

The electrical generator is made up of permanent magnets on each side with a rectangular coil connected to a commutator, which is a rotary electrical switch. The two permanent magnets on each side create a magnetic field. As the rectangular coil spins between the two poles of permanent magnets, as shown in Figure 2, an electrical current is generated. This electrical output is then used as electrical energy (Layton, 2012).

Figure 2: The internal structure of an electrical generator (Layton, 2012).


Hydrogen fuel cells

A fuel cell is a power storage device that stores chemical energy and converts it into electrical energy. The fuels used range from hydrogen, methane to gasoline. For the purpose of this lab, hydrogen will be used as a fuel so these are hydrogen fuel cells. The main components that make up the fuel cell are an electrolyte, an anode chamber, a cathode chamber, and bipolar plates. The electrolyte acts as a separator that keeps the reactions from interacting with each other by separating the anode and cathode chambers. When the water molecules are broken down, the hydrogen is stored in the anode chamber and oxygen in the cathode chamber. The bipolar plates collect the current generated by the fuel cell when the reaction takes place. Figure 3 shows the internal structure of a fuel cell (Tyler, 2012).

Generally, the gas used by a fuel cell is separated prior to use with a fuel cell using various separation methods, such as using an electrolyzer, which is a device that separates distilled water into hydrogen and oxygen. In some cases, fuel cells can be used to initiate this reaction. These fuel cells are called reversible fuel cells. When supplied with water, the reversible fuel cell separates the distilled water into hydrogen and oxygen. The stored hydrogen and oxygen can then be supplied to the fuel cell to generate electrical energy. Hydrogen fuel cells can be used to power computers, cars, power plants, and even whole cities. Due to the nature of producing and storing the gas required to generate large amounts of electrical energy, fuel cells are generally very large. This becomes a problem when used in vehicles.

Figure 3: This is the internal structure of a fuel cell (Tyler, 2012).


Electrical Components

In electrical engineering, different electrical components are represented by different symbols. Figures 4a and 4b show two symbols.

Figure 4a: Cell

Figure 4b: Battery


A cell is a single unit for the conversion of chemical energy to electrical energy. A battery is comprised of multiple cells linked together.

A capacitor is an electrical device that is used to store charge temporarily. Some capacitors can be used in place of a battery, but they operate very differently from a battery. A capacitor is charged by a voltage source logarithmically, as shown in Figure 5.

Figure 5: Capacitor charging curve


Because of their design, capacitors are sensitive to the polarity of the voltage applied to them. The capacitors used in this lab must be connected with the proper polarity or they will fail. Be sure to check the capacitor used to make sure the negative sign on the capacitor is connected to the negative applied voltage. Failure to do this will cause the capacitors to fail.

Figure 6: Polarized laboratory capacitor


The total energy a capacitor holds is given by the equation E = CV2 / 2. Note that the energy holds is proportional to the square of the voltage.

A diode is a device that allows current to pass through it in only one direction. This means that it has polarity and will only allow current to pass from its positive side to its negative side. A light emitting diode (LED)  passes current and lights up when it is passing current.

Different combinations of electrical components allow engineers to design different devices. Resistors, inductors, and capacitors can be arranged in three different ways. In a series circuit, the elements are connected end to end. The current in a series circuit remains the same in all the electrical elements. In a series circuit, as shown in Figure 7, the sum of the voltages across each element is equal to the voltage of the power source (Vout = VA + VB + VC).

Figure 7: A series circuit.


In a parallel circuit, as shown in Figure 8, the elements are connected at opposing ends. The current that is supplied by the voltage source equals the current that flows though elements D and E. The voltage across the elements that are parallel is the same (Vout = VD = VE).

Figure 8: A parallel circuit.


The motor provided is a 9V motor that will operate with voltages lower than 9V, but with reduced torque and speed. A motor with no load draws 9mA; a stalled motor draws well over 350mA. By increasing the voltage provided to the motor, the motor speed will be increased. By increasing current, the torque is increased.

Design Considerations

  • Which source yields the most voltage per unit cost?
  • Which circuit configuration will provide the most desirable voltage across the load? Parallel or series?
  • Which aspects of the competition formula are most advantageous?

Materials and Equipment

Materials with Price List

  • A Horizon wind-turbine: $5.00 each
  • Solar battery panels: $10.00 each
  • A Horizon hydrogen fuel cell: $12.00 each
  • A 1 Farad 2.5V capacitor: $3.00 each
  • Alligator cable sets: $0.50/pair
  • A standard Lego car chassis plus Lego parts kit: $0, limit one per group
  • A Lego to alligator cable clip connector: $0.10 each
  • Tape: $0.10/feet

Equipment Used

  • A Horizon Wind-Turbine
  • A Sunforce 50013 1-Watt solar battery charger
  • An adjustable Table fan
  • A heat lamp
  • A DMM (Digital Multi-meter)
  • A Music voltmeter
  • A 2V DC motor
  • A Horizon hydrogen fuel cell
  • A 1 Farad 2.5V capacitor
  • A mini electric propeller
  • An LED (Light Emitting Diode)
  • 3 Alligator cable sets
  • A standard Lego car chassis plus Lego parts kit
  • A Lego to alligator cable clip connector
  • Scissors
  • Tape

Procedure

Part 1: Testing the power sources

Wind turbine

  1. Connect the wind turbine to the mini propeller using the alligator clips provided. Place the wind turbine in front of the fan and measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
    Figure 9: Voltage measurement circuit

    Figure 10: Current measurement circuit.

  2. Adjust the position of the turbine to find the highest voltage and current that can be generated.
  3. Calculate and record the power generated by the turbine.

Solar panel

  1. Connect the solar panel to the mini propeller using the alligator clips provided. Place the solar panel near the heat lamp and measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
  2. Adjust the position of the solar panel to find the highest voltage and current that can be generated.
  3. Calculate and record the power generated by the solar panel.
    Caution! The heat lamps and solar panels may become extremely hot when used for a long duration of time. Do not touch them immediately after use and turn them off when not in use.

Part 2: Testing the power storage devices

Preparing the hydrogen fuel cell

  1. Place the 2x4cm (small) length pieces of rubber tube into the bottom right pin on the hydrogen fuel cell (on both sides) and insert a cap (red for oxygen and black for hydrogen) into the other end of the tube.
  2. Insert the two longer tubes into the top left pin of the hydrogen fuel cell (Figure 11).
    Figure 11: Hydrogen side of fuel cell.

  3. Take the two cylindrical beakers and place them on top of the stand provided locking it in place then fill the two beakers with distilled water until the water level reaches zero (Figure 12).
    Figure 12: Beakers filled with 30ml of distilled water.

  4. 1. Place the two inner containers into the cylindrical beakers. Make sure the side openings on the inner container are not blocked by the inner ring on the beakers (Figure 13). The distilled water from the beaker will fill out the inner container at this point.
    Figure 13: The cylindrical beaker and inner container.

  5. Connect the two longer tubes to the inner container on each of the beakers corresponding to oxygen and hydrogen on the fuel cell. Make sure there is no air in the inner containers.
    Figure 14: Oxygen tube inserted into the tip of the inner container.

  6. On the oxygen side of the fuel cell (Figure 14), connect the syringe to the uncapped tube (first remove the red cap on the smaller tube). Fill the reversible fuel cell with distilled water using the syringe until all the air is removed from the long tube (Figure 15). Afterwards place the red cap on the smaller tube.
    Figure 15: Oxygen side of fuel cell with a syringe inserted to fill oxygen tubes side with distilled water.

    IMPORTANT: Make sure the connections of the wires to the fuel cell match (red to red, black to black) otherwise it may lead to failure of this part of the experiment and damage to the fuel cell. If this problem occurs the students will have to take full responsibility for replacing the parts.
    Hint: Place the longer tube above the oxygen beaker to hold the water coming out of the longer tube.
  7. Connect the 3V power supply to the positive and negative inputs on the fuel cell and turn on the power supply.
  8. Charge until the H2 inner container is filled with gas. The O2 should be half because the fuel cell is converting H2O and the stoichiometric coefficients demand that balance.
  9. Discharge the charged fuel cell by connecting it to the mini propeller provided (Figure 16).
  10. Measure the voltage and current across the mini propeller using the DMM provided. The connections for measuring voltage and current across the mini propeller are shown in Figures 9 and 10.
  11. Calculate and record the power produced by the hydrogen fuel cell.
    Figure 16: Mini Propeller and 3V power supply with extended cables.

Charging a capacitor

  1. Connect an alligator clip to each of the cables coming out of the 3V power supply. (red is positive and black is negative).
  2. Connect one of unconnected alligator clips to the ammeter (multimeter setting).
  3. Connect the rest of the unconnected cables (one from ammeter and one alligator clip) connect to pins of the capacitor with correspond polarity (Figure 10).
  4. Charge until the current is zero.
  5. Discharge the charged capacitor by connecting it to the mini propeller provided.
Figure 17: This is circuitry for charging a capacitor.


Part 3: Renewable car competition

  1. Assess the materials and consider the data produced from Part 1 and Part 2. Choose materials for the car design, keeping in mind the competition ratio. Create preliminary sketches during this process. Different combinations of power sources and power storage devices may be used for the design.
  2. The design must be able to hold the power storage devices on top of it during the trials. The design can be modified. Prepare a price-list for the renewable energy-powered vehicle based on the design and materials chosen. Have a TA sign the sketches and the price-list.
  3. A TA will provide the materials needed for the design. If the design is modified during construction, note the changes and describe the reasons for them. If the modifications required more materials, make sure the price list is updated and a TA approves it. Designs may be modified between trials.

Before entering the competition, test the motor.

Competition

The renewable energy vehicle must be able to carry its power storage device (e.g. fuel cell, capacitor). If a capacitor is used, it may only be powered using the power sources provided. Violations to these rules will result in a failing grade for the lab report for this lab.

When requested by the TA, the renewable energy car will be positioned and the necessary connections will be completed before the trial begins.

The design that has the highest competition ratio will win the competition (Equation 1).

Equation 1: Competition ratio.

The TA will record the test data after five minutes or when the car stops moving, whichever occurs first. The TA will then calculate the competition ratio. The tabulation for the whole class will be provided.

Assignment

Individual Lab Report

Follow the lab report guidelines laid out in  Specifications for Writing Lab Reports in the Technical Communication section of this manual. The following points should be addressed in the appropriate section of the lab report:

  • Describe the rules of the competition in your introduction. What consequences did the rules have for design decisions? Use the appropriate equations in the answer
  • Explain how solar panels and wind turbines work
  • Explain the concepts of the hydrogen fuel cell and capacitors
  • Discuss the advantages and disadvantages of the solar panel and wind-turbine
  • Discuss the advantages and disadvantages of hydrogen fuel cell compared to other storage devices (e.g. capacitors or batteries)
  • Describe the renewable energy vehicle design and explain the design choices
  • Discuss minimal design. Were all the materials purchased used? Describe the importance of minimal design and explain how it was employed in the design
  • Describe how the design succeeded or failed. What choices would be made to improve its final standing in the competition?
  • Discuss how to improve the competition ratio and compare the ratios
  • Describe the power source chosen for the design
  • Include spreadsheet with every designs’ results. Describe the results and talk about other designs in the class

Remember: Lab notes must be taken. Experimental details are easily forgotten unless written down. EG1004 Lab Notes Paper can be downloaded and printed from the EG1004 Website. Use the lab notes to write the Procedure section of the lab report. At the end of each lab, a TA will scan the lab notes and upload them to the Lab Documents section of the EG1004 Website. One point of extra credit is awarded if the lab notes are attached at the end of the lab report. Keeping careful notes is an essential component of all scientific practice.

Team PowerPoint Presentation

Follow the presentation guidelines laid out in the EG1004 Lab Presentation Format section of this manual. When preparing the presentation, consider the following points:

  • Since one term in the competition ratio is cost, present the cost of the vehicle. Use the page How to Show Cost Data in Presentations for instructions on how to do this
  • How can the performance of the renewable energy powered car be improved?

References

NextEra Energy Resources, LLC., . "Benefits of Renewable Energy." NextEra Energy Resources. NextEra Energy Resources, 2012. Web. 24 Jul 2012. <http://www.nexteraenergyresources.com/content/environment/benefits.shtml>.

Locke, S.. "How does solar power work." Scientific american. Scientific American, 2008. Web. 24 Jul 2012. <http://www.scientificamerican.com/article.cfm?id=how-does-solar-power-work>.

Layton, J.. "How Wind Power Works." How stuff works. Discovery, 2011. Web. 24 Jul 2012. <http://science.howstuffworks.com/environmental/green-science/wind-power.htm>.

Reg Tyler, . "Types of Fuel Cells." Energy efficeny and renewable energy. U.S. Department of Energy, 2011. Web. 24 Jul 2012. <http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html>.

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