Sustainable Energy Vehicle Competition
The experimental objective of this lab is to evaluate different sources of renewable energy and use the results of that evaluation to design a vehicle that is powered by a renewable energy source or a capacitor that is charged by a renewable energy source. The design will be entered in a competition that is judged by a ratio that uses distance traveled, travel time, and cost. The highest ratio wins.
While humans have been using renewable energy sources, such as sails to power boats, windmills to pump water, or water-driven wheels to power machinery that mills grains, for millennia, the environmental impact of burning fossil fuels, such as oil, natural gas, and coal, has prompted greater interest in and greater investment in renewable energy sources, including solar power, wind power, and hydroelectric power. But some renewable energy sources cannot generate power consistently, notably solar power and wind power, so there is equal interest in developing energy storage devices that can operate at grid-scale or hold sufficient energy to power entire communities for an extended time after being charged by a renewable energy source.
Capacitors have many uses in circuits and signal processing. In this lab, a capacitor can be used as the power source for the renewable energy vehicle. Fundamentally, 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 1.
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. In the lab, the capacitor’s negative lead must be connected to the negative applied voltage (Figure 2). Failure to do this will cause the capacitor to fail.
The energy a capacitor holds is proportional to the square of the voltage across the capacitor (1).
In (1), E is the energy, C is the capacitance, and V is the voltage.
Types of Renewable Energy
Renewable energy is a type of energy that can be harnessed from naturally replenished resources. Some examples of this are sunlight, wind, and water. There are many benefits of using renewable energy. They are clean energy sources, and they come from an abundant source that do not become depleted. If these renewable resources can be harnessed efficiently, they can solve the problems with using non-renewable energy sources, such as fossil fuels (NextEra Energy Resources, 2012).
Sunlight, like any other type of electromagnetic radiation, contains energy. Typically, when sunlight hits an object, the energy that it contains is converted into heat. Certain materials can convert the energy into an electrical current. In this form, it can be used as a power source and it can be stored as energy.
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 movement within the crystal. When the electrons move around the crystal structure an electrical current is generated. The reaction that occurs when sunlight hits a solar panel is shown in Figure 3 (Locke, 2008).
Older solar panels use large crystalline structures made from silicon. When sunlight hits the silicon on the solar panel, the photons from the sunlight energize the electrons in the material. These energized electrons create a higher electrical potential in the material that is measured as a voltage between that material and ground.
The material copper indium gallium (di)selenide (CIGS) is also used in the production of solar panels. Panels made from CIGS have a smaller crystalline structure and are less expensive than their silicon counterparts. CIGS panels 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. CIGS panels are not as good at converting 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, 2008).
Wind turbines are used to capture the wind’s energy and convert it into electrical energy. The blades on wind turbines are slanted so that as the wind passes over the blades it creates an uneven pressure on each side, causing them to rotate. The spinning blades drive a low speed shaft connected to a gearbox. 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 where mechanical energy is converted to electrical energy (Layton, 2011).
A basic electrical generator is made of permanent magnets on each side with a rectangular coil connected to a commutator, which is a rotary electrical switch (Figure 4). The two permanent magnets on each side create a magnetic field. As the rectangular coil spins mechanically, the magnetic field through the area of the coil changes, creating an alternating current through the coil. The commutator switches the polarity of the coil just as the polarity of the alternating current changes, creating a direct current. The current is then output from the wind turbine (Layton, 2011).
The design of a circuit determines its behavior. In this lab, one circuit design will increase speed and the other will increase torque. In electrical engineering, different electrical components are represented by different symbols. Figures 5A and 5B show the symbols for a cell and a battery, respectively.
Diodes and light emitting diodes (LEDs) were introduced in the Prototyping with Microcontrollers, Sensors, and Materials lab. A diode has polarity and will only allow current to pass from its positive lead to its negative lead. A light emitting diode (LED) not only passes current, but also lights up when it is passing current. LEDs have a forward voltage and a reverse voltage. In the forward direction, the forward voltage and resistance are low and determined by the material used in the LED. The reverse voltage has a much higher resistance and a higher reverse voltage that prevents the flow of electrical current. The characteristic of the diode is to have low resistance to electrical flow in the forward direction and high resistance in the reverse direction. This provides the ability to control the flow of electricity in one direction only.
There is a threshold voltage in the forward direction for the LED to emit light. Below the threshold voltage, there is no light. At and above the threshold voltage, the LED emits light with intensity roughly linear with the forward voltage magnitude. The symbol for an LED is shown in Figure 6.
Different arrangements of electrical components allow engineers to design different devices. Components like resistors, inductors, and capacitors can be arranged in two 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 9, the sum of the voltages across each element is equal to the voltage of the power source (Vout = VA + VB + VC).
In a parallel circuit, as shown in Figure 10, 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 (Vout = VD = VE).
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.
- 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
- Horizon wind-turbine: $7.50 each
- Water turbine: $5.00 each
- Solar battery panels: $10.00 each
- 1 Farad 5.5V capacitor: $3.00 each
- Alligator cable sets: $0.50/pair
- Standard Lego car chassis plus Lego parts kit: $0, limit one per group
- Lego to alligator cable clip connector: $0.10 each
- Duct Tape: $0.10/feet
- Horizon Wind-Turbine
- Sunforce 50013 1-Watt Solar Battery Charger
- Adjustable Table fan
- Heat Lamp
- DMM (Digital Multi-meter)
- Music Voltmeter
- 2V DC Motor
- 1 Farad 5.5V Capacitor
- 3 Alligator cable sets
- Standard Lego Car Chassis plus Lego parts kit
- Lego to Alligator Cable Clip Connector
Every group will be designated to test the power storage device and a single power source.
Part 1: Testing the Power Storage Device
Charging a Capacitor
- Connect an alligator clip to each of the cables coming out of the 3V power supply. (red is positive and black is negative)
- Connect to the one of unconnected alligator clips the ammeter (multimeter setting measuring current)
- 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)
- Charge until the current is zero.
- Discharge the charged capacitor by connecting it to the music voltmeter provided.
Part 2: Testing the Power Sources
Each team will analyze one type of renewable power source, determined by the TA. Both voltage and current must be measured and recorded, and power must be calculated.
- Connect the wind turbine to the music voltmeter using the alligator clips provided. Measure the voltage and current across the music voltmeter using the digital multimeter provided. The connections for measuring voltage and current across the music voltmeter are shown in Figures 9 & 10.
- Adjust the position of the turbine to find the maximum voltage and current that can be generated.
- Calculate and record the power generated by the turbine and give information to TA.
- Connect the solar panel to the music voltmeter using the alligator clips provided. Place the solar panel near the heat lamp and measure the voltage and current across the music voltmeter using the digital multimeter provided.
- Adjust the position of the solar panel to find the maximum voltage and current that can be generated.
- Calculate and record the power generated by the solar panel and give information to the TA.
- 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.
- Connect the red wire of the water wheel to the positive (red) end of the multimeter and the black wire to the negative (black) end of the multimeter. Set the multimeter to measure voltage.
- Notify the TA once the connections have been set up. The TA will then take you to the AUV room's sink to measure the voltage and (electrical) current produced by the water coming from the sink. Be very careful to keep water off of the multimeters.
- Calculate and record the power generated by the water wheel and give information to the TA.
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 make preliminary sketches during this process.
- Your design must be able to hold the power storage device on top of it during the trials (you may modify your design to fit the power storage device as you deem fit). Prepare a cost list for your renewable energy powered vehicle based on the setups and materials you have chosen. Have your TA sign the sketches and the cost 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 cost list and that your TA approves it. (Note: You may modify your design between trials)
Before entering the competition, test if both your motor and cable are working, and that the motors turn in the desired direction of travel.
The renewable energy vehicle must be able to carry the power storage device you choose to use on it (e.g. capacitor). You may only power your capacitor 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.
The competition will be won by the team that has the highest 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.
Team Lab Report
Note: You will be writing a team lab report rather than an individual one. See the Team Authoring Strategies page in the Technical Communication of this online manual for guidance of how to do this.
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:
- 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.
- Include competition ratio and explain variables
- Explain how solar panels and wind turbines work.
- Explain the concept of the capacitor.
- Discuss the advantages and disadvantages of the solar panel and wind-turbine.
- Describe your renewable energy vehicle design and explain the choices you made in your design.
- Discuss the possible power sources and their effectiveness. How did the voltage measurements of the power sources impact 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.
- Specify the power source chosen for the design.
- Include spreadsheet with every team's 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 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?
 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>.
 Perlman, Howard.. "Hydroelectric power: How it works." U.S. Geological Survey, 2016. Web 4 Jan 2018. <https://water.usgs.gov/edu/hyhowworks.html>.