Sustainable Energy Vehicle Competition (Virtual)

Objective

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.

Overview

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.

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).

Solar Power

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 1 (Locke, 2008).

Figure 1: A Silicon Solar Panel Showing the Electron Flow

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 Energy

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 2). 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).

Figure 2: The Internal Structure of an Electrical Generator (Layton, 2011)

Energy Storage

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 3.

Figure 3: Capacitor Charging Curve

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 4). Failure to do this will cause the capacitor to fail.

Figure 4: Polarized Capacitor

The energy a capacitor holds is proportional to the square of the voltage across the capacitor (1).

$E={\frac {CV^{2}}{2}}\,$

(1)

In (1), E is the energy, C is the capacitance, and V is the voltage.

Electrical Components

The design of a circuit determines its behavior. In this lab, one circuit design will increase the speed output of a motor and the other will increase the torque output of a motor. In electrical engineering, different electrical components are represented by different symbols. Figures 5A, 5B, and 5C show the symbols for a battery, capacitor, and DC source, respectively. They are all forms of energy storage devices.

Figure 5A: Symbol for Battery

Figure 5B: Symbol for Capacitor

Figure 5C: Symbol for DC Source

Different arrangements of electrical components allow engineers to design different devices. Components, such as resistors, inductors, and capacitors, can be arranged in two different ways. In a series circuit, the element's components 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 6, the sum of the voltages across each element is equal to the voltage of the power source (2).

$V_{out}=V_{A}+V_{B}+V_{C}$

(2)

In (2), V_out is the voltage output and V_A, V_B, and V_C represent the voltage of the individual components.

Figure 6: A Series Circuit

In a parallel circuit, as shown in Figure 7, the element's components 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 (3).

$V_{out}=V_{D}=V_{E}$

(3)

In (3), V_out is the voltage output and V_D and V_E represent the voltage of the individual components.

Figure 7: A Parallel Circuit

A digital multimeter will be used in this lab to read the current and voltage across components in circuits. Multimeters usually have two leads that directly touch two nodes in a circuit or the leads of an electrical component. Please read the Digital Multimeter Guidelines before performing this lab in order to understand how to properly operate a digital multimeter. Digital multimeters are indicated by different symbols in electrical circuits, depending on the value being measured by the multimeter. When measuring voltage, the multimeter is referred to as a voltmeter (Figure 8A). When measuring current, the multimeter is referred to as an ammeter (Figure 8B).

Figure 8A: Symbol for Voltmeter

Figure 8B: Symbol for Ammeter

Depending on whether voltage or current is being measured in a circuit, the multimeter will be arranged in the circuit in a different manner. To measure the voltage across an electrical component, the multimeter must be placed in the circuit in parallel (Figure 9A). To measure the current across an electrical component, the multimeter must be placed in the circuit in series (Figure 9B).

Figure 9A: Multimeter in Parallel

Figure 9B: Multimeter in Series

After measuring the voltage and current across a component in a circuit, the electrical power output of that component can be calculated using the Power Law (4).

$P=IV$

(4)

In (4), P is the power in Watts, I is the current in Amperes, and V is the voltage in Volts.

VEX Robotics Fusion 360 Parts

Vex Robotics is used globally for students to understand the fundamentals of robotics. In this lab, you will be using VEX robotics parts in order to construct the chassis in Fusion 360.

The motor used in the lab is a 9V VEX motor.

Figure 10: 9V VEX Motor

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

Table 1: Materials and Costs

Material	Unit	Cost Per Unit
Horizon Wind-Turbine (Lemon Battery)	1	$7.50
Solar Panel (Potato Battery)	1	$10.00
1 F 5.5V Capacitor	1	$3.00
Wires	1 pair	$0.50
VEX Kit (Limit One Per Design)	1	$0.00

Equipment Used

• Computer with downloaded software

Procedure

The power storage device and power sources will be tested individually. The results of the tests will be used in determining the best power source in designing the sustainable energy vehicle.

1. Starting a New Circuit in TinkerCAD

1. TinkerCAD is an online 3D modeling program and will be used in this lab to simulate the circuits.
2. Go to tinkercad.com and sign in with an Autodesk account.
3. To start a new circuit, on the left side of the home screen select Circuit > Create new circuit.
4. If a template link is provided in the procedure:
   1. Open the TinkerCAD link for the part of the lab you want to work on. The links are provided in the procedure below.
   2. Select the Copy & Tinker option. This will copy the template to the workspace so it can be edited.

2. Testing Series and Parallel Circuits in TinkerCAD

Explore a series and parallel circuit in TinkerCAD.

1. Copy this template to the TinkerCAD workspace using the steps in Starting a New Circuit in TinkerCAD.
2. Click and drag a multimeter on the workspace.
3. Click on it to get the multimeter dialogue box. To measure current go to the Multimeter dialogue box > Mode > Amperage. To measure voltage go to the Multimeter dialogue box > Mode > Voltage.
4. Based on the guidelines, add a multimeter to both the series circuit and the parallel circuit.
   1. Measure the voltage across both circuits. Make sure that the multimeter is wired in parallel to measure the voltage.
   2. Measure the current across both circuits. Make sure that the multimeter is wired in series to measure the current.
5. Record and compare the two measurements for the series circuit and the parallel circuit.

3. Testing the Power Storage Device

Charging a Capacitor

1. Open a new tinkerCAD circuit. Refer to the Starting the New TinkerCAD Circuit procedure to open a new tinkerCAD circuit.
2. The circuit to charge a capacitor will be made in this part of the lab. The circuit is shown in Figure 11.
3. Click and drag a 9V battery, capacitor, and multimeter on the interface as shown in Figure 11
4. Wire the negative end of the 9V Battery to the negative end of the multimeter. To wire these two components, simply click on the negative terminal of the battery, and click once again on the negative terminal of the multimeter.Red is the positive temrminal and black is negative terminal.
5. Similarly, wire the positive end of the multimeter to terminal 1 on the capacitor. Wire terminal 2 on the capacitor to the positive terminal of the battery.
6. To charge the capacitor click Start Simulation. Charge the capacitor until the current in the circuit is zero ampere (0A).
7. Click on Stop Simulation once the multimeter reading is zero ampere (0A).
8. Take a screenshot of your circuit.

Figure 11: TinkerCAD Circuit to Charge a Capacitor

4. Testing the Power Sources

One type of renewable power source will be assigned and analyzed per team, as determined by the TA. Both voltage and current must be measured and recorded, and power must be calculated. Due to limitations of the components available on tinkerCAD a lemon battery and potato battery will be used to represent the renewable power sources listed below.

Wind Turbine (Lemon Battery on TinkerCAD)

In this part of the lab, a lemon battery represents a wind turbine power source.

1. Click and drag a lemon battery and a multimeter on the interface. If the lemon battery is not visible in the components menu on the right, click on Components > All.
2. Wire the positive terminal of the lemon battery with the positive terminal of the multimeter.
3. Wire the negative terminal of the lemon battery to the negative terminal of the multimeter.
4. Create a series circuit using at least two lemon batteries. Click on Start Simulation and record the final voltage produced by the circuit in series.
5. Create a parallel circuit using at least two lemon batteries. In order to create the circuit, diodes are required in order to connect more than two wires. Click on Start Simulation and record the final voltage produced by the circuit in parallel.
6. Take a screenshot of both the circuits with the voltage reading.

Solar Panel (Potato Battery on TinkerCAD)

In this part of the lab, a potato battery represents a wind turbine power source.

1. Click and drag a potato battery and a multimeter on the interface. If the potato battery is not visible in the components menu on the right, click on Components > All.
2. Wire the positive terminal of the potato battery with the positive terminal of the multimeter.
3. Wire the negative terminal of the potato battery to the negative terminal of the multimeter.
4. Create a series circuit using at least two potato batteries. Click on Start Simulation and record the final voltage produced by the circuit in series.
5. Create a parallel circuit using at least two potato batteries. In order to create the circuit, diodes are required in order to connect more than two wires. Click on Start Simulation and record the final voltage produced by the circuit in parallel.
6. Take a screenshot of both the circuits with the voltage reading.

Competition Rules

The competition rules must be followed at all times during the competition. Violation of any of these rules will result in the disqualification of the design.

• The renewable energy vehicle must carry its power storage device (e.g. capacitor)
• The highest competition ratio (CR) wins (5)

$CR={\frac {Distance\left[{\text{ft}}\right]}{1\left[{\text{s}}\right]+Time\left[{\text{s}}\right]}}\times {\frac {100}{Cost\left[\$\right]}}+Distance\left[{\text{ft}}\right]\,$

(5)

In (5), distance is distance traveled in feet, time is the travel time in seconds, and cost is the cost of the design in dollars.

5. Sustainable Energy Vehicle Competition

In this part, a simple vehicle will be designed and assembled in Fusion 360. This vehicle will utilize one motor that is powered by the capacitors in the previous steps. First, decide whether your group will use the solar panel (potato battery) or the wind turbine (lemon battery) as your main source of energy. Keep in mind the price, voltage, and current obtained from the previous parts for each power source during your decision. Your lab TA will provide you with the distance and time values for the source of energy that you decide to use.

Importing VEX Robotics Parts

1. Download the [Car_Parts_(2).zip zip file] of the vehicle parts here. The latest version of Fusion 360 must be downloaded for the parts to appear properly.
2. Unzip the parts to a space on the computer.
3. In Fusion 360, open the Data Panel (icon with 9 boxes at the top left) and click Upload. Select the unzipped part files to upload them to Fusion 360’s cloud memory (Figure 12). Fusion 360 can only import files uploaded to its cloud.

Design the Vehicle

Review the parts that are available. Consider the following restraints while designing your car:

• Only one motor is allowed.
• The design must be able to hold the capacitors on top of it.
• Modify the design to have a location to store the power storage device.
• The motor must be connected to a minimum of two wheels.
• The capacitors must be connected to the motor via wires.

1. Design a circuit consisting of the capacitor or capacitors and the power source on TinkerCAD which will power the vehicle. Take screenshots of the designed circuit.
2. Do not worry about inserting nuts and bolts. Primarily focus on the general shape of the design with shafts, wheels, and the structural components.
3. Construct a cost table based on the materials used.
4. Have a TA approve the sketches and the cost list, indicating the total cost of the initial design.

Assemble the Parts

1. Ensure that the Design workspace is open in Fusion 360. This is indicated at the top left.
2. The VEX part files can be inserted into a new Fusion 360 file by simply dragging and dropping them from the Data Panel into the space. Alternatively, right click the components and select Insert into Current Design. Save the blank file before assembling the vehicle by going to File > Save as.
3. Import the other parts based on the design that was sketched. Connect all the parts using the Align tool to complete the model. Use the tips from the Fusion 360 section from the Boom Construction lab.
4. Once the assembly has been completed, create wires from the capacitor or capacitors to the back of the VEX motor (Figure 13) using the sweep tool. Review the CAD Competition lab for tips on how to use the sweep tool.

Figure 13: Wire insertion on the back of VEX Motor

Assignment

Team Lab Report

Follow the lab report guidelines laid out in the EG1004 Writing Style Guide in the Technical Writing section of the manual. Use the outline below to write this report.

• Describe the rules of the competition in the introduction. What consequences did the rules have for any design decisions? Use the appropriate equations in the answer
• Include the competition ratio and explain the 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 the renewable energy vehicle design and explain the choices made in the design
• Discuss the power sources and their power output. How did the voltage measurements of the power sources impact the design?
• Discuss minimal design. Were all the materials purchased used? Describe the importance of minimal design and explain how it was employed it in the design. Did the design minimize cost?
• Describe how the design succeeded or failed. What choices would improve the design’s standing in the competition?
• Discuss how the competition ratio can be increased, and how the design compared to the other designs
• Specify the power source chosen for the design
• Include the spreadsheet with every design'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 EG1004 Lab Presentation Format in the Technical Presentations section of the 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 would the renewable energy vehicle be improved?

References

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

Locke, S.. "How Does Solar Power Work." Scientific American. Scientific American, 2008. Retrieved 24 July 2012. <http://www.scientificamerican.com/article.cfm?id=how-does-solar-power-work>.

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

Perlman, Howard.. "Hydroelectric Power: How it Works." U.S. Geological Survey, 2016. Retrieved 4 Jan 2018. <https://water.usgs.gov/edu/hyhowworks.html>.

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