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This video will help you on how to attach the power supply correctly.

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SunEzoon and Ray Catcher Sprint Deluxe – Attaching Power Supply

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The article says there is no correct way to build a solar car, but you do need to consider things such as friction, mass, and the angle of the solar panel.

Per.5
Group 1
Car 5.1
Andi, Jackie, Ty, Lucas

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Abstract

Do you want to build a solar-powered car? How about enter it in a competition and race it against other people's designs? If so, this is the project for you! These instructions will show you how to get started building a solar-powered car that you can enter in a science or engineering fair. No experience needed. If you want, you can even compete in the Junior Solar Sprint, a regional competition for solar-powered cars. Get more information about your regional competition.

Are you a teacher? Try the classroom lesson plan version of this project. It contains special information just for educators.

Summary

Objective

Design and build a solar-powered car.

Introduction

Solar power is power we get from the sun. Unlike fossil fuels, which can cause significant pollution and emit greenhouse gases when burned, solar power is clean and renewable. However, solar power is not without its drawbacks-it is not available at night or on a cloudy day.

Solar panels convert sunlight into electrical energy, which can be used to power machines like motors. They must be connected to the motor by wires to form a circuit. A motor can be used to drive the wheels of a solar-powered car (Figure 1). In order to build a solar car, you need to be familiar with the basic parts that make up a typical car:

The chassis is the car's frame, or body.

The axles are straight, rigid rods that support the wheels.

The bearings connect the axles to the chassis and allow them to spin.

The motor converts electrical energy from the solar panel into spinning motion. It has a metal shaft that spins.

The transmission transmits rotating motion from the motor's shaft to an axle.

There are several different types of transmissions that you can use for a solar car, shown in Figure 2.

In a friction drive, a disk on the motor shaft rubs directly against another disk on the axle.

In a belt drive, a disk on the motor shaft is connected to a disk on the axle by a belt (e.g. a rubber band).

In a gear drive, a gear on the motor shaft meshes with a gear on the axle.

There are different engineering and physics concepts you will need to take into account when designing and building a solar car. Some decisions may involve trade-offs between different factors. There is no single "correct" way to build a car. Some of the factors you should consider are listed below. Additional resources listed in the Bibliography can help you learn more about these topics.

Mass and stiffness: what material(s) will you use to make your chassis? Different materials have different densities (mass per unit volume) and stiffnesses (resistance to bending/flexing). In general, you want a chassis to be stiff and not too flexible. Your motor will have a hard time moving a very heavy chassis. However, if a chassis is too light, it could be blown around easily by the wind, or its tires might slip because there is not enough friction with the ground (see next point).

Friction is the force that resists two surfaces sliding against each other. Sometimes friction is bad-you want your bearings and axles to have as little friction between them as possible, so the axles can spin freely. However, sometimes friction is good-you want your tires to have a lot of friction with the ground so they do not slip.

The gear ratio is the ratio between the diameter of the drive gear on the motor shaft and the driven gear on the axle. This number tells you how many times the driven gear will rotate for each rotation of the drive gear. For example, if the driven gear is five times bigger in diameter than the drive gear, then whenever the drive gear completes one full rotation, the driven gear will complete 1/5 of a rotation. Note that this concept also applies to friction drives and belt drives, and more generally can be called the transmission ratio.

Adjusting the transmission ratio allows you to adjust the speed of your motor, measured in rotations per minute or RPM, and the torque of the motor. There is a trade-off between these two quantities (if you increase the RPM, you decrease the torque, and vice versa). You may need to experiment to find out what gear ratio makes your car go the fastest.

The angle of the solar panel relative to the sun's rays affects how much electrical power it produces. It will produce the most power when the panel is perpendicular to the sun's rays.

If you experiment one by one with a few of these variables, and keep track of your results, you can design a great solar-powered car. Optionally, you can enter your car in the Junior Solar Sprint contest if there is one in your area. For more information, check your regional branch.

Terms and Concepts

Questions

What materials could you use to build the different parts of a solar car?

What are the different types of transmissions?

Materials and Equipment

At a minimum, you will need to purchase an official solar panel and motor for your car. Decide if you want to build the other components from scratch, or purchase a kit that includes additional parts. The official vendors for the Junior Solar Sprint competition, Solar Made and Pitsco, have a variety of options (ranging from just the motor/solar panel to a complete car kit, including a balsa wood chassis, axles, gears, and wheels):

If you want to build your own parts from scratch, here are some suggestions for materials:

Chassis: corrugated cardboard, balsa wood, Styrofoam®, milk/juice cartons, cardboard tubes

Axles: metal coat hanger (cut a straight section), wooden skewer or dowel, any other thin metal rod

Bearings: drinking straws, eye hooks, holes drilled in chassis material

Wheels: bottle caps, circles cut from a rigid material (plastic, wood)

Tires: rubber bands, hot glue along the edge of the wheel

Transmission: gears salvaged from toys or an electronic device like a VCR or DVD player, small disks (like Dremel® rotary tool attachments), rubber bands

Depending on the materials you choose, you may need other miscellaneous tools or supplies (power drill, hot glue gun, scissors, pliers, etc.). Important: make sure you use tape/glue that won't melt or soften in the sun on a hot day!

You will also need a flat, paved, sunny area to test your car, and a volunteer to help catch your car (they can be fast!).

Download a free project packet to draw your sketches, organize your project, and make sure you have all the parts you need to enter the Junior Solar Sprint competition.

Download examples of technical drawings for information on how to make professional drawings of your final solar car design.

Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support scibuddy@sciencebuddies.org.

Experimental Procedure

Teachers, try our classroom lesson plan version of this project instead. It has extra resources for schools. Students, this version of the project was made specifically for you.

Planning Your Solar Car

1. Sketch what you want your solar car to look like. What materials will you use? How will all the parts fit together? You can use the free project packet to do your sketches and keep track of your project. If you are thinking of racing your car in a local Junior Solar Sprint competition, using the project packet will help make sure you have all the parts you need to enter the competition!

2. If you are considering entering the Junior Solar Sprint competition, make sure to follow the car sketching and building rules in Table 1. More detailed, official rules can also be downloaded.

Building a Starter Car

Now it is time to build your car. The video and step-by-step directions in this section show you how to build a very basic solar car. It is pretty rickety though and will fall apart easily! It is meant as an example. Feel free to build it, it won't take long, and then use the information you learned from building and testing it to build an awesome version of the car you sketched. Remember to fill in the pages of your project packet as you work!

Depending on where you purchased your motor, you will need to solder wires to it and/or crimp alligator clips onto the wires (Figure 3).

1. If necessary, solder two wires to the tabs on the back of the motor (get an adult to help you with soldering).

2. Remove the plastic covers from the alligator clips, and slide them onto the wires.

3. Use needle-nose pliers to tightly crimp the alligator clips onto the bare metal ends of the wires.

4. Slide the plastic covers back over the alligator clips.

Connect your wheels, axles, and bearings. Figure 4 shows axles (metal rods) inside the bearings (straws). Each axle has two wheels (plastic discs with rubber tires) that are press-fit onto the ends of the axle. One of the axles also has a plastic gear pressed on, which will form part of the transmission. You need to plan ahead to think about how this gear (the driven gear) will align with the gear on the motor shaft (the drive gear).

1. Construct your chassis.

2. Connect your axles/bearings to your chassis. Figure 5 shows the axles/bearings connected to the underside of the chassis (a piece of corrugated cardboard) with tape.

Connect the motor to the chassis and align the transmission. This can be one of the most difficult steps. If your transmission uses gears like the one in Figure 6, you need the teeth of the gears to mesh firmly. If they are too loose or not touching at all, then the motor will just spin without making the axle turn. However, if they are too tight, there might be too much friction and they could jam. You will need to see how it works when you connect the solar panel.

Attach supports for your solar panel to the chassis (Figure 7).

Attach the alligator clips to the two tabs on the back of the solar panel, and secure the solar panel to the chassis (Figure 8). Note: the solar panel is fragile. Make sure you handle it carefully.

1. Now it is time to test your car! Take your car outside in direct sunlight, but do not put it down yet. Hold it in your hands and aim the solar panel towards the sun. If the motor and axle both spin, congratulations! Move on to the next step. If not, try these troubleshooting steps:

1. If your motor does not spin at all:

1. Make sure you are outside, in direct sunlight, on a sunny day, with the solar panel facing towards the sun. Your solar panel might not generate enough power to spin the motor if you are in the shade or it is cloudy.

2. If your motor still does not spin, double-check your circuit. Make sure the alligator clips are firmly connected to the solar panel's metal tabs. If you soldered or crimped your own wire connections, make sure none of them are loose or broken. Repair them if necessary.

3. If your circuit is OK, make sure your axle or transmission are not jammed. Does the axle spin if you twist one of the wheels by hand?

2. If your motor spins, but the axles does not, make sure the gears are touching each other. You might need to realign your motor or the axle to make sure the teeth of the gears mesh together firmly.

2. Once your motor and axle both spin when you hold the car in the sun, it is time to put your car on the ground and watch it go! But be careful-a working car can move pretty fast. It is a good idea to test your car in a flat, open area free of obstacles that it could crash into. Aim your car towards a volunteer who can catch it, or something soft like a pillow. The solar panel is fragile, so try to avoid letting your car crash. Watch your car carefully when you put it down. How fast does it go? Does it go straight?

Making Your Car Better and Faster

Think about how you could make your car faster. Here are a few suggestions:

1. Try to reduce friction in the axles. Could you use other materials for the bearings?

2. Make sure the axles are parallel to each other so they roll smoothly without getting stuck.

3. Can you make your car lighter by removing material?

4. Can you change the angle of the solar panel so it faces the sun directly? Can you make the angle adjustable so you can tilt the panel towards the sun when racing at different times of day or in different directions?

5. Make sure your transmission is not slipping. Do you hear a grinding/scratching/rattling noise? Even if your axle is spinning, the gears might occasionally be slipping against each other. Align your transmission so the gears are firmly pressed against each other.

6. Try changing the gear ratio. What happens if you use different size gears? You will probably need to realign your motor and/or axle if you try this.

Competing in the Junior Solar Sprint

You will need to make technical drawings of your final solar car design as part of your entry into the Junior Solar Sprint. Directions on how to do this are included in your free project packet. You can also download these examples of technical drawings for more help.

Now you are ready to race! Enter the regional branch of the Junior Solar Sprint nearest you and have fun testing your car against the competition.

Ask an Expert

Variations

Do you live in a cloudy climate, or are you unable to do this project outdoors for some reason? Do not worry! You can still build and test a battery-powered car and apply many of the same engineering principles. Instead of a solar panel, purchase a 2xAA battery pack and connect it to your motor.

Instead of a solar-powered car, can you make a different solar-powered machine? What about a solar-powered fan or artwork with moving parts?

If your school does not allow engineering projects for their science fair, consider doing a science project with your car. Perform an experiment to determine how changing one variable, like the gear ratio or angle of the solar panel relative to the sun, affects the speed of the car.

Careers

If you like this project, you might enjoy exploring these related careers:

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Cite This Page

General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Finio, Ben. "Build a Solar-Powered Car." Science Buddies, 6 May 2022, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p043/energy-power/how-to-build-solar-powered-car. Accessed 11 Mar. 2023.

APA Style

Finio, B. (2022, May 6). Build a Solar-Powered Car. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p043/energy-power/how-to-build-solar-powered-car

Explore Our Science Videos

# data[].attributes.attachment_link.title
Build a Solar-Powered Car | Science Project

# data[].attributes.attachment_link.description
Do you want to build a solar-powered car? How about enter it in a competition and race it against other people's designs? If so, this is the project for you! These instructions will show you how to get started building a solar-powered car that you can enter in a science or engineering fair.

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Solar Panel Angle for the Junior Solar Sprint

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Solar Panel Angle for the Junior Solar Sprint

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This video will show you how to angel the solar panel to the sun. It will help with collecting more energy from the sun. So we got to find out where the sun will be at 1:00pm (according to Ms. Sanchez)
5.5 (Yair Perez Estrada, Sebastian Vazquez, Julian Garcia)

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Solar Panel Angle for the Junior Solar Sprint

# data[].attributes.body
A design to best minimize air resistance. This reduces the load on the axles and motor.

Per. 5, Group 5.2
Levi P, Kael M, Max M, Max L

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Abstract

Forced convection cooling of photovoltaic modules mounted on the surface of moving solar car is considered. It is shown that the shape of the car should be optimized not only to reduce aerodynamic drag but also to enhance heat removal and to increase power generated by photovoltaic modules. The module is modeled by local energy balance equation providing boundary condition for equations of aerodynamics. Experimental data on surface temperature are obtained for a flat module and compared to engineering approximate relation and numerical simulations. Simplified approach is proposed based on solving energy equation separately from equations of momentum and continuity. Unlike analytical approximations, it provides accurate results if power generation depends on surface temperature. The results of numerical simulations for two different shapes of the solar car demonstrate that photovoltaic modules placed in flow separation regions should be treated as separate blocks, otherwise they can limit the performance of the whole system. Linear analysis of the power loss of photovoltaic array due to partial overheating or shading is also performed.

Introduction

Present industrial requirements for saving energy and using renewable energy sources lead to emergence of new aerodynamical applications, such as the problem of solar car surface cooling, which is treated in this study. These applications cannot be solved by the present-day commercial CFD codes as they contain specific physical phenomena, which are not taken into account in these codes. Instead, an adequate physical model with additional equations and boundary conditions has to be elaborated and experimentally verified by scientific community for the use in future engineering software. This is accomplished in the present study for the perspective solar car design, presenting an example of application with extremely high demand on aero- and thermodynamical efficiency, which will undoubtedly be the urgent issue of the nearest future.

Solar cells are usually installed to collect energy for the stationary structures: solar power plants, residential or commercial buildings. To be used as auxiliary power source for the cars, solar cells must meet several important requirements: small weight, high efficiency under varying conditions and moderate price. A review of photovoltaic technologies related to the car industry was presented by Giannouli and Yianoulis (2012). The demand of high solar cell efficiency becomes of vital importance if a solar car prototype, powered by solar energy only, is considered. Races of solar cars have been held for more than twenty years (see King, 1991 and other papers in this special issue). These vehicles are extremely lightweight (about 200-300 kg), the power generation is limited by surface area and the conventional approach to their design is to minimize aerodynamic drag, which dominates over rolling resistance at high speed (Ozawa et al., 1998). However, another opportunity to enhance a solar car performance is to increase power generation by cooling the photovoltaic modules. Simple estimate shows that typical solar cell, having power efficiency from 15% to 25%, under illumination of one sun with heat removal coefficient about 10 W/(m ² K) (i.e. cooling by natural convection and thermal reradiation only) would increase its temperature for 70-80 K. Hence, it would lose about 30% of its efficiency (Skoplaki and Palyvos, 2009). Active cooling with water flow through microchannels can provide sufficient cooling even for concentrated illumination up to several hundred suns (for further information on active cooling see the review by Royne et al. (2005)), but the weight of the water required would be comparable with the weight of the car itself. The only cooling still available is forced convection by the air flow, related to solar car motion. Photovoltaic module temperature and efficiency are thus affected by aerodynamical design of the car body. Beside reducing the drag, engineer gets another goal: to provide efficient heat removal from the module surface. Since individual photovoltaic modules are electrically connected and the performance of the whole system or its part can be limited by the most heated module, heat removal should be uniform or, at least, predictable, so that electric circuit could be designed with account for predicted temperature of the cells. A detailed computational model of the solar car dynamics, including efficiency dependence on temperature and irradiance, was elaborated by Craparo and Thacher (1995). However, the temperature of the solar cells was determined from the heat balance equation using average Nusselt number for entire panel treated as a flat plate in a parallel flow. As shown below, the temperature and efficiency of individual solar cell depend on the local flow conditions. Thus, for accurate prediction and optimal design the conjugate problem should be solved, including aerodynamics equations as well as heat balance and electrical relations.

The rest of the paper is organized as follows. First, in Section 2 thermal model of solar cell to be used in aerodynamical calculations is described. Then, in Section 3 experimental measurements of temperature of the flat plate surface, containing photovoltaic module, are presented and compared to theoretical predictions using known approximate correlations and numerical simulations. Simulation results for two different shapes of the solar car are discussed in Section 4. The effect of partial overheating on the performance of the entire photovoltaic array is considered in Section 5. Finally, conclusions are summarized in Section 6.

Section snippets

Solar cell model

Thermal behavior of solar cell under given illumination is usually described by steady energy balance equation (Royne et al., 2005, Skoplaki et al., 2008). It allows finding the solar cell temperature in the steady state if the efficient heat transfer coefficient for heat removal is known. However, for photovoltaic modules installed on the surface of moving solar car, the illumination level and heat transfer coefficient vary with space and time. The solar cell temperature is then governed

Simulations for solar car model

2D numerical simulations for the complete set of aerodynamical equations with (1) as boundary condition were performed for a small 25 cm-long model of the solar car. Low-Mach approximation of unsteady Navier-Stokes equations was used. Time advancement was performed using third-order Runge-Kutta scheme for convective terms and Crank-Nicolson method for the diffusion terms. Fractional-step method was used to ensure satisfaction of continuity equation at each time step. Spatial discretization of

Power loss in photovoltaic array with partial overheating or shading

Simulation results, presented in Section 4, show that, depending on the car shape and velocity, stagnant flow region can be formed, leading to substantial overheating of a small group of solar cells. Also, different regions of the solar car roof can have different irradiance level, especially when the sun is low or in the city, where the car gets partially or fully shaded by the buildings. The influence of this nonuniformity of temperature and irradiance upon the power generation of the entire

Conclusions

Improving the power generation by cooling photovoltaic modules is, together with drag reduction, an important issue of solar car design. For a lightweight vehicle use of active cooling is impossible and the forced convection related to the car motion is the only source of cooling. In contrast to stationary photovoltaic systems, flow conditions, which affect solar cells temperature, can be quite different for solar cells in different regions due to the complex shape of solar car roof.

The solar

Acknowledgment

The authors acknowledge the support of Russian Foundation for Basic Research and Taiwan National Science Council (RP09E12 Joint Research grant).

View full text

# data[].attributes.attachment_link.title
Solar car aerodynamic design for optimal cooling and high efficiency

# data[].attributes.attachment_link.description
Forced convection cooling of photovoltaic modules mounted on the surface of moving solar car is considered. It is shown that the shape of the car should be optimized not only to reduce aerodynamic drag but also to enhance heat removal and to increase power generated by photovoltaic modules.

# data[].attributes.body
A design to best minimize air resistance. This reduces the load on the axles and motor.

Per. 5, Group 5.2
Levi P, Kael M, Max M, Max L

# data[].attributes.attachment_link.readable_text
Abstract

Forced convection cooling of photovoltaic modules mounted on the surface of moving solar car is considered. It is shown that the shape of the car should be optimized not only to reduce aerodynamic drag but also to enhance heat removal and to increase power generated by photovoltaic modules. The module is modeled by local energy balance equation providing boundary condition for equations of aerodynamics. Experimental data on surface temperature are obtained for a flat module and compared to engineering approximate relation and numerical simulations. Simplified approach is proposed based on solving energy equation separately from equations of momentum and continuity. Unlike analytical approximations, it provides accurate results if power generation depends on surface temperature. The results of numerical simulations for two different shapes of the solar car demonstrate that photovoltaic modules placed in flow separation regions should be treated as separate blocks, otherwise they can limit the performance of the whole system. Linear analysis of the power loss of photovoltaic array due to partial overheating or shading is also performed.

Introduction

Present industrial requirements for saving energy and using renewable energy sources lead to emergence of new aerodynamical applications, such as the problem of solar car surface cooling, which is treated in this study. These applications cannot be solved by the present-day commercial CFD codes as they contain specific physical phenomena, which are not taken into account in these codes. Instead, an adequate physical model with additional equations and boundary conditions has to be elaborated and experimentally verified by scientific community for the use in future engineering software. This is accomplished in the present study for the perspective solar car design, presenting an example of application with extremely high demand on aero- and thermodynamical efficiency, which will undoubtedly be the urgent issue of the nearest future.

Solar cells are usually installed to collect energy for the stationary structures: solar power plants, residential or commercial buildings. To be used as auxiliary power source for the cars, solar cells must meet several important requirements: small weight, high efficiency under varying conditions and moderate price. A review of photovoltaic technologies related to the car industry was presented by Giannouli and Yianoulis (2012). The demand of high solar cell efficiency becomes of vital importance if a solar car prototype, powered by solar energy only, is considered. Races of solar cars have been held for more than twenty years (see King, 1991 and other papers in this special issue). These vehicles are extremely lightweight (about 200-300 kg), the power generation is limited by surface area and the conventional approach to their design is to minimize aerodynamic drag, which dominates over rolling resistance at high speed (Ozawa et al., 1998). However, another opportunity to enhance a solar car performance is to increase power generation by cooling the photovoltaic modules. Simple estimate shows that typical solar cell, having power efficiency from 15% to 25%, under illumination of one sun with heat removal coefficient about 10 W/(m ² K) (i.e. cooling by natural convection and thermal reradiation only) would increase its temperature for 70-80 K. Hence, it would lose about 30% of its efficiency (Skoplaki and Palyvos, 2009). Active cooling with water flow through microchannels can provide sufficient cooling even for concentrated illumination up to several hundred suns (for further information on active cooling see the review by Royne et al. (2005)), but the weight of the water required would be comparable with the weight of the car itself. The only cooling still available is forced convection by the air flow, related to solar car motion. Photovoltaic module temperature and efficiency are thus affected by aerodynamical design of the car body. Beside reducing the drag, engineer gets another goal: to provide efficient heat removal from the module surface. Since individual photovoltaic modules are electrically connected and the performance of the whole system or its part can be limited by the most heated module, heat removal should be uniform or, at least, predictable, so that electric circuit could be designed with account for predicted temperature of the cells. A detailed computational model of the solar car dynamics, including efficiency dependence on temperature and irradiance, was elaborated by Craparo and Thacher (1995). However, the temperature of the solar cells was determined from the heat balance equation using average Nusselt number for entire panel treated as a flat plate in a parallel flow. As shown below, the temperature and efficiency of individual solar cell depend on the local flow conditions. Thus, for accurate prediction and optimal design the conjugate problem should be solved, including aerodynamics equations as well as heat balance and electrical relations.

The rest of the paper is organized as follows. First, in Section 2 thermal model of solar cell to be used in aerodynamical calculations is described. Then, in Section 3 experimental measurements of temperature of the flat plate surface, containing photovoltaic module, are presented and compared to theoretical predictions using known approximate correlations and numerical simulations. Simulation results for two different shapes of the solar car are discussed in Section 4. The effect of partial overheating on the performance of the entire photovoltaic array is considered in Section 5. Finally, conclusions are summarized in Section 6.

Section snippets

Solar cell model

Thermal behavior of solar cell under given illumination is usually described by steady energy balance equation (Royne et al., 2005, Skoplaki et al., 2008). It allows finding the solar cell temperature in the steady state if the efficient heat transfer coefficient for heat removal is known. However, for photovoltaic modules installed on the surface of moving solar car, the illumination level and heat transfer coefficient vary with space and time. The solar cell temperature is then governed

Simulations for solar car model

2D numerical simulations for the complete set of aerodynamical equations with (1) as boundary condition were performed for a small 25 cm-long model of the solar car. Low-Mach approximation of unsteady Navier-Stokes equations was used. Time advancement was performed using third-order Runge-Kutta scheme for convective terms and Crank-Nicolson method for the diffusion terms. Fractional-step method was used to ensure satisfaction of continuity equation at each time step. Spatial discretization of

Power loss in photovoltaic array with partial overheating or shading

Simulation results, presented in Section 4, show that, depending on the car shape and velocity, stagnant flow region can be formed, leading to substantial overheating of a small group of solar cells. Also, different regions of the solar car roof can have different irradiance level, especially when the sun is low or in the city, where the car gets partially or fully shaded by the buildings. The influence of this nonuniformity of temperature and irradiance upon the power generation of the entire

Conclusions

Improving the power generation by cooling photovoltaic modules is, together with drag reduction, an important issue of solar car design. For a lightweight vehicle use of active cooling is impossible and the forced convection related to the car motion is the only source of cooling. In contrast to stationary photovoltaic systems, flow conditions, which affect solar cells temperature, can be quite different for solar cells in different regions due to the complex shape of solar car roof.

The solar

Acknowledgment

The authors acknowledge the support of Russian Foundation for Basic Research and Taiwan National Science Council (RP09E12 Joint Research grant).

View full text

# data[].attributes.attachment_link.title
Solar car aerodynamic design for optimal cooling and high efficiency

# data[].attributes.attachment_link.description
Forced convection cooling of photovoltaic modules mounted on the surface of moving solar car is considered. It is shown that the shape of the car should be optimized not only to reduce aerodynamic drag but also to enhance heat removal and to increase power generated by photovoltaic modules.

# data[].attributes.body
http://www.cei.washington.edu/lesson-plans/solar-car-derby/, This picture from this website helps you angle your solar panel so it can capture the most light and be the most optimal it can be which can be very useful because we're trying to make them go as fast as we can.

Tyler E., Presley R., Lena C., Leanna I. 5.7

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This article says that it is important to consider mass and support of the stucture to support itself, especially with the rods for the wheels.
5.8

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Abstract

Do you want to build a solar-powered car? How about enter it in a competition and race it against other people's designs? If so, this is the project for you! These instructions will show you how to get started building a solar-powered car that you can enter in a science or engineering fair. No experience needed. If you want, you can even compete in the Junior Solar Sprint, a regional competition for solar-powered cars. Get more information about your regional competition.

Are you a teacher? Try the classroom lesson plan version of this project. It contains special information just for educators.

Summary

Objective

Design and build a solar-powered car.

Introduction

Solar power is power we get from the sun. Unlike fossil fuels, which can cause significant pollution and emit greenhouse gases when burned, solar power is clean and renewable. However, solar power is not without its drawbacks-it is not available at night or on a cloudy day.

Solar panels convert sunlight into electrical energy, which can be used to power machines like motors. They must be connected to the motor by wires to form a circuit. A motor can be used to drive the wheels of a solar-powered car (Figure 1). In order to build a solar car, you need to be familiar with the basic parts that make up a typical car:

The chassis is the car's frame, or body.

The axles are straight, rigid rods that support the wheels.

The bearings connect the axles to the chassis and allow them to spin.

The motor converts electrical energy from the solar panel into spinning motion. It has a metal shaft that spins.

The transmission transmits rotating motion from the motor's shaft to an axle.

There are several different types of transmissions that you can use for a solar car, shown in Figure 2.

In a friction drive, a disk on the motor shaft rubs directly against another disk on the axle.

In a belt drive, a disk on the motor shaft is connected to a disk on the axle by a belt (e.g. a rubber band).

In a gear drive, a gear on the motor shaft meshes with a gear on the axle.

There are different engineering and physics concepts you will need to take into account when designing and building a solar car. Some decisions may involve trade-offs between different factors. There is no single "correct" way to build a car. Some of the factors you should consider are listed below. Additional resources listed in the Bibliography can help you learn more about these topics.

Mass and stiffness: what material(s) will you use to make your chassis? Different materials have different densities (mass per unit volume) and stiffnesses (resistance to bending/flexing). In general, you want a chassis to be stiff and not too flexible. Your motor will have a hard time moving a very heavy chassis. However, if a chassis is too light, it could be blown around easily by the wind, or its tires might slip because there is not enough friction with the ground (see next point).

Friction is the force that resists two surfaces sliding against each other. Sometimes friction is bad-you want your bearings and axles to have as little friction between them as possible, so the axles can spin freely. However, sometimes friction is good-you want your tires to have a lot of friction with the ground so they do not slip.

The gear ratio is the ratio between the diameter of the drive gear on the motor shaft and the driven gear on the axle. This number tells you how many times the driven gear will rotate for each rotation of the drive gear. For example, if the driven gear is five times bigger in diameter than the drive gear, then whenever the drive gear completes one full rotation, the driven gear will complete 1/5 of a rotation. Note that this concept also applies to friction drives and belt drives, and more generally can be called the transmission ratio.

Adjusting the transmission ratio allows you to adjust the speed of your motor, measured in rotations per minute or RPM, and the torque of the motor. There is a trade-off between these two quantities (if you increase the RPM, you decrease the torque, and vice versa). You may need to experiment to find out what gear ratio makes your car go the fastest.

The angle of the solar panel relative to the sun's rays affects how much electrical power it produces. It will produce the most power when the panel is perpendicular to the sun's rays.

If you experiment one by one with a few of these variables, and keep track of your results, you can design a great solar-powered car. Optionally, you can enter your car in the Junior Solar Sprint contest if there is one in your area. For more information, check your regional branch.

Terms and Concepts

Questions

What materials could you use to build the different parts of a solar car?

What are the different types of transmissions?

Materials and Equipment

At a minimum, you will need to purchase an official solar panel and motor for your car. Decide if you want to build the other components from scratch, or purchase a kit that includes additional parts. The official vendors for the Junior Solar Sprint competition, Solar Made and Pitsco, have a variety of options (ranging from just the motor/solar panel to a complete car kit, including a balsa wood chassis, axles, gears, and wheels):

If you want to build your own parts from scratch, here are some suggestions for materials:

Chassis: corrugated cardboard, balsa wood, Styrofoam®, milk/juice cartons, cardboard tubes

Axles: metal coat hanger (cut a straight section), wooden skewer or dowel, any other thin metal rod

Bearings: drinking straws, eye hooks, holes drilled in chassis material

Wheels: bottle caps, circles cut from a rigid material (plastic, wood)

Tires: rubber bands, hot glue along the edge of the wheel

Transmission: gears salvaged from toys or an electronic device like a VCR or DVD player, small disks (like Dremel® rotary tool attachments), rubber bands

Depending on the materials you choose, you may need other miscellaneous tools or supplies (power drill, hot glue gun, scissors, pliers, etc.). Important: make sure you use tape/glue that won't melt or soften in the sun on a hot day!

You will also need a flat, paved, sunny area to test your car, and a volunteer to help catch your car (they can be fast!).

Download a free project packet to draw your sketches, organize your project, and make sure you have all the parts you need to enter the Junior Solar Sprint competition.

Download examples of technical drawings for information on how to make professional drawings of your final solar car design.

Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support scibuddy@sciencebuddies.org.

Experimental Procedure

Teachers, try our classroom lesson plan version of this project instead. It has extra resources for schools. Students, this version of the project was made specifically for you.

Planning Your Solar Car

1. Sketch what you want your solar car to look like. What materials will you use? How will all the parts fit together? You can use the free project packet to do your sketches and keep track of your project. If you are thinking of racing your car in a local Junior Solar Sprint competition, using the project packet will help make sure you have all the parts you need to enter the competition!

2. If you are considering entering the Junior Solar Sprint competition, make sure to follow the car sketching and building rules in Table 1. More detailed, official rules can also be downloaded.

Building a Starter Car

Now it is time to build your car. The video and step-by-step directions in this section show you how to build a very basic solar car. It is pretty rickety though and will fall apart easily! It is meant as an example. Feel free to build it, it won't take long, and then use the information you learned from building and testing it to build an awesome version of the car you sketched. Remember to fill in the pages of your project packet as you work!

Depending on where you purchased your motor, you will need to solder wires to it and/or crimp alligator clips onto the wires (Figure 3).

1. If necessary, solder two wires to the tabs on the back of the motor (get an adult to help you with soldering).

2. Remove the plastic covers from the alligator clips, and slide them onto the wires.

3. Use needle-nose pliers to tightly crimp the alligator clips onto the bare metal ends of the wires.

4. Slide the plastic covers back over the alligator clips.

Connect your wheels, axles, and bearings. Figure 4 shows axles (metal rods) inside the bearings (straws). Each axle has two wheels (plastic discs with rubber tires) that are press-fit onto the ends of the axle. One of the axles also has a plastic gear pressed on, which will form part of the transmission. You need to plan ahead to think about how this gear (the driven gear) will align with the gear on the motor shaft (the drive gear).

1. Construct your chassis.

2. Connect your axles/bearings to your chassis. Figure 5 shows the axles/bearings connected to the underside of the chassis (a piece of corrugated cardboard) with tape.

Connect the motor to the chassis and align the transmission. This can be one of the most difficult steps. If your transmission uses gears like the one in Figure 6, you need the teeth of the gears to mesh firmly. If they are too loose or not touching at all, then the motor will just spin without making the axle turn. However, if they are too tight, there might be too much friction and they could jam. You will need to see how it works when you connect the solar panel.

Attach supports for your solar panel to the chassis (Figure 7).

Attach the alligator clips to the two tabs on the back of the solar panel, and secure the solar panel to the chassis (Figure 8). Note: the solar panel is fragile. Make sure you handle it carefully.

1. Now it is time to test your car! Take your car outside in direct sunlight, but do not put it down yet. Hold it in your hands and aim the solar panel towards the sun. If the motor and axle both spin, congratulations! Move on to the next step. If not, try these troubleshooting steps:

1. If your motor does not spin at all:

1. Make sure you are outside, in direct sunlight, on a sunny day, with the solar panel facing towards the sun. Your solar panel might not generate enough power to spin the motor if you are in the shade or it is cloudy.

2. If your motor still does not spin, double-check your circuit. Make sure the alligator clips are firmly connected to the solar panel's metal tabs. If you soldered or crimped your own wire connections, make sure none of them are loose or broken. Repair them if necessary.

3. If your circuit is OK, make sure your axle or transmission are not jammed. Does the axle spin if you twist one of the wheels by hand?

2. If your motor spins, but the axles does not, make sure the gears are touching each other. You might need to realign your motor or the axle to make sure the teeth of the gears mesh together firmly.

2. Once your motor and axle both spin when you hold the car in the sun, it is time to put your car on the ground and watch it go! But be careful-a working car can move pretty fast. It is a good idea to test your car in a flat, open area free of obstacles that it could crash into. Aim your car towards a volunteer who can catch it, or something soft like a pillow. The solar panel is fragile, so try to avoid letting your car crash. Watch your car carefully when you put it down. How fast does it go? Does it go straight?

Making Your Car Better and Faster

Think about how you could make your car faster. Here are a few suggestions:

1. Try to reduce friction in the axles. Could you use other materials for the bearings?

2. Make sure the axles are parallel to each other so they roll smoothly without getting stuck.

3. Can you make your car lighter by removing material?

4. Can you change the angle of the solar panel so it faces the sun directly? Can you make the angle adjustable so you can tilt the panel towards the sun when racing at different times of day or in different directions?

5. Make sure your transmission is not slipping. Do you hear a grinding/scratching/rattling noise? Even if your axle is spinning, the gears might occasionally be slipping against each other. Align your transmission so the gears are firmly pressed against each other.

6. Try changing the gear ratio. What happens if you use different size gears? You will probably need to realign your motor and/or axle if you try this.

Competing in the Junior Solar Sprint

You will need to make technical drawings of your final solar car design as part of your entry into the Junior Solar Sprint. Directions on how to do this are included in your free project packet. You can also download these examples of technical drawings for more help.

Now you are ready to race! Enter the regional branch of the Junior Solar Sprint nearest you and have fun testing your car against the competition.

Ask an Expert

Variations

Do you live in a cloudy climate, or are you unable to do this project outdoors for some reason? Do not worry! You can still build and test a battery-powered car and apply many of the same engineering principles. Instead of a solar panel, purchase a 2xAA battery pack and connect it to your motor.

Instead of a solar-powered car, can you make a different solar-powered machine? What about a solar-powered fan or artwork with moving parts?

If your school does not allow engineering projects for their science fair, consider doing a science project with your car. Perform an experiment to determine how changing one variable, like the gear ratio or angle of the solar panel relative to the sun, affects the speed of the car.

Careers

If you like this project, you might enjoy exploring these related careers:

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Cite This Page

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MLA Style

Finio, Ben. "Build a Solar-Powered Car." Science Buddies, 6 May 2022, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p043/energy-power/how-to-build-solar-powered-car. Accessed 11 Mar. 2023.

APA Style

Finio, B. (2022, May 6). Build a Solar-Powered Car. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p043/energy-power/how-to-build-solar-powered-car

Explore Our Science Videos

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Build a Solar-Powered Car | Science Project

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Do you want to build a solar-powered car? How about enter it in a competition and race it against other people's designs? If so, this is the project for you! These instructions will show you how to get started building a solar-powered car that you can enter in a science or engineering fair.

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Solar Car Tips and Tricks (Zack, Kaius, Adam)

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Solar Car Tips and Tricks (Zack, Kaius, Adam)

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This article shows how to build your solar car in the most efficient way possible and the materials and everything else needed.

https://www.homesciencetools.com/article/solar-car/

Car number: 5.6
period:5
Group: 6

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Building a solar-powered car will introduce your students to alternative energy concepts while incorporating problem-solving, design, and modeling. In addition, students will experience using hand tools as they construct their solar vehicle.

Make Your Own Solar Car

Adult supervision is recommended for this project.

What You Need for a Solar Car Project

Small electric motor (Look at hobby or electronics stores, and make sure you get one with a motor pulley)

For the car body: cardboard milk carton, water bottle, cardboard, foam board, or similar materials

For the front wheels and back wheels: plastic bottle caps, film canister caps, toy wheels such as K'nex, etc.

For the axles: Stiff wire or wooden shish-kabob skewers

Straws or eye screws to mount the axles

How to Build a Solar-Powered Car

1. Choose a material for the car body, which is called the chassis. Think carefully about this: you want something strong, but also something lightweight so it needs less power for the motor to move it. (But be careful - if it's too light, it can easily get blown about by the wind.) A big part of engineering is finding the right balance between weight and strength.

2. Use a nail to poke a small hole in the center of your wheels. Make sure the stiff wire or wooden skewers you use for axles fit in the holes tightly. Take an extra cap and cut off the sides, leaving just the top part, which usually has a small inner rim to help keep the bottle from leaking. Glue this cap to one of your wheels. You have just created a pulley for your driving wheel; the inner rim of the extra bottle cap will support your car's drive belt. (You can try using a film canister cap for this step instead of cutting a bottle cap. If you are using toy wheels like K'nex, you can just use a smaller wheel mounted on the inside of your main wheel to act as the pulley.)

3. Now, mount your axles onto the chassis. Depending on what your chassis is made of, you can thread the axle through eye screws mounted on the bottom. Another easy method is to tape straws on the underside of the chassis and threads the axles through them. (Use our balloon rocket car project as a reference for how to do this.)

4. Attach the small motor pulley to the motor shaft. Determine where to mount the motor by connecting the driving pulley with the motor pulley using an elastic band as a drive belt. Position the motor so the band is slightly stretched (but don't stretch it too much!). Mount the motor with glue or tape it in between a small frame of wood or cardboard blocks.

5. Use clear plastic tape to attach the two solar cells together side-by-side; then connect them in a series circuit using the alligator clip leads. Connect the positive terminal of one cell to the negative terminal of the other. Connect the remaining terminals to the motor. If the motor spins the wrong way, switch the leads where they connect to the motor. Once it's connected properly, you'll probably want to use tape to help keep the wires under control.

6. Mount the solar cells on the chassis at an angle where they will receive the most sun. Take your car outside to a sunny sidewalk, connect the drive belt, and watch it go!

7. Designing and building a car from scratch involves a lot of perseverance and trial and error, so don't be discouraged if yours doesn't work perfectly right away. Experiment to see if you can improve the design of your solar car. How fast does it go? Does it drive straight? How would it perform with only one solar cell? What if you used smoother wheels for less friction? Keep testing new ideas to make your car work better.

Once you've perfected your car, think about other ways you could experiment with solar power.

Could you build a solar boat or water pump?

Maybe you'll be the next scientist to help find out!

For more solar science fun, check out these science projects:

Solar Power Science Lesson

The Sun: The Ultimate Power Source

Every morning the sun rises, bringing light and heat to the earth, and every evening it sets. It seems so commonplace that we rarely spare a thought for that bright object in the sky. Yet without it, we wouldn't exist!

Deep in the core of our local star, hydrogen atoms react by nuclear fusion, producing a massive amount of energy that streams in all directions at the speed of light (that's the mind-boggling speed of more than 186,000 miles per second). In just eight minutes, that energy travels 93 million miles to earth.

We use many different forms of energy here on earth, but here's the thing: almost all of them originate with the sun, not just light and heat (thermal) energy!

The law of conservation of energy says that energy can't be created or destroyed, but can change its form. And that's what happens with energy from the sun -it changes into lots of different forms:

Plants convert light energy from the sun into chemical energy (food) by the process of photosynthesis. Animals eat plants and use that same chemical energy for all their activities.

Heat energy from the sun causes changing weather patterns that produce wind. Wind turbines then convert wind power into electrical energy.

Hydroelectricity is electrical energy produced from moving water, and water flows because heat energy from the sun causes evaporation that keeps water moving through the water cycle.

Right now, much of human activity uses energy from fossil fuels such as coal, oil, and natural gas. These energy sources are created over very long periods of time from decayed and fossilized living matter (animals and plants), and the energy in that living matter originally came from the sun through photosynthesis.

The sun sends more energy to the earth in one hour than the whole planet needs in a year. Imagine if we could capture that energy directly and convert it to a form that could power our cities, homes, and cars!

Many scientists around the world are researching how we can improve our use of the sun's energy. One way is to use solar thermal panels to collect thermal energy to heat air and water.

Another way is to use photovoltaic (PV) cells, also called solar cells, to convert sunlight directly into electricity. ('Photovoltaic' essentially means 'light electricity'.)

PV cells use a material such as silicon to absorb energy from sunlight. The sunlight energy causes some electrons to break free from the silicon atoms in the cell.

Because of how the solar cell is made, these free electrons move to one side of the cell, creating a negative charge and leaving a positive charge on the other side.

PV cells today are still only able to capture a small fraction of the sun's energy, so acres of them are necessary to collect enough light to create electricity on a large scale.

A lot more scientific work needs to be done to make them more efficient and take up less space. Despite the challenges, solar panels are used to power many things such as emergency signs, school crossing lights, and more.

Many people are also able to power their homes by mounting solar panels on the roof, and this will only get easier as the technology continues to advance.

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Building a solar-powered car will introduce your students to alternative energy concepts while incorporating problem-solving, design, and modeling. In addition, students will experience using hand tools as they construct their solar vehicle. Adult supervision is recommended for this project.

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0* is the best angle because it generates the most energy.
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Solar Panel Angle for the Junior Solar Sprint

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Need some search inspiration?  Try these:
Junior Solar Sprint
How to Build a Junior Solar Sprint Racer
Solar Derby
Junior Solar Sprint Tips and Tricks
Junior Solar Sprint Advice
Ray Catcher Instructions
Junior Solar Sprint Gear Ratios

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There are many ways to post to padlet- click this resource if you need some help!

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Junior solar Sprint rules and regulations.pdf

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Pitsco Ray Catcher Sprint Deluxe- these are the kits that we build and innovate from.

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All the materials needed to build a complete solar car for the Junior Solar Sprint competition!

Looking for standards-based activities to accompany these materials? The Solar Vehicles Teacher's Guide is available for print here, or you can download a digital copy for free here.

Order 30 kits to build a class pack!

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All the materials needed to build a complete solar car for the Junior Solar Sprint competition! Looking for standards-based activities to accompany these materials? The Solar Vehicles Teacher's Guide is available for print here, or you can download a digital copy for free here. Order 30 kits to build a class pack!

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Include:
A. A brief descriptive title of your "find"
B. A summary of the information that is useful to the class. (1-2 sentences should do it!)
C. The link you your file or resource.
D. Your Period and group number.

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Where the adventure begins!

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Southern California Junior Solar Sprint!

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The Junior Solar Sprint at Calavera will be held in Accordance with the Regulations for the National Junior Solar Sprint Event.  As you design your car, please keep in mind these key requirements:

Safe for contestant and spectators

Maximum Vehicle Dimensions: 30 x 30 x 60 cm

Leave a Space for Your Number (3 x 3 cm)

Sunlight is the only power source

Energy enhancing devices must be attached.

Steering via guidewire, using 1-2 attached eyelits

Must have a 3D chassis, solar panel must be easily added and removed.