The use of solar panels in electric vehicles seem to be of interest to several car manufacturers around the world. I have seen cars with solar panels on the roof and there is even an airplane that also uses them as the only source of energy during the flight. Maybe at some time we will see vehicles totally covered with panels, even with some special types of panels placed in the windows and windshields. I have some doubts:
Will it be possible to also have panels on wheels? Will it be worth using these spaces? Will the rotational movement negatively influence power generation? I have not found information to clarify these doubts but I decided to look for my own answers. In this INSTRUCTABLE I propose a toy car powered by a solar panel. I clarify that we will not see the type of classical toy car with a panel at the top and a small electric motor coupled to the wheels through gears or pulleys. The panel is the WHEEL, LITERALLY! The electric motor has been coupled in an unconventional manner (the rotor is the stator and vice versa). It may be crazy, but it was fun for me. Building it has enabled me to investigate this topic. It has taken me several hours to get to this design but I think it is super easy to be built following the steps that I give you below. I hope you like it, and make your own version. I think it would be interesting to build it in a school environment and listen to the children and adults' opinions .

Supplies

Small DC motor

Velcro strip with adhesive

Small round shaped solar panel

Electric Tape

3D printed parts or CNC machined parts

Instant Glue

2.5 mm shaft toy car

3D Printer or online 3D Printing Services or CNC Machine

Scissors

Pliers

Soldering iron

Step 1: Glue a Piece of Velcro Strip to the Back of the Small DC Motor

The piece of velcro strip is not required to be perfectly trimmed, but it should cover the entire rear of the DC electric motor. Also, make sure that the Velcro is fully glued and remains fixed in one position.

Step 2: Solder the Cables of the Small DC Electric Motor to the Solar Panel

Verify that you make a good quality solder. Do not exceed 10 or 20 seconds in each one because you run the risk of melting down the rear part of the panel or melting down the plastic coating of the cables. A 30W soldering iron is suitable for this purpose.

Step 3: Cover the Electrical Welds With Electrical Tape

The body of the electric motor is made of metal and is an electric conductor, if you cover the soldered parts you made previously with electric tape, you will avoid possible short circuits. The electric motor cables should not be loose, use tape to organize and fix them to the back of the solar panel.

Step 4: Attach a Piece of Velcro Strip to the Center Back of the Solar Panel

Generally these solar panels come with a central mark on the back. This is acquired in the manufacturing process itself and can be used as a reference to glue the Velcro piece. If in doubt, you can also use a measurement ruler and intercept 2 or more diameters. You can also locate the center with that procedure.

Step 5: Join the Small DC Electric Motor to the Solar Panel

When joining the DC electric motor to the solar panel, verify that they are well connected. The motor shaft must be perpendicular to the rear surface of the solar panel and its center. Since the union is through Velcros, you can correct some deviation just by taking them off and joining them again. If the alignment is still incorrect, you will notice excessive vibration when testing its operation.

Step 6: Check That the DC Electric Motor and Panel Assembly Rotate Properly

Before continuing with the following steps it is appropriate to verify that everything works as expected. Fix the motor shaft with pliers, a clamp or similar, and place the solar panel perpendicular to the sun's rays. The set must turn and reach a relatively high speed. When you move it away from the influence of the sun, it must spin a few more seconds before stopping. When I did this test it was night and I used a 50W incandescent car bulb with an external DC power source set at 12 volts. I was surprised that the solar panel was sensitive to these types of light bulb emissions. Investigating later on Internet, I discovered that there were studies and that step confirmed it.

Step 7: Print the Designed Parts in a 3D Printer

In FUSION 360 it was relatively easy to design the toy car chassis. It is an essential part, since this will be coupled to the motor-panel and front wheels. The design should be printed with the lightest possible material without compromising structural integrity. In my case I used PLA.

Step 8: Glue the Motor Shaft to the Chassis

The motor shaft should be fixed to the chassis as shown in the image. To do this, place it inside the hole which was created for this purpose. Do not allow the motor body touch the chassis as it will generate unnecessary friction and it will detriment the performance of the toy. BE SPECIAL CAREFUL in not letting glue from the shaft penetrate inside the electrical motor, since it will clog it and consequently the electric motor will not work. It happened to me and I had to redo everything. One way to avoid this error is to glue the shaft to the chassis while the panel points to the ceiling and let it rest until it dries out.

Step 9: Place the Wheels on the Chassis

Each wheel has its axis tip. Glue each to its corresponding wheel. Slide the axle inside the hole created for this purpose and glue each wheel to its position. It is important that the axle slide very smoothly and with little friction, allowing the wheels to spin freely.

Congratulations, with this step you must have completed the construction process of this toy car. The only remaining step will be to prove it under the sunlight or with the method of the light bulb that I previously exposed.

Step 10: My Conclusions

I have interacted with this toy for several days and I am able to present a series of ideas about it. First of all, I found fascinating how simple is to make it.
I concluded it is possible to use the real car wheel spaces to generate electricity. As far as I have seen, I do not believe that the rotation has a negative influence on the electrical performance of the solar panel. I must admit that committing a small solar panel to the direct propulsion of a regular sized car still seems like an utopia and I do not think that at the moment it is a practical practice beyond this toy. However, the wheel panels can be used to recharge cars' batteries and perhaps others may come up with new ideas derived from this simple model. Hopefully, we will see cars totally covered by solar panels even ON WHEELS in the near future. :).