A solar car uses photovoltaic cells to transform energy from the sun to charge a battery or to power the vehicle directly. The land speed record for a solar car is 55.2 miles per hour, set on Jan. 7, 2011 by the Sunswift IV with its 55-pound battery removed. Reaching such speeds requires carefully planned aerodynamics and the sacrifice of comfort, according to HowStuffWorks.
One of the problems of solar vehicles is the fact that they only charge when the sun is shining. Nights and overcast days limit their ability to maintain the power needed to move the car. The addition of a battery adds weight, requiring more power to move the vehicle. However, the addition of a battery allows charging to take place, even when the owner parks the vehicle.
Photovoltaic cells are semiconductors made of silicon and other metals. When photons of light hit these materials, they excite the electrons to cause an energy flow. Silicon photovoltaic cells are approximately 15 percent efficient at the conversion. Other semiconductors offer greater efficiency and create more electricity, but are also more expensive.
In the course of the day, and as the Earth rotates around the sun, the optimal angle for the photovoltaic cells changes. Solar panels that are in a fixed position on the vehicle experience some periods when they are less efficient. A slight turn in the road robs the vehicle of power. Some solar cars address this issue with adjustable solar panels that move to maximize the power available.