Problems with Solar Cars
Solar cars exist, and the notion of electric vehicles that run on free energy is appealing, but the realities of making solar cars work are harsh. Sunlight doesn't have enough energy to power a typical car, and is easily compromised by weather and time of day. Solar cars in 2011 cannot match traditional gas-powered vehicles for practicality, reliability or cost.
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Low Energy Density
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On a clear day, energy from sunlight comes to Earth at a density of about 1,000 watts per square meter of area . This means if you had a one square meter solar panel that worked at 100 percent efficiency, you could run a hair dryer with it. The engine in a typical car develops about 50 kilowatts of energy. Your perfect solar panel would have to measure 27 feet by 27 feet to produce this much power.
Low Efficiency
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Commercially-available solar cells that produce electricity from light do not have 100 percent efficiency, but instead top out at around 15 percent. To compensate for the reduction in energy due to low efficiency, you'd have to make your solar panel bigger. To make 50 kilowatts of energy, you would need a solar panel 85 feet by 85 feet.
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High Costs
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Though sunlight itself is free, the technology to collect it is not. Though coming down, the cost of electricity from solar cells is still expensive compared to other energy sources. Solar cars need a lot of costly technology, including light materials to keep weight down and batteries to store electricity. Competitions to build solar-powered cars subsidize the high costs of design by using student labor or by writing off the expenses of a company's engineering team. A solar car sold commercially would have to recoup those design costs in the price of the car, which would be very high.
Unreliable Sunlight
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The 1,000-watt-per-square-meter figure quoted above is the most energy you can get from sunlight. The least is zero. Cloudy weather, nighttime and passing shadows all reduce the amount of solar energy available. Solar cars can use batteries to store energy for use when the sun is absent, but batteries carry a heavy weight penalty.
Impractical Design
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In 2011 the kinds of solar cars that carry their own solar panels are limited to competition vehicles. Their bodies are low, flat and smoothly aerodynamic. They have barely enough room for a driver, who rides lying on his back. The cars have no bumpers, side-view mirrors or windshield wipers. Because they have to work with a very limited energy budget, their designs call for extreme efficiency, precluding many safety and convenience items found on regular cars.
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