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Solar cells on electric cars make cents
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Toyota Prius
Adding solar cells to any electric car will reduce the cost to operate the car and reduce consumption of oil. It can also make economic sense.
Toyota announced that they would be adding solar cells to their popular Prius electric hybrid. The intention is to use the solar cells to power the air conditioner. It would be better to have the solar cells recharge the battery, although a large enough battery for the plug-in Prius may have to wait until 2010.
Let’s assume that Toyota puts solar cells with 200 watts of power on the car. With 6 hours of charge time, the battery could gain 1.2 KW hours of power. That amounts to equivalent of about 1/10th gallon of gasoline. Assuming $4 per gallon for gasoline, that provides a payback of $0.40 per day or $146 per year. Assuming that the solar cells cost an extra $2,000 then the rate of return on the solar cells is 7.3%, and you are making a small contribution to cleaning up the environment. The solar cells may be eligible for a tax credit, which would make the rate of return higher.
Let’s say you use your Prius to commute to work 15 miles each way. Let’s also assume that you can charge the 1.2 KWh battery at home before you leave and that you travel slow enough to use the entire 1.2 KWh of power on the 15 mile trip to work. The car gets about 50 mpg so the battery could power 1/3 of the trip. On the trip to work you get 75 mpg. On the way home, the solar panels recharge the battery and you again get power for 1/3 of the trip. You get 75 mpg on the way home. You save 1/10th of a gallon of fuel. If you didn’t recharge at work you would burn 0.5 gallons netting 60 mpg.
Shorter trips with longer stays would produce higher gas mileage while longer trips would produce gas mileage closer to 50 mpg.
Solar cells on cars make more cents than solar cells on houses. On a house you are replacing utility power at a rate of 8 cents to 15 cents per KWh. Replacing gasoline for 40 cents (or higher) produces a greater economic return. The rate of return for putting solar cells on cars is great enough to justify demand without incentives, which should be good news for the solar cell manufacturers. This would be particularly true for solar companies that make very efficient solar cells as surface area on the car is limited.
