Solar-Powered Vehicles

A young reader asks me about building a car powered by nothing but sunlight.

I happen to be very friendly with the first guy on the West Coast of the U.S. (Wally Rippel) to do exactly that, at least at a working scale.  In 1968, he headed up the team at Cal Tech that raced cross-country against MIT with solar-powered cars.

Of course, the issue they faced is the limited power per square meter that we receive from the sun, about 1000 Watts (one horsepower and change). Thus you either need a heck of a lot of area for your solar panels or you need a really light vehicle (of course, their design incorporated both). In actual fact however, the latter idea doesn’t contribute much; even if the car itself weighed a pound, when a 150-pound man got in and sat down, it would be a 151-pound vehicle, which would hardly budge, even if it had two or three square meters of PV on its roof, like some of the Priuses that do this more to promote the existence of solar energy than any real payback.  The average ride-on lawn mower has about six times that much horsepower.

Of more practicality is building extremely light airplanes whose wings are made of PV; since planes need large wings anyway, this really isn’t a terrible idea. In fact, it was one of the most significant contributions of the late Dr. Paul MacCready (pictured above).