“Cool” was the first word out of University of Minnesota aerospace engineering prof Jeff Hammer’s mouth when I told him Toyota’s Prius may soon come with its own rooftop solar generating system. But does it make sense? Not really, says Hammer: “The car is not always in the sun and there’s no surface facing the same direction all the time. The best thing to do is set [your solar panels] somewhere fixed that’s always in the sun and use the energy directly. That’s what the economics would tell you to do.”
That’s pretty damning coming from Hammer, whose job is to help turn solar energy into motive power. Well, sort of. Hammer is faculty advisor for an engineering team that put together one of 18 solar-powered vehicles competing in the 2008 North American Solar Challenge — a 2,400 mile race from Dallas to Calgary that got underway this weekend. His job is actually to help engineering students learn. “The main thing that solar car racing does to help automakers is that engineering students get a better education,” says Hammer. “We don’t think of building a solar car as a research activity or technology development activity.”
So what is Toyota doing offering solar panels that will be largely wasted? Showing once again that it is the master of green marketing. For the full story, see my full report — “Does Car-Mounted Solar Make Sense?” — at MIT’s TechReview.com today.
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Peter Fairley 
it might actually be desirable to have a solar car because you can increase the range of the car, especially if you’re willing to wait for it to recharge. Case in point: drive 2 hours along highway, then stop for a burger. While you’re eating your burger, your car battery is recharging. When you’re done with your burger, hop in your car and now you have a few more miles of range. This works best with plug-in hybrid configurations because they have deeper battery discharge parameters.
And remember, eat slowly and fully chew every bite!
If solar cell prices, the price of installing them on a car roof-top, and the environmental cost of producing the cells and associated materials go low enough, it might actually be worth it.
Meaty points to chew Alan. Cost reductions would certainly change the equation for roottop solar on cars. And for those that can afford today’s prices, it will indeed extend the vehicle’s EV range. My point is simply that one will get a much bigger bang from the same solar panel by immobilizing it atop your garage.