How Close Are We To Automotive Solar Power?

Last week, the Japanese publication Nikkei reported that the new Prius will incorporate solar panels to help charge the vehicle's auxiliary battery. Toyota would not confirm or deny the Nikkei report, but adding solar collectors to a vehicle isn't a new idea. After all, the North American Solar Challenge, which started on Sunday and ends on July 22, pits solar powered vehicles against each other in an international road race. Entries come from universities, and must not have more than 6 square meters of solar collection area on the vehicle. The race covers thousands of miles, so solar power can indeed power a vehicle. (Interestingly, this year's race is sponsored by Toyota.)

Technology Review has an in-depth article on the state of solar power integration into vehicles. According to the article, several companies already offer solar roof kits for vehicles, and the National Renewable Energy Laboratory in Golden, CO., has put these kits to the test. Their conclusion? Solar energy is more hype than help, but could be used in recharging automotive batteries.

A better approach, say the researchers from NREL, is to use solar energy to operate stationary rechargers. The main problem with rooftop solar panels is that they can't easily be oriented to the sun, a necessity for highly efficient solar collection. In tests, the panels were able to store about 165 watts of energy, not nearly enough to power the vehicle, and only enough to increase the efficiency of the car by a modest few percent.

According to the Nikkei story, the solar array will be used to charge a lead-acid auxiliary battery that will power the vehicle's air conditioner and a few other accessories. In the long term, however, in the absence of significant developments in solar cell technology, the inability to orient solar panels to achieve the best efficiency will limit the use of solar cells in vehicles.

Source: Technology Review
Photo: Stefano Paltera / North American Solar Challenge