Suddenly, Solar-Powered Cars Have a Bright(er) Future

Toyota tests plug-in Prius with its battery range provided by the sun.

byBertel Schmitt| UPDATED Jul 4, 2019 7:09 AM
Suddenly, Solar-Powered Cars Have a Bright(er) Future

Driving a car on pure and free sunshine mostly remained an (often abused) dream. Toyota thinks it could come a few steps closer to make the dream come true. In a test project in Japan, it will be shown how much range a solar roof can really add to the car.

Toyota, together with Sharp, and the public/private NEDO initiative, is putting a solar-cell festooned car on the roads of Toyota’s hometown Aichi province, as a pilot project with aim “to contribute to the creation of a new solar battery panel market, including the transport sector, and find solutions for energy and environmental issues,”  says Toyota's press release.

The solar Sharp-made solar cells are of the triple-junction compound type, sporting a conversion efficiency of 34 percent, and occasionally more. The car is a plug-in Prius PHV, the solar battery cell is a thin film of about 0.03 mm in thickness that can wrap around the curves of the car. The roof, the hood, the rear hatch door, and assorted other parts of the Prius now are adorned with solar cells.

A Prius PHV (sold in the U.S. as Prius Prime) would be the logical car for such a test, after all, it had a solar roof since 2017, at least in its Japanese and EU incarnations. Back then, I asked Shoichi Kaneko, Deputy Chief Engineer of the plug-in Prius, how far a sunny day in Tokyo will get me, and he said “around 5 kilometers.” That would be 3 additional miles, courtesy of the sun, and probably not worth the effort.

The new experimental version changes that in in big way. The solar module with an 860 Watts output enough to power a small microwave could add 44.5 km, or some 28 miles, to the pure-electric range of the car. What’s more, the new module provides solar power also when the car is driven, resulting in a total sun-provided pure battery range of 56.3 km, or 35 miles. All data as per Toyota’s press release, non-EPA, your solar mileage may differ.

 Considering that Toyota rates the pure electric range of a standard-issue Prius PHV at 68 km (42 miles), or 25 mile EPA, the bottom line of this experiment is that with those new solar cells, owners of a plug-in Prius would no longer have to plug in. On a fair-weather day, the juice would be provided by the sun, a big improvement especially for people who don’t have their own garage. The solar roof could morph from mostly a marketing-device to a helpful feature.