Solar panels on cars to charge traction battery???

[snoltor]

I've noticed that many of you are long time devotees of EVs, and that several of you are engineers. So I figured you might have an answer for my question: Why currently available EVs don't include solar panels to charge the traction battery? I have a Prius with a fairly large solar panel on the roof, so price isn't that big of an huge issue, but as you all probably know the Prius solar panel runs a fan to keep the car cool when it's sitting in the sun on hot days (as an aside I've tested the temp inside the car on sunny 100+ days and the solar fan cools the interior temp of the car by up to 20 degrees F). Main point, the Prius solar panel does not charge the traction battery. I'd noticed that some models of the Leaf have a solar panel, but then read that it charges the auxiliary battery, not the traction battery. You can imagine cars sitting in the sun all day taking in all those free photons to charge the traction battery.... seems ideal. So what gives? Too costly to put enough panels on the car to get enough charge? Would a solar panel not provide enough juice to make it worth the extra cost? Are there technical issues that prevent this from happening, or is it just a matter of dollars and cents?

 

[TonyWilliams]

Weight, cost, performance, etc.

If you could get a few hundreds watts up there, how much would you pay? It wouldn't even charge the car at ONE mile per hour of charging.

 

[snoltor]

10-4

Weight, cost, performance, etc.

If you could get a few hundreds watts up there, how much would you pay? It wouldn't even charge the car at ONE mile per hour of charging.

 

[occ]

Main reason: Not enough area. The amount of energy you get does not justify the cost.

Roof space in a typical car is no more than 1 1/2 panels worth AT MOST. A panel is ~230watts, so at most you get 345watts max. Usually for solar rooftops, the calc is 4.4hr * system rated wattage, so for our hypothetical best case, 4.4*345 = 1.5kwh or 5-6 miles. 4.4hr is how much you would expect, on yearly average, of direct sunlight in a day in Southern Cal. 7hr may be max for Arizona, for example. This is optimum tilt and placement of a stationary panel (usually south). In a car, don't expect even 1/2 that, or 3 miles per day, IF your car outdoors all day, every day, all year.

I've seen est. of panels on a prius roof for ~$5-8K. At 1.5kwh/day = 547kwh/yr or around $87/year payback vs. charging from your house....~50-100yr payback...that is if your car is always in the sun at optimum angle and placement.

Rough calc above.

 

[Dsinned]

The Fisker Karma tried this and we all know what happen to that company!

 

[cwerdna]

We had some discussion of this on MNL at http://www.mynissanleaf.com/viewtopic.php?f=27&t=6316.

 

[snoltor]

Thanks

We had some discussion of this on MNL at http://www.mynissanleaf.com/viewtopic.php?f=27&t=6316.

 

[snoltor]

To further answer my question from 2 months ago, we'd need the wingspan of a 747 to put enough solar panels on the car to get it crawling down the highway:

http://www.nytimes.com/reuters/2013/07/06/us/06reuters-solar-plane-usa.html?hp

 

[ufojoe]

The Fisker Karma tried this and we all know what happen to that company!

The Karma did not do that, the Karma's panel works the same as the Prius panel, it cools the inside of the car on hot days........It was NEVER intended to provide power to the traction motors....

 

[snoltor]

You probably saw this already, but next week at the CES in Las Vegas Ford says they'll show off a new CMAX Energi with 1.5 square meters of solar panels on the roof and a lens that will concentrate the suns rays to provide enough photons to charge Ford's 7 kWh battery with 4 hours of sunshine. Lens sold separately:

http://www.autoblog.com/2014/01/02/ford-c-max-solar-energi-concept-ces-official-video/