"Otherwise, the power generated from solar panel goes to waste because it's not wired to the main battery."

Personally, I think that the way in which they are doing it is actually a good idea.  Or, if not strictly a "good idea", at the very least it's an innovative idea.  When you actually want the ventilation system running to cool down your car in the parking lot, it's probably because the sun is beating down on it.  And if the sun is beating down on it, then you've definitely got some juice coming out of your solar panel to actually run the ventilation system.  So it sounds like an idea which should reduce the load on your air conditioner (and your batteries, too) when you start up your car in mid-July.

With regards to the power being wasted because it's not going into the main battery, that gets to the heart of why we will never be driving solar-powered cars.  Think about it: you're charging your solar panels into a battery.  When the battery is not full, this is all well and good.  When the battery IS full, however, the solar panels are not going to be making themselves useful.  If you compare the kWh produced by the solar panels on a car with the kWh produced by the same panels in a stationary application, the stationary application will win because it doesn't have any periods where the energy produced is wasted.  Thus, using a solar panel on a car is not the best investment of your money on a strict "HOW CAN I SAVE ENERGY?" basis.  The use of solar panels on cars requires some other justification, such as the desire for an emergency-backup power source to charge your car, or the desire to lower the stress on your batteries.

In short, I agree that the panel on the Prius will waste power most of the time, but I think that putting solar panels on a car is a waste to begin with.

I was privileged to meet the 2010 Generation III Prius in January, at a private event held in Detroit.

The solar panel makes perfect sense, if you live somewhere (like Arizona, for instance) where the engine would otherwise have to run extensively to cool the car down. Since the solar panel runs the ventilation system, and pre-cools the car, the engine can run LESS, which SAVES GAS.

Also, the Gen III Prius is more comfortable, with more seat adjustments, telescoping steering adjustment, and more rear head room. The larger engine gets better fuel economy at highway speeds, which is the key to the increased MPG ratings.

While I did not have the opportunity to drive the car, I was able to crawl under the car, speak with the chief engineer, and also disassemble a few parts to get 'into the works' of the Gen III Prius.

Having important driving information now in the line-of-sight while driving is a major safety improvement! The Touch Tracer system is a unique innovation that makes an incredible amount of sense.

Now, we just wait for the plug-in version...