Maybe someone ought to create a solar window shield to recharge the battery. Keeps the car cool, recharges the battery, and would be cheaper than the roof panel.

It can harvest as much electricity during the day as it has solar collector area and efficiency. Probably not all that much compared to the main motor's requirements. If the battery is full, it could also send power back into the grid. I'd think it might add something like 5% milage to the batteries storage.

I'd be more impressed if the whole car's body and window tinting was painted with amorphous cells.

While not especially useful, this can help get transport integrated photovoltaics ramped up to useful production levels and ease the rollout of mass production. Just like the first Prius was pretty awkward, but turned out to be a crucial test bed so Toyota could later own the market segment.

It looks like about half the surface area of the car in the picture is covered with panels. That would be about 4 square meters, given the Prius' dimensions. Averaged over the course of the day or year and over various locations on the surface of the Earth, we might expect such a Prius with 20% efficient panels to generate 200 watts of power. At more northerly lattitudes and at night or in winter it would be less; near the tropics, during the day, and during the summer, more. Regardless, on average this works out to about 5 kWh per day. That is about the work that is done by burning a half of a gallon of gasoline at the ~20-30% efficiency an internal combustion engine achieves.
In other words, far from just powering accessories like air conditioning, once we see a PHEV Prius, these solar panels could increase your electric driving range by 20-25 (since the Prius gets about 40-50 mpg) miles per day, partially recharging your battery while you are at work or the mall or the beach or whatever. Very cool possibilities.

I like this for less technical reasons. A good portion of urban dwellers and suburbanites alike park out on the street or in a parking lot all day. They have no access to "plug in" electricity in an ad hoc parking situation.

For a solid 6 or more hours each work day a vehicle can sit in the sun while the owner does his/her job and then take a trip home on a battery that is "topped off."

I would tend to agree that this is not very useful if it's only powering a portion of the air conditioning system. However, I would speculate that this is simply a test bed for integration of solar cells into the PHEV Prius that Toyota has added to it's product plan. As one comment already stated, a great many commuters out there, myself included, leave their vehicles sitting on streets or uncovered parking areas during the day. Even a small photovoltaic array can provide value-add to the owner by making use of otherwise wasted energy to top off the batteries after a morning commute. Thumbs up to Toyota for taking the initiative.

I like Doug's idea. Some versions of this story hint at the panels powering the A/C. But just as in houses, while the car is parked you can keep the car cool by reducing the solar gain. Automatically deployable all-round PV window shades would also increase security.

What I'd also like to see in cars is some kind of high- and low-level vents to allow warm air to escape the cabin (more secure than leaving the sunroof or windows open).

In a relatively good climate you're unlikely to get more than a few hours of sunshine worth harvesting per day on average because of weather, shade from buildings or vegetation, parked in an underground garage.

At 20% efficiency and a surface normal pointing up instead of sloping south I think you're going to get less than half a kWh in an average day.

There are people who have actual uses for solar cells, such as people who live in remote areas or want them for portable gadgets; there are people who have actual uses for silicon and limited indium supplies(people who manufacture displays for instance). Putting solar cells on a car is very close to just taking indium, energy and silicon production capacity down the toilet.

Make it half the weight, half the size, and covered in solar and it would make a lot more sense. the Prius is still a large car, much larger than what most people need.

I am a little disappointed. Solar panels are costly and to only run AC is kinda dumb why not charge a larger battery pack when it's parked. While there at it why not put cord out the side so we can use proven plug-in hybrid technology and get 100+MPG

you could cover the bonnet (american: hood)as well!

I cant see it being worth the added cost. Wouldnt it be much more efficient to install on the roof of a house? (assuming you have a suitable location). Between garages, parkades, trees etc I cant see what little it would generate being worth the thousands it would cost. The panels should be cheaper to install on your home and generate much more electricity. Hopefully which can then be transfered to a plugin hybrid or just for household use.

with solar powered mobile air conditioning all that toyota needs now is to use recycled CO2 (R744) as a refrigerant to be really environmentally friendly, thereby getting rid of R134a the Gobal Warming chemical that they currently use.

With better fuel efficiency, no GWP, no ODP R744 MACs are the perfect complement to solar panels. For more info go to www.R744.com

before anybody says that this is a dumb and useless idea, how bout you guys try driving with the windows up and no airconditioning. u will save approximately 10 to 15% more fuel and that my friend, means 10-15% LESS CO2 and other harmful particles in the air. If you have to use air conditioning, just keep the temperature in your home, office or car at no less than 24 degree Celsius and you will be doing the planet a big favour!

Even if 'all' this does is run the A/C, I think it is great! Imagine a few years into the future, the giant California Traffic Jam. All huge number of hybrids sitting bumper to bumper -- but with no emissions from any running engines, and yet everyone staying cool because the solar panels are keeping them cool.

Anything more that comes out of this is completely just gravy.

This is an option for the uneducated.

Far too many people ask for solar panels on an electric car thinking they will work. The power generated (max 1/2 hp) is not near enough for driving, but might keep the batteries up to charge and drive a few accessories, or let you make a weekly trip into town for groceries. It has minimal benefits.

Still, it does introduce more people to solar panels, and may encourage more people to invest in rooftop solar.

There's already an aftermarket company that makes a Prius solar panel. This site reported on it. It cost $9000 and gave the car a 10% boost in mileage. Of course, it doesn't charge while the car is off because of how the prius is wired (for safety reasons. I suspect a Toyota OEM version would charge while the car was off) so an official solar roof would be great. It might be lower milage, however, because the roof might use cheaper panels to keep the cost down.

What this would be really great on would be semi-trucks and their trailers. They're really long vehicles that are heavy on the accessories because the drivers often end up sleeping in the vehicles and they need AC or heat. A battery powered alternative to the current engine powered systems would probably save a ton of gas, and the trailers are long enough to have a ton of panels. It could also maintain a refrigerated trailer.

If you live in an area with a lot of shade, it's probably not for you. Your car is in the shade it, so it doesn't need the AC on right? My car is in the sun almost the entire time I'm not at home. Buildings over 4 stories tall are somewhat rare here. There aren't big trees everywhere here. There isn't covered parking everywhere.

If you get stuck at the train tracks on a hot sunny day, you'll be DREAMING of owning this. Oh, and bikes, motorcycles and scooters get stuck too. Even if it only takes the edge off the peak heat, it will be appreciated.

There's also nothing saying that they couldn't make it heat a LITTLE BIT in the winter time. Assuming your roof isn't covered with snow. They could make it heat in the winter, cool in the summer and in mild weather charge the main batteries. I know there's not tons of power to make use of...

Another option is a flexible sun shade the rolls out from the A-pillars and has PV cells inside the shade(s). It could also fold down like BIG sun visors...

Maybe they could make it fold out when you're parked? So, if you know it's going to be REALLY HOT and sunny, instead of pulling out a car cover or a sun shade you could unfold the roof over the hood or something. Sounds like it would be easier to do with a Mini Clubman than a Prius. Or you could open a second hood (would need lots of safety features) over the windsheild with a solar panel in it.

I've often thought of putting a roof rack on a car with a standard solar panel and trying to make it slightly more aerodynamic with fiberglass addons. Even the shade of the solar panel over the roof of the car would reduce the heat in the car on a sunny day.

I'm full of it today... Oh well. I'm looking forward to see Toyota's implementation.

Seems like a waste to invest solar into cars which have such a short life span. We should be investing into plug-in vehicles and more long lasting solar solutions like Solar Plug-in stations.

If those panels did nothing but keep the car cool when you parked in the sun I say it would be worth it.