Most of the comments seem to be skeptical of the amount of value adding the panels can bring, but Canadian engineer Steve Lapp can provide actual data since he modified his 2001 Prius back in 2005 to include solar panels on the roof. His initial three panel system generated around 270W, but he was hoping to boost that to 360W with the addition of a fourth panel.

Air Conditioning?

The reports from the Nikkei paper suggest that Toyota’s intention here is to be able to help run the A/C in the car using solar power, but given Steve’s data above, they’ll only be able to cover 10%-15% of the power needs of an air conditioning unit.

Perhaps a better use would be to allow those solar panels to charge the batteries all day while the car sits out in the parking lot. Even more interesting though, the next generation Prius is also a plugin hybrid, so having an array of solar panels on the roof would allow all those parked cars to potentially feed solar energy back into the grid through a V2G scheme. A single 300W car might not make much difference, but imagine a parking lot or two of them all feeding into the grid during those peak sunshine hours when our power demand is at its maximum.

[Information about Steve Lapp's solar Prius, and photo via TreeHugger.]

Only one Toyota Prius was there, and despite being painted in RechargeIT.org colours and saying that it was a plugin hybrid, it was not actually plugged in. Furthermore, we couldn’t actually see any obvious place to plug it in (normally, the after market conversions have a small connector on the rear bumper).

Why a Plugin Hybrid?

So, why buy a brand new hybrid car like the Prius, which already has better fuel consumption figures than most of the cars on the roads in the US, and spend more money on an after-market plugin conversion? Well, Google’s dashboard for the RechargeIT project gives some idea of why:

So, 50% better gas mileage is a pretty good reason for the conversion, and the further reduction in the CO2 emissions is a bonus. But there must be more…

Taking it Further

Why is Google looking at this technology though? Their plans go beyond a 50% improvement in fuel economy for sure. Perhaps one of the most interesting aspects of what they’re doing is a joint project with PG&E (the electricity utility for much of northern California) to explore vehicle-to-grid technology. That’s an idea that uses the batteries in plugin hybrid cars to store electricity when there is plenty available, and feed it back into the grid when there is more demand than the grid can supply.

During the daytime electricity usage can peak as people switch on heating or cooling systems, and during those times many cars will be safely parked and plugged in ready to supply extra electricity. Any electricity that they supply back to the grid is paid for too, so the owner gets a nice little bonus for plugging in their car all day that goes beyond the mileage improvements.

The other time this technology might be useful is for those who have solar panels on their property. During the day, at least here in California, there is plenty of sunlight for generating electricity. At night though things change dramatically! To solve this, you can either store the excess power generated during the day, or you can buy power from the grid overnight (and sell the excess during the day to them). Now, if you have a plugin hybrid, it can act as your storage unit while it is plugged in, help you get through the night without needing power from the grid and probably still have enough charge to get you to work in the morning without using much gas.

Want to Learn More?

Check out the RechargeIT site for lots of good information and links to other resources. Follow the Google team’s blog, and check out some of their video materials too, like this one explaining some of the benefits of plugin hybrids: