Kyocera Corporation has announced its successful bid to supply solar panels for the new Toyota Prius. The Kyocera solar panels will power a ventilation system, an optional feature for the hybrid car. The system will drive the fans while the car is parked during the daytime; automatically moderating temperature rise inside of the vehicle even during hot seasons. Kyocera Solar Panels Chosen For Toyota Prius : Renewable Energy News More importantly The Prius rooftop solar array will generate up to 56 watts of power and each solar cell has a conversion efficiency of 16.5%.
Wow. 16.5%? That's high. I recall a few years ago when my sister worked for sunpower. She stated that they had the highest efficiency at the time, and I believe it was around 16%.
Yes, you can see why it doesn't recharge the traction battery. 56 watts for one hour is about one 'car' symbol on the energy display. Max drain on the traction battery is 27 kilowatts on the new car, so your hour's worth of charge would dissipate in about 7.5 seconds at this rate. 56W is reasonable for running a cooling fan, of course.
The Prius battery pack has 1,310 Watt hour of total energy. The target SOC is 60% and the "Full" is 80%. You really have 20% left to "top off". That comes out to 262 Watt hour. The solar panel can "top off" in 5 hours.
Our Sunpower rooftop panels are 18.5-ish % efficiency ... and they were 2nd from the highest efficiency that Sunpower had last October, when we picked them out for our system. Their mongo-top-of-the-line model was 22% efficiency ... can you imagine that? Those 3'-5' panels put out over 300 watts ! ! Of course you pay up the wazoo for 'em. Still, it'd be cool if Toyota would have opted for a more powerful panel ... had it not increased the cost a bunch.
... if the sun is parked directly overhead and the batteries have nearly perfect efficiency. In the real world, the sun is never parked, very few of us live in places where it is ever directly overhead, and the Prius has NiMH batteries which are far from this efficiency. But I still think it makes sense to send this to the traction battery. The problems Toyota mentioned earlier are certainly fixable, once they have time to deal with these issues.
After accounting for battery efficiency, and lack of an automatic sun tracker to keep the panels tilted towards the sun for maximum possible solar capture, the battery will not get fully topped off in a single day. For those who have any shade, any clouds, or live north of the Tropic of Cancer or south of the Tropic of Capricorn, the panel will collect even less.
Nowadays, single crystal solar cell can achieve 18-20%. Multi-crystal can achieve 2% lower, which is chealer to manufacture. 22% is not impossible given more sophisticate process, which also brings up cost as well. 16.5% is nothing to brag about. It is just average.
kyocera solar panels are glass like a window and could break. They are warrantied for 25 years,but the prius won't last that long. It's better to park in the shade. Solar panels should be at your home facing south at the correct angle to make the most of them. This is a cute idea but not a great one. Solar panels are about $4 a watt, higher for small ones like this, so this is about $200 bucks.
Can't see why the Prius wont last that long, I have a 41 year old Toyota Crown which drives and looks great. Apart from that point I agree with you 100%.
But here where it gets cold, just ask the Aussie, a solar panel to keep the 12 volt topped off and perhaps use any extra energy to warm the hybrid battery is a great idea. Wayne
To save HV battery life cycle is the second reason I've heard so far. The first one was the interference with the radio.
