While I’m on the subject of solar power, let’s look at the possibility of solar powered cars.  From yesterday, we know we can get one kilowatt per square meter.  A typical car is about 15 feet long and about 7 feet wide, or about 10 square meters.  So on a sunny day I can expect 10 kW to be hitting the surface of my car.  Even assuming those fictional 100% efficient solar cells, we’re only talking 13.5 horsepower (which, incidentally, is the power rating on my riding lawn mower).  A figure of 4 horsepower, maximum, is more reasonable, and even that’s probably on the high side.  But reasonable performance for a practical car requires about 20 hp to be delivered to the drive train.  There simply isn’t enough sunlight hitting the car, even at 100% efficiency, to power a useful car, even if the solar cells could recharge batteries while the car is parked.  See this web site for some ideas on the numbers, or do a Google search on “solar car” and see what the universities are doing.