You really should learn a bit about polycarbonate - better known as Lexan (that's the Sabic trademark for PC). It's extremely durable, very shatter resistant, highly UV resistant, and generally THE choice for fighter aircraft canopies (which have just a little bit of UV exposure). Snell itself says there are many polycarbonate, Snell-rated helmets on the market.
Additionally, all Shoei shields (as well as pretty much everyone else's shields) are polycarbonate. In testing, polycarbonate helmets tend to transmit less energy into the brain, because it flexes better than fiberglass/carbon fiber. It's a great material, great for impact resistance, stable, and fairly lightweight.
You could easily plug your washer into the car for the necessary short burst of juice, and then let the car charge back up from the sun.
But how do I get my car down my stairs? The stairwell to the basement is too small...