solar panels, at best, convert what, 12-15% of the available energy into electricity? And any internal combustion engine will outdo an electric car in the realm of range and refueling (except Honda's FCX Clarity, a stunning vehicle if you live in California near a hydrogen refueling station) And to increase a battery powered vehicle's range, you have to increase its weight substantially.
The best happy medium? I think a diesel hybrid. But instead of adding a battery large enough to power the vehicle several miles on electric power alone, add a smaller battery which allows easy restart from the stoplights but is not so heavy to shoot itself in the foot with a heavy payload. Plain ole diesel cars can get crazy mileage and can run on biodiesel, or even veggie oil when using a dual fuel setup.
However, the promises of more efficient gas powered engines are coming true. The direct injection gas engines are showing good promise, and there is the diesotto engine being designed by mercedes
Mercedes-Benz unveils DiesOtto - the “future of the gasoline engine”
It basically says it takes a 1.8 L inline 4 cylinder engine with 238 hp and 295 ft/lbs torque and puts it in a mercedes s-class which weighs nearly 4500 lbs and a Cd of .26 to .28. Depsite all this, it still gets 40 mpg- in a gas driven luxury car.
The Honda FCX Clarity might be an awesome car, but this Diesotto engine is hard to ignore.