Comment: If you're hunting for the best overall solution

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If you're hunting for the best overall solution

you should look into http://www.switch2hydrogen.com/h2.htm
Video on his first page.

This is by far the cheapest, lightest, smallest and safest way to store energy on-board a car. By 'condensing' hydrogen into the hydride mixture inside, you can store 400 miles worth of range in 4 small scuba sized tanks.

When full, these tanks are not under any pressure. They simply hold the volume of hydride but they're still made from strong and lightweight carbon fiber. If you destroy the tank, nothing happens. If you destroy it with something burning, like an incendiary round, the spilled powder will just glow like tiny embers as the heat harmlessly boils hydrogen slowly away.

When you want hydrogen out to use in an engine or a fuel cell, you simply turn on a small heater coil and boil some hydrogen out of it. These guys boil it out at around 4 PSI just to get it to flow out the hoses to the engine.

By using hydrogen instead of compressed air, you get a burnable fuel instead of just a pressure out. This means much less weight, size and cost for the same energy. This is why they get 400+ mile range while an air car only gets 150 or so.

Putting the stuff into the tank is virtually the same process as with an air tank. Energy (usually electricity) must be provided to some process and the result loses some amount. Air compression loses roughly 50% but hydrogen losses can be down to 30% (electrolysis). This means that hydrogen can be done with 2/3rds of the solar of the air car. Both can be stored en mass in a garage tank so low power solar can provide the initial energy.