[BigV]

I didn't conceive of this expression, but I can't attribute it properly as I've forgotten where I read it (somewhere in the whole biomass--xyz--hydrogen fuel cell cycle blah blah blah) but ... But the author said that hydrogen isn't a fuel source, it's a transmission method.

His point was that (it's coming back to me now...) hydrogen as a fuel does indeed make only water as the "exhaust", so NO carbon is emitted. At the point of combustion. But creating that tankful of hydrogen, transporting it to the consumer, these activities and more are decidedly NOT carbon neutral, let alone carbon FREE processes. Come to think about it, "carbon neutral" is about as precise as "lower taxes". I should probably not get started. Anyhow. Anyhow.

The most efficient method of storing that surplus solar-->electricity might be batteries. Might be hydrogen. Might be gravity. Might be heat. I don't know. Yet.

The other thought your comments sparked is that transmission methods for the energy to be had is another critical, though less sexay than energy sources discussions. Oil and gasoline are easily transportable, easily storable. Huh, seems this is just an extension of the earlier thought. Transmission, transmission. Places where solar energy's advantages are most abundant, like deserts, the very nature of those advantages means that the consumers of that energy are not there. We have fewer people living in the desert than in the cities. Even mature energy technologies have a crucial transmission element in them. Witness the current debate in this country over the proposal to build a very (very very) long pipeline from Canada to the Gulf of Mexico. Why? Oil is in Alberta, refineries are in Texas.