I've asked this question years ago (it got a mention at this very blog in 2007): couldn't you potentially get around the "unreliable base load" issue with large scale solar power (at least for plants built near a permanent water supply) by devoting a portion of the electricity being produced on a good sunny day to electrolysing water into hydrogen, storing it, and then burning it to get a gas turbine going for a rainy day?
Seems that it wasn't such a stupid idea after all:
If Germany is to meet its ambitious goals of getting a third of its electricity from renewable energy by 2020 and 80 percent by 2050, it must find a way to store huge quantities of electricity in order to make up for the intermittency of renewable energy.Some day my rightful place as CEO in charge of the Earth will be recognized by the planet, or at least aliens reading this blog who may have a better chance of installing me to that position. They need to get a move on, though.
Siemens says it has just the technology: electrolyzer plants, each the size of a large warehouse, that split water to make hydrogen gas. The hydrogen could be used when the wind isn't blowing to generate electricity in gas-fired power plants, or it could be used to fuel cars.
Producing hydrogen is an inefficient way to store energy—about two-thirds of the power is lost in the processes of making the hydrogen and using the hydrogen to generate electricity. But Siemens says it's the only storage option that can achieve the scale that's going to be needed in Germany.
Unlike conventional industrial electrolyzers, which need a fairly steady supply of power to efficiently split water, Siemens's new design is flexible enough to run on intermittent power from wind turbines. It's based on proton-exchange membrane technology similar to that used in fuel cells for cars, which can operate at widely different power levels. The electrolyzers can also temporarily operate at two to three times their rated power levels, which could be useful for accommodating surges in power on windy days.