Storage for Solar & Wind Energy

Both solar and wind power-plants require a storage mechanism in order to deliver energy to the grid in a controllable manner that won't put stress on other energy producers.

It looks like the idea here is to produce Hydrogen & Oxygen via electrolysis when the output is strong (or demand is weak), and to use them to produce energy when the output is weak (or demand is strong). Less expensive materials (catalysts) will lower the cost of electrolysis but this, like any form of storage, still increases the cost of the wind or solar power-plants. It would be interesting to see how these costs compare to the cost of a modern nuclear plant.

Solar Energy, All Night Long - Forbes.com:
. . .
"Nocera's discovery--a cheap and easy way to store energy that he thinks will be used to change solar power into a mainstream energy source--will be published in the journal Science on Friday. 'This is the nirvana of what we've been talking about for years,' said Nocera, the Henry Dreyfus Professor of Energy at MIT. 'Solar power has always been a limited, far-off solution. Now we can seriously think about solar power as unlimited--and soon.'

Plants catch light and turn it into an electric current, then use that energy to excite catalysts that split water into hydrogen and oxygen during what is called photosynthesis' light cycle. The energy is then used during the dark cycle to allow the plant to build sugars used for growth and energy storage.

Nocera and Matthew Kanan, a postdoctoral fellow in Nocera's lab, focused on the water-splitting part of photosynthesis. They found cheap and simple catalysts that did a remarkably good job. They dissolved cobalt and phosphate in water and then zapped it with electricity through an electrode. The cobalt and phosphate form a thin-film catalyst around the electrode that then use electrons from the electrode to split the oxygen from water. The oxygen bubbles to the surface, leaving a proton behind.

A few inches away, another catalyst, platinum, helps that bare proton become hydrogen. (This second reaction is a well-known one, and not part of Nocera and Kanan's study.)

The hydrogen and oxygen, separated and on-hand, can be used to power a fuel cell whenever energy is needed.

"Once you put a photovoltaic on it," he says, "you've got an inorganic leaf."

Chemists, it turns out, are always worrying about the stability of their catalysts and end up doing backflips to try to synthesize materials that won't corrode. Photosynthesis, though, is so violently reactive that the catalysts involved break down every 30 minutes. The leaf has to constantly rebuild them. Maybe, thought Nocera, instead of fighting corrosion, he should work with it. "It's a bias a lot of scientists have. We want something to be structurally stable. But all it has to be is functionally stable."

This thinking led Nocera to try his cobalt-phosphate mixture. He knew it wouldn't hold together, but he thought it might still work. Sure enough, Nocera's catalyst breaks down whenever the electricity is cut, but it assembles itself again when electricity is reapplied.

Nocera's discovery is still a science experiment. It needs plenty of engineering before it can be a useful device. The cobalt and phosphate at the center of Nocera's work is cheap and plentiful, but the hydrogen reaction uses platinum, which is rare and expensive. The electrode needs to be improved so the oxygen-making process can speed up. And the system needs to be integrated into some kind of electricity-producing device, ideally powered by solar or wind on one end and a fuel cell on the other."

Also see this link, for pictures of the process etc.