Green Energy After Dark

One big problem of converting to solar generated electricity is what to do when the sun goes down. To ensure electrical current on the grid doesn’t sharply fall off, requires an industrial-scale electrical storage system to smooth out short term fluctuations. It’s a problem at the heart of realizing a renewable energy economy.

There’s an added urgency for storage systems when considering the California Public Utilities Commission recently mandated that retail sellers of electricity purchase 20 percent of their power from renewable sources by 2010, and the New York Public Service Commission is mandating 24 percent by 2013.

The quest for a large-scale electrical storage system is a complex and challenging proposition. Being able to stockpile electricity for later use has been an area of active research projects for the U.S. Department of Energy Office of Basic Energy Sciences. There are six promising energy storage technology research areas being pursued: pumped hydropower, compressed air energy storage, batteries, flywheels, superconducting magnetic energy storage and electrochemical capacitors. Because of the wide range of applications, there’s no one storage technology that’s suitable to span the power requirements from the low end of hundreds of kilowatts to ten gigawatts.

This proposed compressed air storage solution
will store any surplus electricity from the grid.
(Photo: Argonne National Labs)

And there are several start ups like EEStor, AltairNano and A123 trying to crack open the problem with varied approaches for industrial scale storage device that connect to the grid.

What to do now in terms of storing energy?

Massachusetts Institute of Technology chemist Daniel Nocera and his postdoctoral student Matthew Kanan devised an innovative, low energy approach for extracting oxygen and hydrogen from water using small amounts of electricity, common chemicals and a room temperature glass of water. Removing these elements from water is no simple feat. It typically requires lots of energy and lots of maintenance to make it work.

The beauty of the MIT scientists’ discovery is the elegant simplicity of the science at work. The researchers announced their discovery recently in the journal Science.

It’s a given that oxygen and hydrogen are energy rich fuels. So it makes sense that some research efforts have focused on using solar electricity to spit water into those elements. That would generate an energy source, which could be stored long after the sun has set.

Here’s how it works.

To generate oxygen, the researchers had room temperature water and then mixed in cobalt and phosphates. In that mixture, they inserted a glass electrode that conducts electricity. When a current was applied to the mixture, a dark film formed on the electrode and tiny bubbles of oxygen started to appear. The two researchers analyzed the film on the electrode and determined that the cobalt-phosphate mixture was present.

Nocera and Kanan think this mixture acts as a catalyst to break water molecules apart and thus creating oxygen gas. What’s especially intriguing about the water splitting effort is that hydrogen nuclei are released during the process as protons and pick up electrons which allows them to convert back to hydrogen at a partner electrode. It’s this release of hydrogen which has tremendous potential for generating one of the most abundant and cleanest forms of energy known to man.

The MIT researchers also found evidence that the cobalt and phosphates catalyst mixture seems to regenerate itself. That bodes well for a far simpler system for oxygen extraction, but needs further experimentation to confirm.

The catch is there’s still a good deal of work to do. And it will take several years to scale the bench-top science research into industrial scale systems and test them. But the researchers believe they have the right stuff to help power a sustainable energy system, green and efficient for future generations.

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