Harnessing the Sun When It Doesn't Shine

Daniel G. Nocera, the Henry Dreyfus Professor of Energy at the Massachusetts Institute of Technology, thinks the key to our energy future may be found in the cells of plants.

He is working on an “artificial photosynthesis” system that uses sunlight to generate hydrogen gas that, in turn, can be used to power a hydrogen cell.
The design, which approximates the energy-generating chemical reactions that happen naturally in plants, he says, helps overcome what is cited as the most nagging problem of solar energy: the inability to generate electricity when the sun is not shining.

Mr. Nocera recently agreed to answer some questions for Green Inc. on his research. Excerpts from that e-mail exchange follow.

Q: Critics of solar energy point often to the fact that solar panels can’t provide energy when the sun isn’t shining. How do your designs compensate for this problem?

A: When the sun is shining, we take some of the output from the PV system and feed it to a water-splitting electrolyzer to produce hydrogen and oxygen. Then we store the oxygen and hydrogen, either as a gas or by fixing it with carbon. Then, when the sun goes down, we can recombine the oxygen and hydrogen in a fuel cell in order to get the energy back out.

Q: By the looks of your designs, the home would become a sort of miniature solar power plant. What are the advantages and/or disadvantages to this type of decentralized power generation?

A: I only see advantages. The individual is in control of his own energy production. You can’t have a greater energy security. It is carbon neutral. And all people would be empowered — from the smallest village in the underdeveloped world, to the rural areas of the developed world. Of course, producing energy in a city this way does not seem as feasible to me. That is why you need both centralized (e.g., concentrated solar power delivered from a grid), and decentralized power.

New York Times