MIT develops way to bank solar energy at home

CAMBRIDGE, Massachusetts (Reuters) - A U.S. scientist has developed a new way of powering fuel cells that could make it practical for home owners to store solar energy and produce electricity to run lights and appliances at night.

A new catalyst produces the oxygen and hydrogen that fuel cells use to generate electricity, while using far less energy than current methods.

With this catalyst, users could rely on electricity produced by photovoltaic solar cells to power the process that produces the fuel, said the Massachusetts Institute of Technology professor who developed the new material.

"If you can only have energy when the sun is shining, you're in deep trouble. And that's why, in my opinion, photovoltaics haven't penetrated the market," Daniel Nocera, an MIT professor of energy, said in an interview at his Cambridge, Massachusetts, office. "If I could provide a storage mechanism, then I make energy 24/7 and then we can start talking about solar."

Solar has been growing as a power source in the United States -- last year the nation's solar capacity rose 45 percent to 750 megawatts. But it is still a tiny power source, producing enough energy to meet the needs of about 600,000 typical homes, and only while the sun is shining, according to data from the Solar Energy Industries Association.

Most U.S. homes with solar panels feed electricity into the power grid during the day, but have to draw back from the grid at night. Nocera said his development would allow homeowners to bank solar energy as hydrogen and oxygen, which a fuel cell could use to produce electricity when the sun was not shining.

"I can turn sunlight into a chemical fuel, now I can use photovoltaics at night," said Nocera, who explained the discovery in a paper written with Matthew Kanan published on Thursday in the journal Science.

Companies including United Technologies Corp produce fuel cells for use in industrial sites and on buses. Automakers including General Motors Corp and Honda Motor Co are testing small fleets of fuel-cell powered vehicles.

POTENTIAL FOR CLEAN ENERGY

Fuel cells are appealing because they produce electricity without generating the greenhouse gases associated with global climate change. But producing the hydrogen and oxygen they run on typically requires burning fossil fuels.

That has prompted researchers to look into cleaner ways of powering fuel cells. Another researcher working at Princeton University last year developed a way of using bacteria that feed on vinegar and waste water to generate hydrogen, with minimal electrical input.

James Barber, a biochemistry professor at London's Imperial College, said in a statement Nocera's work "opens up the door for developing new technologies for energy production, thus reducing our dependence on fossil fuels and addressing the global climate change problem."

Nocera's catalyst is made from cobalt, phosphate and an electrode that produces oxygen from water by using 90 percent less electricity than current methods, which use the costly metal platinum.

The system still relies on platinum to produce hydrogen -- the other element that makes up water.

"On the hydrogen side, platinum works well," Nocera said. "On the oxygen side ... it doesn't work well and you have to put way more energy in than needed to get the (oxygen) out."

Current methods of producing hydrogen and oxygen for fuel cells operate in a highly corrosive environment, Nocera said, meaning the entire reaction must be carried out in an expensive highly-engineered container.

But at MIT this week, the reaction was going on in an open glass container about the size of two shot glasses that researchers manipulated with their bare hands, with no heavy safety gloves or goggles.

"It's cheap, it's efficient, it's highly manufacturable, it's incredibly tolerant of impurity and it's from earth-abundant stuff," Nocera explained.

Nocera has not tried to construct a full-sized version of the system, but suggested that the technologies to bring this into a typical home could be ready in less than a decade.

The idea, which he has been working on for 25 years, came from reflecting on the way plants store the sun's energy.

"For the last six months, driving home, I've been looking at leaves, and saying, 'I own you guys now,'" Nocera said.

(Editing by Vicki Allen)