Technology stores solar energy

MIT researchers have discovered a simple, inexpensive and efficient process for storing solar energy. Solar power has traditionally been a daytime-only energy source, because storing extra solar energy for later use is prohibitively expensive and inefficient.

Inspired by the photosynthesis performed by plants, Daniel Nocera, the Henry Dreyfus Professor of Energy at MIT and senior author of a paper describing the work, and Matthew Kanan, a postdoctoral fellow in Nocera's lab, developed a process that will allow the sun's energy to be used to split water into hydrogen and oxygen gases. Later, the oxygen and hydrogen may be recombined inside a fuel cell, creating carbon-free electricity.

"Solar power has always been a limited, far-off solution. Now we can seriously think about solar power as unlimited and soon," Nocera said .

The key component in the process is the catalyst that produces oxygen gas from water; another catalyst produces valuable hydrogen gas.

The catalyst consists of cobalt metal, phosphate and an electrode, placed in water. When electricity runs through the electrode, the cobalt and phosphate form a thin film on the electrode and oxygen gas is produced.

Combined with another catalyst, such as platinum, that can produce hydrogen gas from water, the system can duplicate the water splitting reaction that occurs during photosynthesis.

The new catalyst works at room temperature, in neutral pH water, and it's easy to set up, according to Nocera.

Currently available electrolysers, which split water with electricity and are often used industrially, are not suited for artificial photosynthesis because they are very expensive and require a highly basic (non-benign) environment that has little to do with the conditions under which photosynthesis operates.

More engineering work needs to be done to integrate the new scientific discovery into existing photovoltaic systems, but Nocera said he is confident that such systems will become a reality.

Nocera hopes that within 10 years, homeowners will be able to power their homes in daylight through photovoltaic cells, while using excess solar energy to produce hydrogen and oxygen to power their own household fuel cell.