This direct conversion enables solar energy to be stored in the form of the heat of combustion of hydrogen fuel. It competes with traditional solar-PC cells coupled to electrolysis to make H2 and O2, and is a welcome addition to an array of approaches to store solar energy, besides thermal energy storage, pumped water, compressed air, etc. It remains to be seen how the economics will compare. The MIT researchers claim that theirs is a simple, inexpensive, room-temperature process, highly efficient process for storing solar energy.  Will the cobalt- and platinum-based catalysts be available to low enough cost? More engineering work needs to be done to make the new scientific discovery compatible with existing photovoltaic systems, but Nocera said he is confident that such systems will become a reality.

    James Barber, a leader in the study of photosynthesis who was not involved in this research, called the discovery by Nocera and Kanan a "giant leap" toward generating clean, carbon-free energy on a massive scale.

    "This is a major discovery with enormous implications for the future prosperity of humankind," said Barber, the Ernst Chain Professor of Biochemistry at Imperial College London.

    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. Electricity-by-wire from a central source could be a thing of the past.

    The project is part of the MIT Energy Initiative, a program designed to help transform the global energy system to meet the needs of the future and to help build a bridge to that future by improving today's energy systems. MITEI Director Ernest Moniz, Cecil and Ida Green Professor of Physics and Engineering Systems, noted that "this discovery in the Nocera lab demonstrates that moving up the transformation of our energy supply system to one based on renewables will depend heavily on frontier basic science."

    This project was funded by the National Science Foundation and by the Chesonis Family Foundation, which gave MIT $10 million this spring to launch the Solar Revolution Project, with a goal to make the large scale deployment of solar energy within 10 years.