Reports of new developments in the area of solar power are an almost daily event here at Gizmag. The main focus of research seems to be on improving the efficiency of solar cells, but others are working at developing an inexpensive method of locally storing the energy generated by solar systems. Because society relies on a continuous energy supply and solar energy is diurnal, storage systems are integral to what some see as an inevitable move towards the era of “personalized solar energy”, in which the focus of electricity production shifts from huge central generating stations to individuals in their own homes and communities.

A new paper by Massachusetts Institute of Technology (MIT) professor Daniel Nocera describes the development of a practical, inexpensive storage system for achieving personalized solar energy. At its heart is an innovative catalyst that splits water molecules into oxygen and hydrogen that become fuel for producing electricity in a fuel cell. The new oxygen-evolving catalyst works like photosynthesis, the method plants use to make energy, producing clean energy from sunlight and water.

Nocera says that low-energy densities characterize most current methods of solar storage, including batteries. Consequently they present formidable challenges for large-scale solar personalized energy implementation. Though considerable efforts are currently being devoted to battery development, most advances have little to do with the energy density, but rather they are concerned with the power density (i.e., the rate at which charge can flow in and out of the battery) and lifetime. Energy densities of batteries are not only low (~0.1−0.5 MJ/kg), but there is little room for improvement because the electron is stored at a metal center of an inorganic network juxtaposed to an electrolyte.

However, because the energy density of liquid fuels (~50 MJ/kg) is greater than or equal to 100 times larger than the best of the current methods of solar storage, Nocera’s approach of using the solar energy to produce fuel for a fuel cell could be the key to offering affordable personalized solar energy in the not-too-distant future. Nocera also sees his solar storage solution as being a great leveler between the developed and developing world.

"Because energy use scales with wealth, point-of-use solar energy will put individuals, in the smallest village in the nonlegacy world and in the largest city of the legacy world, on a more level playing field," states the report entitled "Chemistry of Personalized Solar Energy", which appears in the American Chemical Society’s journal Inorganic Chemistry.