Photochemical Aspects of Solar Energy Conversion and Storage

Abstract

Most of the current and proposed applications of solar energy involve its conversion to heat for space and water heating or to drive a Carnot engine to produce mechanical work or electricity. There are, however, some applications of solar energy which involve its conversion directly into electricity or to be stored as chemical energy without any thermal step in the process. These applications are quantum processes in that solar photons are employed to drive photophysical and photochemical processes. In this article, I will define qualitatively and quantitatively the thermodynamic and kinetic limits on the photochemical conversion and storage of solar energy as it is received on the earth's surface, evaluate a number of possible reactions with particular emphasis on the generation of solar fuels such as hydrogen from water and the generation of electricity. A. General Requirements on the Photochemical Reaction Many authors have considered the general requirements for useful