Conversion of solar energy is an important contemporary research field with the objective of substituting fossil and nuclear power sources. The author, research director at the prestigeous A.N. Frumkin Institute of Electrochemistry, Moscow, USSR, summarizes and critically discusses photoelectrochemical solar energy conversion and its storage. After an introduction to the fundamental physics of the semiconductor/electrolyte interface, technical cells for water electrolysis for the generation of fuel-hydrogen and the electrochemical conversion of other energy rich chemicals are explained. The application of new electrochemical, e.g. microheterogeneous semiconductors, liquid-junction solar cells and electrode coatings, are discussed. The book provides an overview of current processes and potential technical applications for students, researchers, and engineers.