Solar fuels: status and perspectives

Utilization of water as an inexhaustible supply of a fuel (hydrogen) was predicted over a century ago by Jules Verne in The Mysterious Island. Since the oil crisis of 1973, considerable progress has been made in the search for alternative energy supplies. Although the water splitting process to generate simultaneously hydrogen and oxygen has been demonstrated (albeit the process is inefficient) by utilization of light energy, the technology is not mature enough to seriously bring it to pilot-plant demonstration. Much fundamental research remains to be done. The present paper examines the present status and looks at the perspectives of the technological progress, particularly in the high temperature thermochemical and photochemical fields with emphasis in the utilization of solar quantum and thermal photons.