Developments in the production of hydrogen by thermochemical water decomposition

Recent developments in hydrogen production by thermochemical water decomposition are reported, with an emphasis on hydrogen production from non-fossil energy sources such as nuclear and solar. Numerous developments have been made on sulphur-iodine, copper-chlorine and other thermochemical cycles. Efforts are described to lower the temperatures required in thermochemical cycles, so as to broaden the range of potential heat supplies, including developments in the copper-chlorine thermochemical cycle, which has significant potential due to its requirement for process heat at lower temperatures than most other thermochemical processes. The thermodynamic evaluation of thermochemical water decomposition processes is explained and illustrated by applying informative methodologies like exergy analysis, which can assist in improving efficiencies and identifying limiting efficiencies. Thermochemical water decomposition has several advantages relative to other hydrogen production processes that could make it a competitive future option for hydrogen production, which is a key component of a hydrogen economy. Recent developments, particularly using such non-fossil energy sources as nuclear and solar, suggest that thermochemical hydrogen production could become commercial, and help meet the anticipated future demand for hydrogen as an energy currency in the context of a hydrogen economy. Consequently, research is likely to continue to improve thermochemical water decomposition processes.