Hydrogen production using fusion energy and thermochemical cycles

Abstract

Thermochemical cycles for the production of synthetic fuels would be especially suited for operation in conjunction with controlled thermonuclear fusion reactors because of very high temperature energy which such reactors could supply. Furthermore, fusion energy when developed is considered to be an inexhaustible supply of energy. Several high-temperature, two step thermochemical cycles for the production of hydrogen are examined. A thermodynamic analysis of the Fe 3O 4-FeO, CrCl 3-CrCl 2, and UCl 4-UCl 3 pairs reveals the feasibility of the processes. A more detailed process analysis is given for the Fe 3O 4-FeO system using steam as the heat transfer medium for decomposing the higher valent metal oxide for oxygen production, and hydrolyzing the lower oxide for hydrogen production. The steam could be heated to high temperatures by refractory materials absorbing the 14 MeV neutrons in the blanket region of a fusion reactor. Process heat transfer and recovery could be accomplished by regenerative reactors. Proposed operating conditions, the energy balance, and the energy efficiency of water decomposition process are presented. With a fusion blanket temperature of 2500 K, thermal efficiencies for hydrogen production (HHV) of 74.4% may be obtained.