Economic comparison of hydrogen production using sulfuric acid electrolysis and sulfur cycle water decomposition. Final report

An evaluation of the relative economics of hydrogen production using two advanced techniques was performed. The hydrogen production systems considered were the Westinghouse Sulfur Cycle Water Decomposition System and a water electrolysis system employing a sulfuric acid electrolyte. The former is a hybrid system in which hydrogen is produced in an electrolyzer which uses sulfur dioxide to depolarize the anode. The electrolyte is sulfuric acid. Development and demonstration efforts have shown that extremely low cell voltages can be achieved. The second system uses a similar sulfuric acid electrolyte technology in water electrolysis cells. The comparative technoeconomics of hydrogen produced by the hybrid Sulfur Cycle and by water electrolysis using a sulfuric acid electrolyte were determined by assessing the performance and economics of 380 million SCFD plants, each energized by a very high temperature nuclear reactor (VHTR). The evaluation concluded that the overall efficiencies of hydrogen production, for operating parameters that appear reasonable for both systems, are approximately 41% for the sulfuric acid electrolysis and 47% for the hybrid Sulfur Cycle. The economic evaluation of hydrogen production, based on a 1976 cost basis and assuming a developed technology for both hydrogen production systems and the VHTRs, indicated that the hybrid Sulfur Cycle could generate hydrogen for a total cost approximately 6 to 7% less than the cost from the sulfuric acid electrolysis plant.