Limiting and achievable efficiencies for solar thermal hydrogen production

作者：Mallapragada Dharik S; Agrawal Rakesh^*

来源：International Journal of Hydrogen Energy, 2014, 39(1): 62-75.

DOI：10.1016/j.ijhydene.2013.10.075

• Membranes
• Thermochemical
• Electrolysis
• Water-splitting
• Concentrators

For reversible conversion, we derive theoretical Sun-to-H-2 (STH2) efficiencies for water-splitting processes harnessing solar energy as heat predominantly. At solar concentration ratios (C) of 2,000-10,000, the derived STH2 efficiency limits are 72.4-80.1%. For real processes with irreversibilities, we conceptualize direct and two-stage thermal water-splitting processes to estimate the achievable STH2 efficiency, the favorable operating conditions and design challenges that must be overcome. For direct thermal water-splitting, achievable STH2 efficiencies between 35 and 50% are possible at reaction temperatures of 1300-2000 K, and C = 2,000-10,000. This STH2 efficiency range is greater than the estimates of achievable values available for low and high temperature water electrolysis or single bandgap methods for generating H-2. The direct process requires efficient heat integration, and high temperature membranes for H-2(g) and O-2(9) separation to surpass reaction equilibrium limitations. Alternatively, for two-stage water-splitting using Fe3O4/FeO with solar heat recovered at 1600-2300 K, the calculated estimates for the achievable STH2 efficiency are 38-54%.

• 出版日期2014-1-2