Solar-Hydrogen Production Efficiency

If handled as a cryogenic liquid, about 12 kWh is required to liquefy each kilogram of H2 and about 1 kWh is needed to store and transport it, for a total of about 13 kWh, which is about 33% of the HHV of the liquid. In Table 1.46, some approximate data are provided on the costs and efficiencies of H2 processing steps. 

Equipment Efficiencies and Energy Costs of Hydrogen Production 

Process Step Energy Cost in (kWh/kg) Energy Used as a % of the HHV of H2 (39.3 kWh/kg) Equipment Efficiencies Partial List of Suppliers 

Electrolysis Theoretical 33 83 100% Proton Energy, Hgenerators , Hydrogenics Corp., H2Gen Innov., Teledyne 

Compression 4 7-16 84%-l-stage Ariel, CompAir, Dresser-Rand, Fluitron, Greenfield, 

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Higher efficiency, higher cost multijunction solar cells, such as the Ill-V materials systems capable of 20-40% PV conversitm efficiency are also commercially available. Using these materials, 14-28% STH would be achievable using PV-electrolysis. In today s market, however, such systems would be prohibitively expensive for any large-scale deployment. The 5-7% mark for lower cost amorphous silicon technology is a more appropriate near-term benchmark for practical solar hydrogen production. Alternative PEC-based schemes need to meet or exceed this benchmark to be viable. 

The goal of this research field is to produce hydrogen by usage of solar energy, the so-called solar hydrogen production. In order to utilize solar energy efficiently, it is indispensable to develop visible-light-driven photocatalysts [3]. 

Wang Y, Wu J, Zheng J, Jiang R, Xu R (2012) Np — doped ZnxCdl-xS photocatalysts from single-source precursors for efficient solar hydrogen production under visible light irradiation. Catal Sci Technol 2 581-588... 

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