Energy storage is crucial for incorporating low-emissions, intermittent electricity generation into the power grid. Thoughtful global stewardship requires critical evaluation of different storage technology options using life-cycle assessment approaches such as net energy analysis. Here, we apply net energy analysis to evaluate a regenerative hydrogen fuel cell (RHFC) as an energy storage system. To compare RHFC's to other storage technologies, we use the energy stored on invested (ESOI) ratio: the ratio of energy stored in the device over its lifetime to the energy required to build and operate the device. Our sensitivity analysis shows that the ESOI ratio of a RHFC installation is strongly sensitive to the lifetimes of the electrolyzer and fuel cell stacks, and also to the ratio of hydrogen storage capacity to the fuel cell power. The ESOI ratio is only weakly sensitive to the efficiencies and embodied energies of the electrolyzer, hydrogen storage system and fuel cell. We first consider a reference scenario with existing technology performance characteristics (alkaline electrolyzer stack lifetime of 20,000 h; PEM fuel cell stack lifetime of 5,000 h). In this scenario, the ESOI ratio of an RHFC is similar to that of the best battery technology (Li-ion, ESOI = 10; as determined by Barnhart and Benson, Energy Env. Sci., 2013 , 6, 1083), though still lower than those of pumped hydro (ESOI = 240) and compressed air (ESOI = 210). We then illustrate the opportunities for further technology development to improve the net energy balance of RHFC's. For instance, if the lifetimes of the fuel cell and electrolyzer stacks can both be extended to 50,000 h, the RHFC would achieve an ESOI ratio of approximately 80, well above that of any battery technology.

Sustainability assessment of regenerative hydrogen fuel cells for energy storage

248th National Meeting (2014)

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