Conceptual Design of Ammonia-Based Energy Storage System: System Design and Time-Invariant Performance

Chemicals-based energy storage is promising for integrating intermittent renewables on the utility scale. High round-trip efficiency, low cost, and considerable flexibility are desirable. To this end, an ammonia-based energy storage system is proposed. It utilizes a pressurized reversible solid-oxide fuel cell for power conversion, coupled with external ammonia synthesis and decomposition processes and a steam power cycle. A coupled refrigeration cycle is utilized to recycle nitrogen completely. Pure oxygen, produced as a side-product in electrochemical water splitting, is used to drive the fuel cell. A first-principle process model extended by detailed cost calculation is used for process optimization. In this work, the performance of a 100 MW system under time-invariant operation is studied. The system can achieve a round-trip efficiency as high as 72%. The lowest levelized cost of delivered energy is obtained at 0.24 $kWh, which is comparable to that of pumped hydro and compressed air energy storage systems. (C) 2017 American Institute of Chemical Engineers AIChE J