Pumped Thermal Energy Storage and Bottoming System Part B: Sensitivity analysis and baseline performance

This paper (Part B) presents the results of sensitivity, baseline performance, and levelized cost of energy analyses of a recently proposed Pumped Thermal Energy Storage and Bottoming System (Bot-PTES) that uses ammonia as the working fluid. The system model was outlined in Part A of this two-part paper. This analysis focuses on the effects of hot thermal storage utilization, system pressure, and evaporator/condenser size on the system performance. It also presents the estimated performance for a proposed baseline Bot-PTES. Results of this analysis showed that all selected parameters had significant effects on efficiency, with the evaporator/condenser size having the largest effect over the selected ranges. Results for the baseline case showed stand-alone energy storage efficiencies between 51 and 66% for varying power levels and charge states, and a stand-alone bottoming efficiency of 24%. The resulting efficiencies for this case were low compared to competing technologies; however, the dual-functionality of the Bot-PTES enables it to have higher capacity factor, leading to $91-197/MWh levelized cost of energy compared to $262-284/MWh for batteries and $172-254/MWh for Compressed Air Energy Storage.