Impact of Efficiency Calculation Methods on the Adoption of Energy Storage Technologies

Abstract An essential parameter in the performance of energy storage systems is their round-trip efficiency. Batteries are the reigning energy storage option globally and, are believed to be the primary competition to green hydrogen energy storage in terms of system economics. For lithium-iron phosphate (LFP) batteries, two different round-trip efficiency calculation methods were observed i.e., constant efficiency and yearly repeating efficiency in existing literature and professional photovoltaic (PV) designing softwares respectively. Unfortunately, both do not follow the practical scenario. Therefore, a degradation trend shifting method was used to analyse the round-trip efficiency over 10 years of an LFP battery system associated with a 5MW solar PV plant. The primary performance simulation for this method was done using PVsyst. The calculated round-trip efficiencies and the investment cost for the storage systems were then used to calculate the levelized cost of storage (LCOS). The LCOS for the three efficiency trends in batteries was also compared with the LCOS of a green hydrogen energy storage to get an idea about how the differences in the relative system economics affects the perception of an energy storage system. The results indicate that for the constant efficiency and yearly repeating efficiency methods, the difference in the LCOS between batteries and green hydrogen is large. However, for the proposed trend shifting method, the LCOS after 10 years for batteries is slightly less than green hydrogen and after 20 years the LCOS for hydrogen and batteries is comparable.