New definition of levelized cost of energy storage and its application to reversible solid oxide fuel-cell

Abstract

Renewable energy installation capacity has rapidly increased in recent years. Subsequently, developing and commercializing large energy storage systems (ESSs) has become an important research objective. To evaluate development and compare between different ESSs, levelized cost of energy storage (LCOES) has been used. However, current LCOES often includes cost of electricity production in total investment, and neglects off-design characteristic of ESSs. Therefore, we proposed a new definition for the LCOES (LCOES2) to resolve these problems. An ESS using RSOFC coupled with waste steam was investigated for ESS efficiency characterization. The proposed ESSs and LCOES calculations were applied to South Korea case. The hourly average solar power data for each month was used. Hydrogen production and consumption were matched for sizing ESS and estimating electricity demand profile. The results show that, conventional LCOES, which considers charging electricity cost, overestimated the cost by 7.7% and 14.8% compared to the LCOES2, at RSOFC stack cost of $700/kW and $225/kW, respectively. The constant part-load efficiency model resulted in lower LCOES values, by up to 6.3%, due to higher overall round-trip efficiency. The new LCOES definition, considering variable part-load efficiency, was proved to be an efficiency-sensitive and reliable cost indicator.