Organic Rankine Energy Storage (ORES) system

Abstract

In this work we introduce a novel energy storage system based on the Organic Rankine Cycle (ORC), which was named ORES (Organic Rankine Energy Storage). In this system, an organic fluid is pumped to a high pressure storage tank, which can later be used to generate electrical energy in a vapor turbine. Due to the importance of the working fluid in the ORES performance, in this publication we focus our attention on the presentation of a method to select the organic fluid that better fits the storage demand. We first limit this research scope for a set of five fluids based on commercial maturity, environmental and safety parameters and rank them in terms of energy storage cost, round-trip efficiency and overall system CAPEX. We estimate the round-trip efficiency and energy density considering the transient conditions in the storage tanks, for each fluid. Efficiency varied significantly between fluids, with maximum efficiency from 30% for R-152a, up to 72% for R-365mfc, while minimum investment cost is estimated to be around 4,000 USD per kWh. We concluded that the R-365mfc is the working fluid that presented the best performance in this basic topology of the ORES system.