Abstract
There is no doubt that the determination of a smart charging-discharging pattern can be very effective in increasing the cost-effectiveness and overall energy efficiency of an energy storage system. For finding the optimal operation strategy of the energy storage unit of a renewable power plant, the electricity spot price, the forecast data of energy availability, and the regulations of the local power market should all be taken into account. In addition to these economic considerations, the effect of deviation from the nominal load (partial-load operation) on the performance of the energy storage system is a critical parameter that directly affects the optimal operation pattern of the system in real-life energy markets. In this study, the effects of partial-load work of a low-temperature compressed air energy storage system on its overall performance are investigated thermodynamically employing real performance maps of all the components of the system. The results of the study indicate that the energy storage system needs to operate around nominal design conditions if it is expected to perform efficiently. The round-trip efficiency of the unit approaches 68% at a nominal load while it offers the low efficiencies of 52% and 28% if working at 50% and 10% loads, respectively. (C) 2020 Elsevier Ltd. All rights reserved.