Thermo-economic parametric evaluation of different configurations of pumped thermal energy storage system using zeotropic fluids

Solar and wind energy are being explored to meet energy demand with low CO₂ emissions but their unstable operation has increased the attention toward the advancement of energy storage solutions. Researchers are being pushed to develop efficient models of Pumped Thermal Energy Storage (PTES) systems using various working fluids due to their long-lasting, low-cost, and fewer geographical constraints characteristics. But there is a paucity of research work on the PTES using zeotropic fluids. Zeotropic fluids can be a better option to improve the performance because they provide better temperature matching due to the temperature gliding effect thus, decreasing the irreversibility. The intension behind this investigation is to calculate and compare the thermos-economic performance parameters of different configuration of Rankine-PTES (subclass of Carnot Battery) using zeotropic fluids. The conclusion drawn in this study indicate a decreasing trend in the values of Levelized Cost of Storage (LCOS) when there is an increase in the value of Thermal Energy Storage (TES) system temperature. For the conditions specified in this investigation, least LCOS value presented is 0.43 $.(kWh)⁻¹ for R-B at 140 °C with corresponding round-trip efficiency value at 22.86 % while, maximum round-trip efficiency value presented is 27.10 % for RVCHP-RORC at 130 °C with corresponding a LCOS value at 0.50 $.(kWh)⁻¹. Effects of addition of regenerator to heat pump and heat engine are also investigated. Exergy analysis performed resulted in maximum exergy efficiency value of 27.09 % for RVCHP-RORC at 130 °C. Compressor and Turbine are the most expensive component of the Rankine-PTES for all configuration and hot water is the least expensive component making it cost effective storage medium. Effect of change in the concentration of components of zeotropic fluids on different parameters indicated that concentration of components of the zeotropic fluids effects the performance parameters significantly.