Exergy and Thermoeconomic Analyses of a Carnot Battery System Comprising an Air Heat Pump and Steam Turbine

In this study, exergy and thermoeconomic analyses were performed on a Carnot battery system (CBS) comprising an air heat pump and steam turbine. The Carnot battery technology employed in this study stored electricity as heat for 10 h during night-time, when electricity prices were low, and generated electricity for 10 h with power output of 500 MW during the day, when electricity prices were relatively high. The roundtrip efficiency and the energy density of the CBS were approximately 0.37, and 150.0 MJ/m(3), respectively. When the unit cost of electricity supplied to the heat pump system was approximately 23.0 USD/GJ, that of electricity produced by the steam turbine was approximately 70.8 USD/GJ. The thermoeconomic results indicate that the changes in electricity cost flow rate relative to the reference value can be used as an indicator to make purchasing, replacement, and research and development decisions for specific components of the CBS.