Thermo-economic analysis of the pumped thermal energy storage with thermal integration in different application scenarios

Abstract

Pumped thermal energy storage (PTES) refers to a promising electricity storage technology that converts electricity into heat using the heat pump for cheaper storage, and then converts it back into electricity through a heat engine. The integration of an additional low-grade heat source can increase the coefficient of performance (COP) of the heat pump and thus significantly improve the storage efficiency. To evaluate the economic impact of different heat sources including waste heat, solar, or district heating network, this paper constructs the thermodynamic and economic model of thermally integrated PTES (TI-PTES), evaluates the round-trip efficiency and storage cost in five typical scenarios, and explores the effects of key system parameters (storage temperature, temperature difference, component efficiency) and heat source conditions (flow rate, temperature). Results indicate that the storage efficiency competes with the storage cost and capacity for a fixed heat source condition. As the power-to-power efficiency increases from 50% to 120%, the cost could increase by 47%, while the storage capacity could decrease from 1544 kW to 163 kW with a heat source flow rate of 50 kg·s−1. Detailed parameter analysis indicates that a higher heat source flow rate/temperature leads to higher component efficiency. A smaller pinch point temperature difference results in higher efficiency or lower costs. In particular, the energy storage cost is more sensitive to the turbine's efficiency than that of compressor, so it is necessary to prioritize improving the turbine. In terms of typical heat source scenarios, TI-PTES is more suitable to couple with waste heat rather than district heating network or solar thermal scenarios, resulting in a minimum Levelized cost of storage (LCOS) of 0.23 $·kWh−1.