Comparison with Carnot battery of an alternate thermal electricity storage charged by concentrated photovoltaic thermal system and resistance heater

Abstract

In Carnot Batteries (pumped thermal electricity storage), which is known as a low-cost electricity storage method, electrical energy is stored as thermal energy and then converted back into electrical energy using a heat pump and a heat engine, respectively. In the studies carried out to date, different heat source scenarios, heat storage methods, and methods to improve heat pump and heat engine cycles have been applied to increase efficiency and reduce the cost of the Carnot Battery. This study's novelty was using a concentrated photovoltaic thermal system and resistance heaters instead of a heat pump for the charge cycle in thermal electricity storage. This novel thermal electricity storage design aimed to reduce the levelized cost of storage of the system by eliminating the need for a heat pump and reducing the volume of the water storage tank. First, parametric analyses were performed for the specific variables of both energy storage systems. Afterward, the Carnot Battery and the proposed system were compared for the same electricity storage capacity. For charge/discharge times ranging from 4 h to 8 h and electricity storage capacities ranging from 0.5 MW to 2 MW, a 31.8 % to 58 % increase in round-trip efficiency and a 7.13 % to 20.67 % decrease in levelized cost of energy storage were achieved with the novel design.