Experimental study on heat exchange efficiency of rock bed heat storage system based on broken rock mass

Abstract

Energy storage system can significantly improve energy utilization by ”cutting peak and filling valley” for the development and use of renewable energy sources such as wind and solar energy. Although rock packed bed is one of the main forms of sensible heat storage, understanding the variation law of its permeability and heat exchange efficiency is critical to the construction of large-scale heat storage systems. In this paper, we used CO2 as the heat transfer fluid in a self-built experimental equipment to conduct heat injection and extraction experiments on broken rock packed beds with different grain compositions and injection pressures, and we studied the heat exchange efficiency and the variation law of heat storage in the rock bed during the heat injection and extraction process. The results show that: (1) with the heat injection, the permeability of the rock bed filling system decreases gradually; and (2) the rock grain composition has little effect on heat exchange efficiency but a large effect on permeability. The higher the permeability, the greater the heat storage of rock bed; (3) The higher the fluid injection pressure, the greater the heat exchange efficiency and the greater the heat storage of the rock bed. The research results can provide guidance for the economic operation of broken rock bed heat storage system.