Effect of structure aspect ratio on the heat storage and extraction performance in an abandoned mine shaft

Abstract

Combining solar energy with water tank thermal storage is a highly promising method for achieving cross seasonal storage and utilization of low-grade energy. However, the existing research mainly focuses on ground water storage, few investigations are involved in using abandoned mine shaft for water storage and thermal energy storage. To fill this research gap, an actual abandoned coal mine located in Xuzhou city, is selected to make the performance analysis of water and heat storage. The basic design concept is given as follows: The thermal energy obtained from solar collectors is injected into the water body stored in mine shaft all the year round, and the stored thermal energy is extracted for heating for surrounding residential buildings in winter. On the basis of the actual auxiliary shaft of the selected abandoned mine, the thermal storage and heat extraction performance is numerically investigated by using COMSOL software. The effect of the length to diameter ratio of mine shaft on the thermal storage/extraction performance, during continuous thermal storage, natural cooling, and intermittent heat storage and cooling phases, are comprehensively investigated. With some valuable findings obtained, this study is significant to the scheme design and operation regulation on underground thermal energy storage in abandoned mines.