A comparative study on the heat loss of rock cavern type and above-ground type thermal energy storage systems

Abstract

A large-scale high-temperature rock cavern thermal energy storage (CTES) system was numerically modeled, and the heat loss characteristics were analyzed using a commercial code, FLAC3D. As a part of a feasibility study on the storage efficiency of a rock cavern, the operations of the rock cavern type and the above-ground type thermal energy storage systems were simulated for a period of ten consecutive years; the dominant heat transfer mechanism was assumed to be conduction into rock mass for the former and convection in the atmosphere for the latter. The comparison results indicated that the amount of cumulative heat loss in the rock cavern storage over a period of ten-year operation was 69.2% of that in the above-ground storage because of rock heating and thus a reduction in the thermal gradient between the surrounding rock and the storage medium. In terms of long-period operation, the rate of heat loss from the rock cavern type TES was determined to be less sensitive to the performance of thermal insulators than that from the above-ground type TES.