Abstract:

     Based on the investigation of the heat transfer of the energy diffusion and transport during the processes of the energy input, storage and extraction in the underground thermal energy storage(UTES) system, a new concept, the energy flux, was presented to evaluate the effect of the thermal energy storage. Through measuring the diffusion transport degree of storaged energy, the effect of energy flux in the UTES can be analyzed quantitatively, providing a measuring parameter and a basis for the heat diffusion control. Based on this, the energy fluxes of the underground heat exchanger group with different configurations and different multiborehole arrangements were studied to compare their difference on the energy flow intensity in the period of conserving energy stored in soil. The results show that the exchanger group configuration and the multiborehole arrangement determine the underground temperature distribution which plays an important role in the energy diffusion and transport during the processes of energy input, storage and extraction.

Key words: thermal energy engineering, underground thermal energy storage (UTES), energy flux, diffusion, transport