Seasonal underground cold energy storage conception and its experimental study

A novel concept for energy use is presented, namely, the natural cold energy in the air in winter in cold climates is stored in ground and then extracted in summer directly for air conditioning. To verify this concept an experimental system for storing natural cold energy in ground was set up. The characteristics of using the ground to store natural cold energy in winter are investigated, and the operating modes of the system are discussed. During the whole cold storage experiment, the cold capacity stored in ground was 16 025·6 MJ and an energy efficiency ratio of 13·1 was gained. The temperatures of the soil in the cold storage wells (boreholes) and around them both decreased very markedly. These results show that in cold climates the concept of using ground to store the natural cold energy from the winter air is feasible.