Figure 1 Air-conditioning system. OPTIMAL OPERATION FOR HVAC SYSTEM WITH SEASONAL UNDERGROUND THERMAL STORAGE SYSTEM

The present paper proposes an optimal operational strategy of an actual HVAC system with a seasonal underground thermal storage system using simulation. The simulation is a powerful tool for the system because it is difficult to try various operational methods experimentally in the actual system due to the long heat transfer time in the underground. This paper develops the whole system simulation by connecting an underground thermal model, which can simulate the heat exchange between the ground and the pipes buried in the foundation piles, and the models of mechanical components in the air-conditioning system. The optimum operational strategy found using simulation, which is to minimize the energy consumption of the whole system, can save the energy consumption by approximately 30 % and improve system COP from 3.02 to 5.04 compared with the values of the present operational method