Underground thermal energy storage using horizontal heat exchanger for cooling of residential buildings in the Middle East

Norconsult AB has developed a solarhousing concept, a house designed for the warm climate in the Middle East andwith large quantities of solar panels installed. The cooling system for the house was designed in an earlier report, the purpose of this thesis is to investigate the possibility of short and long term storage of thermal energy via an underground energy storage volume. Two different designs of the storage and three different filling materials have been integrated into a model to simulate different cases. The first design consisted of pipes installed in the ground, without insulation. The second design consisted of an insulated concrete box installed to prevent thermal energy from the surrounding soil to flow towards the lower temperature regions within the storage. The three different filling materials were dry saudi sand, water saturated saudi sand and the filling material used by the client for energy storage in Sweden. The results from the simulations show that neither of the designs, regardless of the filling material, managed to extract enough thermal energy from the house to the ground to uphold the demands of indoor climate. One of the reasons for this was the decision not to install a heat pump between the house and the energy storage. The impact of the omitted heat pump was that the maximum temperature allowed to the fan coils is 11 °C. This low temperature refrigerant could be utilized far more efficiently by a heat pump