Thermal exchange from Bangkok subsoil to household air conditioner

Abstract

The demand of energy is increasing at present, so the alternative way of energy management is to reduce energy consumption. Geothermal Heat Pump (GHP) has been widely used in many countries since the World War II to reduce electricity consumption. In Thailand, a systematic installation of GHP was first established in Bangkok. The objectives are to investigate analyze subsurface temperature in study area; to compare soil profiles of Bangkok with the study area and to compare energy saving between normal air-conditioner and GHP. The research work commences with drilling 2 boreholes with the length of about 50 meters. The high-quality PVC pipes were inserted into these holes. The pipes were connected and drilled with 100 meters length without any leakage. The Japanese – made GHP system was established at a small room in Parot Racha Building, Chulalongkorn University. The result displays that subsurface temperatures in a short – term measurement at the depths of 0 to 50 meters fall within the average range of about 29 to 30 °C. The result also shows that the inlet temperature flowing to the GHP is lower than the outlet temperature about at 1.5 °C. The result of the long – term measurement indicates that subsurface temperatures at depth of 1.5 to 8 meters are more constant (29 to 30°C) and lower than the outside air temperatures throughout the whole 2 years. The constant underground temperature condition is useful because the electricity consumption is greatly reduced. When GHP was adopted in the room along with the normal air-condition, it is found that electricity consumption can be reduced a little more than 30 %. Additionally, it is recognized that high humidity greatly decrease efficiency of GHP and increase electricity consumption. The study on subsurface geology of Bangkok reveals that the underground condition of thick sequences of un- to semi- consolidated sediments can be one of the parameters which affects the successful application of GHP.