Geothermal heat pump application for space cooling in Kamphaengphet, Thailand

Abstract

Geothermal heat pump (GHP) system for heating and cooling purposes may be powerful alternative to reduce energy consumption and to contribute to environmental issues. Its intensive utilization may reduce emissions of CO2 and other toxic gases by replacing fossil fuel boiler into GHP. It may also greatly contribute to solve the problem of urban heat island (UHI) phenomenon. Combination of high performance of GHP and reduction of UHI result in a few percent of saving electricity for air conditioner in highly populated cities. GHP is generally not appropriate for space cooling in tropical regions. Since subsurface temperature is generally higher than year-average atmospheric temperature and atmospheric temperature is almost constant through a year in tropics, underground may not be appropriate as “cold heat-source”. However, according to the result of groundwater temperature survey in the Chao-Phraya plain, Thailand, subsurface temperature is lower than daytime atmospheric temperature for 5K or more over four months in several cities (Yasukawa et al., 2009, in this issue). Thus underground may be used as cold heatsource even in parts of tropical regions. A GHP system, borehole heat exchanger, heatpump and fan-coil, was installed for room cooling in Kamphaengphet, Thailand. Temperatures in the subsurface heat exchange tube and of secondary fluid, etc., were monitored during operation of the system. The results of temperature measurements and calculation of system performances are introduced in this paper. Capacity of the subsurface heat exchange system is presented in Tenma et al. (2009) in this issue. Although shallow subsurface temperature in Kamphaengphet is rather high and not quite suitable for a cooling system, the experimental results can be applied for other regions. Thus places more suitable for GHP system will be found as a result of this experiment and regional groundwater survey.