Today, it is important to expand the use of untapped energies for tackling the climate change issues. The energy in the shallow ground is one of the most promising untapped energy sources. However, a geothermal heat pump (GHP) system is not well utilized in Japan, especially in the warm areas. In order to investigate the possibility to introduce the GHP systems in the warm areas of Japan, a comprehensive research was carried out choosing the Kumamoto Area, Kyushu, Japan, as the target area. In this study, a suitability map of GHP systems was developed applying a single ground heat exchanger model at several locations of the plain. The suitability map showed that the center of Kumamoto City, Suizenji, and Kikuyo Town were the good candidates of high performance of GHP systems. Moreover, the amount of CO2 reduction with the application of GHP systems was evaluated on the basis of the performance of the system predicted by the numerical model. From this result, the effect of about 80,000-ton CO2 reduction in a year was shown by introduction of GHP systems in Kumamoto area.
