Study on underground thermal characteristics by using digital national land information, and its application for energy utilization

摘要

This paper describes a method for evaluating characteristics on underground thermal properties and groundwater which are essential for designing system of underground thermal energy utilization. Firstly, the thermal systems using underground are classified into two categories; borehole system with indirect heat exchange and aquifer system with direct usage of underground water. These systems are also divided into thermal storage system and heat source/sink system. Secondly, the characteristics of underground in domestic area are analyzed by using Geographical Information System (GIS) and hydrogeological information. From the viewpoints of regulations on environmental protection, national parks for instance, and existence of the thermal energy demand, the percentage of areas eliminated from underground thermal energy utilization is 77% of a total land area of Japan. The percentage of areas limited to borehole thermal energy utilization is 17% of the applicable areas, while 74% of them is suitable for both borehole and aquifer. Finally, we estimate the thickness of aquifer and groundwater velocity in Sapporo. As a result, it is shown that most parts of area in Sapporo are suitable for Aquifer Thermal Energy Storage (ATES).