地熱発電の現状と技術開発

抄録

Geothermal energy is a renewable energy which can contribute to reduce atmospheric emission of carbon dioxide (CO₂) by stable electric power generation and hot water supply for district heating. Recently, Japanese government has strongly supported geothermal development. Geothermal power plants of a total capacity of 593 MW in Japan and 15,948 MW in the world have been installed in 2020. It is still difficult to survey and develop natural geothermal reservoirs even at shallow depths, because the underground structure is complicated and invisible. Therefore, new technologies called EGS (Enhanced Geothermal Systems) which inject surface water into natural reservoirs, improve natural reservoirs, create artificial reservoirs, and extract heat from supercritical geothermal resources are being developed to reduce developing risks and extend developing areas. Other new innovative technologies which use CO₂ as a heat extraction fluid instead of water are also being studied. For these new technologies, basic studies on creation of artificial fractures, evaluation of natural and artificial fractures, and fluid flow in fractures are needed.