Currently, Japan is actively developing technologies to significantly increase the amount of geothermal power generation as a national policy. In this context, efforts are being made to generate power using acidic and supercritical geothermal fluids that have not been available until now. For example, the figure below shows the acidic geothermal fluid research theme adopted by the New Energy and Industrial Technology Development Organization (NEDO) in 2018. Acidic geothermal fluids and supercritical geothermal fluids corrode materials, so we can see that many research themes to inhibit corrosion have been adopted. In general, thermal power plants use strictly controlled water to rotate turbines and generate electricity. Therefore, in the development of materials to be used in high-temperature and high-pressure environments, research and development on high-temperature strength (high-temperature tensile strength and creep strength) and steam oxidation has been the main focus. Power generation using corrosive geothermal fluids is a rather unique environment, and high temperature corrosion tests in highly corrosive fluids have not been conducted very often. My laboratory is interested in the mechanism of material corrosion in this environment, and is working with the National Institute for Materials Science to develop new materials that can be applied
Now. Our target will be materials for heat exchangers in geothermal power plants. Recently, the use of heat exchangers in geothermal power plants has become an alternative to the direct system, where the steam from the acidic geothermal fluid is fed directly to a turbine to generate electricity. In the indirect system, it is important to have a heat exchanger that is both corrosion resistant and cost effective. The Tokyo University of Marine Science and Technology (TUMSAT) has begun investigating heat exchange methods for indirect systems that are corrosion resistant and reduce scale growth, and is in the process of selecting and developing materials for these methods.