海洋温度差発電の現状と展望

(アンモニア/水を作動流体として用いたシステムへの挑戦)

抄録

The Ocean Thermal Energy Conversion (OTEC) power plant is a system for generating electric power using the temperature difference between the surface and the deep water of the ocean. It is an environment-friendly source of energy. Unlike most of the renewable energy resources which are weather dependents, OTEC system provides a stable source of electricity along the year because the surface and the deep water temperatures are constant. In addition, the seawater used for electricity generation can be further used in many fields, such as desalination of seawater, agriculture, and Lithium recovery. To realize the OTEC system, various studies have been conducted for long time; one of the fields of these studies is on the use of non-azeotropic mixtures as working fluids in order to make use of the increase of the system's exergy. One of the advantages of the ammonia/water mixture is the big difference between its boiling point and its dew point. As the use of ammonia/water mixture as working fluids was in its initial stage, there has been great concern regarding the stability of the cycle because the difference between of the boiling point and the dew point of ammonia/water mixture is larger than that of CFCs. In this paper, it is introduced on the research trend and activity of Ocean Thermal Energy Conversion, especially, the challenge on ammonia/water mixture including multiphase flow research and the OTEC Road map toward 2030 by Japanese NEDO (New Energy and Industrial Technology Development Organization).