Diffuser control of outlet mass flow of separator for stable operation of STEC plant with working fluid of binary mixtures

Spring thermal energy conversion (STEC) is a system that converts heat energy into electricity by using the temperature. difference between spring water and sea/river water. Because of the small temperature difference in a STEC plant, its thermal efficiency is low compared with those of other thermal power plants. In order to improve the thermal efficiency of STEC plant, a new power cycle, in which binary mixtures of water and ammonia were used as the working fluid, was developed recently. Because of the use of binary mixtures, there encounters a serious problem about the composition of working fluid flowing into the turbine. If the composition of ammonia is not high enough, the working fluid may condense in the turbine, which results a fatal damage of turbine. This paper describes the controller design for keeping the composition of working fluid into the turbine. Effectiveness of the proposed method has been verified under a developed simulation system for STEC plant.