For wide use of a power plant utilizing solar energy, improvement of its economics is important. Both the economics and characteristics of a CO2-capturing solar thermal hybrid power generation system are evaluated in this paper. Since a relatively low temperature steam of 220 degrees C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine, the solar collector can attain high heat collecting efficiency. The net fuel-to-electricity conversion efficiency of the hybrid system is estimated to be higher than 60% on the lower-heating-value-basis. It has been estimated that the gross income and the period of depreciation of the proposed system are 34.8 x 10(5) yen/year and 8.89 years, respectively, and that the system is economically feasible, under the assumptions of a solar collector area of 10 ha, a maximum net power output of 4 MW and a heat storage capacity of 2000 m(3). The amount of fuel saving and reduction of CO2 emission of our system, compared to a conventional natural gas firing plant, are also estimated in the paper. (C) 1999 Scripta Technica.
