Performance investigation of a combined cycle power system with concentrating PV/thermal collectors

Abstract A novel integration approach of solar energy and fossil fuel in the combined cycle power system is proposed in this paper. The system consists of concentrating PV/thermal collectors, absorption chiller, Brayton cycle and Rankine cycle. Apart from power generated by the spectral response, the waste heat from concentrating PV is used to drive an absorption chiller for cooling the ambient air, then the cooled air is compressed for fossil fuel combustion, achieving power production in the combined cycle. The reduction in work consumption of the compressor results in the increment of the power output of the combined system, realizing an indirect conversion process from solar energy to power. In this work, the heat transfer model of the PV/thermal collector and the mathematical model of a gas turbine with air-cooling are developed, and the performance enhancement mechanism of the system is investigated. Under the design conditions, the primary energy efficiency of the new system is 50.8%, and the conversion efficiency from solar energy to power reaches 85.8%, which is increased by 63.5% compared with conventional PV systems. The influences of several key parameters on the system performances are investigated, including inlet-air temperature of combined cycle, concentrating PV temperature and ambient parameters (solar radiation intensity and sky air temperature). Compared with the reference system that combines a concentrating PV subsystem and a combined cycle subsystem without absorption chiller, the proposed system achieves a 1.3% increment in the energy efficiency. As a result, the new integration form of solar energy and fossil fuel can significantly improve the conversion efficiency from solar energy to power and the thermodynamic performances.