A solar micro gas turbine system combined with steam injection and ORC bottoming cycle

Abstract

Micro gas turbine (MGT) is an important section in solar-driven power systems, as it can improve system efficiency and provide unique flexibility to meet quickly changing demands. Herein, a solar micro gas turbine (MGT) combined with steam injection and organic Rankine cycle (ORC) is proposed to improve efficiency and flexibility. A steam receiver that produces the steam injected into the MGT is placed around the air receiver aperture to increase the receiver intercept efficiency. A thermodynamic model including a heliostat field, a solar receiver, an MGT and an ORC is developed to investigate the performance of the proposed system, where each sub-model is validated with experimental/referenced data for the subsequence optimization of design and operating parameters. For a 100 kW MGT driven by a solar heliostat field, the simulation results show that the optimized aperture diameter of the air receiver is 1.1 m. On four typical days of a year, i.e. the spring equinox, the summer solstice, the autumn equinox, and the winter solstice, the average optical efficiency of the heliostat field is 0.672, 0.754, 0.672 and 0.597, respectively. Fuel consumption of the MGT during the four days is reduced by 14.8%, 24.6%, 22.4% and 3.7%, respectively. The solar energy share can reach up to 86.0% with a system power efficiency of 19.9% at 12:30 of the autumn equinox. By adding steam injection and ORC, the power output can be increased by 8.29 kW and 30.37 kW, respectively, bringing an increase of the total power output by 37.7% and improving the system efficiency and flexibility. The proposed system can benefit the distributed energy systems especially for remote areas or islands as a flexible option.