Solar Hybrid Combined Cycle Performance Prediction: Influence of GT Model and Spool Arrangement

A modeling procedure was developed to simulate design and off-design operation of Hybrid Solar Gas Turbines in a combined cycle (CC) configuration. The system includes an heliostat field, a receiver and a commercial gas turbine interfaced with a conventional steam Rankine cycle. Solar power input is integrated in the GT combustor by natural gas. Advanced commercial software tools were combined together to get design and off-design performance prediction: TRNSYS® was used to model the solar field and the receiver while the gas turbine and steam cycle simulations were performed by means of Thermoflex®. Three GT models were considered, in the 35 - 45 MWe range: a single shaft engine (Siemens SGT800) and two two-shaft engines (the heavy-duty GT Siemens SGT750 and the aero derivative GE LM6000 PF). This in order to assess the influence of different GT spool arrangements and control strategies on GT solarization. The simulation method provided an accurate modeling of the daily solar hybrid CC behavior to be compared against the standard CC. The effects of solarization were estimated in terms of electric power and efficiency reduction, fossil fuel saving and solar energy to electricity conversion efficiency.