Supercritical Steam Power Cycle For Line-Focusing Solar Power Plants

A recent study between Sandia National Laboratories and Siemens Energy, Inc., published on March 2013 [11], confirmed the feasibility of adapting the Siemens turbine SST-900 for supercritical steam in concentrated solar power plants, with a live steam conditions 230-260 bar and output range between 140-200 MWe. In this context, this analysis is focused on integrating a line-focus solar field with a supercritical Rankine power cycle. For this purpose two heat transfer fluids were assessed: direct steam generation and molten salt HITEC XL. The design-point conditions were 550 degrees C and 260 bar at turbine inlet, and 165 MWe Gross power output. Plant performance was assessed at design-point in the supercritical power plant (between 43-45% net plant efficiency depending on balance of plant configuration), and in the subcritical plant configuration (similar to 40% net plant efficiency with one DRH, and up to similar to 41% with two DRH stages). Direct Reheating was adopted in Rankine power cycle to avoid any intermediate heat exchanger. Seven feed-water heaters optimized the plant performance power output.