Session: 05-06 Other CSP Technologies

Paper Number: 110363

110363 - Supercritical Co2 Recompression Cycle Design Optimization to Maximize Mspt Internal Rate of Return 

Concentrating solar power (CSP) researchers around the world are investigating the integration of supercritical carbon dioxide (sCO2) power cycles with CSP technology. While several sCO2 configurations offer compelling advantages, we focus on the recompression cycle because of its potential for high efficiency and its selection in experimental cycles and planned demonstrations. We evaluate integration of the cycle with Generation Two (Gen2) molten salt power technology (MSPT) because Gen2 performance and cost are better understood than proposed Generation Three technologies. Recuperator conductance, ambient temperature, air-cooler approach temperature, and air-cooler fan power are cycle parameters that influence the cycle design point. Furthermore, the power generation capacity of the recompression cycle decreases when the ambient temperature is warmer than the design ambient temperature. MSPT plants typically are built in hot, arid climates that can experience temperatures warmer than the sCO2 critical point (31.1°C). As such, defining the cycle design-point requires understanding the trade-offs between efficiency on cold days, output on hot days, and the implications of design on total installed cost.

This presentation describes cycle and system level results at different combinations of these sCO2 design parameters where each cycle has a net output of 50 MWe at design. First, we discuss the cycle performance at off-design ambient temperatures and show the capacity degradation as a function design-point ambient temperature. Next, we show the net cycle efficiency, cycle cost, and temperature difference across the primary heat exchanger. We assume ten hours of thermal energy storage (TES) for each MSPT-sCO2 design, so we calculate the cost of TES as a function of temperature difference and cycle heat input. Then, we calculate the MSPT total installed cost that includes unique cycle and TES cost for each case and a fixed solar field and receiver design for all cases. Next, we simulate the MSPT annual performance using NREL’s System Advisor Model (SAM) and compare total receiver and cycle output for each MSPT-sCO2 design. Finally, we present total revenue earned from electricity sales and internal rate of return (IRR) that show how the cost and performance trade-offs balance for each MSPT-sCO2 design.

Presenting Author: Ty Neises National Renewable Energy Laboraotry (NREL)

Presenting Author Biography: Ty is a researcher at the National Renewable Energy Laboratory. His work focuses on component and system modeling of solar thermal technologies, power cycles, and thermal energy storage. Ty also leads development of solar thermal models in NREL's System Advisor model (SAM).