Techno-Economic Comparison Between Conventional and Innovative Combined Solar Thermal Power and Desalination Methods for Cogeneration

The U.S. Department of Energy (DOE) has determined that solar power coupled desalination could be the next step in helping to resolve the water-energy nexus. For many decades, integration of concentrating solar power (CSP) electricity generation for combined power and water production has typically utilized the conventional method of steam Rankine cycles. Current research focuses on an enticing innovative method which combines CSP with Brayton cycles and uses supercritical CO₂ (sCO₂) as a working fluid, allowing for a broader temperature range. This techno-economic study analyzes the power and possible freshwater generation of each cycle and provides a comparison of the techno-economic advantages associated with each technology when applied to desalination processes. The results of this study suggest that recompression-closed Brayton (RCBR) cycle is likely to have the most significant impact in decreasing the levelized cost of electricity (LCOE), almost halving it from combining CSP with the traditional Rankine cycle. Also, to minimize levelized cost of water (LCOW) a smaller scale desalination facility which utilizes multi-effect distillation with thermal vapor compression (MED/TVC) instead of multi-stage flash distillation (MSF) is most applicable. Although the lowest LCOE values are for wet-cooled RCBR with MSF and MED/TVC, in areas where freshwater generation is crucial to be optimized there is only a 0.04 cents/kWh increase for dry-cooled RCBR with MED/TVC to a cost of 9.8 cents/kWh. This suggests the best candidate for optimizing freshwater generation while minimizing both LCOW and LCOE is dry-cooled RCBR with MED/TVC desalination.