Nuclear power plant multi-grade waste heat-enhanced salinity-gradient osmotic energy conversion under reverse temperature gradients

Nuclear energy constitutes a foundational pillar in meeting energy demands while addressing environmental and economic challenges worldwide. However, efficiently utilizing low-grade waste heat from nuclear power plants remains a key issue. Since osmotic energy conversion, as a clean blue energy generation approach, exhibits high sensitivity to low-grade thermal energy modulation, it pertains the waste heat recovery from nuclear power plants. Therefore, this study proposes a reverse temperature gradient driven osmotic energy conversion approach that utilizes nuclear power plant multi-grade waste heat to boost osmotic power generation. Through combined experimental and simulation studies, we demonstrate that the multi-grade waste heat from turbine exhaust steam and warm drained seawater can significantly enhance osmotic energy conversion. Systematic evaluation reveals that peak osmotic power density occurs under summer conditions at full power level of the plant with alkaline seawater. Notably, the reverse temperature gradient configuration between seawater and freshwater improves the maximum osmotic power density by 30.4 % compared to forward temperature gradient operation. This research provides new ideas for synergistically and efficiently utilizing multi-grade waste heat from nuclear power plants and salinity-gradient osmotic energy, contributing significantly to the advancement of low-carbon energy technologies.