Comparative Analysis of a Novel System Integrating ORC, Hydrogen Production, and Seawater Desalination with LNG Cold Energy: Energy, Economic, and Environmental Analyses

The utilization problem of fluctuating power generated by the organic Rankine cycle (ORC) system using LNG (liquefied natural gas) cold energy and saving freshwater was studied using a novel system (CPDH system) by combining power generation, hydrogen production, and seawater desalination. The fluctuating power was transferred to a PEME (proton exchange membrane electrolyzer) for hydrogen production via water electrolysis. Moreover, the residual cold energy after power generation was used directly for seawater desalination to obtain freshwater and improve the utilization efficiency of LNG cold energy. The desalted freshwater was transferred to PEME for hydrogen production. A mathematical optimization model was established with the maximum net earnings of the system as the goal. A case study was conducted to validate the thermodynamic, economic, and environmental performance advantages of the novel system. Results show that the cold energy utilization efficiency of the novel system increases by 72.54, 69.43, 68.35, and 80.21% during spring, summer, autumn, and winter, respectively. The cold energy utilization exergy efficiency increases by 1.27, 1.63, 1.41, and 0.91%, respectively, compared to the system without seawater desalination. In addition, the net earning of the system was 65547.18 $/year when the novel system operates at summer ambient temperature, which could save 7688.34 m3/year of freshwater resources and reduce CO2 emission by 111.14 t/year.