Comprehensive assessment of working fluid selection for ocean thermal energy conversion

• Ten working fluids (Ammonia, R152a, R134a, R32, R22, R1270, R600a, R290, R744, R245fa) were analyzed. • Evaluation includes enthalpy, safety, environmental impact, and cost. • Mass and heat balance were modeled using in-house code and ASPEN+ simulations. • Each working fluid affects component size, especially heat exchangers and pumps. • Ammonia shows the highest overall score in the OTEC working fluid assessment. Ocean Thermal Energy Conversion (OTEC) is a type of ocean renewable energy that generates electricity by utilizing the temperature difference between warm surface seawater and cold deep seawater. Despite its vast potential, especially in tropical regions, OTEC technology remains at the pilot stage. To enhance the implementation of OTEC on a commercial scale, this study aims to determine the working fluid by conducting an in-depth analysis of working fluid selection in OTEC systems, focusing on energy efficiency, safety, and environmental impact. The study involved modeling and creating an in-house program to calculate the heat and mass balance, which was validated using ASPEN+ software in the single-stage Rankine cycle system. The working fluid selection optimization study was conducted through two stages of selection. At the initial stage, the selection involved ten candidate working fluids, based on a literature review of their characteristics, safety, environmental impact, and cost. From the initial selection, four candidates with the highest assessment results were selected, namely Ammonia, R134a, R32, and R22. The second selection stage involved assessing the influence of the four fluids on the quality of power generation and the main equipment specifications for the prospective working fluid. The final results show that Ammonia achieved the highest total score of 37, followed by R32 with a score of 28. In contrast, R22 and R134a scored 23 and 21, respectively.