Design and performance assessment of a novel hydrate-based ocean thermal energy conversion system for power generation

Ocean thermal energy is a renewable energy source with tremendous power generation potential, but its utilization faces challenges such as unsafe working fluids and low efficiency. To enhance the safety and efficiency of ocean thermal energy utilization, a novel ocean thermal energy conversion system using hydrate as the working medium is analyzed for the first time. The cycle structure is modified to address the issues of guest gas wet expansion and low system efficiency. To evaluate the applicability of common hydrates, the system's performance with five different gas + promoter double hydrates is evaluated and compared. The impact of six key operational parameters on system performance is also investigated. Results show that, the modified cycle significantly enhances the performance of the proposed system and mitigates the wet expansion issue. Under a gross electric power output of 100 kW and a seawater temperature range of 277-303 K, the HFC-41 + cyclopentane hydrate achieves the highest net electric power output and system efficiency of 65.3 kW and 2.21 %, respectively, while the Kr + cyclopentane hydrate shows the minimal performance fluctuation throughout the year, with an annual net electricity output of 478261.2 kW & sdot;h and an average system efficiency of 1.79 %. Warmer surface seawater is found to improve system efficiency more effectively than cooler deep seawater. Optimal system performance can be attained through the careful adjustment of the mass flow rates of either warm or cold seawater. For practical applications, it is recommended to maximize the hydrate mass fraction and minimize the subcooling degrees.