Simulation And Research Of Ocean Thermal Energy Conversion System Based On The Closed Rankine Cycle

The massive use of fossil fuels causes serious pollution to the environment.Using clean alternative energy to reduce the pollutants and greenhouse gas emission and improve energy consumption structure is the trend of future energy utilizations and has drawn increasing attention.Ocean Thermal Energy Conversion(OTEC)uses the warm water on the sea surface as the heat source and deep-sea cold water as the cold source,with a low boiling point working fluid used to generate mechanical work and electricity based on specific thermal cycle.OTEC has become a highly concerned scientific research topic since it does not consume fuel and generates no pollution.Based on a full investigation of the field devices and combined with field work experience,a closed Rankine OTEC simulation program is developed based on Delphi after a comprehensive theoretical analysis.In order to study the system performance under different operating conditions,working fluids,and capacity systems,the simulation program is used to conduct the following works:Firstly,the performances of 9 working fluids in the OTEC system are analyzed in this thesis,and the environmental protection and safety of the working fluids are compared.Parameters such as the mass flow rate of the working fluid,the heat load of the heat exchanger and the output work of the system under typical operating conditions are calculated by the OTEC simulation program,and the working capabilities of the working fluids are compared.Influences of the thermal physical properties of the working fluids on the system exergy loss are analyzed.The optimization of working fluid is completed by comparing factors such as the environmental protection and safety of the working fluids,compatibility with system and working capability.Secondly,influences of evaporation temperature or condensation temperature as a single variable on the system parameters are studied by using the OTEC simulation program,and the optimization of evaporation and condensation temperatures of the working fluid is completed with the system output work and system thermal efficiency selected as the optimization objectives.Results show that when the evaporation temperature of working fluid is 20.6℃ and the condensation temperature of working fluid is 11.1℃,the maximum output work of the system reaches 6136.57 k W.Impact of installed capacity on the OTEC system is analyzed.Finally,the main equipment of the closed Rankine cycle OTEC system is discussed,including sea water pipeline,heat exchanger,turbine and sea water pump,and the material and structure of the equipment are also analyzed.