Studay On Performance Of Closed-cycle Ocean Thermal Energy Conversion System

Ocean thermal energy is one of the most potential energy accepted by the international community because of its tremendous reserves. In the serious situation of energy shortage, the exploitation of ocean thermal energy, which is clean and renewable energy, is important to adjust our overall energy structure and relieve the pressure of the future energy. The characteristics that the temperature difference of OTEC plant is small,result in the net efficiency of OTEC is very low. Therefore,In order to promote further development of technology of OTEC,we need to study the factors to affect OTEC system and improve OTEC system performance.Based on the Rankine cycle and combined the closed-cycle OTEC system model, 50kW OTEC plant was investigated. The influence of working fluid type on OTEC system performance was researched on the basis of primary design of OTEC power plant. According to the data of the surface seawater temperature in the Spratly islands provided by the state oceanic administration of China, it was studied that the influence of the surface warm seawater temperature on the performance of the system. The mathematical model was established and the simulation was done about unchanged warm seawater flow and constant warm seawater temperature difference, aimed at the influence of microbiofouling on the performance of heat exchanger and the plant. The periodic change of main performance parameters of OTEC plant was attained from the begaining of operation to the microorganisms elimination.Research results showed that ammonia is certainly an ideal working fluid for OTEC power plant and R134a can be used as a good substitute of R22 because of its good environmental protection and high power efficiency compared with the Freon. The surface warm seawater temperature remarkably affected the performance of OTEC power plant. In the annual change cycle of surface water temperature, the total output changed more than 20% of the designed installed capacity. The contrast of different capacity illustrated that increase of installed capacity could make up for the deficiencies of low warm seawater temperature. Consequently large-scale OTEC system is an inevitable trend. Microbiofouling seriously affected the heat exchanger performance of the OTEC system. In a typical period of microbial fouling resistance , the heat flow of heat exchanges reduced 40%～50% and the overall performance of OTEC power plant was affected greatly. Therefore it became the key of OTEC technology development to adopt countermeasures to microbiofouling.