Research On Integrated Characteristics Of Gas-Steam Combined Cycle Units And Solar Energy Thermal Utilization

The finiteness of fossil energy determines that the development of renewable energy will become a necessary approach for human society in the future.Among them,solar energy is considered to be the most valuable one in the 21st world,which makes it to be one of the most promising new energy sources.However,due to its inherent shortcomings such as low solar energy flow density and unstable radiation,the economy of solar energy utilization cannot yet compete with conventional fossil energy resources.The integrated solar combined cycle system is the research object in this dissertation,in which the study about the comprehensive utilization characteristics of the trough solar thermal field and the conventional gas-steam combined cycle to achieve the complementary use of different grades of energy is also deployed.The purpose of the study is to improve the utilization of energy,reduce the fossil energy consumption and the speed of pollutant emission,and achieve energy conservation and emission reduction by the end.The detailed research contents are as follows:(1)The working characteristics of the solar thermal cycle and gas-steam combined cycle are discussed in the dissertation,in which the efficient integration methods of different solar collectors and gas-steam combined cycles are analyzed to provide a theoretical basis for the design of solar thermal utilization and gas-steam combined cycle systems.(2)Due to the shortcomings of solar power calculation with reference to power station method,thermal method,and exergy analysis method,and with the reference of solar-working fluid and flue gas-working fluid heat transfer process,solar power and the actual function of smoke are studied thoroughly.Thereby,references for the improvement of solar gas-steam combined cycle system evaluation indicators are provided.(3)Different solar integration methods and different collector sizes are coupled with gas-steam combined cycles respectively,by modeling a Solar Gas-Steam Combined Cycle System with Ebsilon Software.Then the variation law of coupling system is studied,including turbine power increment ratio,solar contribution and other integration features.Simulations were performed for three typical types of systems:ambient temperature changes,solar radiation changes,and gas turbine low-load operation to study the basic characteristics of the integrated solar combined cycle under variable operating conditions.In order to improve the performance of the system under variable working conditions,optimization analysis targeting at system heat transfer process is conducted at the end.Studies conducted in this dissertation show that the ambient temperature increases by 30℃ and the steam turbine output power increases by approximately 0.3 MW after the E-type unit is equipped with a steam extraction heating device.When the gas turbine load rate drops below 75%,the steam turbine output power increases by approximately 0.5 MW.