Performances Research On Gas Turbine-based CCHP System Combined With Solar And Compressed Air Energy Storage

The increasing environmental and energy problems have attracted close attention.A series of environmental problems,such as the exhaustion of non-renewable fossil fuels,the greenhouse effect and the ozone layer destruction,threat to the survival of human environment.The system of combined cooling,heating and power(CCHP)has received broad attention due to its great advantage in energy-saving and emission-reduction.With the development of energy technology,CCHP has become an important branch of energy system.In gas turbine based CCHP system,the operation mode of following thermal load often causes electric power surplus and efficiency decrease at partial load.In view of these problems,this paper proposed a gas turbine based CCHP combined with solar thermal energy and compressed air energy storage(S-CAES).The S-CAES was designed to enhance the load of gas turbine and balance the electricity load,also,increase the efficiency of S-CAES by introducing the solar energy.This paper has built the off-design mathematical models of the CCHP system and the S-CAES system,obtained the off-design operational characteristics of the coupled system,analyzed the operation characteristics of the coupled system in different energy storage rates,and compared the effects of two different operation modes between adjusting air reservoir discharge flow and adjusting air turbine inlet temperature on the system.And also,optimized the capacity of S-CAES based on the economic benefits and energy efficiency in a typical building load.And the sensitivity analysis was investigated to evaluate the effects of several key parameters on its performances.Finally,the multi-objective optimization of the system was conducted based on NSGA-II.In the multi-objective optimization,the exergy efficiency and the total investment cost per total power output(ICPP)were selected as the objective functions,while the pressure ratio of air compressor,the inlet pressure and temperature of air turbine and the effectiveness of the heat exchangers were selected as the decision variables.The results show that the annual cost saving,annual energy saving and average energy efficiency increment are 466,114 yuan,2.26?106kW and 1.015% respectively based on the selected building load,compared with the corresponding optimized CCHP system without S-CAES.And the optimal exergy efficiency of the proposed system is about 53.10% and 45.36% in maximum heating condition and maximum cooling condition respectively.In order to further improve the energy efficiency of the proposed system,this paper perfected the system configuration,such as adding an ORC cycle to recover the waste heat from the air turbine,the discharge process with an intermediate-reheat two-stage expansion to improve the energe efficiency.The results show that the design energy efficiency of S-CAES with ORC system is 98.30%,and exergy efficiency comes to 68.94% respectively in a round trip.Finally,a case study of the proposed system in a typical hotel building located in South China concludes that,compared with the conventional CCHP,the average energy efficiency increased by7.72%,1.47% and 3.61% in summer,transition season and winter typical days,respectively.