Exergy Analysis And Operation Behavior Study Of Solar-Gas Combined Cycle System

Coal power has long been treated as the cornerstone of China’s energy structure.But in today’s context of achieving carbon peaking and carbon neutrality goals,the vigorous development of new energy power generation has become inevitable.However,the energy development should not only pursue green and low-carbon pattern,but also guarantee safety and stability.In this regard,the development should be targeted at both non-fossil energy and the clean utilization of fossil energy.Therefore,the comparatively clean natural gas power generation becomes the stable choice in this transitional period.The construction of a multi-energy complementary,clean and stable energy supply is about to be the breakthrough point and general direction in the future.And among those multi-energy systems,the solar photothermal-based integrated solar-gas combined cycle technology will also be an important technology connecting the preceding and the following on the road of multi-energy complementary development in the future.This paper proposes a new type of Integrated Solar-gas Combined Cycle（ISCC）system and carries out the exploration and analyses from several aspects,which include the operation,thermodynamic,economic and environmental protection performances.The main research contents and conclusions are as follows:Firstly,a new type of ISCC system is proposed,which mainly consists of the parabolic trough solar photothermal system,gas-steam combined cycle system and lithium bromide cooling system.The ISCC system can produce power and cooling simultaneously.The thermodynamic flow model of the ISCC system is built by using the EBSILON software.Then,the operation performances of the system under rated condition and variable condition are analyzed.The results show that the output power of the ISCC system is 96 MW,the solar output power is 9 MW,the overall thermal efficiency of the ISCC system is 46.83%,and the maximum cooling load is 69657.23 k W.In addition,solar DNI data in four seasons of a year in a typical city are selected for operation simulations,which reveal the operation feasibility of the ISCC system.At the same time,considering the variations of temperature and sunlight intensity,the annual variable condition operation of the ISCC system is simulated,and the operation performance of the system under actual conditions is thus given.Secondly,the exergic analysis of the ISCC system is carried out by using the grey box model.The results show that under the rated condition,the total exergic loss and total exergic efficiency of the ISCC system are 119.1 MW and 44.63%,respectively.The combustion chamber and solar DSG system have the largest exergic losses,which are 56.45 MW and 28.52 MW,respectively.Therefore,the further optimization of the ISCC system should focus on the improvement of solar DSG system and combustion chamber.On the basis of exergic analysis,advanced exergy analyses of typical components are carried out,the endogenous exergy loss,exogenous energy loss,avoidable exergy loss and unavoidable exergy loss in different components of the ISCC system are given.At last,the economic analysis of the ISCC system indicates that the dynamic payback period of the ISCC system is 5.8 years,and the levelized electricity cost is 0.585 yuan/k Wh.When the subsidies for solar power and gas-fired power are considered,the ISCC system is economically feasible.The environmental protection analysis results show that the emission reductions of dust,CO₂,SO₂ and NO_x of the ISCC system are 1412.41t、98730t、2427.97t and2150.5t compared with the coal-fired unit with the same output,indicating that this ISCC system has favorable environmental protection performance.