Performance Study And Optimization On The Solar Aided Coal-fired Power Unit

Nowadays,China is on the way to deepening energy structure adjustment and it's the dominant tendency to decrease conventional coal consumption and develop clean and renewable energy in the world.While the existing solar-electricity generation system technology is hindered to some certain extent because of high initial investment and blockages on techniques.Electricity is mainly produced by coal-fired power plant in China.Considering the situation,it's an efficient way to improve the solar-electricity efficiency of solar field by means of coal-fired plant and decrease the initial solar field investment and LOCE(levelized cost of electricity).When solar steam from solar field is sent to coal for power generation,which can reduce coal consumption and pollution emission directly as well as improve the electricity share of new energy.Thus,it's pretty necessary to study the performance of solar aided coal-fired power plant and provide the theory support for the hybridization system.This paper is mainly composed of:Firstly,parabolic trough solar field model is built and analyzed the influence factors based on Matlab/Simulink platform.According to the mathematical models of main devices in coal-fired power plant,a 600 MW solar aided coal-fired power plant coupling mechanism model is built,which is the basis for the following study.Secondly,when the hybridization system is working on the cons tant power operation mode,solar-electricity efficiency of several different integrated schemes are compared.It's the best integrated scheme when inlet feedwater of solar field is from condenser and is used to replace the first bleed steam in turbine.The more bleed steam is replaced by solar steam,the more turbine works on off-design condition.And the influence of solar steam on coal saving and conversion efficiency is considered on 100%THA,75%THA and 50%THA(turbine heat acceptance),respectively.The coal saving is apparent in integrated system.Annual solar-electricity efficiency of solar field is calculated according to the actual meteorological data when considering the change of condenser pressure.Moreover,the shock effect on hybridization system of DNI fluctuation is also studied.In order to reduce the LCOE of solar field further,a step heating solar field is proposed by combining evacuated tube collector(ETC)with parabolic trough collector(PTC).Optimization of evacuated tube collector layout is studied and the principle of step heating optimization is also revealed.The joint temperature of hybridization solar field varies with radiation condition.Finally,several step heating scheme are evaluated on the basis of LCOE based on the actual meteorological data and the LCOE of hybridization solar field is calculated.The results reveals the cost-effective of evacuated tube collector especially when the low heater bleed steam is replaced and the LCOE of hybridization solar field is lower than that of pure parabolic trough solar field.