Research On Key Problems Of Solar High-temperature Gas Turbine Power Systems With Thermal Storage

Solar thermal power has great potential for future basic power supply because of its stability and disptachability.Parabolic troughs,linear Fresnel,power tower and dish Stirling are getting mataure and have several commercial plants.Solar high-temperature(>600 ℃)thermal power technology is an effective way to improve system efficiency and reduce cost,which needs more research.This thesis proposes a solar two-stage reforming gas turbine system based on a particle receiver and thermal storage.An experimental and simulation study is conducted foucusing on system construction,high concentration,thermochemical energy storage,and thermal power conversion.This system consists of a high-temperature particle receiver-storage system and a two-stage reforming gas turbine system.The former is used to provide stable heat source combined particle receiver and thermochemical reaction of metal oxides.The latter system has two-stage reformer,i.e.,a low-temperature reformer and a high-temperature reformer.The low-temperature reformer is used to recover the waste heat of turbine exhaust gas,improving the energy level of waste heat.The high-temperature reformer is used to absorbe solar energy,increasing the solar share and energy level of solar energy.The two-stage reforming system increases the thermal efficiency and solar share simultaneously,reducing the system cost.The undesired performance of concentrators may results in serious damage to receivers,due to different kinds of error,among which the slope error and alignmen error take important roles.This thesis proposes an assessment and optimization method for a solar dish system.A Monte Carlo ray-tracing method is established to simulate the flux density distribution.A CCD-Lambertian target method is used to measure the flux density distribution of the dish focus region,which matches well with the simulation results with intercept factor difference within 3%.After the optimization,the average concentration ration increases from 500 to 1500,with intercept factor from 0.66 to 0.91,which meets the design requirements.A gravity-driven inclined-plate particle receiver is proposed to achieve high outlet temperature.The particle flow rate and residence time are controlled by a fluidized-bed apparatus.The cold test shows that the particle flow on the inclined plate is a uniform density flow,which has relative uniform velocity in the main region.The particle flow rate is controlled between 1.5g/s to 4.5g/s,with a solid-to-gas ratio from 15 to 32.A radiation-thermal coupled model is established based on Monte Carlo method.The simulation resut shows that the outlet temperature of particle could reach 900℃,with thermal efficiency of 82%.Thermochemical energy storage based on metal oxides could improve the sorage density and reduce cost.In this study,Co3O4/CoO redox pair is tested in thermegravimetry experiments.The result shows that the first order reaction mechanism is suitable for reduction processes,while the second order reaction mechanism is suitbalbe for oxidation processes.The oxygen partial pressure has an important influence on the redox reation.Therefore,the pressure dependence factor should be taken into consideration in the reaction mechanism.The two-stage reforming gas turbine system is analyzed using energetic and exergetic methods.The analysis result shows that the thermal efficiency of this system is 47.7%,which is 10.6 percentages higher than simple gas turbine cycle.The solar share of the two-stage reforming system is 75.0%,which is 12.8 percentages higher than single stage reforming system.In the point view of energy level,the waste heat of turbine exhaust is increased by 38.2%,and the solar themal energy is increased by 17.4%.The two-stage reforming system avoids complex Rankine bottoming cycle,increase the system efficiency and reduce cost.The research in this thesis provides important suggestions for the research of solar high-temperature gas turbine system based on particle receiver and thermal storage,also for other high-temperature solar thermal power technologies.