Research On Dynamic Peak Regulation Performance Of Solar Power Tower Generation

In the process of achieving the national carbon peak and carbon neutral goals,renewable energy will gradually become the main energy source in China.By complementing each other,we can leverage our strengths in various forms of energy,make up for each other's shortcomings,increase the consumption of renewable energy,and accelerate the substitution of clean energy for fossil energy.In the multi-energy complementary system,the molten salt solar tower power plant equipped with heat storage can be used as a peak regulating power source,which can suppress load fluctuation and increase the grid-connected capacity of wind power and photovoltaic power generation.However,the intermittent and fluctuating nature of renewable energy resources and load end factors pose great challenges to the molten salt solar tower power system.Therefore,it is particularly important to study the heat transport characteristics of solar power tower station and to formulate safe and reasonable control strategies.The molten salt solar power tower generation system is composed of a heat collecting field,receiver system,steam generating system and steam turbine power generation system.There are obvious dynamic characteristics in the process of power plant heat transport,including start-stop,variable working conditions,etc.In this paper,the molten salt solar power tower generation system is taken as the research object,aiming at comprehensively and systematically analyzing the heat transport characteristics of the peak-regulating power supply under dual perturbations,and exploring its operation control strategy.Based on the laws of conservation of energy,conservation of mass and conservation of momentum,the detailed system models of the receiver,the steam generation system and the steam turbine were established by using the multi-dimensional modular modelling method,and the static and dynamic models were verified effectively by comparing the existing experimental and simulation data.Based on the model,the heat transport characteristics of molten salt solar power tower generation system in the environmental side and load side double disturbance under the condition of the thermal transport properties is analyzed,the basic control method is proposed and applied to the solar power tower generation system,which provides the theoretical basis for the operation control strategy formulation of a molten salt solar power tower generation system in a pluripotent complementary system used for peak shaving.Through the one-dimensional comprehensive analysis model of the external molten salt receiver,the temperature distribution of the surface and the molten salt and the thermal stress distribution of the heat absorber pipe were analyzed under the conditions of uniform heat flow,non-uniform heat flow and light spot on the surface of the receiver respectively.Along the direction of molten salt flow,the surface temperature and the temperature of molten salt increase gradually,the heat loss of convection and radiation increases,and the thermal stress decreases gradually under the uniform heat flow.The thermal stress at the inlet and the surface temperature at the outlet of the molten salt is the highest,and the cracking of the molten salt near the wall of the tube should be avoided during operation.The formation of surface light spots will produce a large temperature gradient on the surface of the receiver,which improves the local heat transfer efficiency.Long-term operation is also easy to cause fatigue damage of the heat absorbing tube at the center of the light spots.Short-time cloud shading can effectively utilize the thermal inertia of the receiver and suppress the influence of DNI fluctuation on the receiver.The temperature of molten salt outlet changes due to environmental fluctuation,which will affect the heat storage quality.The steam generation system model has been effectively verified by the actual operation data of Solar Two molten salt solar power tower station in the United States.The proposed distribution control method can effectively reduce the fluctuation of system parameters after disturbance and reduce the thermal shock to the steam generation system.By scaled up and integrated with the 50 MW steam turbine model of molten salt solar power tower system established by the node method,the power cycle system is built up,through the disturbance test analysis:water side and molten salt side disturbance experiment will lead to redistribution of the heat load in the steam generating system,especially in the evaporator and superheater heat load change are bigger.Mainly because the active and passive load changes will affect the evaporator's steam production quality(steam pressure and temperature),the main steam parameters will change,and then affect the turbine output.After the load disturbance,the steam temperature at the outlet of the superheater fluctuates greatly,and the thermal stress generated in the superheater will affect its service life.In the process of load fluctuation,the continuous increase or decrease of the water level in the evaporator will affect the quality of steam production of the steam generation system,and the safety of the system will also be threatened.The parameter response curves of the dynamic circulation system were obtained by simulation,and the heat capacity and time constant of the heat exchanger in the system were revealed.Compared with the steam generation system,the thermal inertia of the steam turbine is relatively small,so the thermal inertia of the power cycle system is mainly considered by the thermal inertia of the steam generation system.The basic control structure of the molten salt solar power tower generation system is composed of the temperature control strategy of the receiver and the water level control strategy of the power cycle system,which ensures the heat storage quality and operation safety of the system.The sensitivity of water level control strategy to different load rate is different.