Optimization Research On Thermal Performance Test Bench Of Straight-through Vacuum Collector Tube

In recent years,the global use of fossil energy is increasing in a stepwise manner,which indirectly aggravates the deterioration of people’s living environment,glacier melting,acid rain,haze,etc.bring great trouble to people’s survival.The use of wind,water potential,solar,tidal and geothermal energy from renewable energy sources has brought benefits to people’s lives,but all other energy sources except solar energy are restricted by geography and difficult to promote on a large scale.The use of solar energy is almost not limited by geography,every region can get enough solar energy,its wide distribution,simple collection,low cost,nonpollution and other characteristics by the experts of various countries,gradually become the top of the list of clean energy use.Photothermal conversion is the main direction of solar thermal utilization,among which linear Fresnel type has become the mainstream of current thermal power generation technology with the features of simple manufacturing and cleaning of reflector,strong wind resistance and low cost.In this system,the concentrating collector is the core of the system,and the quality of the vacuum collector tube(collector tube for short),as the key device of the collector link,directly affects whether the subsequent thermal power plant can realize 24-hour uninterrupted power generation and power generation efficiency and cost.The quality of the receiver tube is mainly measured by its thermal performance,and the precise testing of the thermal performance of the collector tube has become the focus of the system’s concentrated heat collection link.This project takes the receiver tube as the test object and establishes the collector heat loss test bench(referred to as test bench)based on the steady-state equilibrium method to accurately evaluate its thermal performance.Firstly,the test method of the collector tube is analyzed with the actual test situation,and the steady-state equilibrium method is selected for the test.The technical difficulties such as larger heat dissipation at the end,uneven temperature field distribution,error of the detection device,and accuracy of the temperature control algorithm in the testing process of the collector tube are analyzed in depth,and improvement ideas and solutions are given respectively.Then,the test characteristics of the test bench and the overall hardware framework,etc.were analyzed to clarify the functions of the temperature and power collection,end thermal compensation,temperature control and other parts of the test bench,and suitable devices were selected for the test bench construction and adjusted according to the actual situation.Visual Basic(VB)language is used for the development of the test bench-based upper computer control software,which can realize temperature acquisition and control,current temperature power acquisition and calculation,storage of historical test data,plotting of historical power and temperature data etc.Finally,in view of the defect that the conventional test bench can only test a single diameter collector tube,a mechanical structure is studied to improve it.The improved test bench can realize the test of different diameter collector tubes,and an optical measuring instrument is installed on the test bench.Characterize the optical performance of the collector tube.The experimental method is used to mathematically analyze the collector temperature control system,and the mathematical model is derived using the step response and parameter identification method to obtain the transfer function.To address the shortcomings of the PID algorithm of the test bench such as low precision and poor efficiency,the algorithms of integral separation,fuzzy control,Particle Swarm Optimization and Comprehensive learning particle swarm are analyzed.The principles of these algorithms are analyzed,and the two types of algorithms are combined to form integral separation PID and fuzzy PID.After comparison,the fuzzy PID control effect is better,and then the fuzzy PID controller is optimized using PSO and CLPSO,and the simulation is verified in MATLAB.The results show that the CLPSO optimized control has the highest precision,faster response and best dynamic performance.The domestic 4060 mm collector tube and PTR70 collector tube are selected for optical performance test and thermal performance test in the range of 150-500 ℃ in the test bench,and the test data are summarized and compared.The optical test results show that: the domestic collector tube has low reflectivity and high absorption in the visible range;the transmittance of the glass cover of both is basically close.The thermal performance test results show that the CLPSO optimized fuzzy PID applied to the test process of the collector tube has significantly improved the test efficiency,the temperature control accuracy reaches ±0.5 ℃,the adjustment time is 33 min,which is 13 min less than before optimization,the system overshoot is reduced by 5%,and the test data is fitted with high correlation coefficient and excellent performance.Comprehensive analysis shows that the algorithm meets the requirements of temperature control accuracy and the data fit is high,which can reflect the heat loss at different temperature points to a certain extent.