| The parabolic trough solar concentrator(PTC)was one of the main technical methods in solar utilization,and has several advantages of wide geometric concentrating ratio,high heating temperature,high solar-thermal conversion efficiency,easy to scale array layout,large amount of thermal energy.The PTC can be found easily in the solar thermal power plant,but it was not good for large-scale application in the field of industrial and agricultural,because the investment cost of the system was too high and the metal-glass tube absorber was expensive and fragile.In the purpose of realizing PTC thermal utilization with low cost and high efficient in the low-medium temperature range,the simulation and optimization of thermal collecting and storage working process of PTC system using a cavity absorber were carried out,and the energy supply coupling feature was researched as follows:(1)The solar-thermal conversion principle of the cavity absorber was analyzed theoretically and also analyzed the heat transfer form of medium pipe and oil storage tank and oil-water transformer and water storage tank,the exit working medium temperature expressions of the components were deduced according to thermal resistance network,then the thermal transfer mathematical model of the trough cavity thermal-collection system and the trough cavity thermal-collection-storage model were established respectively,the introduction of the improved the simulation results of the working medium temperature were improved by the Kalman algorithm.The results show that the relative error of the working medium temperature was within 2.0%,the average relative error of the thermal-collection efficiency and the thermal-storage efficiency was 4.25% and 1.80% respectively,which proved the feasibility of the two mathematical models.(2)The influences of the solar radiation intensity and the working medium temperature and the working medium flow rate and the thermal load and other factors were explored for the thermal-collection characteristics and the thermal-collection-storage properties by using heat transfer mathematical model,the control strategy of exporting stable thermal energy of the thermal-collection system was put forward,the realized method to optimized thermal-storage system efficiency was put forward too.A heat power output of 10 kW could be realized stably in the range of 100~140? by the method of adjusting the working medium flow rate to the optimal value based on the solar radiation intensity.At the same time,system thermal-storage efficiency improves to 20.94%.To improve thermal performance,a solar tracking system based on GPS and Angle sensor was proposed and test results showed that the experimental tracking precision was within 0.23°,which was consistent to the theoretical result.Besides,test results indicated that the tracking accuracy of the concentrator could run stably and the collector efficiency could be improved compared to the traditional electro-optical tracking mode.(3)To settle the heat supply problem in specified area,where there is a low temperature but processes has the good condition of sunshine in winter,a heating system using parabolic cavity thermal-collection-storage with an indoor fan coil was set up,and the several analyses of the heating characteristics and matching coupling were carried out.The exploratory research of the energy utilization question of the PTC system was conducted,the results showed that the sustained heating power was 7.34 kW and the heating efficiency was 22.37%,which could reach 27.39% if the impact of concentrator cosine effect was excluded. |
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