| Solar energy can be used not only to generate electricity,but also to provide hot water for domestic life and to heat or cool residential and industrial buildings.Therefore,the Photovoltaic/Thermal(PV/T)system emerges as expected.The thermal energy generated by photovoltaic modules can be utilized to provide heating or domestic hot water,while further improving the power generation efficiency of photovoltaic modules.PV/T systems produce more solar energy per unit area than photovoltaic panels and collectors alone,and are more efficient,making them more suitable for urban applications.The main work of this paper is to evaluate the effects of different air cooling and glazing methods on the performance of PV/T system by numerical simulation.By designing different PV/T structures,the performances of different PV/T structures are numerically examined and analyzed from the energetic and exergetic point of views.Firstly,five physical models of the hybrid PV/T structures were constructed,and then the numerical simulation analysis models were constructed.The three-dimensional numerical simulation was carried out by using the ANALYSIS software.The experimental and simulation results in the literature were used to verify the numerical model,and then 5 different configurations were compared and analyzed from the energetic and exergetic point of views.The investigated five structures are:single pass double glazed with air gap(PV/T-a),single pass single glazed with air gap(PV/T-b),double pass double glazed(PV/T-c),double pass single glazed(PV/T-d)and Single pass single glazed(PV/T-e)hybrid photovoltaic/Thermal air collector systems.In this paper,the performances of five PV/T structures were analyzed and compared under the air mass flow rate of 0.025 kg/s,based on the climatic conditions of one day in August in Beijing,China.The results show that the solar panel temperature is the highest when the solar radiation intensity is the maximum,and the wind speed and ambient temperature have the most significant effects on the solar panel layers.Under the same conditions,the maximum temperature of the solar panel with the double pass cooling structure is higher than that of the single pass cooling structure,because the contact area between the double pass cooling and the PV cell layer through the upper and lower air ducts is larger.Of all the schemes,the thermal efficiency has the greatest effect on the overall solar energy efficiency,and the higher the thermal efficiency,the higher the total energy utilization efficiency.Among all the schemes,the PV/T-d structure with double glass single glazed plate has the highest average daily total energy efficiency,which can reach 85.07%.Single pass cooling and single glazed system(PV/T-e)has the highest average daily power generation efficiency,but the lowest thermal efficiency and total energy efficiency.Whether it is a single channel structure or a double channel structure,removing the bottom glazing plate can improve the overall energy efficiency and exergic efficiency effectively.The overall energy efficiency can be improved by adding a glazing cover to the photovoltaic module,or by using double channel cooling. |
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