Research On The Performance Of The Air-cooled PV/T System In Cold Regions

The limitation of fossil energy resources and the environmental problems brought about by the exploitation and utilization of fossil energy resources seriously restrict the sustainable development of mankind.China has a huge population base,which makes the energy crisis and environmental problems particularly prominent.Renewable energy has many advantages such as huge resource reserves,wide distribution range,small environmental impact and sustainable use,etc.Therefore,the exploitation and utilization of renewable energy has become an important approach and measure to solve energy and environment problems in China even for the whole world.Solar energy is a typical renewable energy source,which has a lot of advantages of,such as being inexhaustible.In the form of solar energy application technology,the solar photovoltaic thermal system can not only use solar energy to generate electricity,but also use photovoltaic waste heat to meet the needs of architectural life,like supplying heat or providing hot water.Consequently,solar photovoltaic thermal systems have broad development and utilization prospects.However,the solar photovoltaic thermal system has the problem of low comprehensive utilization of solar energy,which severely restricts the promotion and development of solar photovoltaic thermal technology.Air-cooled PV/T system is a representative form of solar photovoltaic thermal system,which has received extensive attention and research in recent years.Based on the application background of the air-cooled PV/T system,this paper establishes three-dimensional physical models and mathematical models for two different types of air-cooled PV/T systems with cooling channels on the upper side of the photovoltaic panel and cooling channels on the lower side of the photovoltaic panel.After verifying the reliability of the model through experimental data,the effects of parameters such as the length of the cooling channel,the height of the cooling channel,and operating conditions on th e performance of the air-cooled PV/Tsystem with different structures are discussed.Then compare and analyze the characteristics of the system performance of the two systems with different cooling channel positions under different cooling channel lengths,cooling channel heights,operating conditions.The results of this study show that the length and height of the cooling channels have similar effects on the performance of the air-cooled PV/T system with cooling channels on the upper side of the photovoltaic panel and the cooling channels on the lower side of the photovoltaic panel.While with the air inlet speeds change,the exergy efficiency of the two system has a certain different change discipline.When the cooling channel structural sizes,the air inlet velocity and air temperature are the same,the thermal efficiency of the system with the cooling channel on the upper side of the photovoltaic panel is always greater than the system with the cooling channel on the lower side of the photovoltaic panel,meanwhile,the average electrical efficiency and total system exergy efficiency of the system with the cooling channel above the photovoltaic panel are always lower than the system with the cooling channel below the photovoltaic panel.From the standpoint of the first law of thermodynamics,the air-cooled PV/T system with the cooling channel on the upper side of the photovoltaic panel is more conducive to the output of thermal energy,while the air-cooled PV/T system with the cooling channel on the lower side of the photovoltaic panel is more beneficial to the supply of electrical energy,from the standpoint of the second law of thermodynamics,the performance of the air-cooled PV/T system with the cooling channel on the lower side of the photovoltaic panel is better than the air-cooled PV/T with the cooling channel on the upper side of the photovoltaic panel system.Wherefore,this paper believes that for the air-cooled PV/T system,the system evaluation index should be selected reasonably combined with the specific application location.After comprehensive evaluation of the system being made,the appropriate structural could be selected.The research results in this paper provide a theoretical basis and design reference for the design and operation of the air-cooled PV/T system.