Thermoelectric Performance Study And Optimization Of Double-layer PV Window In Cold Regions

The large area of glass curtain wall in the outer envelope structure has significantly increased the energy consumption of buildings.Our Country’s Building energy consumption accounts for 46.7%of the total energy consumption in the whole society.Among them,the energy consumption caused by heat transfer from the outer window accounts for about 25%-40%of the total building energy consumption.It can be seen that improving the thermal insulation performance of the external window system and reducing the energy consumption are the key point for a high energy-saving of the building.As a typical application form of Building Integration Photovoltaic in the domain of building energy conservation,semi-transparent photovoltaic window can meet indoor lighting while providing part of the power demand for building,which is considered to be one of the effective ways to achieve green construction development.Therefore,scholars at home and abroad have conducted a extensive research on it.Although the existing literature has studied and optimized the translucent photovoltaic external window system from various perspectives,most of them are concentrated in hot climates,research on cold regions is rare.This paper takes the outdoor conditions in the Taiyuan area as an example,aiming at the heat transfer characteristics and load features of the exterior windows of buildings in different seasons of cold regions,the thermoelectric performance of the double-layer photovoltaic external window was studied by the combination of experiment and simulation,and the thermoelectric performance of the window was improved by optimizing the operation mode of the photovoltaic window so as to further reduce the building energy consumption.Firstly,this paper builds a double-layer photovoltaic windows experimental platform on the roof of a building in Taiyuan.The thermoelectric performance of double-layer photovoltaic window were studied by comparison of experimental,mainly for three different operating modes:closed type,inner loop type and open channel type.The parameters such as the effective heat gain,heat transfer coefficient(U value)and power generation of the external window are used as evaluation indexes to compare and analyze the comprehensive performance of the external window and the energy consumption of the building air conditioner under different ventilation modes.Secondly,based on the verification of the reliability of the mathematical model,the numerical simulation method is used to compare the thermoelectricity of the double-layer photovoltaic external window under three different ventilation modes:closed,outer loop and exhaust in summer conditions.The comprehensive performance of double-layer photovoltaic windows and the air-conditioning energy consumption of buildings under different ventilation modes were evaluated by parameters such as solar heat gain coefficient(SHGC),heat gain from the window and,power generation and other parameters and indicators.Finally,from the perspective of improving the thermoelectric performance of photovoltaic external windows and reducing the energy consumption of buildings,this paper separately makes the studies of simulation optimization on the structure of double-layer photovoltaic external windows under winter and summer conditions.The main findings of this paper are as follows:(1)The experimental results under winter conditions show that compared with the inner loop photovoltaic window and the closed double-layer photovoltaic window,the open channel double-layer photovoltaic window can not only increase the effective heat gain by 27%,but also preheat the fresh air of the building due to the natural heat transfer in the air cavity,thereby effectively reducing the fresh air load and heating energy consumption of the building.(2)Simulation results in summer conditions show that compared with the closed double-layer photovoltaic window and the outer loop double-layer photovoltaic window,the exhaust double-layer photovoltaic window can reduce the total heat gain by 14%and 6%respectively,and the overall temperature of the window is the lowest,has the best performance.The annual generating capacity of the exhaust double-layer photovoltaic window is 20.9 kWh/m~2,which can be increased by 3%and 1%per square meter compared with the closed double-layer photovoltaic window and the outer loop double-layer photovoltaic window.The amount of electricity generated is more conducive to building energy efficiency.Therefore,under the summer conditions,the exhaust double-layer photovoltaic window has better thermoelectric performance and greater energy saving potential.(3)The performance optimization study of double-layer photovoltaic windows under different season conditions shows that the overall performance of the external window is best when the air cavity spacing is set to 80 mm.At this time,in the winter working condition,the inner glass surface of the open channel double-layer photovoltaic external window has the highest surface temperature,and the heat gain of the window is more,the thermal performance is better,and the the heat gain in the winter room can be increased up to 34%compared with the 30 mm pitch.In the summer,the exhaust double-layer photovoltaic window also has obvious advantages in heating the window,which can reduce the heat gain of the window by 18%compared with the 30 mm,it can better exert the energy saving potential of the window and it’s more conducive to building energy conservation.