Comparative Study Of Three Types Of PV-Trombe Wall

With the rapid development of the world economy,the fossil energy on the earth has been over-used in the last century,which has caused serious environmental problems,thus the utilization and development of the renewable energy technology is urgent and necessar.Solar energy is an important alternative energy source,because of its widely distributed,clean,easy to use,and inexhaustible.Considering of the solar energy is low-intensity and high-dispersive,it is very meaningful to integrate of solar energy and buildings.The PV-Trombe wall is a new multi-functional structure,which combines the traditional architectural Trombe wall with photovoltaic modules,aiming at realizing the function of heating and ventilation and provide electricity for the human daily life.The traditional Trombe wall has the weakness of single function and poor aesthetics.The conversion efficiency of photovoltaic module is 10%-16%,and more than 80%of the incident energy is converted into useless heat and it dissipates into the ambient air,which will finally resulte in the increase of working temperature of photovoltaic modules.In this paper,three types of PV-Trombe walls were designed,which integrate the traditional Trombe wall with photovoltaic modules.According to the different positions of the photovoltaic cell,they are called as built-out PV-Trombe wall,built-middle PV-Trombe wall,and built-in PV-Trombe wall respectively.The built-out PV-Trombe wall's photovoltaic modules are attached to the glass of the Trombe wall;photovoltaic modules of the built-in PV-Trombe wall and the built-middle PV-Trombe wall are both attached to the surface of the absorption plate.The location of photovoltaic heat absorption plate of the built-in PV-Trombe wall is in the inner side of the air channel.The solar radiation passes through the glass and was absorbed by the photovoltaic module,then a part of the energy will be converted into electricity,while the rest energy is used to heat the air in the channel.The location of photovoltaic heat absorption plate of the built-middle PV-Trombe wall is in the middle of the structure.The advantages and disadvantages of the three structures arc obvious,for the built-out PV-Trombe wall,its photovoltaic modules is attached to the glass,which will block a part of the sunlight and most of the heat generated by the photovoltaic modules is lost to the environment,which can't be used.As for the built-in PV-Trombe wall,due to the photovoltaic modules is attached to the inside of air channel the shadow of the frame may have a negative influence on the performance of the photovoltaic modules,and the operating temperature of the PV module may be very high which will reduce the PV efficiency.Aiming at balancing the advantages and disadvantages of the two types of PV-Trombe walls,a built-middle PV-Trombe wall was proposed to overcome the shortcomings of two types of PV-Trombe walls.Refering to the existing literatures,this article designed the three types of the PV-Trombe wall with the reasonable size.The experiments for the three types of PV-Trombe Wall has been conducted at hot box in HeFei,east region of china and the electrical and thermal performance were studied in the winter and summer separately.The results showed that the three types of PV-Trombe wall have a significant effect on the heating of the room.Compared with the built-out PV-Trombe wall,the built-in PV-Trombe and the built-middle PV-Trombe wall showed a better air heating effect.ln the first group,the maximum heating efficiency of the built-out PV-Trombe wall and the built-in PV-Trombe wall were 0.37 and 0.43,and the photovoltaic efficiency were 0.13-0.15 and 0.09-0.12.The maximum temperature rise between the upper and lower vent are 13.5 ? and 14.9?,which resulted in that the average temperature in the room equipped with built-in PV-Trombe wall got a higher value of 1.5? than the room equipped with built-out PV-Trombe wall,respectively.In the summer experiment,the average temperature of the room equipped with built-in PV-Trombe wall and the room equipped with built-out PV-Trombe wall were 37.4? and 36.9?.The photovoltaic efficiency of the built-in PV-Trombe wall remained at 10%around,and the photovoltaic efficiency of the built-out PV-Trombe wall was between 13%and 15%In the contrast experiment of the built-out PV-Trombe wall and the built-middle PV-Trombe wall,the maximum heating efficiency of the two walls can reach to 0.43 and 0.35.During the period of experiment,the maximum temperature of the two rooms equipped with the built-middle PV-Trombe wall and equipped with the built-out PV-Trombe wall were 26.7? and 26.5?,respectively.The maximum values of the average temperature in the flow channel of the built-out PV-Trombe wall,were 25.7??27.5 and 29.5? at three days,and these values for the built-middle PV-Trombe wall were 29.3? and 29.5? and 31.4 ?,respectively.The photovoltaic efficiency of the built-out PV-Trombe wall was between 0.14 and 0.16,and the photovoltaic efficiency of the built-middle PV-Trombe wall was between 0.12 and 0.13.The difference of the photovoltaic efficiency of between the two types of PV-Trombe wall was obvious.From the average value of all-day PMV,we can find that the thermal comfort of the built-out PV-Trombe is poor,and the others provide similar thermal comfort to the room.Selecting the photovoltaic efficiency of the built-out PV-Trombe wall was selected to fit the formula for the relationship between the photovoltaic efficiency and the operating temperature of the photovoltaic module.When the average operating temperature of the photovoltaic module is 25.0?,the working efficiency of the photovoltaic module is 15.8%,and the slope is 0.0047.Through this formula,the effect of the border shadow on the photovoltaic cell power generation efficiency of the built-in PV-Trombe wall and the built-middle PV-Trombe was analyzed.