An Experimental Investigation of Free Cooling by Natural Convection of Vertical Surfaces for Building Integrated Photovoltaic (BIPV) Applications

An experimental study is carried out to investigate the effect of the geometrical configuration on the thermal performance of a series of vertical heaters cooled by natural convection of air. The aim of the work is to investigate the physical mechanisms which influences the thermal behaviour of a double-skin photovoltaic (PV) facade. This results in a better understanding of the related phenomena and infers useful engineering information for controlling the energy transfers to the building where the PV system is applied. In real applications, the PV integrated double facade allows local production of electricity and heat to be employed for the building needs. Furthermore increasing the heat transfer rate from the PV surfaces increases the conversion efficiency of the PV modules since they operate better as the working temperature is lower. The test section consists in a double vertical wall, 2 m high, and each wall is constituted by 10 different heating modules 0.2 m high. The separating distance between the walls is varied from 0.03 to 0.16 m, and the convective heat flux at the wall ranges from 75 to 200 W/m. In this study, the heated section is 1.6 m in height. Different heating configurations are analysed, including the uniform heating mode and two different configurations of non uniform, alternate heating. The experimental procedure allows the wall temperature and local heat transfer coefficient to be inferred and shows that the proper selection of the separating distance and heating mode can noticeably decrease the surface temperatures and hence enhance the conversion efficiency of PV modules