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Building integrated photovoltaics (BIPV) 

Photovoltaic (PV) systems represent the most used technology to convert solar radiation into electricity. A PV module is a grid of cells of semiconductor material, which is able to convert sunlight (photons) to electricity (voltage potential). Most typically, PV panels are installed on roofs or on the ground. Nevertheless, a promising application which can boost the use of solar energy is to integrate PV systems directly into the building envelope.

Source: https://es.wikipedia.org/wiki/Archivo:BAPV_solar-facade.JPG 


By definition from the European Construction Product Regulation CPR 305/2011, a PV module is considered building-integrated (BIPV) if it forms a product and construction system that provides a function (beyond energy collection). Therefore, BIPV systems are necessary for the integrity of the buildings’ functionality [1]. If the BIPV is dismounted, it has to be replaced by a suitable and compatible construction product.  The main building´s functions of BIPV include: mechanical rigidity (structural integrity), weather protection, energy economy (shading, daylighting, and thermal insulation), fire and noise protection, separation between outdoor and indoor environments, security, shelter or safety. Therefore, compared to standard PV, BIPV modules have special features to fulfil the architectural and structural requirements of the building. Moreover, BIPV have a strong impact on the energy consumption of the building and, other than the electric conversion efficiency, other performances to take into account during the design are the thermal insulation level, solar heat gain coefficient and optical properties [2]. A BIPV module is made of a PV laminate which consists of a front cover, a front encapsulant, PV cells, a rear encapsulant, and a back cover. Regarding PV cell technologies, crystalline silicon, both polycrystalline and monocrystalline, is the most used. The front cover of BIPV modules can be made of either glass or polymer material [3]. Polymeric covers are often used in roofing membranes, ventilated facades or bonded to other components. Opaque BIPV systems come in different textures and colours.  In most BIPV applications, glass front covers are used and the module is often designed as a glass-glass module. PV glass laminate can be in the form of double or multiple glazing to improve thermal insulation. Some BIPV can use low-emissivity coatings or integrate a vacuum insulate glass [2].  PV cells can be integrated into different parts of the building using different BIPV systems including discontinuous roof, rainscreen (ventilated facade), external integrated devices, skylight, prefabricated systems, and curtain walls [4]. BIPV modules can be available in different colours and shapes to meet architectural requirements with different degrees of transparency. Indeed, BIPV can be also integrated into windows. In this case, semi-transparent modules can contribute to energy savings to the building and improve the visual comfort of the occupants and, although they can be less efficient than other BIPV systems, they can contribute to the visual aesthetics and architectural flexibility of the building.  In order to improve the efficiency of those systems, BIVP/T is a promising technology that combines the generation of electricity with thermal energy. In this case, a heat transfer fluid (air, water or refrigerant) can be used to cool down the PV cells and to provide thermal energy to support space heating, domestic hot water production or to be coupled with heat pumps [5]. 




BIPV is a mature technology (TRL9) and there are many case studies available [6]. However, today the BIPV market is relatively small and this technology still comes with a high cost. Nevertheless, research is putting effort to develop innovative BIPV systems that are more cost competitive and efficient.  

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