Building Integrated Photovoltaic Systems- Part I
by Paolo Francesco Lamacchia
This contribution wishes to raise questions that aim at comparing the potential of photovoltaic material to conventional construction materials, and to suggest the possible steps needed to overcome the barrier of acceptance of PV in different urban contexts, different historic centers and different cultures.
As stated in the previous article, sustainability, energy efficiency and onsite or nearby renewable energy sources are the most important concepts that contemporary architecture pursues for a zero energy or emission building model (ZEB). All cities and buildings around the globe are going to keep all the benefits that the wind and solar power have already witnessed on the earth surface. Photovoltaic (solar electric) modules are clean, safe and efficient devices that have long been considered a logical material for use in buildings.
Recent technological advances have made photovoltaic (PV) systems suitable for direct integration into building construction. PV module size, cost, appearance and reliability have advanced to the point where they can function within the architectural parameters of conventional building materials. A building essentially provides free land and structural support for a PV module, and the module in turn displaces standard building components. The added value of colorful photovoltaic panels give to designer new opportunities of integrating artistically colored photovoltaic systems. Someone says that the PV panels disfigures the landscape, but a spontaneous question raises: who has declared that the red color of a tile or the grey color of the cement is better for all than a cobalt blue color of the PV cell?
Optimizing BIPV applications is a function of many variables: construction methods and materials, photovoltaic technology and module fabrication, insulation levels and orientation, and electrical costs. Architectural application of PV systems is winning for curtain walls, balcony, skylights, atria, facade, rooftops and besides some outstanding products generating electric energy from transparent glass surfaces, like Glass to Power’s photovoltaic windows, are in market uptake.
Another helpful installation is on flat roofs that would seem to present the least degree of engineering difficulty for BIPV installations, largely because the technology for ground based arrays is generally applicable. Flat roofs differ from inclined ones primarily in the nature of the watertight layer (eg. asphalt, membrane). Roof mounted systems which are not fully integrated may be either ballast mounted or rack mounted. Anyway, fully integrated BIPV roofing systems must perform the function of a standard roof and hence issues such as water tightness, drainage, and insulation are important for all systems.
It is really incredible how, despite of the low cost of PV per KW, many Italian building’s flat rooftops are not yet endowed with PV panels. Moreover, the flat position avoids, in those terraces with border curb, the problem of environmental constraints or aesthetic ones and also a flat PV panels layer-made rooftop displaces forward the maintenance costs of a standard floor terrace, this last one subject almost every 25 years to high costs of regeneration.
In the II part of BIPV we will highlight the technologies for the integration of renewable energy sources on the façade, skylight, atria and shading elements.