Photovoltaic (PV) technology is one of the most promising renewable energy technologies to directly produce electricity from sunlight without any direct harm to the environment during operation. These devices are capable of producing electricity out of sunlight without noise, pollution, maintenance and depletion of materials.
Integrating PV elements into the envelope of the building is growing worldwide. Designers across the world are now exploring creative ways of incorporating PV technology into the buildings. A building integrated PV (BIPV) system is one such innovative system that can provide savings in electricity costs and materials, reduce emission of ozone depleting gases and use of fossil fuels. While most of the BIPV systems are connected to utility grids, BIPV may also be a stand-alone, off-grid system.
Video - Building Integrated Photovoltaics - an Introduction - Run time - 11:27mins
BIPV can be integrated in many ways including into a building façade, replacing or complementing roof structures, spandrel glass or into awnings thereby increasing access to direct sunlight and providing passive shading. BIPV in roofing systems replaces the use of traditional 3-tab asphalt shingles, seam metal roofing and batten. It can also be integrated to skylight systems.
PV integrated into the building envelope constitutes a BIPV system. These PV modules avoid the use of conventional building envelope materials and power generator thereby reducing the incremental cost of PV. Therefore, BIPV systems have lower overall costs than other PV systems. The BIPV system constitutes the following:
- Power storage system comprising a utility grid in utility-interactive systems or a number of batteries in case of stand-alone systems.
- Charge controller for regulating the input and output of power from the battery storage bank in case of stand-alone systems.
- PV modules that might be crystalline or thin-film, transparent, semi-transparent, or opaque.
- Backup power supplies that include diesel generators
- Power conversion equipment having an inverter for converting the DC output of PV modules to AC compatible with the utility grid.
- Support and mounting hardware, safety disconnects and wiring.
Buildings that produce power with the help of renewable energy sources avoid the need of conventional utility generators, and hence reducing the overall gas emissions.
Guidelines for Designing Architecture to Include BIPV systems
Some key guidelines for designing BIPV systems into building architecture for a sustainable building are listed below:
- Application of energy-efficiency measures or design practices is required for reducing the energy requirements of the building.
- PV conversion efficiencies are influenced by elevated operating temperatures. Hence appropriate ventilation behind the modules is needed to dissipate heat and improve conversion efficiency of the system.
- PV modules must be arranged properly as array orientations may have significant impact on the annual energy output of the system.
- Designers must consider the climatic and environmental impact on the array output. Hot, overcast days will have low energy output, and cold, clear days will have high energy output.
- Collection and utilization of solar thermal resource developed by heating of the PV modules may optimize system efficiency. This thermal energy can be used for pre-heating of incoming air in cold climates.
- Batteries must be incorporated into certain grid-tied systems when the peak building loads do not match the peak power output of the PV array.
Merits and Demerits
BIPV technologies employ crystalline silicon that is suitable for inexpensive, large-scale production, and dye-sensitized solar cells composed of low-cost materials that do not need high energy consuming manufacturing device. BIPV systems offer energy conservation and high insulation value. Additionally, they reduce carbon footprint.
However, the high cost of BIPV is one of the biggest challenges over normal crystalline PV modules. Installation of BIPV system is more complex, and requires high labor charges. BIPV modules made of thin films have low efficiency.
Photovoltaic Transparent Glass
This glass developed by Onyx Solar when fitted on the roofing system of the building enables a user to clearly view through the building while avoiding infrared radiation and UV radiation. It is available in different colors and transparency degrees of 10%, 20% or 30%.
BIPV systems / materials have the potential to contribute to zero energy buildings, while complementing the utility grid to supply most or all of the building's electrical needs, with excess energy sold back into the grid. According to a recent NanoMarkets Report, the BIPV glass market alone is likely to reach $6.4 billion within the next four years.
Although BIPV-specific incentives are not very popular, the need for inexpensive, aesthetically unobtrusive solar materials is increasing globally. Some European countries offer additional incentives for BIPV in addition to subsidies provided for stand-alone PV systems.
BIPV has a great opportunity to play a vital part in the renewable power generation sector of future. In spite of certain economic challenges, the value of generating power using flexible BIPV modules is being slowly realized, which may help overcome the barriers of current BIPV applications.