In the KnowJuly 31st, 2020 | Category: Architects' Guide to Glass and Metal
The Challenges to BIPV’s Growth
Green building is more than a passing trend— it has become fundamental to the way architects design buildings. Building-integrated photovoltaics (BIPV) is one piece of the green pie, and the size of that piece is expected to grow in the next five to ten years.
As It Stands
BIPV incorporates photovoltaic (PV) technology seamlessly into the building envelope. There are two types of PV currently used: crystalline silicon solar cells and a thin layer of PV material placed on a glass or metal substrate. When integrated into a building, PV serves as both a means to convert the sun’s light into energy and a replacement for traditional materials on the building skin. A building’s entire BIPV system also includes a charge controller, power storage system, power conversion equipment, backup power supplies and supporting hardware.
The BIPV cells currently used in the market typically are a dark blue color due to an anti-reflective coating that is conducive to absorbing light energy. However, BIPV can be created in several colors as demonstrated by the new Heineken brewery in Chihuahua, Mexico. The brewery features red, green and transparent photovoltaic glass custom engineered for the project.
The photovoltaic glass was engineered by Onyx Solar, based in Ávila, Spain. It’s integrated on the curtainwall and rainscreen cladding system. According to the company, it will filter 99 percent of ultraviolet rays and 95 percent of infrared radiation.
While vertical integration of BIPV with the façade results in less sunlight reaching the photovoltaic cells compared to a rooftop or skylight application, the increased area afforded by façade integration can make up for the difference.
According to Daniel Decroupet, research and development coordinator for the AGC Technovation Centre in Charleroi, Belgium, the cost, aesthetic and required energy storage are major challenges hindering the growth of BIPV usage in commercial architecture.
It can take more than a decade for a company to see a return on investment from the energy savings created by BIPV. However, because BIPV replaces some of a building’s traditional materials, those savings can be factored into the cost. As the technology advances, the cost to implement BIPV into the building façade could become less costly.
The aesthetics of BIPV can be a deterrent to many architects, who can find other ways to increase the energy-efficiency and LEED points of a building.
“Usually in big cities, architects want perfectly glazed facades with glass of the same color,” says Decroupet.
He notes that glazing increasingly is being used throughout the entire façade of a building as architects continue to favor an all-glass aesthetic, which reduces the spandrel area needed for BIPV integration. Another likely place to integrate BIPV is the roof of a structure, but commercial buildings often have small roofs packed with HVAC equipment, elevator motorizations and window cleaning systems.
Even if there is a place for the BIPV to be integrated, Decroupet says architects can be hesitant to specify BIPV because the color rendering is not aesthetically appealing when compared to other energy-efficient glazing solutions.
“I have the impression that opaque BIPV will have trouble growing in an important way,” he says.
Decroupet adds that one challenge BIPV also faces in the retrofit market is that the cabling required is often rejected. It is easier to integrate cables on a façade as it is constructed rather than during a retrofit project.
In Europe, many residential architects are faced with BIPV’s peak acquisition being too high for consumption.
“There’s no way to store that energy locally for the moment and the backflow from panels is difficult for the electric companies to manage,” says Decroupet.
He suggests that architects find a way to store the excess energy locally, such as batteries, so that the building can be energy independent. It’s also important to calculate the expected energy consumption of a facility when planning the design.
As LEED drives energy-efficient building further in the U.S., Decroupet expects that more architects will turn to BIPV as a solution for zero-energy applications.
“Our estimates of BIPV’s growth from five years to the present are less than 10 to 20 percent realized. Integration is behind what we expected, but there should be dramatic growth in BIPV within the next five to ten years,” says Decroupet.
He believes that a transparent BIPV solution with good neutrality and high energy capture capabilities will help the technology grow as solar energy becomes more vital to reducing a building’s energy waste.
Several companies and researchers are exploring ways to create transparent BIPV solutions with high energy absorption. As the technology advances, it could be the key to unlocking BIPV’s growth globally.
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