The market for a seamless integration of PV in buildings seems to lie especially in the energetic renovation of historic buildings. A recent study found that when PV modules are colored to match the roof or façade of an existing building, then social acceptance increases. But striking the balance between aesthetics and energy yield has presented a challenge for solar researchers until now: Solar modules for building-integrated applications need to behave optically like a traditional colored element while still generating as much power as possible.
Taking inspiration from the 3D photonic structures on a Morpho butterfly’s shimmering blue wings, scientists at Germany’s Fraunhofer Institute for Solar Energy Systems ISE have developed colored solar panels that can be incorporated into a building’s exterior practically invisibly while maintaining high efficiency.
In 2024 the Institute of Psychology at the University of Freiburg, Germany, and the neighboring Fraunhofer Institute for Solar Energy Systems ISE conducted a joint study on the social acceptance of building-integrated photovoltaics (BIPV). The conclusions showed that the acceptance of integrated photovoltaics in urban areas is generally very high and that PV on modern buildings is viewed more positively than on historic buildings.
The study also showed, however, that when PV modules are colored to match the building’s roof or façade so that they are practically invisible, then social acceptance is increased to the point where no difference is detected between the different building types. “An important finding of the study is that the social acceptance of PV systems depends on the type of building and visual impression. These two factors weigh much more heavily than personal variables such as personal values, political attitudes, or environmental concerns,” summarized the authors of the study.
Market expectations for building-integrated PV
Today, 75% of installed PV in Germany is located on buildings. The market for photovoltaics on buildings is growing continuously and holds great potential. Around 400 GW of installed PV power will be required by 2045 for the energy transition in Germany to succeed. With a technical potential of around 1,000 GW, photovoltaics on buildings can make a significant contribution to the decarbonization of the building sector and built infrastructure – without taking up additional land area.
This “double use” of already sealed surfaces appeals to urban areas all over the world and allows cheap electricity to be generated where it is needed. However, solar panels can sometimes look out of place when installed on roofs and facades, especially in the historical centers of cities. From the study on the social acceptance of BIPV, it can be concluded that for existing buildings it makes more sense to select colored PV modules that blend homogeneously into the building’s appearance rather than using PV as an architectural detail. Therefore, for the PV industry it is important to offer a wide range of aesthetically different PV modules to match the different existing buildings.
Color inspired by a butterfly
The sticking point for colored BIPV products has been their lack of efficiency. Simply painting the cover glass of a PV module results in the color pigments blocking out the sun and inhibiting it from reaching the solar cells. To avoid this, the research team at Fraunhofer ISE looked to nature for inspiration and found it in the Morpho butterfly. The 3D photonic structures on the butterfly’s wings allow for an intensive, angularly stable colored impression thanks to a fundamentally low-loss interference effect. Following this biological model, the scientists succeeded in using a vacuum process to apply a similar surface structure to the back of the glass covering their solar panels. Depending on the fine structure, glass coverings in a large variety of colors and also colored foils can be produced.
The coating system developed for colored solar panels has now surpassed the biological model in terms of its properties. Independent measurements confirm that colored solar panels with structural rather than painted coatings can achieve about 95% of the power of a comparable uncoated panel. The plug-in solution can be used with all standard commercially available solar technologies as well as those foreseeable in the future, plus it can be manufactured industrially at low cost. Cell and panel technologies such as rear contact solar cells with a uniform appearance are an especially good fit.
If you want to read the study, please visit this website.
Author: Thomas Kroyer
This article is part of a series contributed by RD20, a global initiative of leading research institutes of the G20 countries and regions with the aim to strengthen international collaboration in R&D and promote innovation towards a carbon-neutral society. Articles under this column are contributed by individual RD20 member institutes and are the sole property of the designated author(s).
For more information: https://rd20.aist.go.jp/
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