True Colors: Photo voltaic Panels to Improve the Exteriors of Buildings

Photovoltaic modules, which can be produced in a single color spectrum using a technology inspired by butterfly wings, are being developed by the Fraunhofer Institute (credit: Fraunhofer Institute)

Photovoltaic modules, which can be produced in a single color spectrum using a technology inspired by butterfly wings, are being developed by the Fraunhofer Institute for Solar Energy Systems (ISE).

Dr. Tom Kroyer, Head of Group Coating Technology and Systems, Fraunhofer Institute for Solar Energy Systems

The goal, explains Dr. Thomas Kroyer, head of the coating technology and systems group at the organization, is to make solar panels more aesthetic to encourage designers to incorporate them into buildings.

“We see a lot of potential for these modules in building-integrated photovoltaics (BIPV). BIPV is a technology that can significantly improve a building’s carbon footprint, ideally down to a zero-energy or plus-energy building. “

Butterfly wings

BIPV involves the use of photovoltaic modules in place of traditional building materials in areas such as roofs, skylights and facades. Despite their advantages and the recently improved aesthetics of solar modules, photovoltaic modules are still not popular design features with developers, planners and architects.

However, the Fraunhofer ISE modules combine functionality with beauty and will be available in different colors to enhance or merge with the building on which they are mounted, explains Dr. Kroyer:

“Conventional methods of coloring solar cells or covering glass offer a limited selection of colors and have one major disadvantage – they cause comparatively high energy losses. Our process produces colored modules with minimal transmission losses and thus minimal energy yield losses. ”

In the Fraunhofer ISE process, a layer of dielectric materials with a photonic 3D structure is added to the back of the photovoltaic glass.

“This structure is inspired by the morpho butterfly, whose bright blue wings are not produced by pigments, as is the case with other butterflies, but by a surface structure with lamellae [a thin layer of organic tissue] in the nanometer range. The miniature lamellae, which can only be seen under an electron microscope, cause light to be diffracted and interfered. The many lamellas reflect light of a certain wavelength, in this case blue; The reflections reinforce each other so that a really brilliant color is achieved. “

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Light transmission

The special highlight of this structure is that it remains transparent for the other wavelengths. It is therefore ideal for generating brilliant colors with high light transmission at the same time. Compared to uncoated cover glass, the colored modules show a relative power loss of only seven percent, an efficiency that is unique in the construction sector. Hues can be set by adjusting the spacing between the slats within the 3D structure on the surface of the glass so that any color can be made, says Dr. Kroyer:

“The more complex the photonic structure used, the better the quality of the color, for example in terms of angular stability and efficiency.”

Prototypes are expected to be produced this year. The panels could hit the market in 2022.

“The biggest challenge in the project is to find a compromise between the production effort – cost and time – and the color effect. Our current research focus is to achieve the best possible color effect at a reasonable cost for solar module manufacturers. “

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