Colorful solar modules through »Morpho Color«

German Fraunhofer Institute for Solar Energy Systems ISE has developed processes to produce solar panels with a homogeneous and brightly colored surface. The colored components could be integrated almost invisibly into a facade or roof.
The principle was borrowed from the wing of the Morpho butterfly. »The idea for the development was not to color the cover glasses of the modules with colored pigments, but rather to imitate the physical effect of the butterfly's wing,« says Thomas Kroyer, head of the Coating Technologies and Systems group. If glass were coated with pigments, it would lose much of its efficiency because the light would no longer be able to pass the module's surface unhindered.
In contrast, the butterflies that live in the tropical rainforests of Central and South America create a color impression not through colored pigments, but through an optical effect. »The butterfly wings have a micrometer-fine surface structure that specifically reflects a narrow wavelength range, i.e. a color.« The Fraunhofer ISE experts have succeeded in applying a similar surface structure to the back of the cover glass of their photovoltaic modules using a vacuum process. Depending on the fine structure, cover glasses in blue, green or red can be produced in this way. »Around 93 percent of the light can penetrate this layer - only around seven percent is reflected and triggers the color effect,« says Thomas Kroyer. The Freiburg researchers named their technology »Morpho Color« after the blue Morpho butterfly.
The cover glasses, which are vaporized in a vacuum process, can be laminated into photovoltaic modules or integrated into a collector for solar heat generation. In the future, photovoltaics and solar thermal energy could be provided with the same color »and mounted virtually invisibly next to each other on the roof or facade.« If the color is matched to the rest of the building, a house wall with an absolutely homogeneous exterior can be realized.
Moreover, the Fraunhofer researchers have found a new approach for mounting solar cells. To prevent the photovoltaic cells, which are soldered together, from shimmering through the colored cover glass like a checkerboard, they have developed a method reminiscent of the principle of roof shingles. Roof shingles are laid overlapping on top of each other to allow rain to run off. Accordingly, the Freiburg solar researchers produce photovoltaic cells in strips, which they glue together overlapping by a few millimeters to form a larger module. This creates »a homogeneous whole without any disturbing gaps or visible contact wires.«
The colored and the shingled modules will be presented from January 13 to 15, 2021, at the BAU trade fair, which will be held digitally this year.

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