The new photovoltaic modules can be manufactured in the desired colour, © Fraunhofer ISE

Generating power from the sun is taken for granted these days. Photovoltaic panels have also long established themselves as a standard technology. Unlike 20 years ago, they are now produced in large volumes at economical prices. However, there is still one thing that has not truly changed: the way the modules look. They are consistently formed of glossy black plates with a protective layer of glass covering solar cells that are soldered to each other like a chessboard. From an aesthetic point of view, modules such as these do not have much of a charming effect when they are attached to a building facade. These sorts of solutions are equally unpopular among developers and architects. Yet with the energy revolution in mind, it would make good sense to equip both rooftops as well as building walls with systems that generate power.

In order for the modules to be incorporated into facade designs more harmoniously – from an architectural standpoint – researchers at the Fraunhofer Institute for Solar Energy Systems ISE have developed methods that can be used to manufacture solar systems with a homogeneous, brightly coloured surface. The components can be made in a desired colour to add the final touch to buildings with rainscreen cladding, while the actual purpose served by them is no longer visible at first glance. “The brainwave behind this development was not to colour the modules’ protective glass with pigments, but to imitate the physical effect of butterfly wings,” explains Dr Thomas Kroyer, Head of the Coating Technologies and Systems Group.

While pigment-coated glass absorbs light and therefore limits the effectiveness of the modules, these innovative coverings utilise an optical effect seen on the wings of the morpho butterfly. These insects live in the tropical rainforests of Central and South America and achieve an iridescence through a microscopic surface structure that reflects just one narrow wavelength, that is, one specific colour. The Fraunhofer experts successfully applied a similar surface structure to the rear of the protective glass on its solar modules by using a vacuum process. The protective glass consequently appears blue, green or red, depending on the microstructure. Fittingly, the scientists named their technology MorphoColor, after the radiant, iridescent blue butterfly. “About 93% of the light can penetrate this layer, with only 7% being reflected to trigger the colour effect,” explains Kroyer. The development also offers a further benefit: in addition to being laminated onto solar modules, the protective glass can also be integrated into a collector for solar heat generation. That means both modules will be able to be given the same colour and installed side by side without any visible difference, such as on an energy-plus house.

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