New solar technology inspired by butterfly wings

Photovoltaic and solar thermal systems are not generally thought of as aesthetically pleasing. New custom-coloured modules, being developed at the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany, aim to challenge that perspective.

Inspired by the phenomenon that causes the shimmering shades of blue or green on the wings of the Morpho butterfly, the underlying mechanism of spectrally selective reflectance allows finished modules to be a homogenously uniform colour — from bright, stand-out tones to more subdued greys.

Issues with current designs

The appearance of rooftop solar panels has evolved with advances in technology, and modern solar panels now feature a sleek design to maximise kerb appeal. However, some less-than-desirable aesthetic elements still remain and are the result of variances in the solar panel design including make, model, cell type, backsheet, frame and busbars.

Solar modules can be integrated almost invisibly into facades and roofs, but they are not seen as a design feature among building owners and architects. The new panels can be manufactured in a specific desired colour and integrated fully into both roofs and facades — a key requirement to fully utilise available space.

They can even give the finishing touch to modern buildings with a ventilated curtain-wall facade.

“The brainwave behind this development was not to colour the protective glass on modules with pigments, but to imitate the physical effect of butterfly wings,” said Dr Thomas Kroyer, head of the coating technologies and systems group.

If glass was coated with pigments, the modules would lose a greater portion of their efficiency because the light could no longer penetrate unhindered. The MorphoColour panels allow around 93% of light to penetrate, with only around 7% being reflected to cause the colour effect.

Aesthetically pleasing

The MorphoColour coated protective glass is produced using vacuum technology and can be laminated to form photovoltaic modules or used in a collector for solar heat generation. In the future, it will be possible to have photovoltaic and solar thermal modules in the same colour, mounted almost invisibly next to each other on the roof or the facade. When the colour is matched to the rest of the building, the result is an exterior wall with a perfectly uniform finish and a facade that supplies electricity as well as heat. In that sense, future homes can be aesthetically pleasing plus-energy houses, supplying more energy than they consume.

New assembly design

Colour alone does not make for a visually appealing design. The Fraunhofer researchers found another solution to make PV systems more attractive: to prevent soldered photovoltaic cells from shimmering through the coloured protective glass, they developed an assembly method that evokes the effect of roof shingles.

Roof shingles are laid on top of each other so that the rain runs off. In a similar fashion, the solar technology researchers in Freiburg are now producing photovoltaic cells in strips that overlap by a few millimeters, gluing them together to form a larger module. This creates a homogeneous overall look without unsightly gaps or visible connecting cables.

The panels were on display at the BAU trade fair in mid-January.

Image ©Fraunhofer ISE