When solar power collecting windows were announced a few years ago, I was a skeptic; they were only 5 percent efficient and I thought (and still think) that they were a dumb idea. I wrote:
First, build an efficient wall with no more glazing than is needed for light and view, to reduce energy demand;
Second, get some power out of the opaque parts; then, maybe, worry about pulling energy out of the glass. But it is really, a very distant third.
Those solar windows came around on many sites including TreeHugger a few weeks ago, and they are still vapourware, still ridiculously inefficient, and I think they are still a dumb idea. Meanwhile, C.F. Møller Architects have completed the Copenhagen International School in Nordhavn that shows how it's done: The building cladding is a giant grid of 12,000 very pretty Swiss solar panels. The windows are windows. Mads Mandrup Hansen, lead architect, is explains to Jennifer Geleff in Architizer:
..we can create a new aesthetic of solar cells that moves away from the dreariness that architects often associate with them. With this project, we broke through a barrier, and realized that solar cells can be an extremely beautiful and colorful building component. We also showed that solar panels can go not only on the roof, but also all over the sides of a building. We think this project is a big page turner.
This is the key -- they are not the usual black panel, but a special one developed at the Ecole Polytechnique Federale in Lausanne. The architect explains how it works:
"EPFL has developed a special glass filter that allows the solar panel to take on one single color. The filter determines which wavelengths of light will be reflected as a visible color," Mandrup said. The rest of the sunlight is absorbed by the solar panel and converted into energy." After 12 years of research, they have figured out a way to do this without using pigment and without reducing the the energy efficiency of the glass. The science is very complicated, but the way it works is very similar to the Iris Effect, and how you sometimes see a colorful rainbow reflected on thin surfaces like soap bubbles."
Interestingly, all the panels are the same colour, but mounted tilted at slightly different angles. “It just depends on the way the panel is angled, and how the sun hits its individual surface,” Mandrup said.
Swissinso, the solar panel manufacturer, describes their Kromatix panels as "the only attractive alternative to today’s black and dark blue panels, without compromising on panel performance, efficiency, or architectural design." But their site shows buildings that look like glass boxes. By doing the different angles, C.F. Møller have made them into something really special.
I have no information as to how efficient these solar panels are because, apparently, this is glass that goes on top of the solar panel to make it look good, with "virtually no effect or compromise in panel performance and efficiency." I also worry a bit about the angling, and the amount of water that gets behind them when you do it this way, although Mandrup says, "We tested the panels at a climate lab in Spain, where we threw large gusts of wind at them."
But I really do believe that this is the future of solar façades, where windows are windows and walls have solar spandrels at far greater efficiency. Lots more images at Architizer, who get it with their title How C.F. Møller Architects Altered the Face of Building-Integrated Solar Panels.