A solar sandwich to power future buildings

Jun 08, 2012 By Jan Overney
Credit: Silly Little Man / Flickr under creative commons license

All in one: A new electricity generating building component is being developed at EPFL.

Most modern buildings are composed of several layers of materials, each with its own important function: the concrete core supports its weight; the regulates its heat exchange; the facade contributes to its . Now, engineers at EPFL are developing a single building block that does all of that, and produces electricity. This new component will provide a sleek alternative to traditional , and will be lighter, safer, and more energy efficient.

“We use a composite sandwich construction to make this multi-functional building element,” explains Thomas Keller of the Composite Construction Laboratory (CCLab). The sandwich comprises a dense foam interior encased between layers of glass-fibre reinforced polymer. “We started working on these composite materials over 10 years ago and used them in 2009 for the roof of the Main Entrance Building at the Novartis Campus in Basel, Switzerland,” he says.

That was before trying to add electricity generation to the mix. “Now our goal is to encapsulate a thin flexible sheet of photovoltaic cells beneath a translucent layer of glass fiber reinforced polymer,” he continues. If they succeed, this material could contribute to making solar panels more attractive to architects by offering them more flexibility than traditional construction materials based on reinforced concrete, rigid solar panels, and glass.

The solar cell technology comes from Flexcell, an EPFL startup that became famous for its flexible sheets of photovoltaic cells, as thin as a sheet of paper. Despite lower efficiencies than conventional photovoltaic cells, their light weight, small volume, and low production costs make them ideal for encapsulation into building elements. And the ease of fitting curved surfaces with them will open new avenues in sustainable architectural design.

On top of that there are the other, already demonstrated advantages of these lightweight sandwich components. Prefabrication means that they can be assembled in a factory under ideal conditions before being transported to the construction site, increasing the quality and the safety of the buildings and shortening construction times. And since they are modular, individual elements are easy to repair or to replace if they fail.

Perfecting the ingredients

The glass fiber reinforced polymer (GFRP) plays a double role in this sandwich. A layer of GFRP a few millimeters thick encases the foam core, giving the building block its remarkable stability. Another layer of it encapsulates and protects the solar cells, drawing on an interesting optical property of the GFRP: when applied thinly, it is almost as transparent as glass, with an optical transmittance only four percent lower. Currently, a PhD student at the CCLab is perfecting this layer’s thickness to find the best compromise between structural stability and optical translucence.

“Besides the optical issues,” says Keller, “we are dealing with temperature related issues. Heating the resin leads to a loss of efficiency in light transmission. Beyond a certain critical temperature, the material could degrade and fail to recover its original state when it cools down.” But so far it has withstood temperatures beyond those expected even in the hotter parts of the world, without showing signs of degradation.

Not yet two years in to the project, the scientists involved are optimistic. Solar generation is here to stay, and considering the widespread use of curved concrete surfaces in contemporary architecture, there could be great potential for this new solar sandwich.

Explore further: Chinese scientists unveil liquid phase 3-D printing method using low melting metal alloy ink

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TrinityComplex
5 / 5 (1) Jun 08, 2012
I recall a quote 'I have seen the future, and it is shiny', referring to the fact that buildings seem to be more and more reflective. I'm curious how much visible light these materials will reflect. Add the solar cell windows to a building like this and nearly the entire structure could generate electricity. I'm entertained that, despite this being a new, cutting edge technology, it's building with prefabricated blocks. Sounds strangely reminiscent of...bricks. The more things change the more they stay the same?
kaasinees
3.7 / 5 (3) Jun 08, 2012
What happened to all those solar energy trapping windows?
Terriva
2.3 / 5 (3) Jun 08, 2012
What happened to all those solar energy trapping windows
The same question can be raised about 99% of solar energy related findings and concepts, presented here at PO during last years. Despite of huge effort and money invested, the absolute majority of solar cell industry relies to rather simple and uncomplicated solar cells made of polycrystalline silicon from China, which were known at the end of 60's of the last century already. If some progress exists here, then it manifests itself rather with decreasing of production cost. The manufacturing price limits the scope of all other futuristic applications. We shouldn't forget, that most of solar cell installation is actually subsidized with government, as it's economically infeasible by itself. The solar cell industry actually increases the fossil fuel consumption on background, but the governments are investing into it, as it can provide the (partial) replacement of fossil fuels (a hope for energetic independence) for future.
TrinityComplex
5 / 5 (2) Jun 08, 2012
I was able to find one company that is at least working on them, if not selling them for commercial use:
http://www.newene...arwindow
kaasinees
5 / 5 (1) Jun 08, 2012
Thanks for the link, good to know they are still working on it, there is probably a lot of money yo be made in that field... Would be a good motive for Beijing to clear its skies to get more solar energy on their buildings 8]