A solar sandwich for 21st century buildings
Imagine a building that, like a plant, uses its entire surface to capture sunlight and convert it into energy.
It’s not an average rectangular building with black solar panels jutting out from the roof; instead, picture an aesthetic, organic structure with solar cells built right into its undulating facade.
By giving architects unprecedented freedom in designing buildings with curved, power-generating surfaces, a composite construction element that we are developing at École polytechnique fédérale de Lausanne (EPFL) could help put an end to one of the more pervasive arguments against solar panels: that they are ugly.
In most of the developed world, the way buildings are built has hardly changed over the past century. A robust structure made of steel, concrete or masonry carries the building’s weight. A layer of insulation keeps the heat in or out, and the whole is polished off with a facade.
This approach has become so commonplace – and so cheap – that it is likely to hold its ground even as new building materials are developed.
Because of their higher price, non-traditional building approaches have to be designed to outperform traditional ones, technically or aesthetically, to establish themselves on the market.
The approach we have adopted in a project with EPFL Middle East aims to excel technically while still looking good. It integrates the functions of the load-bearing concrete, the insulation, and the facade into a single, multifunctional building block.
In a composite design, we encapsulate dense insulating foam between two thin layers of transparent, fibreglass-reinforced polymer composites. Flexible thin-film solar cells are embedded into the outer layer of the sandwich.
At half the thickness of a conventional wall or roof, the resulting material is strong enough to bear the weight of a multi-story building as well as wind or seismic loads.
It can be designed to take on any shape, and still generate electricity to run the air conditioning or other electrical appliances inside.
We are currently putting our composite construction modules through a battery of tests to assess their long-term performance in the hot and humid Middle Eastern climate.
We are not the first to push for the use of composites in construction. After the Second World War, chemical companies tried to tap into the construction market and market composites as the building material of the future. Their products could be mass-produced, easily transported, and rapidly assembled at a reasonable cost.
And they looked, briefly, like they were in with a chance. The Monsanto House, which became a famous exhibit at Disneyland in California, was on the verge of becoming one of the first mass-produced composite homes.
But it never caught on. The construction market, traditionally very conservative, was unwilling to support the change in paradigm. And homeowners were given little or no freedom in the design of their homes – each house was prefabricated according to the same plan.
Still, the Monsanto House had a lot going for it. Prefabricated building blocks could be assembled under ideal working conditions and quality tested before being transported to the construction site.
Rapid assembly could save time and money during construction, and once completed, faulty elements could be replaced on demand.
Now, more than five decades later, we would like to go several steps further and develop a system that is both modular and individual.
It must allow individual pieces to be efficiently produced in large numbers, while giving architects and home designers as much freedom as possible.
These multifunctional 21st-century building blocks might not find their way into your neighbour’s house in the near future. But we expect them eventually to offer architects new horizons in designing iconic sustainable buildings.
Prof Thomas Keller is director of the composite construction laboratory at EPFL in Lausanne, Switzerland