POL has taken part in the recent Horizon 202 EU-funded project called “BrightWall” to create a translucent concrete wall that allows in natural lighting, without the associated loss of heat. POL provided consultancy on the optical design, optical materials selection and lightguide manufacturing aspects of the project.
The new material – named ‘BrightWall’, after the project – has such good insulation properties that it can help a building retain twice as much energy as a standard concrete panel and up to five times more than glass walls and windows. It also reduces the need for electric lighting and air conditioning. This makes it the ideal building solution and could help the EU to meet its targets of cutting electricity use and achieving a 20% increase in energy efficiency by 2020.
The BrightWall material is a concrete sandwich panel, comprising of two layers of reinforced concrete, with insulation in between. This sandwich construction provides the wall with its strength, load-bearing qualities and ability to withstand extensive fire testing. But it’s the innovative little tubes — light guides — that give the new wall its high energy-saving potential.
BrightWall project coordinator Johannes Portielje Rauff Greisen explains that these ‘light guides’ were a key project achievement. A light guide is a tube made of optical fibres. It works like a mirror tunnel; it transmits and reflects light that shines onto the opening of the tube. “The project team passed 5 000 light guides through all three sections of the first BrightWall to produce a facade that is fully insulating and that allows controlled daylight to pass through into the building,” says Greisen. When placed within the concrete, the light guides transfer so much daylight into a room that the total window area needed is significantly reduced. The light guides and a slight modification of the concrete casting process have enabled researchers to create a building material that is really a wall and a window all in one.