Windows made from wood? Seems inconceivable doesn't it but the exciting reality is that scientists in Sweden and the USA are endeavouring to scale up prototypes ready for mass production.
Sweden, the pioneer country of renewable forestry is the source of some 51 billion trees, so it is hardly surprising that Swedish researchers and scientists are constantly innovating ecologically friendly uses for Sweden's ample and ready source of timber.
Material Scientists at The University of Maryland and the Wood Science Center in Stockholm have designed a process that removes the molecule in wood lignin that makes it rigid and dark in colour. The remaining colourless cellulose cell structure is then filled with epoxy or polymer to give it strength, and lo and behold, there remains a semi-transparent wood composite. This process results in optically transparent wood that is twice as strong as plexiglass and able to transmit 85 per cent of light falling on it.
Credit: Maryland NanoCenter
The Maryland Scientists sliced the Linden wood in two ways to compare how the materials performed and how light transferrence would be affected. One cut was made with the grain of the wood, so that the channels passed through the lengthways through the block. They also tried slicing it against the grain, so that the channels passed through the width of the block. The short channel wood proved slightly stronger and a little less brittle.
They then investigated how the different cell alignments of the wood affected the way the light passed through it. They found differences in the opacity of the wood due to the initial direction of the wood grain.
So, what are the potential advantages of 'transparent wood' over glass?
- The researchers claim it will be stronger, tougher, lower in density
and lower in thermal conductivity. - Light is diffused as it travels through the cell structure thus
reducing solar glare. - It is much less breakable than glass because the cell structure
inside resists shattering.
Early in 2016 researchers from KTH Royal Institute of Technology in Stockholm demonstrated their version of 'transparent wood' that they believe will revolutionise the architecture of tomorrow. Its properties of transparency will assist the incorporation of natural light and will be available in differing grades of opaqueness to offer differing degrees of privacy. Benefits would include savings on the cost of artificial lighting and they talk of the potential for solar cell windows.
(Photo: Peter Larsson)
Lars Berglund, a professor at Wallenberg Wood Science Center at KTH in Stockholm is excited about the possibilities of introducing 'transparent wood' into the manufacture of solar cells. He states it's advantages including its low cost, ease of availability and above all that it is a renewable resource. He envisages a future where it will be deployed in large scale solar projects covering large surface areas. Solar cell fabrication based on 'transparent wood' substrate is currently being undertaken by the KTH team.