A new type of modified wood that can trap heat and then release it when needed could help buildings cut down on their energy use.
Scientists say that the revolutionary material, which is biodegradable, can bear heavy loads and could open the door for ‘eco-friendly’ homes and other buildings.
The researchers, from KTH Royal Institute of Technology in Sweden, produced technically transparent wood, which allows light to pass through it.
They did this by removing a light-absorbing component called lignin from the wood’s cell walls and adding polyethylene glycol (PEG), which stores heat.
After adding acrylic – which stops the light from bouncing around – into the porous wood, the resulting material is physically strong and and virtually clear.
The material is not completely transparent but its hazy appearance provides enough privacy without shutting out external light.
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A new type of modified wood that can trap heat and then release it when needed could help buildings cut down on energy usage. Here, the new transparent wood becomes cloudier (right) upon the release of stored heat.
The material is able to absorb heat before it reaches the indoor space, making it cooler inside and at night it releases the heat indoors.
Céline Montanari, a PhD student student at the University said: ‘Back in 2016, we showed that transparent wood has excellent thermal-insulating properties compared with glass, combined with high optical transmittance.
‘In this work, we tried to reduce the building energy consumption even more by incorporating a material that can absorb, store and release heat.’
As economic development progresses worldwide, energy consumption has soared.
Much of the energy is used to light, heat and cool homes, offices and other buildings.
Glass windows can transmit light, helping to brighten and heat homes, but they don’t store energy for use when the sun goes down.
Three years ago, lead investigator Professor Lars Berglund and colleagues at KTH reported an optically transparent wood in the journal Biomacromolecules.
The researchers made the material by removing a light-absorbing component called lignin from the cell walls of balsa wood.
To reduce light scattering, they incorporated acrylic into the porous wood scaffold, which also protects from humidity.
The light-diffusing timber is also able to absorb, and release heat, potentially saving people money on energy costs. Scientists say that the revolutionary material, which is biodegradable, can bear heavy loads and could open the door for ‘eco-friendly’ homes (stock image)
Ms Montanari said: ‘During a sunny day, the material will absorb heat before it reaches the indoor space, and the indoors will be cooler than outside.
‘And at night, the reverse occurs – the PEG becomes solid and releases heat indoors so that you can maintain a constant temperature in the house.’
She said the team encapsulated PEG within the de-lignified wood scaffold, which prevented leakage of the polymer during phase transitions.
The researchers say that the transparent wood has the potential to be more environmentally friendly than other building materials such as plastic, concrete and glass.
In addition to its thermal-storage capabilities, the researchers say that the transparent wood could be easier to dispose of apart from the acrylic.
Professor Beglund said that the PEG and wood are both bio-based and biodegradable.
‘The only part that is not biodegradable is the acrylic, but this could be replaced by another bio-based polymer.’
The researchers estimate that transparent wood could be available for niche applications in interior design in as little as five years.
They are also trying to increase the storage capacity of the material to make it even more energy-efficient.
The research team were due to present their finding at the American Chemical Society (ACS) Spring meeting in Orlando, Florida.
