Houses made of high-tech wood could help us stay cool and also reduce carbon emissions by cutting energy used on air conditioning.
Liangbing Hu at the University of Maryland and his colleagues created the material by removing the lignin—a component of the cell walls in trees—from natural wood using hydrogen peroxide.
The remaining wood is mostly made of cellulose, another component of plant cell wall. Cellulose reflects visible light and only absorbs very low levels of near-infrared light. This means the cooling wood reflects most of the components of sunlight right back to the environment. As a result, a building made from this material would transmit barely any heat indoors.
The team also found that the material can absorb heat produced indoors, which is emitted at a different wavelength range to sunlight. During cooler nights, the wood helps release the heat outside, making it useful day and night.
Hu says the cooling wood is very dense and has a tensile strength of around 404 megapascals, making it 8.7 times stronger than natural wood and comparable to metal structure materials including steel.
To investigate how much energy the wood could save, the team simulated replacing the exterior walls and the roofs of some apartment buildings in 16 US states, representing a variety of climate conditions. They found the wood could reduce cooling energy requirements by an average of 20 to 35 per cent.
However, because cooling wood prevents heat from the sun from getting indoors, it will result in additional heating costs in winter. Therefore, Hu says the material is best suited for warm areas with long summers and short winters, such as Arizona and Hawaii.
cbeair on May 24th, 2019 at 13:25 UTC »
This is a very misleading title. I do my research in wood science and they’re talking about a few different things here. Holocellulose isn’t a new idea (de-lignified Wood). Application to a construction product wood be (as lignin is the matrix that keeps wood cohesive like a composite). But they only tested their holocellulose panels for reflectivity, not structurally.
The other thing is the strength values. They’re reporting tensile strength values from individual nano-cellulose fiber testing, not structural testing of the panels they created. Some of my friends research nano-cellulose and it’s an amazing material but we still don’t have great ideas for making it a robust building material. Individual fibers are very strong and quite ductile, but the problem comes back too traditional composite mechanics With aligning and binding those fibers.
SpeckledFleebeedoo on May 24th, 2019 at 08:14 UTC »
Since the article itself doesn't mention it: the density is 1.2 g/cm3 according to the supplementary materials.
That's less than half the density of aluminium, but with significantly higher yield stress.
OliverSparrow on May 24th, 2019 at 07:52 UTC »
H2O2 has long been used to make straw and woody cellulose digestible by ruminants. Shell's Amsterdam labs found that peroxide plus high pressure steam made wood extrudable in whatever shape you wanted: complex cross sections - pipes to curtain rails - pressed fittings, things like combs and so on. It was not, however, cost competitive with plastics.