Low-cost smart windows
Smart windows, varying the amount of light coming through the glass, can now be produced economically
A new type of wood, able to reflect infrared radiation without any additional coating, has been developed.
At the Imnovation-Hub we have previously covered passive cooling solutions for buildings. These technologies improve power efficiency and contribute to a more sustainable architecture. Considering the global warming predictions for the next years, scientists and engineers are logically looking for alternatives to traditional air conditioning units. Saving energy with efficient building materials is now possible. Some of these alternatives include reflective paint and green covers or even the use of ancient Egyptian pigments. However, both require applying a special coating or covering the building. Could a special material featuring these characteristics be developed to make life easier for builders? That was the starting point for the scientists at the University of Maryland. After all, it was not for nothing that the had already developed mid-infrared-reflective coatings, which send the radiation back to the outer space. And so they came to develop a new type of wood.
When a material emits short-wave infrared radiation, the surrounding air warms up, which means that heat is not dissipated. Therefore, the first step would be to strip it of lignin, a powerful infrared emitter. To achieve it, they soaked lime tree wood in a hydrogen peroxide solution, which breaks down the lignin molecules. The next step in the process was to wash the wood and press it with a hot press to compact the remaining cellulose and hemicellulose. Not only did they have now a strongly reflective material, but also eight times harder than conventional wood. Also, once the lignin is removed, the wood turns white, which scatters sunlight besides absorbing heat and emitting it as mid-infrared radiation.
The outcome of the research is a treated wood that can reduce the temperature of the surface by up to 10º C, an efficient building material which, thanks to its properties, will succeed in reducing the energy consumption of buildings. According to the researchers, the power savings could well reach up to 60 %. There are still some obstacles to overcome though, as the material is flammable, and wood is not commonly used for roofing. For the time being, it could be used for walls together with other treatments for roofs such as those mentioned earlier on.
Usually, lignin is a byproduct of paper manufacturing and it had so far been discarded as waste. However, researchers have already set their sights on this biopolymer as a promising material with a host of applications. One of the latest is its use in asphalt, a mixture in which there has already been experimentation with the inclusion of textile fibers from used tyres. The development of a bioasphalt with lignin is an initiative carried out by the Dutch Wageningen Food & Biobased Research. The center made the first tests four years ago, paving a one-hundred meter stretch of a road with an asphalt mixture with 50 % of lignin. Four years later, the results seem encouraging as even the traffic noise has been slightly reduced. However, the researchers warn that the wait to establish the durability of the material is not over, as roads have an expected life between ten and fifteen years. However, they feel cautiously optimistic and believe that in a few years’ time there could be 100 % lignin asphalts in the market, which would allow reducing the amount of oil-based asphalts.