Cool buildings without air conditioning
In the US, air-conditioning systems are responsible for about 15% of the energy consumed by the building sector. With the new material, still in the laboratory, invented by researchers at Stanford University, substantial savings could be made in this area.
Stanford University engineers have developed an innovative coating to help cool buildings. Their findings, recently published in Nature, indicate that their process would maintain the interior temperature to around 5 ° C below the outside temperature. Without having to rely on any energy source. At the heart of the invention, an ultra-thin material (only 1.8 microns thick) and multilayer whose action is twofold. One, it helps to reflect radiation from the sun to prevent heat from entering the building; two, it can absorb the heat inside the building to return it to the outside, without heating the surrounding air.
In the South, the homes are usually covered with a white roof that reflects sunlight. What limit the heat input into the houses. The same principle applies with remarkable efficiency, the coating invented by the team of Professor Fan Shanhui. The material refers in fact 97% of solar radiation that strikes it. The real innovation, however, based on its second property. Recall that the objects, like living beings emit heat as infrared radiation, invisible to the naked eye. It is the heat of this radiation we feel, for example, when we stand before a closed furnace. This even as the coating developed by Stanford researchers can evacuate to the outside of buildings.
This new material is composed of seven layers of varying thickness of silicon dioxide (SiO2) and hafnium (HfO2) deposited on a thin silver layer. These layers constitute a structure which is capable both of reflecting the incoming radiation but also to absorb heat to the inner retransmitting to infrared wavelengths between 8 and 13 micrometers. The molecules in the air can not absorb the heat emitted in the wavelength: the surrounding air does not heat, heat is directly released into space.
Some technical difficulties to solve
For now, the prototype is not larger than a pizza. Its designers ensure that such material can be economically viable if it is shaped so as to find practical applications. One solution could come from spraying the material onto a solid support may be installed on the roofs. He will still find a way to guide the internal heat to the outer coating so that it can evacuate it.
Despite these difficulties, the team is confident Shanhui Fan. Professor of Electrical Engineering sees this project as a first step in the use of the universe as a heat sink accessible and unlimited scope. Until its coating can be installed on the rooftops of the world, it ensures that it can improve the performance of existing cooling systems, helping them to evacuate their waste heat into space.
No Comment to " Cool buildings without air conditioning "