Engineers from Stanford University found a revolutionary new way to decrease the level of heat radiation buildings absorb on hot summer days. The invention is incredibly energy efficient, cheap and it could be a green solution to the traditional air conditioning systems.
The mirror-like invention is designed to reflect back the heat energy coming from the sun that heats tall buildings in cities during summer. The mirror is in fact a seven-layered coating made of silicon dioxide (SiO2) and hafnium oxide (HfO2) on top of a silver layer. All the layers are not thicker than the thinnest aluminum foil.
Researchers say that this new coating radiates the heat away from buildings, through the atmosphere, and sends it back into space. Before being sent into space, the solar heat (or UV light) gets transformed into infrared radiation (IR) in a process called photonic radiative cooling.
But infrared energy, along with CO2 emissions, plays a huge part in global warming process. After hitting Earth, solar energy naturally returns into atmosphere as infrared radiation, but, instead of going upwards directly into space, this radiation is absorbed by CO2 particles located in the atmosphere and sits there warming up the planet. This process is natural and without it we would have had a cold planet, but nowadays, due to the high levels of CO2, it works against us.
The Stanford researchers say that the infrared energy reflected back by their mirror is able to dodge the carbon oxide particles and get into the cold outer space because their device transforms the energy into IR radiation with frequencies incompatible with the greenhouse particles of CO2.
Professor Shanhui Fan says that any object that radiates heat energy needs a “heat sink” to drop this energy into it. The heat sink of the warming buildings during hot summer days will be the “coldness of the universe”. The Nobel Prize award winning physicist Burton Richet was also amazed that the invention was so uncomplicated and worked.
The new discovery could also replace air conditioners from our houses and considerably lower the energy costs. Its inventors say the device is able also to absorb the heat inside structures and redirect it towards the exterior. As a result, a building that has only 10% of its rooftop covered with this mirror-like coating could spare 35% of its energy previously used in cooling during the hottest months.
Researchers also hope that their high-tech mirror that cools down buildings will help poorer regions to benefit from their photonic radiative cooling effect using zero electricity, and big cities will lower their energy and air conditioning demands.
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