Throughout most of its history, mankind has had to devise strategies to cool food and buildings without the convenience of air conditioners and refrigerators. In fact, the oldest and most basic system for escaping solar radiation is shade. Another solution seen in the villages that dot the Mediterranean Basin since recorded history is the use of white paint to reflect solar radiation.Considering the latter, currently Passive diurnal radiative cooling (PDRC) technology adds an infrared emitter while exploiting the reflective properties of the material. That is, it can give off more heat than it receives. Achieving such results requires very sophisticated materials and frequent means. nanotechnology, can reflect certain solar wavelengths and send them back into space. At MIT, however, we turned to very simple materials to achieve passive cooling. And this first result is technology project It seems really encouraging.
In fact, the system created by Bikram Bhatia and other members of his team is a high-tech version of the classic parasol. The point is the combination of a base that emits mid-infrared rays and a reflector that blocks direct sunlight. Solar blocking strips are designed to provide shade at different times of the day without the need for an active solar tracking system. Under it, the researchers placed a box with several elements for different purposes. first, infrared emitter, which is a copper plate painted white and placed on top of an insulator. Next, he has two layers of polyethylene with small gaps that minimize scattered solar radiation. Finally, the remaining perimeter of the box is covered with silver foil to prevent parasitic heat load transfer, i.e. heat transfer from one surface to another. With all these elements working together, he achieved a 6°C cooling in the first test.
However, this test was conducted in the Boston area, a coastal city where high atmospheric humidity interferes with infrared radiation. The researchers believe that the efficiency of this technology project will be much higher in arid regions, with a theoretical maximum cooling capacity of he 40 degrees Celsius. This simple device can be very useful in areas with scarce power supplies, or can be added to existing cooling systems to reduce power consumption. .
cooling paint
In a previous article, Innovative energy saving projectdescribed the remarkable properties of Egyptian Blue, an ancient pigment that reflects infrared radiation and can passively cool buildings. One of the latest developments in this field is a polymer-based paint introduced by Columbia Engineering, which belongs to Columbia University. Its nanoporous materials can be spread over buildings, water deposits and other structures, achieving efficiencies similar to passive cooling systems created by his Bhatia at MIT. In our own tests, we managed to lower his surface temperature by 6°C. Currently, the team is researching commercial applications and scalability of the paint. AC systems appear to be facing stiff competition.
