Throughout most of history, humans have had to devise strategies for cooling food and buildings without convenient AC systems or refrigerators. Indeed, the oldest and most basic system for escaping solar radiation is tree shade. Another solution found in villages dotted along the Mediterranean coast since the dawn of history is to use white paint to reflect solar radiation.Based on the latter, the current Passive radiative cooling during the day (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 and often relies on highly sophisticated materials. nanotechnology, which can reflect certain solar wavelengths and send them back into space.And the first result of this is technology project Really encouraging.
In fact, the system created by Bikram Bhatia and the rest of his team is a high-tech version of the traditional parasol. The point is the combination of a base that emits mid-infrared rays and a reflector that blocks direct sunlight. Sunblocking strips are designed to provide shade at different times of the day without the need for an active solar tracking system. Under it, researchers placed a box with several elements for different purposes. first, infrared emitteris a copper plate painted white and placed over an insulator. Then there are two layers of polyethylene with small gaps that minimize diffuse 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. All these factors worked together to achieve a cooling of 6 degrees Celsius in the first test.
However, the tests were conducted in the Boston area of the coastal city where atmospheric humidity is high and infrared radiation is blocked. Researchers believe that the efficiency of this technology project is much higher in arid regions, with a theoretical maximum cooling temperature of 40C. This simple device is very useful in areas without electricity or can be added to existing cooling systems to reduce power energy consumption. .
cooling paint
In one of my previous articles about Innovative energy saving projectmentioned the remarkable properties of Egyptian Blue, an old pigment that reflects infrared rays and can passively cool buildings. It is a polymer-based paint that has been announced. Their nanoporous materials can spread over buildings, water deposits, and other structures, achieving efficiencies similar to passive cooling systems created by Bhatia at MIT. In our own tests, we managed to lower his surface temperature by 6°C. The team is currently investigating commercial applications and paint scalability. AC systems appear to be facing serious competition.
sauce: MIT, Physics
