Passive cooling technology, a process that uses no electricity, has made progress thanks to research at the Massachusetts Institute of Technology. Postdoctoral researcher Zhengmao Lu and his colleagues recently succeeded in passive cooling to 19 degrees Fahrenheit (9,3 degrees Celsius), according to a statement from the university.
In order to provide much more cooling than was possible before, the system combines two independent passive cooling methods used in the past with thermal insulation. This technology saves you from building a refrigerator without having to dig a hole underground, and the only maintenance required is the addition of water. Local humidity will also affect how often this occurs.
What is the Working Mechanism of the Non-Electric Cooling System?
The researchers demonstrated their invention on the roof of a building at MIT, using boxes that are four inches (10 cm) wide and can replace solar panels. Three layers of material were used to create the devices that served the dual purpose of cooling the water and allowing heat to pass through. Airgel, a sponge-like structure made of air-filled polyethylene, forms the top layer. This substance is inherently insulating, but at the same time allows the passage of water vapor and infrared rays.
Underneath the airgel is a layer of hydrogel, another sponge-like material whose cavities are filled with water. Finally, a mirror-like layer reflects all incoming light back to other parts of the device, preventing the contents of the storage box from overheating.
Evaporative cooling occurs when the heated water in the hydrogel turns into water vapor and moves upward, carrying some of the heat with it. Infrared radiation (radiative cooling) can also carry some of the heat from the device directly above the air and into space, as the vapor can pass through the airgel.
According to the press release, the cooling achieved in this way can be used to keep food 40% longer in humid environments and three times longer in dry environments.
Are there any obstacles to commercialization?
By cooling them, this method can also be used to reduce the load on air conditioning compressors. This will increase the efficiency of the air conditioner and save energy. There is a significant obstacle to the commercial dissemination of this technology.
Previous attempts at passive cooling have had only limited success, as the evaporative materials used in the process will heat up in the sun and not provide adequate cooling. The MIT team created the airgel used in these trials, and it requires an expensive manufacturing method.
Airgel fabrication solvents must be carefully removed without compromising the structural integrity of the airgel. The critical point drying (CPD) process is possible with special equipment that raises the price.
Researchers are currently investigating whether cheaper techniques such as freeze drying or the use of substitute materials can eliminate the need for CPD and thus save money. The team is currently unsure when exactly this will be feasible.
Source: interestingengineering
📩 23/09/2022 18:54
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