The technology for passive cooling, a process that uses no electricity at all, has progressed thanks to research at the Massachusetts Institute of Technology. According to a university news release, Zhengmao Lu, a post-doctoral researcher, and his colleagues recently succeeded in passive cooling up to 19 degrees Fahrenheit (9.3 degrees Celsius).
In order to provide substantially greater cooling than has ever been possible before, the system combines two independent passive cooling methods that have been employed in the past with thermal insulation. The technology saves you from have to make a refrigerator without having to dig a hole underground, and the only maintenance required is the addition of water. The local humidity would also affect how frequently this occurred.
How does the system work?
On the roof of a building at MIT, the researchers displayed their invention using boxes that were four inches (10 cm) across and could easily mistaken for solar panels.
Three layers of material were used to create the devices, which have the dual function of chilling water and allowing heat to travel through. Aerogel, a sponge-like structure made of polyethylene with cavities filled with air, makes up at the top layer. The substance is insulating by nature, but it also permits the passage of infrared light & water vapour.
A layer of hydrogel, another sponge-like material with cavities filled with water, is positioned below the aerogel. Finally, a mirror-like coating reflects all incident light onto the other components of the device, components heating-up them rather than the contents of the storage box.
Evaporative cooling occurs as heated water in the hydrogel evaporates, carrying part of the heat with it as it moves upward. Additionally, because the vapour can pass through the aerogel, some heat from the device can be sent directly into space by infrared radiation (radiative cooling).
According to the press release, the cooling therefore accomplished might be used to store food for 40% longer in humid environments and for three times longer in dryer conditions.
Roadblock to commercialization
The method can also be used to cool air conditioning compressors, reducing the load they experience. By doing so, the effectiveness of the air conditioner would be improved, and energy would be saved. Before this technique is scaled up for commercial use, there remains a significant obstacle.
Since the evaporative materials employed in the process would heat up in the sun and be unable to offer adequate cooling, previous attempts at passive cooling have only had limited success as per previous attempts. The MIT team created the aerogel used in these trials, and it requires a costly production method.
The aerogel’s manufacturing solvents must be carefully removed without compromising the aerogel’s structure. The critical point drying (CPD) process is made possible by specialist equipment, which raises the price.
The researchers are currently investigating whether less expensive techniques like freeze drying or the use of substitute materials could eliminate the requirement for CPD, hence saving money. The team is now unsure on exactly when this would be possible.
The findings were published in the journal Cell Reports Physical Science.