The production of key crops can be negatively impacted by heat waves, droughts, and energy supply issues caused by a warming planet. Thus, in a world where temperatures are on the rise due to a warming climate, it has become essential to find environmentally friendly ways to address the challenge of keeping the growing population cool while also maintaining an adequate food supply.
Image Credit: MIT
Now, researchers at MIT have developed a sophisticated eco-friendly solution in a system that utilizes passive cooling to preserve food crops and support traditional air conditioners in buildings. The system does not need an active power supply and requires only a small amount of water to enable it to run.
Through a combination of radiation and evaporation, the team says that the system has the potential to improve the safe storage time of food by up to 40% in humid conditions and threefold in an arid environment.
Their work has been published in the journal Cell Reports Physical Science. The team claims that, with further research and advancement, the novel system could one day have a key part to play in meeting the cooling needs of populations where water scarcity and energy shortages are prevalent.
Combining Evaporative and Radiative Cooling
The system is housed in a thermally insulated compact package that protects the radiation and evaporation cooling systems by offering cooling temperatures somewhere in the region of 19 degrees Fahrenheit (9.3 degrees Celsius) from the ambient temperature.
This innovative technological application would potentially facilitate safe food storage to meet future demands.
This technology combines some of the good features of previous technologies such as evaporative cooling and radiative cooling.
Zhengmao Lu, Co-Author and Postdoctoral Researcher, MIT
Conventional systems are often limited when it comes to functionality in certain environments. However, this combination demonstrates the possibility of significantly extending food life, “even in areas where humidity levels are high,” says Lu.
To achieve significantly more cooling, the system combines what were once independent cooling designs that alone deliver limited amounts of cooling power. However, when combined, these systems generate enough cooling power and efficiency that would prevent food losses and avoid spoilage which would help those places already suffering from food supply issues.
Enhancing System Efficiency
Moreover, the technology the MIT researchers have proposed has the potential to enhance system efficiency in existing air conditioning systems in buildings. The combination system can help significantly reduce the load on conventional systems by transporting cool water to the condenser, which is the warmest part of the system.
By lowering the condenser temperature, you can effectively increase the air conditioner efficiency, so that way you can potentially save energy.
Zhengmao Lu, Co-Author and Postdoctoral Researcher, MIT
While there are other projects working with passive cooling technologies, the main obstacle has been overcoming environmental conditions. However, by putting forward a novel passive cooling system that synergistically combines evaporation, radiation, and thermal insulation, Lu and his colleagues have developed a novel technology that can perform exceptionally well in a range of harsher ambient conditions.
The system relies upon a top layer that is made of an aerogel, which is predominantly air encased in a polyethylene structure resembling a sponge. This aerogel layer has exceptionally good insulation properties while allowing infrared radiation and water vapor to permeate its structure.
The other layers in the novel cooling system include another spongy material that contains water below the aerogel and a mirror layer below that. The layer that contains the water acts as a source from which the vapor forms, and the mirror prevents any sunlight from warming the system. Additionally, the aerogel acts as an effective solar reflector protecting the system even when exposed to intense sunlight.
“The challenge previously was that evaporative materials often do not deal with solar absorption well,” Lu says.
With these other materials, usually when they’re under the sun, they get heated, so they are unable to get to high cooling power at the ambient temperature.
Zhengmao Lu, Co-Author and Postdoctoral Researcher, MIT
While more research is required to fine-tune this novel eco-friendly passive cooling system, one of the advantages is that many of the materials are cost-effective and readily available. However, finding a way to scale up and mass-produce the aerogel will also require more work.
Nonetheless, this research marks a positive shift towards developing an alternative to conventional cooling systems, which has practical application in a world looking to find new ways to simultaneously preserve the food supply and keep cool.
References and Further Reading
Chandler, D., (2022) Passive cooling system could benefit off-grid locations. [online] MIT News | Massachusetts Institute of Technology. Available at: https://news.mit.edu/2022/passive-cooling-off-grid-0920
Lu, Z., Leroy, A., Zhang, L., Patil, J., Wang, E. and Grossman, J., (2022) Significantly enhanced sub-ambient passive cooling enabled by evaporation, radiation, and insulation. Cell Reports Physical Science, [online] p.101068. Available at: https://www.cell.com/cell-reports-physical-science/fulltext/S2666-3864(22)00362-9
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