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· collected 2026-08-28 · by TOI Science Desk
MIT researchers, led by Zhengmao Lu and Evelyn Wang, built a compact device in 2022 that cools without electricity. The device, which measures only 4 inches tall, uses three passive cooling methods: evaporation, heat loss through infrared radiation, and thermal insulation. In tests, the device achieved a temperature reduction of about 9.3 degrees Celsius (18.7 degrees Fahrenheit) relative to its surroundings, demonstrating a significant difference without consuming electricity. The team's design combines multiple cooling effects to overcome their individual limitations, providing a potential solution for areas with scarce power or infrastructure.
Written by the local model on 2026-08-28,
using this article's own text rather than the other coverage of the
same event (that is the story summary below).
On a hot roof in Cambridge, Massachusetts, a small experimental device sat in the sun without a fan, compressor or electrical connection.
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device → sit → fan
Its job was simply to get colder than the air around it.
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job → get → it
Water moved through one part of the device, heat escaped through another, and layers of insulating material helped keep the cooling from being undone by sunlight.
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layers → move → sunlight
That rather quiet experiment points to a problem that is becoming harder to ignore.
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that → point → problem
Cooling is increasingly important as temperatures rise, yet conventional air conditioning depends on electricity and reliable infrastructure.
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conditioning → rise → electricity
In places where either is scarce, keeping food, water or indoor spaces cool can be difficult.
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keeping → keep → food
An MIT team has been testing a different approach, combining several passive cooling methods in a single compact structure.
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team → test → structure
MIT researchers combined three cooling effects without electricity
The idea is not to replace air conditioning with a single miracle material.
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idea → combine → material
Instead, the system brings together three familiar physical effects that have usually been used separately: evaporation, heat loss by infrared radiation and thermal insulation.
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that → bring → radiation
Individually, each has limitations.
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each → have → limitations
Evaporative cooling becomes less effective when the surrounding air is already humid.
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air → become → ?
Radiative cooling can struggle when sunlight warms the surface it is supposed to cool.
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it → struggle → surface
Insulation does not create cooling by itself; it simply slows the movement of heat.
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it → create → heat
The MIT design places these functions together so that the weaknesses of one component are partly offset by the others.
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weaknesses → place → others
As reported by MIT News, in tests, the small device produced a temperature reduction of about 9.3 degrees Celsius, or 18.7 degrees Fahrenheit, relative to the surrounding air.
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device → report → air
That is a substantial difference for something that does not consume electricity.
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that → consume → electricity
The researchers described the system in a 2022 paper published in Cell Reports Physical Science.
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researchers → describe → Science
The work involved Zhengmao Lu, Arny Leroy, Jeffrey Grossman, Evelyn Wang, Lenan Zhang and Jatin Patil.
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work → involve → Lu
The three-layer device reflects sunlight, evaporates water and sheds heat
The device is designed around three main layers.
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device → reflect → layers
The arrangement matters because sunlight, water and heat all have to move in particular directions.
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sunlight → matter → directions
At the top is an aerogel made from polyethylene.
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aerogel → make → polyethylene
Although it looks solid, much of the material is actually empty space.
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much → look → material
Its porous structure traps air, giving it strong insulating properties, while still allowing water vapour and infrared radiation to pass through.
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vapour → trap → properties
Water from the layer underneath can evaporate upwards, taking heat with it.
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Water → evaporate → it
At the same time, thermal radiation can pass through the upper material and escape towards the sky.
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radiation → pass → sky
An air conditioner moves unwanted heat from inside a building to the outside air.
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conditioner → move → air
This passive system can send some of its heat upward through infrared radiation, taking advantage of wavelengths at which the atmosphere is relatively transparent.
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atmosphere → send → which
Its pores hold water, providing the supply needed for evaporation.
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pores → hold → evaporation
As water reaches the surface and changes into vapour, it carries heat away from the structure.
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it → reach → structure
The bottom layer has a different task.
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layer → have → task
It behaves like a mirror, reflecting sunlight back upwards instead of allowing that energy to be absorbed and turned into heat.
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energy → behave → heat
The aerogel itself also helps with solar protection.
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aerogel → help → protection
Its insulating and light-reflecting properties reduce the amount of heating caused by strong sunlight.
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properties → insulate → sunlight
It is a fairly simple sequence: reflect as much sunlight as possible, prevent heat from moving in, evaporate a small amount of water and allow infrared energy to escape.
Why humidity has been a problem
Evaporative cooling works best when the surrounding air can accept more water vapour. In dry conditions, that is relatively easy.
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that → reflect → conditions
In humid weather, the air is already carrying a large amount of moisture, so evaporation slows down.
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evaporation → carry → moisture
That has made many evaporative cooling systems less useful in humid regions, even though those areas can have significant cooling needs.
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areas → make → needs
Radiative cooling has its own complications.
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cooling → have → complications
A surface may be able to radiate heat towards the sky, but if it absorbs too much sunlight during the day, the solar heating can cancel much of that benefit.
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heating → radiate → benefit
The MIT design attempts to deal with both problems at once.
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design → attempt → problems
Evaporation provides one route for removing heat, while radiative cooling provides another.
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cooling → provide → another
…and 45 more, not listed.
