System provides cooling with no electricity

Posted: October 31, 2019 by oldbrew in innovation, research, Temperature

Credit: scienceblog.com


It’s claimed this invention could be used to improve any type of cooling system.

Imagine a device that can sit outside under blazing sunlight on a clear day, and without using any power cool things down by more than 23 degrees Fahrenheit (13 degrees Celsius).

It almost sounds like magic, but a new system designed by researchers at MIT and in Chile can do exactly that says TechXplore.

The device, which has no moving parts, works by a process called radiative cooling.

It blocks incoming sunlight to keep from heating it up, and at the same time efficiently radiates infrared light—which is essentially heat—that passes straight out into the sky and into space, cooling the device significantly below the ambient air temperature.

The key to the functioning of this simple, inexpensive system is a special kind of insulation, made of a polyethylene foam called an aerogel.

This lightweight material, which looks and feels a bit like marshmallow, blocks and reflects the visible rays of sunlight so that they don’t penetrate through it. But it’s highly transparent to the infrared rays that carry heat, allowing them to pass freely outward.

The new system is described today in a paper in the journal Science Advances, by MIT graduate student Arny Leroy, professor of mechanical engineering and department head Evelyn Wang, and seven others at MIT and at the Pontifical Catholic University of Chile.

Such a system could be used, for example, as a way to keep vegetables and fruit from spoiling, potentially doubling the time the produce could remain fresh, in remote places where reliable power for refrigeration is not available, Leroy explains.

Minimizing heat gain

Radiative cooling is simply the main process that most hot objects use to cool down. They emit midrange infrared radiation, which carries the heat energy from the object straight off into space because air is highly transparent to infrared light.

The new device is based on a concept that Wang and others demonstrated a year ago, which also used radiative cooling but employed a physical barrier, a narrow strip of metal, to shade the device from direct sunlight to prevent it from heating up. That device worked, but it provided less than half the amount of cooling power that the new system achieves because of its highly efficient insulating layer.

“The big problem was insulation,” Leroy explains. The biggest input of heat preventing the earlier device from achieving deeper cooling was from the heat of the surrounding air. “How do you keep the surface cold while still allowing it to radiate?” he wondered.

The problem is that almost all insulating materials are also very good at blocking infrared light and so would interfere with the radiative cooling effect.

Continued here.

Comments
  1. A C Osborn says:

    Sounds good.

  2. JB says:

    Imagine what that kind of insulation would do for domicile heating and cooling needs. Now imagine it less expensive than cellulose….

    As a teen, I heard my father lament about how the family before I was born, did not have cooling capabilities to preserve produce during WWII. At the time, and I still do, think my dad was quite myopic about the problem. Passive cooling techniques have been around for millennia, and every so often someone comes up with a hi-tech material to improve that.But the real break-through is one that boosts efficiency while using common materials available everywhere.

  3. vuurklip says:

    “… efficiently radiates infrared light …”
    But doesn’t that mean that infrared light from the environment will easily radiate back into the device? So it ends up at the same temperature as the environment?

    Sounds like a variation of Maxwells daemon where the insulation acts as the daemon?

    Help me out here!

  4. Gamecock says:

    Shade.

  5. oldbrew says:

    ‘The new device is based on a concept that Wang and others demonstrated a year ago, which also used radiative cooling but employed a physical barrier, a narrow strip of metal, to shade the device from direct sunlight to prevent it from heating up. That device worked, but it provided less than half the amount of cooling power that the new system achieves because of its highly efficient insulating layer.’

  6. In talking about cooling there is no mention of timing. Naturally if one allows something to occur at night and then insulate it and stop the sun warming it, it will be cooler in the day than if it had no insulation. In the desert it can be below freezing at night and very hot in the day. With the 2nd law of thermodynamics heat can only flow from the surface of a body if the temperature of the surrounds are lower than the temperature of the body. Having insulation which will block short wave radiation in but allow long wave radiation out seems a good idea. The CO2 alarmists will not be happy because they think CO2 blocks outgoing long wave radiation (which it does not except at the wavelength of 14.8 micron and then only a small unmeasurable amount) because that is their excuse for lowering the amount of CO2 in the atmosphere

  7. Dodgy Geezer says:

    Sounds ideal for space vehicles…

  8. Dodgy Geezer says:

    …or, indeed, vehicles generally…

  9. pochas94 says:

    Just as long as you keep the surface good and clean.

  10. Jim says:

    I would agree, this is cool. But. Always the but, I would agree with one of the commenters above, the one of ww2, except for the why. There is no repository for advances of mankind that is freely available to all of mankind. It is all hidden under copyright. Or will be. And the educational system is one of the worst offenders. It hides each of the baby steps as a “new” process. It shows none of the baby steps, only a perfected result, and hides all prior knowledge and research under a trademark. And those away from the “trade” center, will never hear of the question answered, or of the process and it’s function.

  11. ivan says:

    Looking at the lack of technical information and the pictures in the article, it looks to be more pie in the sky thinking.

    Where is the the real world unit test. It is OK to show a small box but, if as they say, it could be used for keeping fruit and vegetables for longer they need a much larger container, something like a barn or house.

    When they can show it cooling a house down to a reasonable level, or even a refrigerator in a house then they would have something to talk about. Until such time they would be better off improving Peltier cells for use in refrigerators.

  12. Gamecock says:

    “It is all hidden under copyright.”

    Pls learn the difference between copyright and patent.

    “And the educational system is one of the worst offenders.”

    And you are a victim of it.

  13. stpaulchuck says:

    I didn’t see any cost figures for installed material/units. We know what the cost per BTU is for current heating and cooling devices. What is it for this?

    Under what conditions does it NOT work? Is this another “windmill”?

  14. Kelvin Vaughan says:

    But we are told the world is heated by back radiation which is infrared.

  15. oldbrew says:

    Best not to believe everything we are told, without checking 🤔

  16. Pablo says:

    All objects give off heat in the form of infrared radiation, an invisible form of light just to the right of red on the spectrum.

    The atmosphere itself, mainly in the form of water molecules, also radiates back a portion of the heat.

    But a sliver of emissions in the mid-infrared range (with wavelengths between eight and 13 micrometers, for those keeping score) slips through, escaping through what has been described as a “window into space.” Materials emitting radiation in that range literally cast it into the cold expanses of space, or at least the cool upper atmosphere, allowing the surfaces themselves to dip below the temperature of the surrounding air. This natural phenomenon is what causes frost to form on surfaces under the open night sky, like car windows and blades of grass, even when temperatures don’t reach freezing.

    A critical challenge for harnessing this mechanism in useful ways has been that during the day, the heat from the sun generally offsets any cooling effect. But in research first published in Nature in late 2014, the scientists behind SkyCool Systems got around that problem by developing an advanced material tuned to radiate infrared light in the range that slips through the atmosphere while also reflecting away 97 percent of sunlight. Placed on a roof under direct sunlight, the material remained 4.9 ˚C below ambient air temperatures, a “cooling power of 40.1 watts per square meter.”

    from…https://www.technologyreview.com/s/608840/a-material-that-throws-heat-into-space-could-soon-reinvent-air-conditioning/

  17. ivan says:

    a “cooling power of 40.1 watts per square meter.”

    They forgot to add ‘until the surface becomes covered in dust and grime when the ‘cooling power’ drops to zero’.

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