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Science Forum

  1. 05 Sep '17 21:38 / 3 edits
    Using radiative sky cooling to cool a building isn't a new idea but still interesting I think;

    https://techxplore.com/news/2017-09-cooling-electricity.html
    "...the radiative sky cooling effect can enable cooling below the air temperature even on a sunny day..."

    I wonder if that could be scaled up to cool the whole planet to counter global warming? -probably a rather expensive 'last-resort' kind of solution.
  2. Standard member sonhouse
    Fast and Curious
    08 Sep '17 17:02
    Originally posted by @humy
    Using radiative sky cooling to cool a building isn't a new idea but still interesting I think;

    https://techxplore.com/news/2017-09-cooling-electricity.html
    "...the radiative sky cooling effect can enable cooling below the air temperature even on a sunny day..."

    I wonder if that could be scaled up to cool the whole planet to counter global warming? -probably a rather expensive 'last-resort' kind of solution.
    Seems like it would end up heating the atmosphere over cities more than happens now if that tech were to be adopted big time.
  3. 08 Sep '17 17:17 / 4 edits
    Originally posted by @sonhouse
    Seems like it would end up heating the atmosphere over cities more than happens now if that tech were to be adopted big time.
    how do you figure that out?
    Most of the heat in the troposphere comes from conduction and convection and radiation of heat from the ground (or building surfaces in the case of dense cities) thus if that ground was made cooler then there would be less heat to heat up the air above.
    A reflective surface on the ground would mean less sunlight gets converted to heat and more gets reflected up and visible light passes both upwards and downwards through the atmosphere with less absorption than the infrared radiating upwards.

    That said, my idea may be too expensive for that. Can you just imagine the scale need for its implementation to have any real measurable effect on global climate!? -Definitely a last-resort plan only to be implemented if things get dire.
  4. Standard member sonhouse
    Fast and Curious
    08 Sep '17 19:30
    Originally posted by @humy
    how do you figure that out?
    Most of the heat in the troposphere comes from conduction and convection and radiation of heat from the ground (or building surfaces in the case of dense cities) thus if that ground was made cooler then there would be less heat to heat up the air above.
    A reflective surface on the ground would mean less sunlight gets converted to ...[text shortened]... ct on global climate!? -Definitely a last-resort plan only to be implemented if things get dire.
    I think they said it was a IR reflector which could cool down the interior of a building but that heat has to go somewhere, and I imagine some of that heat would raise the temp of the tropo and such to say nothing of clouds.
  5. 08 Sep '17 21:28
    Originally posted by @sonhouse
    I think they said it was a IR reflector which could cool down the interior of a building but that heat has to go somewhere
    yes, to outer space.
  6. Subscriber joe shmo
    Strange Egg
    08 Sep '17 22:58 / 1 edit
    Originally posted by @humy
    yes, to outer space.
    I think it warms the atmosphere first. How does it radiate directly to outer space?

    EDIT: Never mind, I forgot that it is near perfectly reflected as visible light and our atmosphere is a poor absorber of visible light.
  7. Standard member sonhouse
    Fast and Curious
    08 Sep '17 23:54
    Originally posted by @joe-shmo
    I think it warms the atmosphere first. How does it radiate directly to outer space?

    EDIT: Never mind, I forgot that it is near perfectly reflected as visible light and our atmosphere is a poor absorber of visible light.
    I thought it was dealing with IR.
  8. Subscriber joe shmo
    Strange Egg
    09 Sep '17 01:36
    Originally posted by @sonhouse
    I thought it was dealing with IR.
    My understanding of how this would work is not there. They weren't clear in the article. What is the water giving its heat off to?
  9. 09 Sep '17 06:49 / 3 edits
    Originally posted by @joe-shmo
    I think it warms the atmosphere first. .
    not totally in this case else this cooling system wouldn't work. Much heat DOES radiate directly from the Earth's surface to outer space without heating the atmosphere first (google that if you don't believe me) else, if you think about it, there wouldn't be such thing as frost pockets. How else can the ground temperature, like it often does, and sometimes a layer of air a few meters thick just above it, fall below that of the air just above that?
    The answer is that much of the heat radiates directly to outer space straight through the air above it without heating it. It is just the way physics works.
  10. 09 Sep '17 06:50
    Originally posted by @joe-shmo
    ... What is the water giving its heat off to?
    -outer space.
  11. Subscriber joe shmo
    Strange Egg
    09 Sep '17 12:22 / 1 edit
    Originally posted by @humy
    not totally in this case else this cooling system wouldn't work. Much heat DOES radiate directly from the Earth's surface to outer space without heating the atmosphere first (google that if you don't believe me) else, if you think about it, there wouldn't be such thing as frost pockets. How else can the ground temperature, like it often does, and sometimes a l ...[text shortened]... er space straight through the air above it without heating it. It is just the way physics works.
    The heat the water is giving off is Infrared, it is not visible light. Infrared in DOES NOT mostly radiate directly to space bypassing our atmosphere. It warms it. Please see: "The Greenhouse Effect"

    "How else can the ground temperature, like it often does, and sometimes a layer of air a few meters thick just above it, fall below that of the air just above that?"

    This effect you mention is dependent on the specific molecules that make up those gas pockets. Its not radiating it directly to space. In those conditions the pocket of gas in contact with the earth is an inefficient absorber of radiation ( because the water molecules are condensed out of it ). So instead, it is radiated to layer of (greenhouse - water vapor) gas above it which is a better absorber of IR.
  12. Subscriber joe shmo
    Strange Egg
    09 Sep '17 12:22 / 2 edits
    Originally posted by @humy
    -outer space.
    Directly so - it does not.
  13. Subscriber joe shmo
    Strange Egg
    09 Sep '17 12:31
    Also, the title "A cooling system that works without electricity" is a blatant lie. Lets see if you can figure out why this is the case?
  14. 09 Sep '17 13:03 / 1 edit
    Originally posted by @joe-shmo
    Directly so - it does not.
    yes it does.
    This is just common physics knowledge that heat can be transferred via radiative transfer. I am NOT just making this up! I learned this at university physics. See https://en.wikipedia.org/wiki/Radiative_transfer if you don't believe me.
  15. 09 Sep '17 13:05
    Originally posted by @joe-shmo
    Also, the title "A cooling system that works without electricity" is a blatant lie.
    no it isn't a lie. The only electricity used is the small amount for the pump for pumping around the water.