[HN Gopher] Using a solar oven as a radiant refrigerator at night
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       Using a solar oven as a radiant refrigerator at night
        
       Author : ColinWright
       Score  : 20 points
       Date   : 2024-03-03 22:06 UTC (53 minutes ago)
        
 (HTM) web link (solarcooking.org)
 (TXT) w3m dump (solarcooking.org)
        
       | jack_riminton wrote:
       | I'm missing the basic premise here, how does pointing an
       | insulated box at the sky at night cool whatever's in the box?
        
         | mateo1 wrote:
         | I'm guessing he just froze water when the temperature dropped
         | below zero at night, and everything else is nonsense.
        
           | hifikuno wrote:
           | I wonder how you prove/disprove this. I imagine if you had a
           | control box with water exposed to the air that wasn't
           | "radiating heat," then that should show if the solar freezer
           | was indeed working or not.
        
         | punnerud wrote:
         | Almost all surfaces radiates heat. You can heat and cool using
         | radiation. It's the same way satellites is cooled, when you
         | can't cool with convection (interact with other atoms).
         | 
         | Black absorb more radiation, but it also radiates more
        
         | vladms wrote:
         | I guess that not having other warm objects pointing at the
         | water, will not warm the water (example: a wall radiates
         | infrared so it heats the water if the wall has "sight" over the
         | water).
         | 
         | Insulating the walls of the container with the water servers
         | the same purpose - not have the water get heat from the
         | surroundings.
        
         | JohnVideogames wrote:
         | A black body will emit radiation (and receive radiation) until
         | it's in equilibrium with its surroundings. In theory, the black
         | bit of box radiates heat into space, and receives some of the
         | CMB until both are at ~3K. It's how we cool satellites and
         | spacecraft.
         | 
         | But the effect is quite small, and I'm suspicious of it (as the
         | nearest surroundings are the hot planet, which transfer heat
         | more effectively!)
        
         | ano-ther wrote:
         | It uses the infrared window to radiate the heat into space.
         | That's why they need a view of the sky and also remove a glass
         | pane.
         | 
         | https://en.m.wikipedia.org/wiki/Infrared_window
        
       | toss1 wrote:
       | Cool. Might be able to do even better with self-cooling paint
       | [0,1] during the day to reject heat and Vantablack [2] at night
       | to radiate it? (although I wonder how Vantablack would do at
       | radiating with its microstructured surface)
       | 
       | [0] https://www.parc.com/technologies/self-cooling-paint/
       | 
       | [1] https://www.purdue.edu/newsroom/releases/2021/Q2/the-
       | whitest...
       | 
       | [2] https://www.abc.net.au/news/science/2017-01-13/vantablack-
       | wh...
        
       | nothercastle wrote:
       | It's good for a couple degrees I think you can get water to
       | freeze at 36 on a clear night for example
        
         | huytersd wrote:
         | As in when it's 36 outside?
        
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       (page generated 2024-03-03 23:00 UTC)