It’s good for a couple degrees I think you can get water to freeze at 36 on a clear night for example
As in when it’s 36 outside?
Using a solar oven as a radiant refrigerator at night
11–20 of 94 posts
Re: Using a solar oven as a radiant refrigerator at night
#12Cool. 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-w…
That self-cooling paint works at night as well. It's not just white paint that reflects light, it also radiates heat pretty well. The YT channel NigthHawkInLight developed a variation that can be produced with (more or less) household ingredients and it cools to 3-4 degrees below ambient temperature if I remember correctly.
Re: Using a solar oven as a radiant refrigerator at night
#13Earlier quoted context omitted.
I'm guessing he just froze water when the temperature dropped below zero at night, and everything else is nonsense.
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.
You could build a few test configurations.
One as stated, insulated fridge, open on top.
One, insulared fridge, open on top, under an open air shelter, no walls, just a roof, where the roof is a significant distance away from the top of the fridge, so airflow is not impacted, but there's no view or the sky. Possibly variations on this with the roof being ir transparent or not.
Another test configuration could have the fridge closed, but with forced air ventilation.
Re: Using a solar oven as a radiant refrigerator at night
#14I’m missing the basic premise here, how does pointing an insulated box at the sky at night cool whatever’s in the box?
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!)
Snow is a near perfect black body radiator
Re: Using a solar oven as a radiant refrigerator at night
#15Re: Using a solar oven as a radiant refrigerator at night
#16I’m missing the basic premise here, how does pointing an insulated box at the sky at night cool whatever’s in the box?
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!)
If you grow crops, your crops can freeze when it's a clear sky at night with stagnant air even though the air temperature only goes close to freezing.
In some agri areas, you'll see "wind machines" to blow the warmer air around the crops to keep them from radiating their heat and frosting.
https://www.ontario.ca/page/wind-machines-minimizing-cold-in...
Re: Using a solar oven as a radiant refrigerator at night
#17I’m missing the basic premise here, how does pointing an insulated box at the sky at night cool whatever’s in the box?
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!)
It's possible to make ice in the desert with this effect. Not too hard to believe.
Re: Using a solar oven as a radiant refrigerator at night
#18Earlier quoted context omitted.
I'm guessing he just froze water when the temperature dropped below zero at night, and everything else is nonsense.
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.
He did try a basic control with his first version: “i got ice consistently over several nights, even though there was no frost on the ground, and pots of water sitting next to the box cooker did not freeze.”
Re: Using a solar oven as a radiant refrigerator at night
#19Re: Using a solar oven as a radiant refrigerator at night
#20I’m missing the basic premise here, how does pointing an insulated box at the sky at night cool whatever’s in the box?
I'm guessing he just froze water when the temperature dropped below zero at night, and everything else is nonsense.
Humans have been using this technique (radiating heat into the cold of space) to freeze water in hot places, for a very long time.
https://www.realclearscience.com/blog/2018/07/09/how_people_...