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Radiative cooling

 
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kenneal - lagger
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Joined: 20 Sep 2006
Posts: 12348
Location: Newbury, Berkshire

PostPosted: Sat Oct 17, 2020 3:16 pm    Post subject: Radiative cooling Reply with quote

This article explains how the cool of space can be used to cool buildings and liquids using virtually no energy.

Used in conjunction with a storage medium, say concrete or water, this could be used to keep buildings cool during very hot days with just a circulation pump to send water around a building. Water pipes in a concrete ceiling could cool the structure which would then cool the air. The great thing about this new material is that it will cool during the day because it doesn't absorb the sun's heat.

If you couldn't afford the film you could use the night time radiation to cool a thin pool of water on a flat roof and pump that water through a coil of pipe in a concrete ceiling so that it would keep the structure cool during the day.

I might have to redesign my house roof for when the UK climate gets really hot. The system could also be used with suitable shading to run a "cool house" rather than a green house to grow stuff during over hot summers.

A new toy!! I'm excited.
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adam2
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Joined: 02 Jul 2007
Posts: 8096
Location: North Somerset

PostPosted: Sat Oct 17, 2020 4:11 pm    Post subject: Reply with quote

Such technology has its merits and shows some promise.

I have maintained an office building with "chilled ceilings" cooled by the circulation of only moderately chilled water. (from an electric chiller, but radiative chilling could be used)
It worked fairly well, but tended to produce unpleasantly humid conditions. The room air was cooled from say 30 degrees to say 23 degrees, but could not be cooled below the dew point or condensation resulted.
This rendered the air very humid.

To reduce this humidity the fresh air supplied from the air handling unit had to be cooled to only just above freezing point in order to remove as much moisture as possible. This consumed significant energy.

A certain amount of tinkering by myself improved the system somewhat.
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Catweazle



Joined: 17 Feb 2008
Posts: 2602
Location: Little England, over the hills

PostPosted: Sat Oct 17, 2020 6:50 pm    Post subject: Reply with quote

It might find applications on refrigerated vehicles, they have to burn diesel to stay cool.
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BritDownUnder



Joined: 21 Sep 2011
Posts: 781
Location: Hunter Valley, NSW, Australia

PostPosted: Sun Oct 18, 2020 10:52 am    Post subject: Reply with quote

Sounds good in theory. A highly mirrored roof may not be allowed in some places such as near airports.

Humidity will always get you if you try to chill air without dehumidifying at the same time. I tried to use my roof (by passing air between a piece of corrugated plastic above a corrugated metal roof) for heating air but ended up with mouldy, dank damp air from condensation the previous nights.

I think the Japanese invented a 'passive' fridge with no moving parts that used some type of ether that boiled at about 15C. It had an evaporator that surrounded the 'fridge' part that was to be cooled and then when the liquid ether boiled off it migrated to a higher part of a sealed system where it condensed on a radiator plate that was exposed to the sky on certain clear nights. Heat was thus lost and cooled liquid flowed back under gravity to the evaporator to repeat the process.

I could see a similar system upgraded to a house sized scale.
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