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Reflective planetary cooling system

combat global warming by reducing solar gain
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Jumping on the band-wagon with the whole reflective/radiative space-cooling thing: [Worldgineer]'s "Green Solar Powered Ice-Based Refrigeration, With Radiative Heat Rejection" and [BunsenHoneydew]'s "Cosmic Background Refrigeration".

An idea mechanically simpler than the GSPIBR and the CBR.

To temporarily combat global climate change, reduce the radiation absorbed from the sun and increase the radiation rejected by the planet to space.

Selecting a large area with high insolation and low cloud cover, (probably a desert) - a very large array of louvres, mirrored on one side, and black on the other.

In the day time, the mirrored side faces upward, reflecting incoming radiation (although some would be absorbed by the array, and some IR absorbed by the atmosphere, the net gain would be lower than the bare desert earth)

In the night, the black (or other IR emmissive coated) surface faces upward, radiating infra-red into space (again some, but not all, is re-absorbed by the atmosphere)

The energy used to run the array is only that needed to turn the louvres - fairly minimal.

Net effect is to fractionally reduce the planetary solar gain.

Frankx, Aug 08 2006

Green solar powered ice based refrigeration Green_20Solar_20Pow..._20Heat_20Rejection
credit to [Worldgineer] [Frankx, Aug 08 2006]

Cosmic Background Refrigeration Cosmic_20Background_20Refrigeration
...and hats off to [BunsenHoneydew] [Frankx, Aug 08 2006]

Albedo management Ping_20Pong_20Albedo_20Enhancement
Albedo management using white biodegradable ping pong balls [django, Aug 08 2006]

Dave's Solar reflectors http://www.wwn-oneworld.co.uk
www.wwn-oneworld.co.uk [WaveyDave, Aug 24 2007]

[link]






       If you've reflected this heat away during the day, where's the heat coming from that you're emitting at night?
ldischler, Aug 08 2006
  

       The black side absorbs heat from the surroundings during the day - by IR from the soil at ambient shade temperature, and by convection from the air.   

       Overall, it wouldn't be a particularly efficient way of doing it (you could increase efficiency using pumped liquids etc), but it would be relatively simple and cheap.
Frankx, Aug 08 2006
  

       //The black side absorbs heat from the surroundings during the day // Then it has a huge heat capacity, eh? Almost magical.
ldischler, Aug 08 2006
  

       Ooh! A floating version would be better! Oceans, (low albedo - between 5 and 10%) would produce a greater benefit (than deserts, albedo 25-30%), and having an array of floating cylinders, one could absorb heat more efficiently by conduction from the water.   

       And you could cover a large area more easily - less structure required, not having to buy large expanses of land etc.
Frankx, Aug 08 2006
  

       Absolutely the oceans would be better. Desert heat comes and goes every day, but the oceans absorb it all and hold on to it. Water expands when it gets hot, and thermal expansion is actually a greater contributor to rising sea levels than melting glaciers.
ldischler, Aug 08 2006
  

       So...I'm thinking of a floating array, kilometres square, of many barrels. Each half-filled with water, and with a simple drive mechanism (possibly using wave power) to rotate them about their axis, so as to point the reflective (say white-painted) side upward during the day, and the black-painted side upward at night. Located at or near the equator, for maximum benefit.   

       During the day, the reflective side minimises solar gain to the ocean, while the water inside reaches temperature equilibrium with the water outside. The cooler ocean water forms a down-sinking plume, drawing in warmer water from the surrounding ocean.   

       At night, the barrels rotate to present the radiative side, rejecting IR to space and cooling the internal water.   

       Definitely not very efficient. Probably a huge floating reflective blanket deployed during the day and drawn in at night would work nearly as well.
Frankx, Aug 08 2006
  

       If they're half filled with water, they won't conduct very well, and your night radiation will suffer. As for propulsion, I vote for monkeys.

Anyway, with the clouds and humid air you get over the ocean, ejecting heat into the night sky might not be practical.
ldischler, Aug 08 2006
  

       Ahh, monkeys - why didn't I think of that!   

       If the array was computer controlled, it could be also used as a huge video display for sending messages to astronauts with faulty radios.
Frankx, Aug 08 2006
  

       [django] - I'll grant that there are other ideas for reducing net solar gain of the planet - there are many - but each sufficiently different for them to co-exist without being [mfd]
Frankx, Aug 09 2006
  

       [Frankx] true, and it's actually a pretty good idea, except for the potential fragility of the system (think violent desert storms).
django, Aug 09 2006
  

       Same principle as my idea fully worked out and on line at www.wwn-oneworld.co.uk basically thousands of reflective tents placed in deserts.They do not get covered in sand and only cost a few $billion rather than tens of billions that stern report states.
WaveyDave, Aug 24 2007
  
      
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