Half a croissant, on a plate, with a sign in front of it saying '50c'
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Space Heating Vacuum Boxes

A box which can have air sucked out of it to form a vacuum is placed in a room. You instantly have less volume of air to heat up, thus saving on fuel bills and energy.
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This idea revolves around the issue of reducing the volume of air to be heated up in a room. A box is connected to a pump that sucks all the air out of it thus creating a vacuum. If there is no air in the box, there is therefore no air to be heated up. Less air to be heated up, means less energy expended which means a saving on fuel costs coupled with a saving in energy and is therefore much friendlier to the environment. The box can be placed in a room and hidden out of the way or made to look like a piece of art or furniture. If the seal on the box is good, it will not need ‘vacuuming’ for some time!
NumboJumbo, Sep 17 2007

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       Live inside the box. Just don't suck the air out.
the dog's breakfast, Sep 17 2007
  

       Air has a low heat capacity. So the energy savings will be minimal. Most of the energy of a household heater goes into heating the building itself, not the air.
kinemojo, Sep 17 2007
  

       "don't open that door! we're not heating that room. you could get sucked in."
k_sra, Sep 17 2007
  

       Funny even if it is not meant to be funny. You could do this with a regular airtight box. The air inside would be _freezing cold!_. Alternatively, one could strew the house with packing peanuts. If they were helium-puffed, they should accumulate towards the ceiling, staying out of the way of the inhabitants and displacing warm air downwards, where it can be lolled about in.
bungston, Sep 17 2007
  

       OK, numbers. I have a fresh envelope back before me.   

       Suppose you want to create a vacuum of one cubic metre. Suppose you have a perfect pump system: imagine a 1- metre cubical "cylinder" with a 1m square "piston"; the piston is initially against one wall of the cube. To create your cubic metre of vacuum, you need to pull the piston back 1m, against atmospheric pressure. This pressure amounts to something like 10,000kg force, or 100,000N. To move 1m against this force therefore uses 100,000Nm, or 100,000J. This is equivalent to running a 1kW heater for 100 seconds.   

       I suspect that the same amount of energy would heat that cubic metre of air for a long time.
MaxwellBuchanan, Sep 17 2007
  

       Of course, you'd have to be careful refilling it, as the expansion of gas into the vacuum would in fact cool the building, in accordance with Charles' Law.
coprocephalous, Sep 18 2007
  

       There is a vacuum of understanding here that leaves me with a sudden chill.
4whom, Oct 30 2007
  

       How about an airtight box that's insulated, and then all you have to do is crawl into that box and turn the heat up in there.
quantum_flux, Nov 28 2007
  

       While I agree that this idea is impractical, [MaxwellBuchanan] has a flaw in his equation. The 10,000kg force would only be felt at the end of the stroke, so maybe its only about 50,000J. Excellent point though
ServoMan314, Jun 26 2008
  
      
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