# Could energy be harnessed from the freezing of water?



## Aether (Apr 27, 2010)

Edit: Title should say "Could energy _practically _be harnessed from the freezing of water" since I'm pretty certain you can but perhaps not so efficiently to be a viable energy source.

Say you have a long thin tube of water with it's length being vertical. You put a little thing that floats at the top. Say you leave this out somewhere that the external temperature is below 0. As the water freezes the floaty thing would move upwards due to the expansion of water in its transition to ice (assuming the water freezes from the bottom upwards). This is a change in gravitational potential energy. Surely then, with the right apparatus, electrical potential could be harnessed?

You could use the Earth's change in temperature to achieve this effect. For example, imagine powerplants using this concept all over Antarctica (or the Arctic, whichever has a greater change in area of ice) where the ice melts and water freezes in HUGE quantities each year at its own accord.










Edit: Looks like someone's beaten me to the punch.  Not surprising I guess, seems a pretty obvious idea.

http://www.odec.ca/projects/2008/tern8v2/procedure.htm


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## La Li Lu Le Lo (Aug 15, 2011)

Wait...how can something that radiates heat become colder? o_o

Heat is energy. Something that is colder has less energy.


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## Aether (Apr 27, 2010)

A cup of coffee radiates heat. It becomes colder in the process because its energy is being transferred to its surrounding environment.


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## La Li Lu Le Lo (Aug 15, 2011)

Aether said:


> A cup of coffee radiates heat. It becomes colder in the process because its energy is being transferred to its surrounding environment.


But that's because it first gained the heat energy. When it loses heat it doesn't _freeze_. Coldness is just the absence of heat. If something generates its own heat it stays hot until it loses its energy and if it was heated up it radiates heat into the air until it runs out of energy and cools to the temperature of its surrounding environment.


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## Aether (Apr 27, 2010)

Yeah you're right about things only cooling to room temperature, was moronic to forget that. Forget what I said about that imaginary substance lol.


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## sprinkles (Feb 7, 2010)

LaLiLuLeLo said:


> Wait...how can something that radiates heat become colder? o_o
> 
> Heat is energy. Something that is colder has less energy.


Heat is energy but it is not the only energy. If you throw an ice cube (or better yet, launch it from a catapult) it will have lots of energy. XD

As for getting energy from freezing expansion, it is possible, there are just simply better ways to get energy right now.


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## absentminded (Dec 3, 2010)

The biggest problem that I see is that you have to either refrigerate a liquid or melt a solid before allowing it to refreeze.

In both cases, the process requires more energy than the potential energy gained from the change in height. I can show why if you want.


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## Aether (Apr 27, 2010)

absentminded said:


> The biggest problem that I see is that you have to either refrigerate a liquid or melt a solid before allowing it to refreeze.
> 
> In both cases, the process requires more energy than the potential energy gained from the change in height. I can show why if you want.


Yeah this is true. That's why I suggested using the Earth's natural shift in climate and the effect of this on polar ice cap melting and freezing.










(added to op for future clarification)

The Earth is your refrigerator/melter  Due to climate change the total volume of ice is going down each year but this doesn't really matter when the change in volume is all that is needed. Granted, right now no one's going to build apparatus to cover this vast area, I don't know how the hell they'd manage it and our current tech may not even yield enough energy for it to be economically viable but still I think it's a nice idea that may one day become helpful to us. (If the poles don't melt completely by then anyway lol)


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