Physics/Using expansion of ice to generate power
guybrodway wrote at 2008-08-22 03:51:06
You should study more and type less.
#1 Your 1/10,000 expansion is only until 0C, NOT THE EXPANSION OF ICE, which is 9.4%.
#2 Water will expand and produce up to 120,000psi. Can you say boom.
Jon Dostal wrote at 2009-02-23 20:24:23
Your numbers are incorrect. Ice will expand 9-11% when freezing. You were looking at data for the density change of water around 4 degrees.
Law of Thermodynamics wrote at 2009-08-08 15:42:45
A good answer, but it overlooks an important point. 10,000 liters of liquid water might only expand by one liter, but it will do so with a tremendous force of about 10,000 pounds per square inch, which is what I believe the original question asker was trying to harness.
Something that moves a small distance with tremendous force is a very good candidate for translating with mechanical advantage.
So, yes, you could likely generate power from the freezing of water. The second part of your question will cause you trouble though. You mentioned artifically heating the water to melt it, so that the environmental air temperature could refreeze it and repeat the cycle. The catch here is that water has a high specific heat. It requires a LOT of energy to thaw out 10,000 liters of water. More than what you get out of it when it freezes, actually. This isn't a coincidence. The heat you put in to melt it is equivalent to the heat (power) you take out to freeze it. Friction losses in your gear/generator arrangement will guarantee you won't even break even in your power generation. If you just allow the natural freeze/thaw cycle of the weather to do it's thing though, without any artificial heating, and you'll come out ahead making power. But it won't amount to much when averaged out over time, so it isn't very viable.
josephdupont wrote at 2011-02-02 23:46:31
I just did a youtube on this question.
in many regions you get freezing conditions at night
and thawing during the day.
Thus you could compress air with a check valve every night.
Ice can exert up to 30,000 psi. check out ice and josephdupont youtube dot com.
LC wrote at 2011-05-22 17:52:06
What if you had a device that you could bring inside and put out again, or that was built into the wall of a house so that it's half inside and half out? In arctic regions where it's well below 0 for half the year, and where houses must be heated regardless, you have a reliable source of deep freezing and thawing.
pete wrote at 2012-02-23 04:34:32
Not convinced you should write off this idea so quickly.."it's only about "one part per 10,000." says the answer...actually this refers to density...not volume. If water only expanded this little cans would not explode in the freezer...
The increase in volume of ice is actually about 9%. Pretty significant...
Regarding how to melt it... the daytime sun streaming thru glass provides plenty of melting power... try leaving a bottle of water in your car...(be sure it is not full) on a winter night.. it will freeze during the night..and melt to water the next day as the sun passes thru the car glass... even on a really cold day...
rwoods1220 wrote at 2013-01-09 15:25:50
I have been thinking about this same idea for so long! So much power in the freezing of water! Now then lets move the generator to the moon and use both full sun light and shade. I think a very durable and sustainable power generator could be built to last a long time. Think BIG like 48' tanker trailer size pistons.
Twisted Physicist wrote at 2016-04-28 05:09:35
I disagree with the criticism of this idea and believe this is the temporary answer to the energy crisis. 1m3 off ice in a hydraulic chamber might only push a piston up 6cm, but does it with enough force to lift a whole parking lot full of SUV's. Multiplying the pressure defined by a bulk modulus of 2.0x 10^9 J/m2 by the change in volume yields a value of energy of about 15MJ. If you are using a stirling engine to capture mechanical energy from the exchange of heat between the ice and the atmosphere, then the efficiency of your engine will dramatically increase. Whatever mechanical energy you are denied by successfully stifling the expansion of the ice will serve to lower the freezing point in the same manner that salt does. This will force the ice to a lower temperature, thus allowing you to extract even more heat energy from the atmosphere. Then, rather than converting the mechanical energy into electricity, use it to compress air. Use oil cooling pipes to capture the heat from the compressed gas and redirect it back to the hot side of the Stirling engine. Finally, release the compressed air into a turbine, bank the mechanical energy, and use the same cooling pipes to refreeze the water. I argue that this infinitely more efficient then generating steam because steam production results in a net loss of energy. If you have a quantity of coal equal to 100 MJ and use it to boil water, then only 7.5% of that energy is converted to mechanical energy by the expansion of the steam. The other 92.5% is converted to internal kinetic energy, specifically, vibrational and rotational, which results in no expansion. Unfortunately, all this internal energy gets blown out the chimney and you have far less energy, albeit mechanical, than you did when it was chemical potential energy. In the absence of some spectacular ly efficient steam recovery system the latent heat of vaporation of about 460 calories per gram is lost by the nature of the phase change. Although the latent heat of fusion is only 80 calories they are not lost when the ice melts. Furthermore, this is heat energy that is given to you as bonus in the phase change from water to ice, whereas the heat energy required by the phase change from water to steam is a penalty.
All in all, this process appears to be self sustaining with an infinitely high efficiency rate. But it is not. In actuality, this process is stealing much heat energy from the atmosphere than it is able to convert to mechanical energy.