Expansion/Contraction Energy from Temperature Difference

[KevinK]

Say you had two tanks of significantly different temperature water (Say 25 deg Celsius, and 70 degrees Celsius) and were trying to generate electricity. What would the benefits / disadvantages of using the liquid to rapidly cool and heat a metal, so that it would expand and contract to generate mechanical motion, which in turn could be converted to electricity. And how do you think it'd compare to something like a thermocouple?

Any insights / formulas / examples of it done would be highly appreciated.

-Kevin

 

[MaxwellsDemon]

It would take a lot more energy to heat and cool the reservoirs than you would be able to retrieve to generate electricity. However, this is kind of the idea behind geothermal power...you exploit the natural temperature difference from a geological source to generate electricity.

 

[KevinK]

Thanks for the reply

It would take a lot more energy to heat and cool the reservoirs than you would be able to retrieve to generate electricity.

Oh yes, of course. But say we already have the temperature difference (perhaps caused by the aforementioned geothermal effect). The question is more about the efficiency of utilizing expansion/contraction compared to more traditional means of generating electricity.

 

[MaxwellsDemon]

I think you'd be better off using a more conventional method to produce electricity from the temperature difference, like making a steam engine. I wouldn't think that the metal would expand enough to make it a sufficient source of power. Even supposing you found an ideal substance, I would worry about fatigue from all the mechanical stress involved in repeated expansion and contraction. I would think you would introduce too many defects into the crystal structure.