Expansion/Contraction Energy from Temperature Difference

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Discussion Overview

The discussion revolves around the concept of generating electricity from the expansion and contraction of metal due to temperature differences, specifically using water at different temperatures. Participants explore the feasibility and efficiency of this method compared to traditional electricity generation techniques, such as thermocouples and steam engines.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant, Kevin, proposes the idea of using temperature differences in water to create mechanical motion through the expansion and contraction of metal, seeking insights on its efficiency compared to thermocouples.
  • Another participant argues that the energy required to heat and cool the reservoirs would exceed the energy retrieved for electricity generation, referencing geothermal power as a related concept.
  • Kevin acknowledges the energy cost but emphasizes the importance of the existing temperature difference, questioning the efficiency of using expansion/contraction compared to traditional methods.
  • A different participant suggests that conventional methods, like steam engines, would be more effective for electricity generation and expresses concerns about the potential fatigue and defects in the metal's crystal structure due to repeated thermal cycling.

Areas of Agreement / Disagreement

Participants express differing views on the viability of using thermal expansion and contraction for electricity generation, with some favoring traditional methods and others exploring the proposed idea. No consensus is reached regarding the efficiency or practicality of the discussed approaches.

Contextual Notes

Participants have not resolved the assumptions regarding the efficiency of energy retrieval versus energy input, nor have they established the specific conditions under which the proposed method could be effective.

KevinK
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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
 
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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.
 
Thanks for the reply
MaxwellsDemon said:
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.
 
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.
 

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