Can plants/solar panels decrease entropy?

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SUMMARY

This discussion explores the theoretical possibility of using waste heat from a refrigerator to generate usable energy through plants or solar panels. It concludes that while plants can convert visible light into chemical energy, they cannot effectively utilize infrared radiation for this purpose. The conversation highlights that the absorption spectrum of plants tapers off around 700 nanometers, marking the transition to near-infrared light, which is not absorbed. Additionally, the principles of thermodynamics indicate that attempting to convert infrared radiation into usable energy would not yield a net gain due to the second law of thermodynamics.

PREREQUISITES
  • Understanding of photosynthesis and plant biology
  • Familiarity with the electromagnetic spectrum, particularly visible and infrared light
  • Basic knowledge of thermodynamics, specifically the second law
  • Concept of energy conversion and efficiency in heat engines
NEXT STEPS
  • Research the electromagnetic spectrum and its relevance to plant absorption
  • Study the principles of thermodynamics, focusing on the second law and its implications
  • Explore the design and efficiency of heat engines that utilize waste heat
  • Investigate advancements in solar energy technology and infrared energy conversion
USEFUL FOR

Researchers in plant biology, engineers in renewable energy, and anyone interested in the intersection of thermodynamics and energy conversion technologies.

schiz0ai
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If in theory there was a very efficient and powerfull refrigerator.

Is it possible that a plant/solar panel could turn that heat into usuable energy, faster then what the frige uses up?
 
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The sun created a lot of entropy to makee that light, so no.
 
im not talking about the sun, i mean the refrigerators heat sink becoming hot enough to radiate light that can be converted by the plant/solarcell
 
schiz0ai said:
im not talking about the sun, i mean the refrigerators heat sink becoming hot enough to radiate light that can be converted by the plant/solarcell

If my fridge/ freezer was getting that hot that it was emitting light i would be switching it off before it burst into flames. It would have to be seriously faulty

Dave
 
schiz0ai said:
If in theory there was a very efficient and powerfull refrigerator.

Is it possible that a plant/solar panel could turn that heat into usuable energy, faster then what the frige uses up?

You could build a heat engine that uses the waste heat of a refrigerator to produce power, but it would only be a fraction of what the fridge is using.
 
So its possible for normal light waves to be converted into chemical energy by plants, but not for infra red spectrum? Where is this so called "wavelength" point where suddenly light can or can no longer be converted? Give me a number if possible, and please keep it theoretical.
 
schiz0ai said:
So its possible for normal light waves to be converted into chemical energy by plants, but not for infra red spectrum? Where is this so called "wavelength" point where suddenly light can or can no longer be converted? Give me a number if possible, and please keep it theoretical.

Not sure why it needs to be kept theoretical, this is a very real thing that happens everyday. But to answer your question, there is no single number for the wavelength that plants simply stop converting. If you were to graph the spectrum that is absorbed by the plant it would taper off gradually as you get to longer and longer wavelengths on the red end. By about 700 nanometers the absorption is "practically zero". This corrosponds with the very far end of the visible spectrum and the start of the "near infrared" section.
 
If there was a device that could convert heat into chemical/electrical energy at a decent rate, even at "relatively low" temperatures.
The heat would still flow from hot to the colder(device).
But the exact moment a bit of heat is converted into a chemical bond, the temperature difference between the room and the device wil lincrease.
Would that violate the 2nd law of thermal dynamics?
 
  • #10
Plants can direct their chemical reactions because they have a source of low-entropy energy (energetic photons, as visible light), and can emit high-entropy energy (heat, for example as infrared photons) - the difference allows them to use some fraction of the energy for photosynthesis.
If you try to use infrared radiation both as input and output, your chemical reactions will always end in some equilibrium and you cannot extract energy.
 
  • #11
Thanks for the info about plants, i didnt know exactly how they worked.
 

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