Concentrating radiation from blackbody with lens

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Discussion Overview

The discussion revolves around the feasibility of concentrating infrared radiation from a blackbody using lenses or mirrors, particularly in the context of geothermal energy applications. Participants explore the implications of temperature differences between the lens or mirrors and the blackbody, as well as the potential for energy transfer versus imaging purposes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants propose that infrared radiation can be concentrated using lenses, as infrared behaves like visible light and follows the law of refraction.
  • It is suggested that a passive lens should be at a lower temperature than the blackbody to avoid interference from the lens's own radiation.
  • One participant discusses the idea of using lenses in geothermal power harnessing, suggesting that shaped cavities filled with liquid could concentrate infrared radiation for energy conversion.
  • Another participant argues that mirrors might be more suitable than lenses for long-term energy transfer applications, indicating a preference for beam shaping with mirrors.
  • There is a question about whether mirrors should also maintain a different temperature from the underground heat source, similar to the considerations for lenses.

Areas of Agreement / Disagreement

Participants express differing views on the use of lenses versus mirrors for energy transfer, with no consensus on the best approach. The discussion remains unresolved regarding the practical implementation of these ideas in geothermal energy systems.

Contextual Notes

Participants highlight the complexity of temperature management in the context of energy transfer and the challenges associated with using water as a heat carrier in geothermal applications.

Stanley514
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1)Is it possible to concentrate infrared radiation from a blackbody with a lens?
2)Should a lens be at different temperature from a blackbody?
 
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Sorry, misunderstood the question!
 
Last edited:
1) Yes. You can buy nowadays infrared cameras with infrared lenses. See http://www.flir.com/thermography/americas/us/products/?id=17972", for example. Infrared radiation is an electromagnetic wave just like visible light, so it obeys the law of refraction just as well and bends through a lens. The trick is to build a lens out of a material is not opaque in the infrared.

2) A passive lens needs to be at a lower temperature then the blackbody, otherwise the lens' own blackbody radiation will swamp out the signal. But this is automatic for typical applications. The temperature of living creatures, machines in use, etc. tend to be higher than the room temperature at which the unmodified lens exists. To image lower temperatures than room temperature, two methods can be used. The camera can be cooled. This can be expensive but effective, as the http://en.wikipedia.org/wiki/Cosmic_Background_Explorer" mission demonstrated. Or the camera can be actively stabilized but not significantly cooled. Using this approach, the system is held at a temperature and differences in temperature are measured.
 
Last edited by a moderator:
I thought on possibility to use a lens method in geothermal power harness.
For exampe underground cavity could be properly shaped and filled with water or similar liquid to concentrate infrared light coming from underground and direct IR ray to the surface where it could be transformed to electricity with help of photocells.I think it could eliminate problem with water cycling and management.But as you said the lens should stay at different temperature from heat source than it makes some complications.
I thought on possibility to reduce amount of holes to cycle water and increase heat harvesting from large underground areas with minimal amount of holes to drill.Unfortunately water is not very energy dense carrier and it requires lot of expensive drilling.
 
Ah, you don't seem to mean for imaging purposes, but for long-term energy transfer purposes. In that case, I think mirrors would be more suitable than lenses for beam shaping.
 
chrisbaird said:
Ah, you don't seem to mean for imaging purposes, but for long-term energy transfer purposes. In that case, I think mirrors would be more suitable than lenses for beam shaping.

This is why it helps to give context when asking questions.

Claude.
 
Ah, you don't seem to mean for imaging purposes, but for long-term energy transfer purposes. In that case, I think mirrors would be more suitable than lenses for beam shaping.
Do you think something similar to what I was thinking about could be practically created?With help of mirrors?Should thouse mirrors stay at different temperature from underground cavity?
 

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