Is a Sun-Solar Cell System Truly Equivalent to a Carnot Engine?

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Discussion Overview

The discussion revolves around the analogy of a sun-solar cell system being equivalent to a Carnot engine. Participants explore the assumptions behind this analogy, the implications of efficiency calculations, and the limitations of solar cell performance in relation to theoretical models.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant mentions a professor's claim that a sun-solar cell system can be modeled as a Carnot engine, using temperatures of the sun and solar cell to calculate efficiency, which they found to be around 100 percent.
  • Another participant argues that this analogy is misleading, pointing out that the sunlight's wavelength is narrow band due to atmospheric effects, which affects solar cell efficiency.
  • Some participants agree that the calculation of Carnot efficiency is not relevant, noting that solar cells face other limitations that prevent them from achieving such efficiencies.
  • One participant expresses skepticism about the professor's approach, suggesting it complicates understanding rather than clarifying it.
  • Another participant mentions that considering black body radiation could yield efficiency estimates closer to actual values, suggesting a range of 16-32 percent.
  • A later reply reiterates the point about black body radiation being a more valid approach than the Carnot analogy.
  • There is a request for actual calculations or resources to support the discussion.
  • A link to a resource on solar cells is provided by another participant.

Areas of Agreement / Disagreement

Participants generally disagree on the validity of the Carnot engine analogy for solar cells, with multiple competing views on the relevance of the analogy and the factors affecting solar cell efficiency.

Contextual Notes

Participants highlight limitations in the analogy, including assumptions about temperature and the impact of atmospheric conditions on solar radiation. There are unresolved questions regarding the accuracy of efficiency calculations based on different models.

Who May Find This Useful

This discussion may be of interest to students of physics and engineering, particularly those studying thermodynamics, solar energy systems, and semiconductor physics.

jontyjashan
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I have undertaken a course on Semiconductors. My professor told us that a sun-solar cell system can be taken as a Carnot Engine. He assumed that the surface temperature of sun is 6000k and that of solar cell is 300k.And then he found out the efficiency by (1-T1/T2), which came out close to be around 100 percent. How far this analogy is true? And on the first note, why is this analogy made? Can I get some serious calculations?
 
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I think it is a major distraction.
The wavelength of the light from the sun is narrow band because it passes through the atmosphere.
The efficiency of a solar cell involves it's band gap energy matching the energy of the available wavelength photons.
 
Agreed. Seems a very odd/pointless calculation. Clearly, right now solar cells are limited by other issues that keep them well below Carnot efficiency.
 
Hmmm. Sounds to me like someone trying to be too damned smart by saying something just to confuse the students. There may be some validity there but he certainly isn't help anyone's understanding of anything.
 
He also said that if we take into account black body radiations , then we can make calculations very close to the actual efficiency(around 16-32 percent).
 
jontyjashan said:
He also said that if we take into account black body radiations , then we can make calculations very close to the actual efficiency(around 16-32 percent).
That part is true and much better than using Carnot.
 
OK. Can I get a link or the actual calculations themselves?
 
http://org.ntnu.no/solarcells/pages/Chap.2.php
 
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