Current at maximum power - PV cell

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Discussion Overview

The discussion revolves around the discrepancies observed in the current measurements at maximum power for a photovoltaic (PV) cell. Participants are examining the differences between the current calculated from the current-voltage characteristic and that derived from the power characteristic, with a focus on methodology and theoretical understanding.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant notes that the current at maximum power calculated from the current-voltage characteristic does not match the current derived from the power characteristic, with the latter being about twice as large.
  • Another participant suggests that understanding the result requires knowledge of how the graph was constructed.
  • A participant clarifies that the current from the power characteristic is through the shunt resistance, while the current from the current-voltage characteristic does not account for shunt resistance.
  • There is a suggestion to compare methodologies to identify whether different measurements are being taken or if the same measurement is being conducted under different conditions.
  • One participant proposes checking if the results align with standard models of solar cells.
  • Another participant references a theory of solar cells and presents equations related to the characteristics of the solar cell, expressing confusion over the results.
  • A participant mentions that various books state that the two currents should be approximately equal, which contradicts their findings.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the relationship between the two current measurements, with some suggesting that they should be equal while others point out the differences based on measurement conditions. The discussion remains unresolved with competing views on the interpretation of the results.

Contextual Notes

Participants have not fully clarified the assumptions behind their measurements or the definitions of the terms used, which may contribute to the discrepancies noted in their findings.

Imperatore
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Hello there !

I got question regarding PV cell.
The current at maximum power Im calculated from current-voltage characteristic doesn't equal to the one calculated from P(Ushunt, as you can see in the attached picture. http://prnt.sc/b864hx
Furthermore, the Im from P(U) characteristic is about 2 times greater.
This is rather strange result for me. I am of the opinion, that these currents should be approximately equal. Maybe I am wrong and you will say it's nothing weird about these results.I hope so :)
 
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To understand the result you need to know how the graph was arrived at.
 
It is my graph ;)

The current from P(U) is the current through the shut resistance, and Im from current-voltage characteristic shows the current without shut resistance. It is that what you mean?
In here http://www.instsani.pl/images/PV8.ht4.jpg you can see, that these currents are equal.
Little confused now.
 
Last edited by a moderator:
OK - compare the methodology: you should find you are measuring different things, or the same thing in different circumstances.
 
Simon Bridge said:
OK - compare the methodology: you should find you are measuring different things, or the same thing in different circumstances.

Imperatore said:
The current from P(U) is the current through the shut resistance, and I am from current-voltage characteristic shows the current without shut resistance. It is that what you mean?

Is it that difference?
 
Why not check and see if your results are consistent with standard models?
 
From that I get:
1) Characteristic U(I):
IL=ID+ISh and ISh= 0, so IL=ID=0,5
2) Characterisitic P(U):
0,5=IL=ID+1,17(it's measured ISh), so ID=-0,67 mA

sth wrong
 
aby book explainig that pheno? It is written in every book I' ve examined that these two currents should be approx the same, what in my case obviously is not met.
 
Last edited:

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