Temperature photovoltaic cells

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blackreed
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Temperature photovoltaic cells




by blackreed » 23/11/10, 10:33

Hello,

As part of a project in engineering school I would like to know how to measure more precisely the temperature of the cells of a photovoltaic panel?
It is intended to raise the temperature in the upper part, in the lower part, in the middle and in a corner of the panel.

I planned to do a simple average of its values, but perhaps a part of the panel has a higher temperature to take into account in this calculation.

Thank you in advance for your possible answers.
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by Christophe » 23/11/10, 10:44

Well it depends on the size of the surface of the cell that you measure ... you will see quickly if there are important deltas or not ...

On a cell of 100 cm² it is probably not exactly the same as on one of 2m².

But I do not think there is much difference (radiation, surface and identical losses = T ° fairly constant).

I think the fastest and most reliable method is to use a non-contact infrared thermometer here are 2 models:

https://www.econologie.com/shop/thermome ... p-132.html
https://www.econologie.com/shop/thermome ... p-326.html

The emissivity of the PV cells must be quite high. To calibrate.

A thermocouple that is not "melted in" will not give a correct measurement.

I remind that beyond 25 ° C, PV panels lose 0.4% every degree!

Other topics that could help you:
https://www.econologie.com/forums/mesure-du- ... t6603.html
https://www.econologie.com/forums/rendement- ... t5179.html
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by sspid14 » 23/11/10, 14:59

It is also necessary to look if the panels are integrated or not, if they are crystalline panels (mono, poly) or others, if the inverter works or not, ...

The temperature is a function of a lot of parameter ... !!

For what purpose do you want to take this temperature? If you just want to average the temperature then you take a maximum of points and you average ... Temperature that should not vary too much from one point to another for a cell ..
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by I Citro » 23/11/10, 15:47

:? When I diagnosed a nonproductive board in my facility, I went to measure the temperatures with an infrared thermometer (without having calibrated for this type of surface).

Well I have not been able to identify the panel out of order by this method. I had done several measurements at different places on each panel.

My 2 photovoltaic strings frame the 2 thermal sensors of my CESI which is equipped with a K1000 probe.
I have seen unequivocally that high temperatures drastically reduce PV productivity.
Since then, I installed 8 roof tiles over the PV field and I think to add ...
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by elephant » 23/11/10, 18:27

Well, come on, hop, little focus.

Christopher said:

I remind that beyond 25 ° C, PV panels lose 0.4% every degree!


Well, actually it's about 0,33 - 0,34, but what you have to understand is that the constructor data is made at 25 ° C. The panels lose this percentage at all temperatures, but it is the 25 ° datum that is the basis of the calculations. (Therefore, one loses in relation to the value with 25 ° beyond 25 ° and one gains BY REASON with the value with 25 ° when the T ° goes down)

This idea of ​​measuring highest point, middle, etc. is a bit quirky: a panel is formed of (usually) 36 to 48 cells in series and in zig-zag

To detect a failed panel, there is only one method in my opinion.

1) identify the faulty string

2) identify which panels are part of the defective string (not obvious in some installers)

3) locate the panel using an ammeter (or easier using a DC ammeter clamp) by successively putting each panel in short circuit on itself. No fear, they easily support this treatment.

Warning: this kind of maneuver can not be improvised.

1) disconnect the inverter downstream (ie at the mains circuit breaker) before disconnecting the strings

2) disconnect the panels with string disconnected (the 2 cards)

3) take the opportunity to replace any damaged plug, the 2 poles of the panel disconnected from the rest of the installation

4) work in dry weather.

remember that 10 panels in series, it is still minimum 270 V DC and that we do not know how to remove his hand during a direct current electrocution.

Handle the panels with their cards. the differential of the house does not protect you.
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by Christophe » 23/11/10, 19:02

elephant wrote:Well, actually it's about 0,33 - 0,34, but what you have to understand is that the constructor data is made at 25 ° C. The panels lose this percentage at all temperatures, but it is the 25 ° datum that is the basis of the calculations. (Therefore, one loses in relation to the value with 25 ° beyond 25 ° and one gains BY REASON with the value with 25 ° when the T ° goes down)


Certainly, thank you for the precision but as we start from the yield given by the manufacturer at 25 ° C, it is strictly the same ... but ok for against the reversibility of the phenomenon under 25 ° C!

Now that we have you on hand, 2 questions:

a) These 0.4% are given in relative or absolute? I have a doubt lat...

Relative = relative to the yield X to 25 ° C is X * 1.04 or X / 1.04
Absolute = we start from the real yield X +/- 0.4

I guess it's relative but ... I prefer to check!

b) How do yield gains behave in negative T °?

It is likely to quickly exceed 100% yield if the gain is linear: towards ...- 23 ° C one would get 100% of yield starting from 15% of yield at 25 ° C and 0.4% of relative gain per ° VS!

In absolute correction it is necessary to go down to -188 ° C to obtain 100%.

Finally it may be an absolute correction!
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by elephant » 23/11/10, 19:57

We are not talking about performance. We talk about power and tension.

Therefore, at equal illumination, 1 ° difference will give 0,34% less (or more). It's independent of performance.

So, if you have a panel that makes 15% yield at 25 ° C, you will have 15% + 3,4% of 15% for 10 ° less for example
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by chatelot16 » 24/11/10, 01:00

to measure the true temperature of silicon I will consider each cell as a real diode whose direct voltage drop is a function of temperature: voltage drop decreases linearly with temperature. phenomenon well known for any silicon junction

when the cell is illuminated and empty, all the photovoltaic current is wasted in the diode constitie the cell: it is possible to calculate the temperature of the silicon with the current in short circuit and the tension in empty

to have the temperature of the different points of the panel it would be necessary to have access to the different cells separately: do, nc assemble a panel especially ... in this case as well to integrate true temperature probes
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by elephant » 24/11/10, 10:55

Ouis, not obvious indeed to access the tin ribbons.

In my opinion, a probe stuck on the tedlar should not be too inaccurate if the panel is ventilated (reported)
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by Christophe » 24/11/10, 11:02

elephant wrote:We are not talking about performance. We talk about power and tension.

Therefore, at equal illumination, 1 ° difference will give 0,34% less (or more). It's independent of performance.

So, if you have a panel that makes 15% yield at 25 ° C, you will have 15% + 3,4% of 15% for 10 ° less for example


Uh you realize all the same that you contradict 2 times in 3 lines? : Shock:

Do not we speak the same language or what? I know you're closer to Flanders than us but still ... : Mrgreen:

But I remember that we speak well in relative correction!

End of HS. Sorry for the noise!
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