Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages?

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Christophe
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by Christophe » 23/11/21, 23:08

So to have partial operation you have to put all these diodes?

Are the bypass diodes to be added too?
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by izentrop » 23/11/21, 23:10

The bypass diodes are already in the panels, in groups of cells. They are used to avoid overcurrent in shaded areas. http://www.photovoltaique.guidenr.fr/in ... y-pass.php
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by Christophe » 23/11/21, 23:14

So be reassured! : Mrgreen:

So with 2 identical strings it would suffice to add the 2 red diodes for it to work?

Why are you saying that it will produce less (than 2 100% independent strings?)? The voltage drop of a diode (red) is low, isn't it? A few Volts?

Is it like the 2 batteries?
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by Christophe » 23/11/21, 23:18

izentrop wrote:The bypass diodes are already in the panels, in groups of cells. They are used to avoid overcurrent in shaded areas. http://www.photovoltaique.guidenr.fr/in ... y-pass.php


Ok that I understood :)

Ideally, there should be a bypass diode in parallel on each cell.

For technical and economic reasons, the number of bypass diodes on a module is generally limited to 5


However, a diode is a few cents ... it would cost less than the micro inverter and shunt ...
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by izentrop » 23/11/21, 23:23

Christophe wrote:So be reassured! : Mrgreen:

So with 2 identical strings it would suffice to add the 2 red diodes for it to work?

Why are you saying that it will produce less (than 2 100% independent strings?)? The voltage drop of a diode (red) is low, isn't it? A few Volts?

Is it like the 2 batteries?
You were talking about two back-to-back panels facing east-west. The production is very low in this case, especially at midday.

A schottky diode has a voltage drop of 0,2 v
0.5 V to 20 A for this one http://www.smc-diodes.com/propdf/ST2045 ... 0REV.B.pdf
However, a diode is a few cents ... it would cost less than the micro inverter and shunt ...
It's just a security to avoid the destruction of the cells, see the fire. No matter how shading is to be avoided.
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by Christophe » 23/11/21, 23:45

Izy the question is not to know if they produce well at noon but if they produce well in the morning for the east and afternoon for the west without worrying about safety and clamping… the inverter would obviously be a mppt…

I'm talking about 2 strings east and west but not necessarily placed vertically ...

If 2 diodes are enough to replace a 2nd inverter that's great !! 8) 8) 8)

izentrop wrote:It's just a security to avoid the destruction of the cells, see the fire. No matter how shading is to be avoided.


The link you gave speaks rather of partial optimization of solar masks ... if I read correctly diagonally : Cheesy:

Less diagonally I understood :) the usefulness of the red diodes !! Since the passage below should apply to the shaded string as well:

In addition, there may be a reverse polarity at the terminals of the shaded cell (the voltage changes sign).

Concretely, this means that the product U × I also changes sign: the cell no longer behaves like a generator but like a receiver.

In other words, it behaves like a dipole which dissipates electrical energy (instead of producing it) in the form of heat.

As a result, the cell heat up which can irreparably damage the cell.

This phenomenon of heating of the cell is called a hot spot.

We see through this example that shadow is a formidable enemy for a photovoltaic module: significant loss of power and heating


Thanks izy
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by izentrop » 24/11/21, 01:26

It's a shame not to take advantage of the solar optimum for the 2 PVs at the same time with a 1 Axis tracker, some electronics and a wiper motor for example, since they are on the ground.
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by humus » 24/11/21, 09:01

Christophe wrote:Hence my question !! : Mrgreen:

How to know simply the blocking capacity of the diode of the panels?


I decline any responsibility in the event of electrocution or breakdown of PV : Mrgreen:

On the Izentrop diagram, already separating the 2 lines to measure each line independently.
then like in the video,

We must look for the zener voltage, it is the equivalent of the breakdown voltage.
This supposes having a power supply delivering a voltage higher than what one seeks to measure and a resistance sufficiently high so that the measurement is not destructive for the diode.
: Arrow: 10K or 100K?

Take care that the admissible power of the resistor is sufficient because if it breaks in a short circuit during the measurement, it breaks down what is behind it. : Mrgreen:


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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by izentrop » 24/11/21, 09:31

Important
For the anti-return diode (red in the diagram I had posted) it will be necessary to provide http://forum-photovoltaique.fr/viewtopi ... t=0#p27515
One of the panels being squarely in the shade, also provide a fuse.

This is the diode that has the lowest breakdown voltage for series diodes.
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Christophe
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Re: Direct parallel connection of 2 EAST and WEST PV solar strings with (very) different panels and voltages




by Christophe » 24/11/21, 09:45

2 diodes and 2 fuses is always cheaper than a new inverter!

Then you have to choose them well and do a clean installation if you want to be quiet for years!

And on this point I'm a little lost ... the one you proposed last night had a blocking voltage of 25V therefore insufficient (300V to be blocked with a safety factor ... so must be put 12 in series)? ? Sorry the electronics of the diodes is not really my thing ... : Mrgreen:

I will carefully read the subject of the other forum, thank you !
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