Who wants to explain to me how a pv panel works?

[netshaman]

No because I'm tired of it, I hear everything and anything, and I get lost ...
In particular with regard to a panel which is in overproduction (supposedly) and which is connected to a device which consumes almost nothing.
I heard everything: the panel will burn, the weakest element slams, there is no juice flowing if the device is plugged in but stopped but also the opposite etc.
We pass on the photoelectric effect which is the principle ...
Precisely what is produced?
Constant voltage, variable intensity (voltage generator)?
A variable voltage, a constant intensity (current generator)?
Or both vary constantly depending on the brightness (generator of chaos? )?
In short what to connect or not to connect and how to connect it?
Ex: live, or not, with a battery or not, a converter will it burn or not etc ...
I don't understand anything anymore, I swim in plain confusion !!!

[Did67]

What is certain is that an unplugged panel does not matter at all: on a stand-alone installation, there is usually a panel, a battery, a regulator. The regulator "cuts" the power to the battery when it is full, so as not to damage it ...

It is common to see panels not plugged in (if only for the time of a construction site, we install, we connect the panels, then we connect to the network ... It can take weeks between these stages ...

[izentrop]

Hello,
Too long to explain everything, I think warned obelix answers will light your solar lantern

Overproduction also means that we have not properly dimensioned our installation in relation to our needs.

[Gaston]

A solar panel is neither a voltage generator nor a current generator.
It can behave "almost" like one or the other depending on the operating point.

The curve (voltage, intensity) for a given lighting generally has the following form:


We see that for a zero intensity, the panel will reach a maximum voltage and for a zero voltage (short-circuit) it will reach a maximum intensity.
The maximum power being reached for a "midpoint" which will depend on the lighting (hence the interest when trying to produce as much as possible to use an MPPT regulator which permanently adapts the operating point. ).

The choice of how to connect the panel therefore depends on the load that you want to supply.

• Can the load withstand the maximum voltage of the panel?
• Does the load need a minimum voltage to operate?
• Does the load need minimum power?
• Can the load operate irregularly?

Depending on the answers, a regulator and a battery will be essential or necessary ... or not.

[elephant]

Okay, I'm going to do it partially too.

For standard illumination at 25 °, a PV gives a given voltage and a maximum current.

The short circuit current is slightly higher than the maximum current. Shorting a panel does not destroy it, the voltage collapses, but the current is still there! (therefore the risk of cable heating too)

It is practically not possible to place a circuit breaker or a fuse on a PV pcq: the DC current is too close to the rated current. Then, because it would be necessary to cut several hundred volts in direct current, which would give a nice arc and would require a distance between contacts of several cm or an arc blowing device. (so putting an "ordinary" switch also poses problems.

When you want to disconnect panels from their inverter. You must first cut the inverter-grid connection so that there is no more current. It is only then that we can then disconnect the plugs

The cards are designed so that we do not put our fingers "ousquinfautas".

[netshaman]

Cut the inverter-grid connection suppresses the short circuit current?
How is it possible ?
What is happening in the inverter itself?

[elephant]

Removes CURRENT, but not voltage.

So, if the inverter complies with the VDE 0261-1 standard, which is a legal obligation, as soon as it is disconnected from the mains, it stops.

Voltage is still present at the terminals of the panels, but they no longer flow (it is as if they were connected to a resistor of very high value). We can therefore disconnect the plugs without having an arc.

To compare, you can do the following experiment.

In a dark room, you plug in an electric heater.

Remove the plug with the active radiator: you will have sparks between the plug and the socket.

starts the operation again with the switch on OFF or the thermostat on the minimum (so the appliance does not heat up). You will have no sparks when removing the plug. (Now, you do have 220 V at the outlet)

[netshaman]

Okay !
Can we put in parallel a backup system against untimely juice cuts based on a battery and a converter / charger, all plugged into the PV panels and isolated from the network?
I imagined a circuit of this kind, I do not know on the other hand if there is not a danger of grilling something ...
A diagram will be more explicit:





The part of the table side is a bit confusing, but in fact it is not connected directly to it, it is isolated so that it does not inject on the network thanks to a dedicated anti-islanding circuit.
This one : http://www.wattuneed.com/fr/materiel-el ... ens26.html

[elephant]

Although I did not understand everything about your diagram, it does not seem suitable to me.

[netshaman]

I might have said that the box between the wks (it is an inverter / charger / converter) and the table it is a switch which switches as soon as there is no more juice on a secondary input ( the wks).
Is that clearer ?
It’s this thing:

http://www.ase-energy.com/selecteur-de- ... BYPASS.cfm

The two solar panels each have their microinverter.
But why, will you tell me?
1) because it costs me less
2) with a conventional grid injection inverter, goodbye to advanced mppt management for each panel!

But not suitable for what?