Hi all
Our install finished yesterday and the battery etc commissioning completed last night. Question - I have 2 solar connections - 5 panels on each. PPV1 and PPV2. I am only seeing generation from PPV1, PPV2 shows 1w and has done all morning??
Anyone know what's wrong, or is this part of the system settling down?
thanks
Is one string in shade and the other isn't?
Vestas
hi no they are both in the sun, and its been the same since the commissioning started.
What's the voltage on the strings?
Vestas
This is the data for the last hours or so
Is the scaffolding still up and casting line shadows on the lower string?
4monks Hi yes the scaffolding is still up but when we checked to see if it was casting a shadow it wasn't, I would also hope that a small shadow of a pole wouldn't cause these differences!
What does the installer say?
Jules, Have a read of my post here:
https://community.givenergy.cloud/d/2296-adding-another-solar-array/2
where I describe quite how weird solar panels are with respect to shading.
If the panels are in the same plane (e.g. all facing south in the same place then the VPV(2) and IPV(2) values do look very low, and I would ask your installer to double check everything, especially for loose connections etc.
If your panels are not in the same plane, then it's much harder to tell if something's wrong from afar.
Also, if the panels do need wire / connection checking, best to have that done whilst the scaffolding is still up - much easier for them.
rivimey hi yes they are all on the same plane. We contacted the installer yesterday and sent them some data from the dashboard. Waiting now for them to come back to us - it does look weird, I would expect figures to be closer
Jules42 It might be worth telling us exactly what you have had installed and what the orientation is.
Orientation and minor shading shouldn't do that. Power from indirect light should be plenty to get some generation.
With only 5 panels on each string you may struggle to reach the startup voltage for the inverter (150V?)
Also, check your grid voltage isn't going too high...
Jules42 If your scaffolding is still up, I'd ask your installer to consider putting all the panels on one string. With ten panels on one string, you will start generating earlier in the day and year and end later in the day and year. You just need to make sure the open circuit voltage of all the panels in series doesn't exceed the maximum for the inverter (usually 500-550V) and that the maximum current for each panel doesn't exceed the string maximum (usually 11A to 16A depending on the inverter).
No idea why the existing arrangement would have high voltage and zero output, unless there's some effect from either grid voltage being too high at the time, or a bug to do with the battery being fully charged.
We have contacted our installer and their aftercare emergency support team are going to contact us. Thank you all for your input, will be sure to ask some of the points you have raised!
Tim Hi Tim, out of interest why would all 10 panels on one string mean we generate earlier in the day and later in the day?? This is exactly the outcome we want - to generate in all daylight hours :-) how does 2 strings change that?
Jules42 The inverter has an input voltage range - e.g. 150V to 550V - and if the panels (combined) produce less than the minimum the inverter just won't "switch on". The reason for a minimum will be complexity of the electronics - being able to accept 15V as well as 500V is a lot harder than 150V and 500V, and it is likely that if your panels are only generating 15V there is hardly any current available either, so it's not worth it. A lower power inverter may go for a different input range - e.g. 10V to 50V - and be fine with that, but then be unable to accept 8V input.
When you put more panels in series you are adding the individual panel voltages together. So e.g. 4 panels might individually have 38V, 36V, 37V and 31V over their individual terminals, making for 142V input, so not enough to start the inverter at 150V. Adding another panel to the string, e.g. at 35V, would make a total 177V, which is now enough to get the inverter running.
The downside is of course that in full sun now you have 5 panels. If each panel has a full-sun open circuit voltage of e.g. 120V (example!**) then you started with 4x 120V or 480V, which was less than the 550V max input voltage, but now have 5x 120V or 600V, which is too high for the inverter. I'm not sure what it will do but I think it shuts down (that input string) at this point, so you get nothing.
Plausibly you could use a home automation and a relay to bypass (not short out!) one panel in the string when the input voltage rises high enough, so you have at least 4 panels worth rather than zero, but that is outside the scope of the GivEnergy product range.
** actual panels will typically have an open circuit Vmpp of around 35-40V, so 120V is just to make my point simple.
rivimey The assumption is that both strings have the same orientation. If you have strings split East and West, your East string will start producing decent power earlier, and the West one later in the day.
I think in most cases startup voltage makes very little difference. Our 4.5KW west-facing string (11 panels, admittedly) would reach startup voltage at 5:20AM in June, but even at 6:30AM it was only producing 130W...
Jules42 @rivimey is right with his analysis except I've never heard of PV panels with a maximum voltage greater than about 40ishV. It all depends on whether your panels all have the same orientation (ie all S or split E/W). The panels we have have a VoC (ie maximum) of 42V and ten in series would give 420V maximum; well within our inverters string maximum of 600V. Our inverters have a maximum input current of 11A/string and the panels have a maximum output of 11A, We have 8 panels on each string, giving a maximum voltage of 336V and current of 11A on each string. The issue for you really is the inverter string start up voltage. Ours is 100V; below that, the inverter doesn't do anything. With more panels on a string, you reach the startup voltage earlier in the day and as long as the maximum voltage of the string is within the specification for the inverter, one string will start up sooner and keep going longer than the same number of panels on two strings. You could do some modelling to work out whether one string of ten panels over the year will give more output than two strings of five. I suspect it would but your installer should be able to advise, if he's asked to make the comparison.