Tigo Optimisers on a string with 2 orientations not optimising as hoped

[Hedges]

I've lived without MLPE so far.
Once I got a clamp DC ammeter, I found a low string. isolating every panel (ground mount not roof), I tested and found 15% of panels were bad. One brand of three I used.

Newer codes require RSD, so I've bought Tigo "Fire" modules. No monitoring or optimizers. I do hope RSD is triggered when AFCI triggers, because I think that will be more effective.

Do the math twice, get your installer to do the modification if appropriate, but I think 13s & 5s will work much better.

Can those optimizers do doubling of current? Because that's the way for them to address partial shading on half-cut panels.
You can experiment shading cells.
Do not leave hard shade over a cell for long while in direct orthogonal sun. Often, bypass diodes can't handle that, only lower current of off-angle sun.

 

[wattmatters]

Here's this week at 09:35. There's a chimney on the west facing roof too which you can see the shadow for:

That layout doesn't really need optimisers, bit of a waste of money (unless they are required for shutdown regulations).
Just run 1 x 13 and 1 x 5 - the panels and MPPTs will sort it out.

But if you were to use them then at most five Tigos tactically deployed to the five eastern most panels of the south facing array.

 

[EastCoastDIYer]

That layout doesn't really need optimisers, bit of a waste of money (unless they are required for shutdown regulations).

No regulations here in UK requiring them. I do have some shading from trees in the winter months and in summer evenings the west facing roof gets partial shading. The total estimated energy recovery from having them is fairly small on the GetPylon shading forecast modeller, but the recovered energy is mostly at the beginning and end of the day and winter months, which is when trying to eek out the last drop of solar is important to me - give my battery system an easier time or extend solar production into peak electricity time so I get higher export rates. Basically giving me options. A1, A2, A3 and probably A4 being optimised definitely was an extravagance as the tree shade doesn't reach them, but it means all of my panels are monitored which is important to me. The panels are 8m up and over a conservatory, so testing for faults isn't really an easy option for me. For reference, it cost less in optimisers and CCA than it did in scaffolding for the install. So, getting them even if it was just for the monitoring feature they gave was money I was mostly happy to spend. And they've highlighted to me that my install isn't optimal, so I'm grateful for that.

Do the math twice, get your installer to do the modification if appropriate, but I think 13s & 5s will work much better.

Thanks again everyone, it's clear a 13 A, 5 B arrangement is the way to go. Much appreciated.

 

[SeaGal]

Ignore me - I didn't read your calcs properly and see that you used -15c. Good stuff!

?... well, I'm a stickler for detail and have lived in East Anglia for over 30 years ?

Further thought... is the chimney actually usable? If not could it be removed.

Do keep us updated how it goes.

 

[EastCoastDIYer]

Further thought... is the chimney actually usable? If not could it be removed.

It's actually a fake brick chimney, I guess people can't handle a proportionally long house having a chimney at one end but not the other. Removing it, whilst costly (unlike removing those fake fibreglass chimneys), it's more that it wouldn't get past the wife...

 

[Quattrohead]

You have storm whatever going on there at the moment, just last lasso
it and pull it down when she's not looking.

 

[SeaGal]

Yep 60mph gusts tonight forecast for here and the local highway bridge is closed - good idea re the lasso, the winds are from the South-West so it will fall away from the PV panels nicely - should pass the SWMBO test

 

[ksmithaz1]

Newer codes require RSD, so I've but Tigo "Fire" modules. No monitoring or optimizers. I do hope RSD is triggered when AFCI triggers, because I think that will be more effective.

Have you tested RSD functionality? I'm considering doing these for the roof, and they can be had without breaking the bank. I've done light reading, it appears you can use the RSD transmitters, instead of the cloud connect thingy?, but I didn't see anything in the spec about how far the the ring can be from the device. Does the device leech power from the panel? Didn't see anything on the spec sheets for that either, but it has to run off something. Further the achilles heel would seem to be if you lose the transmitter, which appears to send a keepalive to the devices, then your array shuts down. This would indicate the need for at least one spare transmitter on the shelf at all times. This fuzziness is the reason I didn't put them on there to start with. I may get one and play with it.

 

[Hedges]

I haven't tested functionality beyond plugging in a PV panel and measuring 0.6V out. I wanted to see if they might be tweaked for SMA, better to have 1V out, but were not.

No cloud thingy for these. They don't send data.
Just some transmitter required, either built into inverter or Tigo's separate one, which I also bought. I don't know if it is a sine-wave tone, or coded data stream.
SMA requires 5V, so 9 of the Tigo in series, to power its keep-alive.
I got dual panel modules (for $40) and single (for $10). I thought dual might put out 0.6 x 2 = 1.2V, but not according to what I've read. Haven't tested. I also got a transmitter (close to $200). Was going to use for TriPower. Will use with older inverters when I move panels on roof.

Sure, it leaches some power. Should be just enough to detect/demodulate keep-alive, and pull up a MOSFET gate.

My newer Sunny Boy and the coming Sunny Boy Smart Energy (with RSD support) have 3x MPPT input. My panels will be 2x 12s, leaving one MPPT input. I think I'll mount a "12V" panel on the roof, about 21Voc, and feed that into input "C" to power keep-alive. It is under 30V, so allowed voltage beyond array boundary.

With two inverters, each has a keep-alive transmitter. Could disable one, use magnetic core to couple both arrays together (I'm guessing). Your spare is the other inverter. Catch is, inverter needs power to be configured. Plan to bypass some optimizers to do that.

 

[SeaGal]

Have you tested RSD functionality?

RSD functionality is not a requirement in the UK, hence not relevant to this thread.

 

[Hedges]

Unless it comes as a "feature" of optimizers, and therefore you have to successfully tell them NOT to RSD.
I assume this is the case, at least for Tigo optimizers.

By the way, do rooftop PV panels not cause fires in the UK?

 

[zanydroid]

My theory on why they spilled over the two planes is that 5 is on the edge of minimum string length. As well it’s possible if 5s is on low end of MPPT TIGOs deciding to buck by 25% for no reason might make the string drop out.

FWIW I feel TIGOs are a bit complicated due to the 25% limitation (and possibly also buck only voltage change), and I’m not really sure the typical resi installer can handle them unless they are diligent at using and listening to their design tools.

I may be being a bit of an ass but the less careful design needed the better for any residential equipment install, solar or otherwise.

 

[wattmatters]

My theory on why they spilled over the two planes is that 5 is on the edge of minimum string length.

Another solution would have been to use different panels for the two strings. High voltage panels for the short string, low voltage panels (i.e. the existing ones) for the long string. No need for Tigos.

 

[zanydroid]

Another solution would have been to use different panels for the two strings. High voltage panels for the short string, low voltage panels (i.e. the existing ones) for the long string. No need for Tigos.

What does high vs low mean in this context?

Half cut panels arranged in 6s instead of 2p3s?

 

[wattmatters]

What does high vs low mean in this context?

e.g.

Lower voltage panel - enables longer strings to remain under MPPT max voltage limit:
Jinko 475 W Tiger NEO
Vmax power 35.21 V
Imax power 13.49 A

Higher voltage panel - helps shorter strings reach minimum MPPT voltage:
Q Cells 475W 156 Half-Cell Mono
Vmax power 44.54 V
Imax power 10.66 A

 

[zanydroid]

Aren't those panels going to be different shapes though?

 

[SeaGal]

Higher voltage panel

Aren't those panels going to be different shapes though?

or even the Trina's with 49V VoC if no space for the big Qcells

 

[wattmatters]

Aren't those panels going to be different shapes though?

I was not suggesting those specific panels, they were just random examples to illustrate that panels of the same rated output are available with significantly different voltage outputs and this can be an important consideration depending on the nature of the rooftop and MPPT(s) in play.

Good solar installers design systems considering these and various other factors. There is no rule that say panels on one MPPT have to match the panels on another MPPT.

 

[Hedges]

More (smaller) cells in same frame size. Here is 54.7 Vmp:

https://www.us.sunpower.com/sites/default/files/sunpower-e-series-commercial-solar-panels-e20-327-com-datasheet-505701-revh.pdf

 

[zanydroid]

Is that a product line design goal for some companies? Multiple voltage options for identical frame size and color?

(I’m FOMO a bit because I bought some $$$$ boomer looking 3BB 72 cell panels and put them on my roof in August 2023 , if I knew how to shop better it would have looked better)