micro-inverters or optimizers when shading is major issue ?

[scrambler]

Bypass diodes are solid state and if the J-Box is located in an area that it gets sufficient cooling (an even bigger problem for optimizers) then there's no 'stress' when it's activated. There's no reason a bypass diode couldn't be 'activated' for the life of the panel.

I am surprised by that and confused, as many articles I read do speak about the not so great lifespan of bypass diodes and the fact that they can be stressed by repeated shade conditions.
In addition to the optimizer review I mentioned earlier, below is another article that also mentions it.

https://www.positronicsolar.com.au/2019/08/02/panels-shade-and-diodes/

It is hard to know where the reality lies with all this.
The fact that apparently some panel manufacturer like LG appears to have mention in the warranty text such as the one quoted in the optimizer review (below)
"LG, state that their panel warranty does not cover: Improper installation or reinstallation and poor solar system design. (Examples of improper installations and very poor system design are modules installed in conditions which put long term stress on the bypass diodes in the modules, and also reduce the system output for the owner – for example prolonged significant strong shadowing of the modules e.g. via trees, walls, gables, overhangs, valleys, chimneys, satellite dishes etc (In such situations a professional solar designer will suggest a micro-inverter or optimiser solution and with such a proper solar system design solution the module warranty is fully applicable)."

[scrambler]

It's also current that causes heat not voltage. The current in the panel doesn't change with an optimizer. If a cell group is shaded in a panel the bypass diode will be activated with or w/o an optimizer and be exposed to roughly the same amount of 'stress'.

The review below seem to contradict that statement, do you disagree with its statement that :
"Before a bypass diode has the time to engage, the Tigo optimisers see the impedance caused by the shade and open a bypass tunnel to match the impeded current. This allows the inverter to work at a higher current without affecting the solar panel bypass diode."

https://mcelectrical.com.au/blog/tigo-energy-solar-panel-optimisers/

[nwdiver]

As you say, they'll just pull the meter (I guess it's simple, never done it).

Yep. Snip the tamper seal, pull the cover, pull the meter. Takes ~5s.

[RShackleford]

If they're responding to a fire they're unlikely to go looking for a AC disconnect. They're usually just going to follow their training and pull the meter...

Yeah, reading a little further, articles talking about how rapid-shutdown is taken care of (without any further effort) if you have micro-inverters, they say as soon as the AC breaker is shut off the micro-inverters shut down (same as they would if the grid goes down). Well, I don't quite picture firefighters looking for whenever my main panel is, then trying to figure out which breaker is the solar connection (plus, isn't it usually just tee'd into the cables from the meter to the main breaker) ? As you say, they'll just pull the meter (I guess it's simple, never done it).

[nwdiver]

A lot to pile into one thread, but this is directly-relevant to the title ...

It appears to me that rapid shutdown isn't really an issue using micro-inverters, because apparently the NEC rapid-shutdown thing only applies to DC strings: https://www.purepower.com/blog/2017-...ortant-changes

With micro-inverters, everything is AC except those very short connections from panel to micro-inverter, and those probably aren't over 80vdc anyhow, maybe barely if you have 2 panels in series per micro-inverter (e.g. Chilicon's new 720 watt unit). Seems odd, I'd think the 240vac from the micro-inverters would put almost as big a hurtin' on a firefighter as 600vdc would (and a hell of a lot more than 81vdc would).

Of course I guess rapid-shutdown is super-easy with micro-inverters: the grid goes down, all the micro-inverters turn off, end of story. Except, doesn't rapid shutdown have to work even if the grid is up, or do firefighters shut-down the grid connection first thing ?

Responding Fire Fighters will pull the meter to the house which kills AC power which kills the micro-inverters. I've always thought the AC disconnect was a bit silly. I have a friend who was a fire fighter. If they're responding to a fire they're unlikely to go looking for a AC disconnect. They're usually just going to follow their training and pull the meter...

[RShackleford]

A lot to pile into one thread, but this is directly-relevant to the title ...

It appears to me that rapid shutdown isn't really an issue using micro-inverters, because apparently the NEC rapid-shutdown thing only applies to DC strings: https://www.purepower.com/blog/2017-...ortant-changes

With micro-inverters, everything is AC except those very short connections from panel to micro-inverter, and those probably aren't over 80vdc anyhow, maybe barely if you have 2 panels in series per micro-inverter (e.g. Chilicon's new 720 watt unit). Seems odd, I'd think the 240vac from the micro-inverters would put almost as big a hurtin' on a firefighter as 600vdc would (and a hell of a lot more than 81vdc would).

Of course I guess rapid-shutdown is super-easy with micro-inverters: the grid goes down, all the micro-inverters turn off, end of story. Except, doesn't rapid shutdown have to work even if the grid is up, or do firefighters shut-down the grid connection first thing ?

[nwdiver]

Forgive my confusion. What do you mean "so long as each string is on an independent MPPT" ? Maybe I could best understand if you tell me how you'd think I should arrange my 15-20 panels.

As you observed earlier; The SMA inverter has 3 MPPT channels. All I mean by 'so long as each string is on an independent MPPT' is that you don't have 2 strings in parallel on 1 channel. Each string must have its own channel so it can operate at its own voltage. If you have 2 parallel strings and a few panels on 1 string are shaded than the unshaded string is forced to operate off its MPPT. This is the only way shaded panels can effect the performance of unshaded panels.... this can't happen if each string in on an independent MPPT.

I would just split your 15-20 panels between 2 channels. If you have 20 panels then put 10 panels in series on Channel A and 10 panels in series on Channel B.

[RShackleford]

The shaded sections are 'deleted' by the bypass diodes so the unshaded sections function just fine. That's the misinformation I referred to in a previous post, the shaded panels do not negatively effect the performance of the unshaded panels (So long as each string is on an independent MPPT). The minimum voltage for the SMA inverters is 100v. If you have a string of 12 with 8 panels fully in shade then you have basically have 4 panels in the string.

Forgive my confusion. What do you mean "so long as each string is on an independent MPPT" ? Maybe I could best understand if you tell me how you'd think I should arrange my 15-20 panels.

[nwdiver]

I thought I'd read that optimization is super-important if you have shading, since one shaded or partially shaded module can bring the whole system's performance down. Or does the MPPT (in an SMA inverter) deal with those issues ?

Also, I'm a bit confused about the statement "i'd need at least 4 un-shaded panels in a string"; is there some minimum voltage below which the inverter won't work ? Specifically, in my situation of of somewhere in the 15-20 panel range, am I going to want to use all 3 string inputs of an SMA inverter, or just one ? Though probably have to use at least two if more than 15 panels, since string voltage can't exceed 600v.

The shaded sections are 'deleted' by the bypass diodes so the unshaded sections function just fine. That's the misinformation I referred to in a previous post, the shaded panels do not negatively effect the performance of the unshaded panels (So long as each string is on an independent MPPT). The minimum voltage for the SMA inverters is 100v. If you have a string of 12 with 8 panels fully in shade then you have basically have 4 panels in the string.

[RShackleford]

It's pretty simple. The Fs are only rapid shutdown. The S adds monitoring. The O adds Optimization. There's also a L that adds buck so you can have longer strings (hence the 'L').

The Tigo home page is the best resource.;

IMO the S, O and Ls aren't worth the cost. Monitoring is kinda fun to watch but it usually gets old quickly. Module failures are so rare I don't think it's worth the cost of monitoring.

I thought I'd read that optimization is super-important if you have shading, since one shaded or partially shaded module can bring the whole system's performance down. Or does the MPPT (in an SMA inverter) deal with those issues ?

Also, I'm a bit confused about the statement "i'd need at least 4 un-shaded panels in a string"; is there some minimum voltage below which the inverter won't work ? Specifically, in my situation of of somewhere in the 15-20 panel range, am I going to want to use all 3 string inputs of an SMA inverter, or just one ? Though probably have to use at least two if more than 15 panels, since string voltage can't exceed 600v.

[nwdiver]

I found another opinion/explanation piece on wordpress. And they think Solaredge is better in actual performance. As well as being cheaper. Since that article has a date of Aug 1, 2013, I'm sure prices have fluctuated so you'd have to look at the prices now.

For a ~5kW system you're going to pay ~$600 less for a SMA system with TS4-Fs vs a SE system with optimizers. Even the SMA inverter is cheaper which is a bit odd since the SE inverter doesn't have MPPT (That's part of the optimizers).

A 5kW SMA inverter is ~$1200 plus ~$30 per panel for TS4-Fs vs a 5kW SE inverter for $1400 plus ~$60 per panel for optimizers.

[foo1bar]

My understanding is that the Tigo optimizers will work with most any string inverter, is this wrong ?
Are you saying Tigo won't handle shading issues as well as SE ? This article would seem to contradict both those:

I don't see anything in that article that says Tigo will be better or worse than Solaredge for handling shading issues.

Tigo does have a whitepaper that compares them to Solaredge.
Obviously since they promote it, it shows them being better in most of the scenarios they show.
Their whitepaper does show solaredge being better in "soiled" test conditions, which I think was interesting.
In the case that Tigo had the most benefit (36.8%), it was still within 5% of SE (32.5%)

It wasn't clear to me if that was all the way to AC power, or if there may have still been differences in the DC->AC conversion. Because I think it's quite probable that the Solaredge inverter is slightly more efficient than the SMA one, as it only needs to accept a more limited range of inputs.


Based on this data (and that it's coming from Tigo) I don't think I'd say Tigo is significantly better than SE.
But it does look like it's fairly similar.

I found another opinion/explanation piece on wordpress. And they think Solaredge is better in actual performance. As well as being cheaper. Since that article has a date of Aug 1, 2013, I'm sure prices have fluctuated so you'd have to look at the prices now.

[nwdiver]

Oh, that's encouraging then; wish they'd state the model numbers of these new inverters, so price could be checked (or are they just the -41 models ?).

I'm confused by the alphabet-soup of TS4 models. Is there a good link for that ?

It's pretty simple. The Fs are only rapid shutdown. The S adds monitoring. The O adds Optimization. There's also a L that adds buck so you can have longer strings (hence the 'L').

The Tigo home page is the best resource.

IMO the S, O and Ls aren't worth the cost. Monitoring is kinda fun to watch but it usually gets old quickly. Module failures are so rare I don't think it's worth the cost of monitoring.

[RShackleford]

'SMA’s proprietary Secure Power Supply function also returns with the new Sunny Boy models. Homeowners can once again access up to 2,000 watts of daytime opportunity power. Secure Power Supply is easily installed, taking only a few minutes, and works with the company’s TS4-R-S and TS4-R-O module-level technologies.'

Oh, that's encouraging then; wish they'd state the model numbers of these new inverters, so price could be checked (or are they just the -41 models ?).

I'm confused by the alphabet-soup of TS4 models. Is there a good link for that ?

[nwdiver]

If you look at the link I posted (post #43) for a -41 inverter, it states "Note that using TS4 optimizers will disable the Secure Power Supply functionality of the inverter."

That appears to be old text for the -40s. Here's the press release from SMA. Looks like the Os and Ss will work too?

'SMA’s proprietary Secure Power Supply function also returns with the new Sunny Boy models. Homeowners can once again access up to 2,000 watts of daytime opportunity power. Secure Power Supply is easily installed, taking only a few minutes, and works with the company’s TS4-R-S and TS4-R-O module-level technologies.'