micro-inverters or optimizers when shading is major issue ?

[ButchDeal]

That demonstrates to me a real understanding of the problem.

Diodes fail and optimizer can detect that, and be proof for warranty claim.

I would say that optimizing PV array output over a wide range of conditions
including shading, is a rather complex technical problem. I am not impressed
with this explanation. It seems to me to be grossly over simplified, inadequately
or poorly explained and justified. I see no curves, pictures of optimizer connections
and explanation of their functions, or adequate explanation of inputs to the math shown.
Perhaps it is really an attempt to justify the product, not to be carefully scrutinized.
Bruce Roe

The argument put forward by NWDiver is that in a heavily shaded environment there is "roughly" the same output for a string system as an optimized system.

with the difference in cost of the equipment assuming SMA inverter in both (he tried to compare to SolarEdge to better his figures) is very little.
If the system requires NEC 2017 rapid shutdown AND OP wants Secure power feature then the price is almost exactly the same (really the same as I am not sure his solution for using the TS4-R-Fs with an Emergency stop switch is approved, but even that would add costs and make the price within a few dollars).
So SMA inverter and TS4-R-O VS TS4-R-F with E-switch hack

I agree there are complex situations often with shadows and they rarely cover just one cell or even cells in one group, or even cells on one PV module.

The SolarEdge document describes the situation with multiple static situations and no not completely with SMA optimizer as they work rather differently but clearly showing situations were the optimizers would produce significantly more (NWDiver has several times talked about <1% and this document is talking > 1% at the least for single cell to cases with much more difference).

Bruce and I disagree about the usefulness of optimizers on UNshaded situations, though this is different. OP needs MLE for NEC 2017 anyway so go full optimizer or just meet NEC 2017 requirements is the proposal by NWDiver, although OP asked Optimizer or micro.

[J.P.M.]

That demonstrates to me a real understanding of the problem.



I would say that optimizing PV array output over a wide range of conditions
including shading, is a rather complex technical problem. I am not impressed
with this explanation. It seems to me to be grossly over simplified, inadequately
or poorly explained and justified. I see no curves, pictures of optimizer connections
and explanation of their functions, or adequate explanation of inputs to the math shown.
Perhaps it is really an attempt to justify the product, not to be carefully scrutinized.
Bruce Roe

This seems a bit like a duel between titans.

Both are experienced and knowledgeable. Something genuinely helpful and informative might come out of it.

I plan on staying tuned - hopeful of learning something.

[bcroe]

I have noticed and diagnosed, and found failed diodes in optimized systems
without setting foot on site

That demonstrates to me a real understanding of the problem.

Here is the best document showing the math:
solaredge.com/sites/default/files/se_technical_bypass_diode

I would say that optimizing PV array output over a wide range of conditions
including shading, is a rather complex technical problem. I am not impressed
with this explanation. It seems to me to be grossly over simplified, inadequately
or poorly explained and justified. I see no curves, pictures of optimizer connections
and explanation of their functions, or adequate explanation of inputs to the math shown.
Perhaps it is really an attempt to justify the product, not to be carefully scrutinized.
Bruce Roe

[ButchDeal]

When one cell group is shaded in an optimized panel the bypass diode is also triggered. Bypass diodes are relied on in optimized systems too. You can still spot a failed diode with string level MPPT. It's not as easy and may take a few more minutes to find the failure but... once again... not worth the cost.

Yes when a whole cell group or most if a cell group are covered, but when one or two cells are partially covered the diode doesn't necessarily activate. Or more likely a cell in ine group, cell or two in another, few cells on a different module, half a cell on another module...

in optimizd systems each module is independent and not effecting the MPP of the rest of the string(s). Without optimizers they are effecting the rest of the string(s) by your own words. The difference though is YOUR insistence that it isn't THAT MUCH. And you try to explain how it isnt that much by using best case situations, of full cell group and only one cell group. In real life situations shadows move across and are usually set at an angle hitting multiple cell groups and modules unequally. It is exactly this unequallness that optimizers are helping with.
they also tend to repeat every day so the effect of small production differences add up pretty quickly.

and yes you can find a failed diode on a system without module level monitoring, but it would be a LOT harder to notice and to find, and would require someone in site testing modules to find. I have noticed and diagnosed, and found failed diodes in optimized systems without setting foot on site, even had replacements shipped under warranty without anyone being in site till the replacements arrive.

Here is the best document showing the math (instead of "roughly" or made up percentages as you keep say ) :

https://www.solaredge.com/sites/default/files/se_technical_bypass_diode_effect_in_shading.pdf

So for one cell in a string of 10 PV modules you are looking at 96.6% vs 98% with optimizers but this is compounded as more cell groups are affected.
and if part of all cell groups in one module then 90% for just blocking diode vs 97% for optimizer... again compounded when multiple modules are affected.

but it is clear you do not think any of this is worth the cost. Maybe you make a lot hourly in repairs..

[nwdiver]

Explain more, please (and what's an "E-stop" ?).

..... 'E Stop' ....

Just has to be labeled for 'Rapid Shutdown'...

[RShackleford]

Iyou could run 12v aux power through an E-Stop to provide SPS power with the Fs and still comply with NEC 2017.

Explain more, please (and what's an "E-stop" ?).

[nwdiver]

That's what I was told on the phone by SMA today.

I also think that secure-power and rapid-shutdown cannot co-exist (be on the same system); because rapid-shutdown turns off the TS4-whatever modules when AC power is lost, so there's no DC coming into the inverter.

The Rapid Shutdown and SPS issue is confusing. Initially I thought the TS4-Fs would work because it's a simple DC line protocol.

Here is the quote from SMA in their press release....

'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.'

I'd love to know why the Ss and Os work but not the Fs... or if this was an error. Even so... you could run 12v aux power through an E-Stop to provide SPS power with the Fs and still comply with NEC 2017.

and you reliance on bypass diodes is just against industry trends as well as silly. We have seen many modules fail with bypass diode issues there are many many more out here failed that are unnoticed because no one is monitoring or looking.

When one cell group is shaded in an optimized panel the bypass diode is also triggered. Bypass diodes are relied on in optimized systems too. You can still spot a failed diode with string level MPPT. It's not as easy and may take a few more minutes to find the failure but... once again... not worth the cost.

[RShackleford]

I think you need the O optimizers to get secure power and they have to be in all the modules.

That's what I was told on the phone by SMA today.

I also think that secure-power and rapid-shutdown cannot co-exist (be on the same system); because rapid-shutdown turns off the TS4-whatever modules when AC power is lost, so there's no DC coming into the inverter.

[ButchDeal]

Then the S which isn't much more than the F.

My sole point with optimization is that if comparing it to string level MPP the only benefit is harvesting energy from shaded panels IF the shade falls across all cell groups. If one cell group is shaded it's ~roughly the same. If that's worth the increased cost... fine. IMO it's almost always more economic to just add more watts instead of squeezing more wh out with optimization. If you're space constrained and REALLY... REALLY want the most kWh you can get ROI be damned... then sure... SE is the way to go.

I think you need the O optimizers to get secure power and they have to be in all the modules.

there are other benefits with optimizers as have been pointed out already many times, like monitoring, easy of layout, multiple azimuths, gains from module differences, as well as shadow production improvement.
your statements ar just miss leading and dismissive of the differences and constantly making up figures and using "roughly" "almost" etc etc.
and you further constantly seem to equate "optimizer" to solardge.

and you reliance on bypass diodes is just against industry trends as well as silly. We have seen many modules fail with bypass diode issues there are many many more out here failed that are unnoticed because no one is monitoring or looking.

[nwdiver]

I said rapid shutdown AND secure power, which OP is interested in.

it is funny how you always seem to negate the figures to some made up percentage every time a figure doesnt fit with your theory.

SMA themselves are making the claim and they sell both optimizers and string systems

Then the S which isn't much more than the F.

My sole point with optimization is that if comparing it to string level MPP the only benefit is harvesting energy from shaded panels IF the shade falls across all cell groups. If one cell group is shaded it's ~roughly the same. If that's worth the increased cost... fine. IMO it's almost always more economic to just add more watts instead of squeezing more wh out with optimization. If you're space constrained and REALLY... REALLY want the most kWh you can get ROI be damned... then sure... SE is the way to go.

[ButchDeal]

You don't need to 'O' for rapid shutdown. The F or S also fulfill that requirement.

Sure... power doesn't remain the 'same' just the ~same... not enough to really even think about. Probably <1%.

I said rapid shutdown AND secure power, which OP is interested in.

it is funny how you always seem to negate the figures to some made up percentage every time a figure doesnt fit with your theory.

SMA themselves are making the claim and they sell both optimizers and string systems

[nwdiver]

Ok follow along. SMA makes optimizers, solaredge is not the only optimizer.
The O optimizer is required for rapid shutdown and secure power, so zero cost difference.

if a shadow is small the. Power does NOT remain the same, close maybe but not the same

You don't need to 'O' for rapid shutdown. The F or S also fulfill that requirement.

Sure... power doesn't remain the 'same' just the ~same... not enough to really even think about. Probably <1%. I have a couple Fronius string systems I've installed that have Voltage and Current monitoring. I'm always amazed at how steady power is with fluctuations in voltage. Voltage goes down a bit but current goes up and power doesn't change much at all.

So it would be zero since the SMA TS4-R-0 is almost exactly the same price as the TS4-R-F

??? Where are you shopping??? The F is usually ~half the price of the O.

[ButchDeal]

I posted pretty clear evidence they do... and if the small shadow isn't enough to trigger the bypass diodes then it's not enough to effect the other panels... MPP is a curve and there's typically more than one MPP within <1% of each other. If the current drops slightly because of a shadow too small to trigger the bypass diodes then voltage increases and power remains the ~same...

Where did you show there was no cost difference??? You disputed my numbers but never provided yours. RES isn't the only place -41 inverters are available for ~$1200... The Powerstore and Renvu also offer a 5kW SMA -41 inverter for <$1200.

Ok follow along. SMA makes optimizers, solaredge is not the only optimizer.
The O optimizer is required for rapid shutdown and secure power, so zero cost difference.

if a shadow is small the. Power does NOT remain the same, close maybe but not the same

[ButchDeal]

Actually, I'e seen TS4-R-O as low as $40, and never P320 for close to that, so no way it's zero, probably not even $20.

The discussion is optimizer vs non-optimizer. So it would be zero since the SMA TS4-R-0 is almost exactly the same price as the TS4-R-F, so optimizer vs non-optimizer as well as need for the O if OP wants rapid shutdown and secure power.
nwdriver is trying to claim optimizer vs non-optimizer but is arguing solaredge vs SMA when SMA has optimizers as well.

[RShackleford]

also as we already showed it is not a $60 difference but closer to $20 and even less ( to zero) if OP wants to have secure power and rapid shutdown

Actually, I'e seen TS4-R-O as low as $40, and never P320 for close to that, so no way it's zero, probably not even $20.