Micro Inverter VS String Inverter (The Lie Verified)

[robbyg]

We all know the advantages and disadvantages of each kind of system but the one major Advantage of Micro Inverters has recently been proven to be untrue and just a marketing gimmick to try and justify the extra expense. (Luckily one company did the comparison in a scientific manor.)

[solarix]

Thank you. I totally agree. I've known this ever since I split my array and ran half on a SolarEdge distributed inverter and half on the old Xantrex string inverter. Xantrex consistently did a little better.

[nerdralph]

I have a test array on my garage with 10 CSI CS3W 144 half-cell panels in a single string. One of the 10 is always shaded in the early morning, and I can barely notice the impact of the shading. I wonder about the impact on the bypass diodes on sunny mornings, so I plan to check the panel with thermal imaging to make sure the bypass diodes aren't getting very hot.

[Mike90250]

............ I plan to check the panel with thermal imaging to make sure the bypass diodes aren't getting very hot.

Often, the diodes are in the Jbox on the back side of the panel, where the wires come out. Scanning from the front side, there may only be a subtle difference only in the vicinity of the Jbox. From the back side, the jbox may take some time to warm up to be visible.

[blueman2]

I have a test array on my garage with 10 CSI CS3W 144 half-cell panels in a single string. One of the 10 is always shaded in the early morning, and I can barely notice the impact of the shading. I wonder about the impact on the bypass diodes on sunny mornings, so I plan to check the panel with thermal imaging to make sure the bypass diodes aren't getting very hot.

The diode heating issue during shading is very real, but that does not make optimizers or microinverters better options than just a regular string. I have a system with LG335 Neon2 panels, and SolarEdge with optimizers. I had 3 out of 16 LG panels fail within 9 months of initial installation. 25% annual failure rate! The cause was diode failure due to shading. So having the SolarEdge with optimizers did not not help out at all. The key is to get good quality solar panels with solid diodes in them which will survive shading. And for me, LG was certainly not the answer.

[solarix]

Wow, LG panels are a good brand. Surprised to hear of failures like that...

[blueman2]

Wow, LG panels are a good brand. Surprised to hear of failures like that...

Yup. The installer said LG was incredulous about that failure rate, but they did indeed confirm that all 3 panels had failed diodes. Warranty replacement took almost 6 months, but they did replace them and paid the installer to do the switch out.

12610 Arroyo.JPG3 bad modules larger picture.JPG

[bcroe]

I have a string that lately, sometimes reduces output current by about 20% compared
the identical string next to it. Some times it seems to run at 100%. Last time that
turned out to be an overheating MC4 connector, which eventually completely burned
out. I was waiting to see if this one had the same problem, but now I am wondering
if the issue could be bypass diodes? This string had been subject to occasional
shade from tree growth, now removed.

Attaching voltmeter test points is a bit of a project, usually under a night spotlight,
not done yet.

I am not convinced, that bypass diodes are under the same strain for a micro inverter,
as a long string. My single panels have 60 cells which tend toward being shaded at
the same time. A string has 720 cells, lots of them running full out even with some
shaded, a different situation.

Bruce Roe

[robbyg]

The diode heating issue during shading is very real, but that does not make optimizers or microinverters better options than just a regular string. I have a system with LG335 Neon2 panels, and SolarEdge with optimizers. I had 3 out of 16 LG panels fail within 9 months of initial installation. 25% annual failure rate! The cause was diode failure due to shading. So having the SolarEdge with optimizers did not not help out at all. The key is to get good quality solar panels with solid diodes in them which will survive shading. And for me, LG was certainly not the answer.

Wow I have LG 365 Neon R panels and I was told they are bullet proof. Luckily I do not have a shading issue but I am still shocked that they died.
I assume it was the panels that get the shade that died?
Only good news is that it's nice to know that they honor the warranty.

[blueman2]

I assume it was the panels that get the shade that died?
Only good news is that it's nice to know that they honor the warranty.

Yes, I had 3 with some partial shading, and all 3 died within 9 months. And yes, they did finally honor the warranty, but it took over 6 months to get them to do it. Overall, I wish I had not gone with LG panels.

[Will792]

I watched video with interest not because of string inverters vs microinverters debate but because of shading impact on panel production. It was snowing yesterday, around 9” of fluffy snow, and I decided to do experiment to see impact of some hard shading on individual panels production. I left a bit of snow on some panels. I have plenty (72) so some production loss for one day is immaterial. All panels are LG Neon2 330 and all microinverters are IQ7. Picture and panel production readings were taken at 12PM. It was rather cold so the amount of the snow in the pictures did not change.

You can see that even very small amount of snow covering panels greatly affected electricity production.


NEproductionWithSomeSnowShading.png

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