micro-inverters or optimizers when shading is major issue ?

[nwdiver]

So secure power is working with your system?

I don't have SPS on any of my systems. I haven't had a chance to install a new -41 yet and none of my customers were that interested since our grid rarely goes out here. The system I have with TIGO is a -40 and would not work with SPS without a workaround to supply power to the TIGO module.

[ButchDeal]

I don't have SPS on any of my systems. I haven't had a chance to install a new -41 yet and none of my customers were that interested since our grid rarely goes out here. The system I have with TIGO is a -40 and would not work with SPS without a workaround to supply power to the TIGO module.

Good to know.

[RShackleford]

Another thought: the following trick would work with micro-inverters or optimizers (or other TS4-X devices), but not with just a simple string. You could put all optimizers/TS4-X's along the top edge of a ground-mounted array, with pairs of wires going from the panels up to the top. So no dangerous voltage anywhere near the ground even if the lower edge of even a fairly small array (3x5) is near grade. Higher cost for cabling, but no fence costs; main motivation for me would be aesthetics of no fence. (See thread: https://www.solarpaneltalk.com/forum...string-systems)

[solar pete]

I actually would love to find a great video or tech document showing the situation of unoptimized, SMA optimized, and SolarEdge optimized, toss in enphase micros too, with a gradually increasing shadow on identical arrays.

Any one see anything like that?

Hello All,

Its about time we had a good old debate about this topic ,as equipment, models/brands come and go its good to keep up, I like this guys stuff, https://mcelectrical.com.au/inverter...rs-optimisers/ as it pains me to give any other Aussie Solar Co seo help but this guy does actual testing, **** he flew to Israel to talk about inverters, worth having a read though, cheers

[RShackleford]

this guy does actual testing ...

Well, this article is pretty on-point about all we've been discussing here. I'm guessing a certain one of us will take issue with its conclusions : https://mcelectrical.com.au/blog/tig...el-optimisers/

[scrambler]

Glad you think this is a good review, it is the one I brought up at post #60
Good to know you judge the info sound

[nwdiver]

Hello All,

Its about time we had a good old debate about this topic ,as equipment, models/brands come and go its good to keep up, I like this guys stuff, https://mcelectrical.com.au/inverter...rs-optimisers/ as it pains me to give any other Aussie Solar Co seo help but this guy does actual testing, **** he flew to Israel to talk about inverters, worth having a read though, cheers

I enjoyed most of what he wrote except this; 'The problem with shading on just one panel is it can bring down the production of half of the panels on your roof.'

Not true if each string is independent which is far more common than not these days. I don't think there's a string inverter on the market anymore with only 1 MPPT channel.

[scrambler]

"it can" does not mean "It will"
It also says "Half of the panel", may be as you said because most Inverter have two MPPT

[ButchDeal]

Well, this article is pretty on-point about all we've been discussing here. I'm guessing a certain one of us will take issue with its conclusions : https://mcelectrical.com.au/blog/tig...el-optimisers/

They seem to fit right along with explanation of each:
REASON 1 – OPTIMISING PREVENTS SHADED SOLAR PANELS FROM DRAGGING THE ENTIRE STRING DOWN.
REASON 2: OPTIMISERS ALLOWS PARTIAL PRODUCTION ON SHADED SOLAR PANELS
REASON 3 – SOLAR PANEL DIODES ARE NOT OPTIMISERS

[nwdiver]

"it can" does not mean "It will"
It also says "Half of the panel", may be as you said because most Inverter have two MPPT

It won't. If you shade a panel, the bypass diodes will engage and the unshaded panels continue producing at full power. The only exception is parallel strings. If you have parallel strings of 12 and 1 panel is shaded you now effectively have a string of 12 and a string of ~11. This problem is easily solved by putting each string on an independent MPPT channel; If 1 panel is shaded on a 4kW string of 12 panels you don't lose 50% or 40% or 30% or 10%. You lose at most ~8%. ~3% if only 1 cell group is shaded. Incidentally if that panel is optimized and only 1 cell group is shade you're STILL gonna lose ~3%.

This is what happens if 2 panels are shaded and each string is independent. The unshaded panels are unaffected. Because this shade is only over 2 cell groups the result would be ~identical with optimization.


screen-shot-2018-07-12-at-11-47-44-am-png.316409.png[/QUOTE]

[ButchDeal]

If you shade a panel, the bypass diodes will engage and the unshaded panels continue producing at full power. The only exception is parallel strings. If you have parallel strings of 12 and 1 panel is shaded you now effectively have a string of 12 and a string of ~11. If 1 panel is shaded on a 4kW string of 12 panels you don't lose 50% or 40% or 30% or 10%. You lose at most ~8%. ~3% if only 1 cell group is shaded.

That is NOT the only exception. The even give an example in the article. If you block enough to start effecting the voltage such that the string voltage is outside the string inverters MPPT range then it will shift them all until it gets back into range.

In this test, the left three panels were significantly shaded. To prevent the inverter from turning off from under-voltage, the inverter reduced the current, so the bypass diodes did not engage. This meant each panel still produced 30 volts, but only 0.5 amps.

With the same amount of shade on the optimised panels, the shaded solar panels performed poorly. But the unshaded solar panels were able to run at a higher current, (so higher power).

Parallel strings are more common in larger systems.

[nwdiver]

That is NOT the only exception. The even give an example in the article. If you block enough to start effecting the voltage such that the string voltage is outside the string inverters MPPT range then it will shift them all until it gets back into range.



Parallel strings are more common in larger systems.

Shading enough panels to drop voltage enough to be outside the MPPT band would be pretty hard; The band for SMA inverters is 100 - 480v. So you'd need to shade ~10 panels on a 13 panel string to be outside the band.

There's no reason to ever have parallel strings on a residential system with current inverter options. I don't think anyone makes an inverter with 1 MPPT channel anymore. All the new inverters I've seen have 2-4 channels. The last string system I installed was 22.77kW using (2) 7.7kW SMA inverters. 6 strings each with its own MPPT channel. Cost <$3k for the inverters. With optimization it would have cost ~$4k more. Instead of spending ~$4k on optimizers I spent $4k on ~2kW of solar. Pretty sure my annual yields will be higher with 22.77kW of unoptimized vs 20.77kW of optimized...

[Ampster]

.......... I don't think there's a string inverter on the market anymore with only 1 MPPT channel.

My Outback Skybox only has one MPPT channel.

[nwdiver]

My Outback Skybox only has one MPPT channel.

Regular grid-tie not a fancy hybrid

But point taken... I'll rephrase to 'The VAST majority.'

[ButchDeal]

Shading enough panels to drop voltage enough to be outside the MPPT band would be pretty hard; The band for SMA inverters is 100 - 480v. So you'd need to shade ~10 panels on a 13 panel string to be outside the band.

Well except the MPPT range for SMA Sunny Boy 7.7-US inverters is 270-480V

There's no reason to ever have parallel strings on a residential system with current inverter options. I don't think anyone makes an inverter with 1 MPPT channel anymore. All the new inverters I've seen have 2-4 channels. The last string system I installed was 22.77kW using (2) 7.7kW SMA inverters. 6 strings each with its own MPPT channel. Cost <$3k for the inverters. With optimization it would have cost ~$4k more. Instead of spending ~$4k on optimizers I spent $4k on ~2kW of solar. Pretty sure my annual yields will be higher with 22.77kW of unoptimized vs 20.77kW of optimized...

So you put 22.77kW of solar on 15.4kW of inverter. I see why you are not worried about optimization there.