Power Optimisers - What are they? And do you really need them?

A companion video to the microinverter I made recently.

Microinverter video:

Voltage and current explained video:

Interactive utility to show the effect of shading on a module and an array:

Solar Panel Shading (Part 1): Are Optimisers and Micro inverters Worth It?:

Solar Panel Shading (Part 2): More on Optimisers and Micro inverters:

MC Electricals’ optimiser review:

MC Electrical Tigo Optimiser Recall:

FLIR Infra-red viewer

Chapters:

0:00 Intro
1:56 Shading
9:08 Accumulation of Dirt
9:52 Panel Degradation
10:38 Panel Failure
11:00 Monitoring
12:58 Safety
13:53 Reliability
18:00 Summary

Corrections:

6:34 I over-simplified how the optimiser manages the current. In reality, the inverter first maximises the power from the panel by adjusting the voltage via MPPT, then performs a DC-DC conversion, decreasing the voltage to bring the current in line with the rest of the string.

7:45 Actually, some of the bypass diodes will only kick in if there is a difference in shading across that particular panel. If there is shading across the whole of the panel (as in the diagram) the optimiser should still be able to manage that.

14:17 Oops - the total production should of course be 3.6kW, not 4.8kW.

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(c) 2023 Gary Does Solar. All rights reserved.

DISCLAIMER
Whilst every effort is made to ensure the accuracy of the content in this video, no warranty for that content is provided, nor should it be implied. Viewers acting on the content, do so at their own risk.

#solar #power #optimiser

[dtm]

I knew nothing about optimizers before this video. Thanks for an excellent and straightforward explanation!

[GaryDoesSolar]

* NOTES SINCE PUBLICATION *

At 6:34 I over-simplified how the optimiser manages the current. In reality, the inverter first maximises the power from the panel by adjusting the voltage via MPPT, then performs a DC-DC conversion, decreasing the voltage to bring the current in line with the rest of the string.

At 7:45, Actually, one or more of the bypass diodes will only kick in if there is a difference in shading across that particular panel. If there is shading across the whole of the panel (as in the diagram) the optimiser should still be able to manage that.

And at 14:17 my maths is clearly rubbish - the total production with 12 x 300W panels would of course be 3.6kW, not 4.8kW!

[tethysenergy]

We replace on average about 2 x Solar Edge optimisers per year, some on our own installations, some on other peoples. We install about 50 domestic projects per year. We can't really compare this rate to either Tigo optimisers or Enphase micro-inverters as we don't install them.

The good thing is that the faulty optimiser can be pinpointed so we don't have to remove half of the array to locate the problem. For the client, Solar Edge will cover the cost of labour and some of the scaffolding costs. For most replacements we can use an aluminium access tower to get up to the roof and locate the fault. The cost of this is easily covered by the Solar Edge warranty. However, the jobs that tend to require a full scaffold are where we need to span over above conservatories or where there is a pitched roof on a lower storey beneath the roof with the panels. For these replacements the client typically does end up having to cover some of the scaffold costs. The more difficult the roof is to access, the more costly it'll be to deal with faults which would need to be factored into any potential client's decision making.

There is an argument to install optimisers & microinverters in the loft space beneath the panels. This would make replacement much easier and less costly. We don't do this as it would mean making a cable penetration through the roof beneath every panel. It would also means installing jumper cables between each panel and it's corresponding optimiser for both the +ve and -ve cables meaning more connections in total. Some attics are converted, so for these it's a non-starter to do this and the optimisers have to go on the roof.

[FelipeM]

This is the best explanation I've found so far, well done!

[notjustageek]

We had a discussion with our installer about Solaredge Optimiser reliability. They were replacing 10 a year over the 20, 000 panels they had deployed, so a 0.05% chance of failure per panel per year. Thought I'd mention here since the data for this doesn't seem to be overly available.

[jamesmartin]

Great video clear and easy to understand. You go over the benefits and downsides of using optimizers. Makes it easy to see what situation you should use optimizers in.

[keithjewers]

Another very informative video. Many thanks for all your effort that goes into them - as a relative non-expert I find them excellent at helping improve my knowledge and they always provide food for thought.

[mpmatt]

Thank you for your interesting presentation. I have a 14 panel system with a Solar Edge inverter and optimisers on each panel which was installed in 2017. In 2021 one of the optimisers failed but caused the entire system to shut down. The optimiser was replaced, at a considerable cost, but just over a year later another one failed, again causing the entire system to shut down. It was replaced again at a considerable cost to me. a couple of months ago a third optimiser failed but I only lost output from the associated panel, until a few days ago when the entire output was lost. The inverter is still functioning and recording a fault on one panel which would suggest that the optimiser has failed completely. Solar Edge has provided replacement optimisers under their "limited product warranty" but they have not offered to provide any support for the labour cost or scaffolding. It does suggest that the undisclosed failure rate of the optimisers is somewhat higher than the advertised reliability.

[Gelp]

Another superbly clear and informative video! Thank you.

[SnarkySolarGuy]

I am so glad I read the video description after watching the video. I had a lengthy reply ready :D Thank you for correcting the errors and covering the highlights optimization and shading effects on solar modules. Although beyond the scope of your video, it is worth noting that while the strings behave as you say, once connected to an inverter, the MPPT will reduce the effects of shading. Some inverters are better than others at this.

Along with optimization, module level monitoring is also an advantage of MLPE. You can see everything you discussed in real-time (or close to it). It is great for digging into the details of system operation, especially when homeowners wonder why their "system isn't working." Thanks again, and take my sub!

[andylees]

Gosh another excellent video, well thought out, presented and most articulate. Great work. Ty Gary!

[markleygordon]

The best explanation I have seen. Thanks.

[FrankPloegman]

Thanks for your video's, Gary! Their quality is unrivaled. I love your crystal clear explanation and balanced discussion of *all* pro's and cons. I have more than a little technical knowledge, but imagine that even laymen can understand the majority of your video's. I know from personal experience that it's anything but easy to distill so much knowledge on a complex subject into short and understandable teaching. Well done! 👍

I wonder if further improvements in panels, e.g. more bypass diodes, can further reduce the already doubtful net value of optimizers and micro-inverters.

[scallywagII]

I have just replaced 2 optimisers that failed in the eighth year after installation. Their tech support guy said that 2 out of 13 was not bad, he had seen worse. He won't hear much from the satisfied customers with no issues.

Found out that Solar Edge have a 12 year warranty on the optimiser, but only contribute to labour and scaffolding for the first five years. My installer quoted £1500 + VAT. I did the job myself after bracing my scaffold tower off the wall and using ratchet straps and wall eye bolts to keep it all steady. The tower also makes cleaning easier. I had begun to have issues with some lichen growing on the panels. Have been told thus is more common in the vicinity of silver birch trees. A large one behind us causes partial shading issues throughout the year, so I am still convinced of the benefit of optimisers for my installation.

[hughrattray]

Great videos - thank you. I watched this video and part 1 and 2 of the Solar Panel shading.
I have a Solaredge inverter and optimisers so I had a look at how they perform with shading. This afternoon one panel was about 80% shaded but still providing over 60% of the output of the unshaded one. So I think this is much better than I would get from the panel if the bypass diodes had kicked in and switched the panel off.
Even when the panels are fully shaded I get some power from all the panels. Again, this seems better than if I relied on the panels alone.
I could send you the photos of the shading and the screen shots of the solaredge data for each panel.
Intriguing subject and fantastic that you are exploring it.

[geoffreycoan]

Thanks Gary, another clear explanation of the pro’s and con’s of the solar setup. Just a question about real-world experience of two of the potential benefits of optimisers from 9:17, dirt on the panels and panel degradation over time.
I’ve had a 16 panel FIT array (2 strings) on a Growatt inverter fitted for 7+ years now. Until we had scaffolding up earlier this year to fit our newer GivEnergy arrays I had never cleaned the panels, and in theory over that duration would start to see some panel degradation, but in fact total annual output each year has been consistently around 3mW, with 2020 and 2022 both generating slight more than in 2016 and 2017. So in my experience there hasn’t been any significant dirt-related or age-related power reduction - or any reduction is masked by the annual variation in solar generation.

[MrSensible]

My son & I have very similar solar systems installed by the same supplier. We both have JA Solar 395W panels (he has 12, I have 8) & both arrays face West. Neither of the arrays have shading issues.
However I have 4 optimisers & he has none. Why the difference? Well I think we both went with what the supplier recommended.
In theory, all things being equal, the ratio of my solar output to his should be 0.666 (8/12) & right now, in Summer, it is. However in the period October to January it consistently ranged from 0.71 to 0.735. It was like I had 8½ panels to his 12. I put this down to my four optimisers. That said, given solar generation in winter is pathetically low, the value of the 'extra' is worth two tenths of bugger all! Had I had my time again, I would NOT have had optimisers put in & saved a few hundred quid.

[hughbence]

And thanks for such excellent research and presentations.

[nicdensley]

Thank you, I'm looking at a string inverter plus optimisers. Very helpful.

[lesbadham]

Thanks Gary. You are very informative. I am just starting to learn about solar panels and hope to get an installation done soon.