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Solar Inverter Shade Test! Are Microinverters Over-Hyped?
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- เผยแพร่เมื่อ 10 ก.ย. 2021
- Microinverters are better than string inverters for handling panel shading issues. Or are they? This commonly held view is put the test in a showdown between Enphase microinverters and the Fronius Gen 24 string inverter. Brace yourself for the results!
For a more in-depth video, check out NRG's full testing:
• Micro and String Inver...
And check out the related blog post here:
www.nrgsolar.c...
This segment is from SolarQuotes TV Episode 8. Catch the full episode here: • 5 Solar Innovations Th...
I don't think completely blocking out all light using cardboard, leaving cells in utter darkness is a good model for shading. With that degree of darkness, obviously the bypass diodes are going to activate and there'd be no difference.
Real life shading doesn't work like that. First, the shadows typically will be coming from faraway objects. There will still be a lot of diffuse light reaching the shaded cells. Secondly, not all shadows are completely opaque rectangles. Many are going to be thinner or scattered. In any of these situations, there's a good chance that the bypass diodes do NOT activate, and that's where you should expect a difference.
Things I'd like you to test, which better represent real world scenarios, are:
- Utility line (thin line) shadow spanning across one or more panels
- Tree branches causing partial shade (still some direct sunlight coming through in between branches/leaves), situated more than 10 meters away as trees would
- Small twigs, bird dropping, or other debris which has fallen onto a panel, not big enough to cover a substantial portion of a cell
Here's a real case study where a tiny shadow caused a string inverter output to drop by as much as 20%: th-cam.com/video/AbxHoQF4ADk/w-d-xo.html
Cool test, but maybe a mention of the humble bypass diodes found in almost all panels these days may help explain the results a bit better. CIGS panels have been using multiple diodes for years e.g. my Miasole 125W has 56 cells and a diode for every two which allows practically 50% of the panel to be completely covered before the voltage drops to low to continue if you only have one.
That would be truth in advertising vs "everyone has been lying to you your whole life! come with me if you want to live" click bait. I didn't know the technicals but I knew there had to be something with those panels. Thank you for the clarity!
MPPT plays an important role also. And not all MPPT algorithms work equally. SMA and Fronius do it best.
The problem is, bypass diodes have a life. Most diodes will fail at less than half of a panel's life, and most people won't realize a diode has failed until some damage has already been done to a panel from reversed current.
In fact most panel manufacturers void the parts warranty if a panel is subjected to more than 100 hours of shading conditions, which is barely a tiny percentage of a panel's life.
MLPEs are critical to prevent a failed diode from ruining an entire string or worse, catching fire on failure.
What if you shade 2 or3 panels?
Great video, very interesting to see that the result did not match up with expectations.
you should have covered a whole panel or 2 panels. because mine get a few panels shaded by a tree for a couple of hours each day.. in what normal circumstances will a tree shade only 1 panel. and obviously you wouldn't install micro inverters if its only 1 small part of 1 panel being shaded ?
They have made a full video for this: th-cam.com/video/UQ9Szhl1ceQ/w-d-xo.html
Basically, it is just the bypass diodes in the panels which cut off the inactive strings within the panel and preventing the series string effect.
would have been better to fully cover 2 panels and see what happens. if the fronius still wins then i probably just go string next time.
Wow, I've been solar installing for years, these results totally contradicted my previous understanding...
Great job, and I loved taking the Mick our of Canavan and Taylor. I've been so happy that despite the roadblocks to solar, businesses and the general public have been doing their bit putting solar on their roof at a rate of knots. I'm hoping so hard Catl manage to nail Sodium batteries at scale!
Fronius with Tigo optimizers is a pretty sweet setup. The reason though that people are moving to microinverters is TCO and MTBF. For a 25-year system, you are going to buy at least 2 string inverters over time and you need to put that in your TCO calculation. The microinverters will last the life of the panel or be replaced under 25-year warranty. Though Fronius builds string inverters at a 20-year goal, they only offer a 10-year warranty in most places globally and extended warranty prices quickly show that indeed they will fail in the 10-25 year range. Hopefully, more durable parts come out and string inverters are longer lasting or cheaper. They are still very efficient and great for long runs and large arrays! Otherwise, competitors to Enphase will have to take that business as they are underpowered and overpriced.
A 25 year warranty doesn't mean they will last 25 years.
Also even if you have to replace a few in 25 years the warrantee we doesn't cover the cost having someone go up to roof, take off the panel and replace the enphase. These are extra cost.
Replacing a string inverter is very fast and low cost.
There are only a few scenarios where a microinverter makes sense. Small number of panels 3, or say many different orientations and angels in a location, 3 panels east at 45 degrees, 4 panels south east at 20 degrees and so on.
but in 90% or more a string will justy do.
There isn't a company or government in the world using micro inverters. None. Homeowners are told: its because they don't place solar panels where there is a shade problem.
Putting a comparatively expensive part (micro inverters) at every panel is on its face stupid. There is truth about central inverters decades ago. There were design flaws that made micro inverters make sense. Today solar panels have diodes and modern inverters have been updated. More than that, those micro inverters all require power (not efficient) and they also cause panels to shutdown in shade conditions due to their load.
Today, they make zero sense. Enphase is still using statistics and comparisons from decades ago. They aren't honest IMHO.
All I have to say... do your own research people. The truth is hard to find. The bs that leads to high costs... easy to find.
This is gold... humor and science
Love the shade models. Very on point
great test. Now do the same with the big paper part not exactly in the middle of the panel, thus creating a difference in produced current.
Can you elaborate? I felt there wasn't anywhere near enough shade on the panel in the second test
Call it what it was given the hype and big money marketing, the much cheaper and less to go wrong string inverter beats the expensive micro inverter with much more to go wrong and is the reality, good video....
Can you show a test where a string vs micro invertor setup has a single panel failure?
Fascinating revelations! BTW live in VIC, but grew up in Richmond, SA
Currently investigating Solar plus battery system to replace existing solar only system (9yrs old 3kW).
Does this mean that micro inverters and optimisers are not necessary even with time partly shaded panels?
Personally, I still like microinverters on systems with shade issues - they are gentler on the panels (lower voltage) and I like the per-panel monitoring .But a good string inverter - like Fronius/SMA - can handle shade better than we thought.
Spot on
What about the enormous cost of the now mandatory safety rules (like scaffolding) to replace a micro-inverter?? I bet the "replaced under warranty" terms don't cover that? Registered tradesmen cant just climb on a roof anymore!
Single inverter in the cool shade will be more efficient. Micro inverters are in the worst location for heat causing power losses and degradation due to heat
But there is always the problem of tolerance errors in panels which cause problems in maximum power point tracking, thereby reducing efficiency of string inverters. But this is only 5-10% and definitely not worth the enormous cost of microinverters which is at least 3times as much as a string inverter