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EEVblog 1426 - WOW! This Problem DROPS Solar Output by 20% !
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- เผยแพร่เมื่อ 8 ต.ค. 2021
- Dave tracks down why his old 3kW system that was moved was now showing a 20% drop in output power at the same time every day.
Is it inverter temperature, inverter mains voltage, solar panel cracking, dodgy connection resistance, or shading?
A shorter 5min version of this video is here: • How a SMALL SHADOW can...
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Due to several requests I have created a 5min version of this video that allows you to share with people who don't want a 30min video:
th-cam.com/video/NoIjTK249D0/w-d-xo.html
You might want to try hotspot free panels, 60 bypass diodes/panel, so every cell has individual bypass (AE Smart Hot-Spot Free). I prefer string inverter (Fronius) and those.
❗21:26 Yes they do! A German brand: AE Solar uses this in their nicely priced and high quality Smart Hot-Spot Free panels.
Good call mate
OVERLY TALKATIVE... this could have been a 2 minute video. WHO has the time??
@@jan_phd Me :)
I took my antenna down when I had panels installed because my guy said it would affect my power production.
I was sceptical, but I trusted him because he knows his stuff.
This video confirmed his advice.
5:51 "one of the curses of being an engineer [...] is you know too much"
So much this - When watching a show, or an art installation you automatically start questioning every little detail and always wonder "how did they do it" instead of just enjoying the show's "magic" in awe like everyone else.
Sadly this works with a lot of fields. I can't quite enjoy video games like I use to. Developer, 3D modeler etc. I see things that we say "well the human eye wants to be fooled so it is okay to leave it like that" too easily. Yes we do say that and yes it is true, and now if you play games you probably will go UV seam hunting or other "minor" issues. Though I will say if game engines ever found a way to implement a certain thing UV seams wouldn't exist. However we can only do so much. I have legit had arguments to thin air (lasting easily a few minutes) while playing games about AAA titltes leaving such an obvious UV seam exposed.
Did you update your SMA inverter with the latest firmware ? They introduced their "magic" shadefix algorithm (basically a quicker MPPT swipe) which greatly improves changing the MPP in case of shade. I'd love to see your update about it !
Yup. A college did a year long study on this and found that ShadeFix actually out performs optimizers and micro inverters in a shaded environment. It's actually brilliant and in my opinion should be a main feature on every MPP inverter.
I'd love it if @eevblog did a demo of this.. with a sample cable .. before and after.
Actually that feature has to be activated in the inverter settings. Check if it is enabled. In older devices it used to be calles "Optitrack global peak". Would be interesting to see the difference.
This software development is very cool, Fronious and other seems to have similar smartness in their algorithms and a few fellow installers now starts to try to verify/bust the Enphase claims that even Dave have taken as truth, and not marketing: th-cam.com/video/TqOw43-hbjc/w-d-xo.html and th-cam.com/video/UQ9Szhl1ceQ/w-d-xo.html. They sure have an interest and bring bias to the party and you have to spot their own "glossing-overs" regarding a few other things (single point of failure, hi vs low voltage on your roof, chunky cables vs slimmer ones and so on) but still good to get the fact checking to ramp up now that the EU HS finally weaken up to solar.
For my of part, living in middle of Sweden, I'd like to see more tests and information on the 200-500W/m2 performance of panels and various inverters. We have more or less free energy most of the summer (mostly hydro) and really needs it during the winter (25-30% of homes are heated with electricity, always good insulated and with 1-2 heat pumps though). Every bit of kWh is gold (prices peaked this december at ~€0.8!!) during -20°C days and half empty hydro dams..
I experienced this as a kid playing with some solar panels. Called it mouse effect after my plush mouse that if I put it on the panel, while only shading one of the cells in the panel, the output of the whole panel was nearly gone.
petition to officially call this the mouse effect
It's a good name
And I invented the smart phone in my head as a kid, by combining the PDA with the mobile phone. Kids are underappreciated.
Light shading and compound shading is tough on older string inverters. Basically your bypass diodes aren't fully conducting, and the shaded cells in the series are limiting the current of the whole array. Modern string inverters can look for alternate maximum power points. I have 3 MPPT channels on my newer Sunny boy, with shading from a water heater stack and plumbing vent that affect two of the channels after a certain time in the day. But I only loose the power of shaded panels (or portions of them) when the stacks throw shade - not the large reduction you see. This tech seminar describes how newer SMA inverters work (most vendors employ similar techniques). th-cam.com/video/Sm0NePRWV9Y/w-d-xo.html
That development is very cool, Fronious and other seems to have similar smartness in their algorithms these days and a few fellow installers now starts to try to verify/bust the Enphase claims that even Dave have taken as truth, and not marketing: th-cam.com/video/TqOw43-hbjc/w-d-xo.html and th-cam.com/video/UQ9Szhl1ceQ/w-d-xo.html. They sure have an interest and bring bias to the party and you have to spot their own "glossing-overs" regarding a few other things (single point of failure, hi vs low voltage on your roof, chunky cables vs slimmer ones and so on) but still good to get the fact checking to ramp up now that the EU HS finally weaken up to solar.
For my of part, living in middle of Sweden, I'd like to see more tests and information on the 200-500W/m2 performance of panels and various inverters. We have more or less free energy most of the summer (mostly hydro) and really needs it during the winter (25-30% of homes are heated with electricity, always good insulated and with 1-2 heat pumps though). Every bit of kWh is gold (prices peaked this december at ~€0.8!!) during -20°C days and half empty hydro dams..
Soo... Exactly what I suspected then.
When we installed a 3kW system many years ago on my dad's house, we put it into operation with the scaffolding still in place. There was just a thin shadow from the railing across half of the panels (essentially as thick as a water pipe). After we took the railing down, the output increased a solid 1kW just because that shadow was gone.
We were quite surprised the effect was THAT significant as well. But at least we figured it out immediately.
So a bird just walking around ,bird poo or dirt could affect the performance by a decent amount of percent .
Newer panels no longer have diodes, instead using a small IC that has an integrated power MOSFET, so that when current is detected flowing through the body diode the tiny bit of circuitry controlling the gate turns the MOSFET fully on, and shorts out the body diode and thus reduces power flow in the device. No power dissipation, and the energy to turn the MOSFET on is stored in a small ceramic capacitor using the normal off state voltage. Turns off the switch every few seconds, to both recharge the capacitor, and also check if the panel shading is transient and thus panel is back at full output.
First I've heard of that. LG don't have them AFAIK?
@@EEVblog 3 companies used to make them. IDEAL diodes is the brand of Microsemi ( hard to source ), ST used to make them but are no longer in production and TI has the SM74611.
Which modules have this feature?
Any way to test for this feature, e.g. run current through cell when dark?
The MAX20800/MAX20801 Cell-String Optimizers do MPPT
Rising voltage in evening is industrial and commercial customers reducing load, along with the home consumers reducing load from electric cooking, so the overall load in the area is dropping, and the input voltage from the power plant is essentially constant, so all those small reactances and resistive line drops add up.
So you can ascertain information about the collective habits of local communities ..
@@das250250 Absolutely! If you're an electrician or plant engineering you will begin to learn the ebb and flow of your local grid. You can even see when your neighboring electrical customers turn on things like stamping presses or other very high draw machinery.
Really glad you went on to explain what the bypass diodes were for, thanks!
Unfortunately right at the start of this video I knew your problem. I was a radio tech from the mid 80 and worked for the police in Queensland. At the time the cells we were running at remote repeater sites were as low as 45W per unit and we used to have large strings of panels to keep sites alive (given there critical use). One particular site we had particular problems with during the Winter and it kept dropping out. We ended up at the site one day and were checking the current output from each cell trying to put a finger on the problem (previously we'd replaced all the cells and the Solrex regulator with no result) and discovered half the panels were low output. We then noticed the guyed wire from the 25 ft wind up Hills master crossed only the panels showing low output. Like a light bulb we'd found the problem after nearly a year of attempts to fix this repeater site. After a further trip we ended up building a new stand for the panels and moved the array away from the tower and the problem was solved. I do follow you on Twitter, I must have missed this series of tweets. Great video, wish we had TH-cam in the late 80 :)
I see your problem...you need to install "wiggle wiggle wiggle yeah" inhibitors :D
I never would have figured partial cell shadows would be that drastic, that's pretty crazy.
It's because of the protection diodes. In order to make it cheap, they protect groups so if one of the cells is out then the whole group is.
It's like squeezing a hose. A very small bottleneck will have drastic effect.
Squeezing a hose doesn't lower output, it speeds up the flow but doesn't change amount that passes. Unless you completely close it, but that's not the case here
@@dimitrijekrstic7567 so how does a nozzle work? It makes the passage smaller through which water can flow....how come when I kink a hose it drastically slows the water down?
@@dimitrijekrstic7567 how come when I pour a glass of water out all the contents come out significantly faster than even shotgunning a can?
Now that was really interesting! Trap for (not so) young players!
I'd like to see an experiment, now that you have the micro-inverters I'd like to see how much dust affects power output. You could do this by washing one of the panels say every other day and see if it outputs any more than the rest.
Also temperature difference (this would be trickier). But I guess this wouldn't be an issue, if not manufacturers would sell a watercooled version lol
I’d go for every other panel to get a better sample size for both the washed and unwashed groups.
Temperature definitely affects solar panel output. However, not by so much that any form of active cooling is really effective, especially when you factor in the added complexity and maintenance.
Sandia Labs did an experiment that showed dusty panels result in ~5% decrease in harvest.
@@mlenstra for sure it does, at least in theory. My question is by how much? Besides, you'd have to add in the loss in water (if you just hose the panel) or a pump (if you do a closed loop)
I believe NASA reported similar issues with one of their Martian rovers. The solar panel outputs were drastically down due to the amount of fine dust accumulating on the surfaces, but was corrected somewhat by dumping actual DIRT (bigger particles) using a robotic arm, then either letting the wind blow it off, or tilting the panel to allow gravity to move them. Sadly, not enough to restore full function, as they couldn't do it for the entire array set.
Effectively when a bypass diode kicks in, you get a second, but lower maximum in the MPPT curve. Not so sophisticated MPPT algorithms will get stuck on this lower maximum and do not search for the higher one. Would be interesting if a reboot of the MPPT controller helps, so it may search the whole area again an sees the higher maximum?
Some inverters have some string shadow management. I think this might do exactly that.
Sma has it but have to update to latest firmware and enable it
Just put the damn pannel on the road.
It seem very efficient 😅🤣
Wow, this looks to have a much bigger impact than it looks to the human eye at first glance. Nice eco-drive watch Dave! It's a pretty good idea on the battery side of things also you never have to worry about WR after a battery change. Love it myself!
Excellent discussion of solar panel architecture. Now I understand why one of my panels outputs exactly 2/3 the voltage of all the others, but the same current. A single bad cell or open internal connection will cause this even though all my panels are in full sun with no trees (or coax cables) nearby. Congrats on solving your problem. Every kWh is important.
Your panels have 60 cells separated into 3 power generating columns protected with bypass diodes. It only takes a slither of shade to drastically reduce the current output of a column. If you know a shadow will traverse the entire panel you can consider reorienting to landscape and only impact one column of 20 cells.
Wow, if that little shadow was able to wreck so much havoc, I wonder how effective a reflector and lens that tracks the sun and reflects onto the panels would be. Well it would be the solar surface area of the reflector divided by the area the lens projects to, not good, and a shadow might still heat your little cells.
What got me thinking, a solar installation with micro inverters could actually work as a huge format camera .It wouldnt be focused at a specific point, but could stil show movements of clouds.
I would love to see an experiment to see how the new array would react to a small diffuse shadow
Hi Dave, Jason from Prohelion here. As an ex solar car racing peep, this makes complete sense. While driving down the Stuart highway at roughly 90 km/h, even the thinnest tree would cause the MPPT to drop its power output by 60-80% for upwards of 3 seconds. Thankfully there is not many trees in the outback. #DontShadeTheArray
I was confused about the direction of those diodes until you explained it. Learned something new today from you.
On some of the Sunny Boy inverters, you have multiply inputs so you can divide your grid into smaller units. In that way shade will only drop output on that smaller grid. The drawbacks are higher cabling costs, and an isolators is needed for each circuit.
Yes, not worth it on such an old system.
Multiple input inverters are much expensive (and have larger rated power etc).
@@EEVblog Does your Sunny Boy inverter have multiple DC inputs? as I've seen a few that do, but mostly go unused.
Hi Dave, absolutely agree with your assertion that we engineers can jump to diagnostic conclusions that satisfy our need for complex, rather than simple, problems. In my early career I spent the better part of a morning attempting to urgently diagnose a "motor won't run" problem with a 3 HP three-phase synchronous motor. It had a complicated relay-based starter & direction-changer control box {this was 1972 - all brute force stuff}. Studied the schematic until my eyes were bleeding, tried many fixes, but no joy. Then a buddy of mine in the same plant dropped by for a chat, and he asked if I'd checked the fuses. Bingo - one of the three 100 ampere fuses for the incoming line was open. Replaced it, and all was well again. I never forgot the lesson...
Dave you might want to check if your old SB3000TL-21 already has the "shade fix" feature. In older firmware versions it might be called "opti trac global peak". This helps a lot with problems like this.
I just checked the datasheet and it does indeed say "Shade management with OptiTrac Global Peak". I'll check the admin settings to see if it's enabled. Thanks.
@@EEVblog You're welcome ... would be nice to see a follow-up about the difference it makes ...
As soon as I saw your time-lapse, I knew exactly the problem. It's the shadow from the antenna. My system, as I was told during installation, a shadow would basically cause the individual panel to stop producing power. Which reminds me, I need to go up and clean my panels. Dust, dirt and grease (from cooktop exhaust) needs to be cleaned off. Which needs to be done before the sun hits the panels. My issue is trying to find a safety observer willing to get up at 0dark30 😅
I have two 100 watt solar panels driving two 12 V ventilation fans in the attic of a separate garage. One panel for each fan. When even the slightest bit of shade hits one of the panels, the fans drop off like crazy. I could even it out with some batteries, but it is nice just to have the panels directly connected to the fans!
I've run across this with a small off-grid system I use when camping. One little shadow covering enough of the panel could mean the difference between a flat battery and a fully-charged one.
FWIW there's also the SolarEdge system. Modified string inverter with an MPPT box on the back of every panel. Fixes this issue and gives per-panel monitoring.
I've designed a couple of mppt chargers and I've noticed how a "small" shadow can make a huge difference to the panels output. Not so bad if a bird poops :0) on one cell , but if a few series cells are obscured , even slightly , it's very noticable.
Dave, noone thought you didn't check your roof for shadows. And just because of that, the simpliest explanation turned out to be right explanation.
working with and teaching solar cells I did not believe that these narrow shadows could drop your output that much with proper bypass diodes installed - but anyway you should see this from the dc current on the solar panels which you could measure with a current clamp.
The shadow of the mast could be perhaps 10% of the area on a cell which would reduce the current in the affected cell and substring in the maximum power point also by 10%, reducing the power by 10%. The bypass diode will only carry current when the substring voltage drops so much that the bypass diode becomes forward biased because the other cells in the string reverse bias the shaded cell. In your case the shaded cell(s) were just reducing the full current by 10-20%...
Now all you need is a rotator motor to turn the house to track the sun.
Or just a manual turning handle like on old windmills, where they turned the entire wooden building to face the wind.
@@johndododoe1411 some solar farms actively turn the panels to track the sun.
This is an excellent video! Very informative and I love how you cover the problem, troubleshooting, fix and explanation.
It would be interesting to cover up that entire panel with something opaque, and see if the power increased, compared to with the fuzzy coax shadow. The 3 diodes should conduct the full current of the remaining panels, and lose only 8.5% of the total power.
I would have never thought that such diffuse shadow would cause an effect that drastic.
You learn something new every day.
Woweeee. I always knew a shadow can create an issue. But that small shadow?! Wow great job discovering this David.
Great video, Dave. Recommend making this a short. It's what all the cool kids are doing!
Now imagine that (in)efficiency on solar roadways...
...Solar FREAKIN roadways...
I knew it was a"moving vertical shadow" the moment I first saw the graphs! (and I don't even know HOW I knew that) glad that you got it sorted :)
yes, you do not have to be an engineer to recognize this fact. eevblog probably knew this right away, but was making an "interesting video" to get the numbers up.
Thanks, I'm amazed at how much that little shadow affected the output
Thanks for the current flow clarification!
Newer SMA inverters have ShadeFix, which is supposed to solve most of the issues with light shading.
Very interesting , I had taken my aerial down , well actually wind had blown it nearly down , so glad I never replaced it
The voltage drops in the evening when demand peaks from everyone having dinner. It rises again as the demand trails off to a minimum at around 4am.
Yeah, I believe that!
I have microinverters with split-cell panels, and early morning sun catches a few thin tree branches, and I can see the low output move across the panels as the sun rises.
One of the reasons I went for a microinverter system in the first place.
+1 for microinverters.
With a string inverter you have one single device and with micro inverters you have many devices. Many devices have a much higher chance of failure and the quality of most microinverters are low
@@LippoM sorry, that doesn't hold up.
A single inverter is a much harder working device than a micro inverters. It has to deal with much higher voltages and currents.
A microinverter's maximum input is only round 40volts, and total power round 300watts.
If a microinverter fails, you just lose the output of that panel. If a string inverter fails, you've lost everything.
I commonly hear you should budget for string inverter replacement at 10 years. My Enphase microinverters are warrantied for 25 years.
And that's before we even get to the big Achilles heel of a string setup... one panel down, all panels down.
Great video!
Would love to see you do an in-depth video on MPP. Another interesting video idea would be teardown and explanation of DC optimizers, going over both DC to DC conversion optimization and the communication method that they use.
I know it's just semantics but impedances for AC on DC circuit's we call it resistance.
You still watch broadcast TV? Wow, I ditched that over a decade ago and never regretted it for a moment.
LOL I ditched cable years ago and never regretted it.
Two words. Kids & Bluey
More fool you - over 10 years of paying to watch adverts instead of recording the few things worth watching on a PVR and skipping the ads.
@@EEVblog ABC iView. My son watches it over and over..
Broadcast TV is free. So..
You can adjust the voltage range in SunnyBoy Inverter but you’ll need a dealer code. In the US this is for installations that are either first or last in line from the power plant.
Yes, I think I mentioned that in the video, I did that to no effect.
@@EEVblog yeah I commented early. You figured it out buddy
I am surprised they don't fab a bypass diode in the individual cells. They're already fabbed silicon. Also, is there any advantage to ganging cells in parallel as opposed to series? You're trading voltage for current, but if you can use microinverters per panel, I'd tend to think resistance and bus gauge issues would be minimal. It definitely would require a completely different inverter design, though.
The answer lays in what we all use for power supply at home . We use roughly a 240 v outlet at up to 10 - 20 amps .typically we use 10 amps to run heavy items like stove and kettles etc. So we need to get close to these two values from solar before conversion to Volt ac to minimise losses and cost . If you paralleled 60 sub panels at 0.6 v per sub panel with a current of 10- 20a rating that would be 1200 amps at 0.6 v per panel. This would represent an incredible amount of current and cable size and danger of fire. The approach would be better to have a moderate voltage matching the supply voltage and 10-20 amp to match current needs and then to invert it to ac voltage to reduce costs and maximise efficiency of conversion.
Diodes have an unavoidable voltage drop, so you can't just put a lot of them in series.
All you had to do was download an update for your Sunny Boy that provides Shade Fix.
Of course, you can also replace the robust string technology with module electronics. It is always a good idea to place complex electronic components on the roof where they are exposed to the maximum possible temperature fluctuations.
Without shading your entire string has only 1 Maximum power Point
With the active shading you get two MPPT points. 1 with all modules on the reduced current of the weakest cell (all other cells will rise in voltage and thus reduce theirs current) or with the MPPT Current of the other cells and the shaded parts disabled via the diodes, thus theirs voltage will be missing on the string.
On modern inverters there is a global MPPT tracking where the inverter cyclicly scans for other better MPPT points.
Maybe the inverter here slowly reduces the current of the entire string when the shade moves in because the shadow is to narrow or is not searching for other MPPT points because the inverter hasn't that GMPPT feature.
I had this exact issue with overhead powerlines on the first small-scale ground install I did for my off-grid building install. Good catch!
That was really interesting! Have you got an old panel you could dissect, at least to the level of the three strings / bypass diodes and conduct tests to show that even the diffuse shading of a cell or two can drop the output like this? The old micrometeorite panel maybe?
I do still have it in the bunker.
Wow, all that difference from a thin shadow?
It's a good job nobody ever thought of putting solar panels on roads, isn't it. ;)
Very interesting.
I remember getting a report at high school, it may have been my leaving testimonial, saying that "Anthony will often overlook a simple explanation in order to seek out a deeper reason for a problem", so you're not alone in that regard!
Yep. Waiting for my new house to be ready so I'm not installing on this house, but I set up 7X 100W panels I got for cheap at an auction to experiment with panels, batteries, charge controllers, etc. I found that one little leaf dropped on a series string had a dramatic impact on output, shockingly so. I knew what your problem was as soon as I saw the video title.
I was hesitant to go to the expense of microinverters for the new house system until I saw the result of even minor shading. It makes me think that regularly washing dust from panels is probably a good idea.
In other words the solar cell turns into an LED, or a Zener diode. I once made a solar LED array to prove a point to some instructors and classmates. The strings weren't long because the voltage would get high enough to turn the LEDS into rectifiers and conduct without a regular diode in series to stop it. It would take many thousands of LEDS to make a solar panel.
I have a client that had similar issues and what I suggested and he did was add 3 more panels to boost the output and that did work. In his case the total daily output was 40% below what was expected it has been over 5 years and the system is still working at full capacity.
This looked like a click bait, but isn't one. Really useful video
Increasingly, panels are now constructed with their own internal bypass diodes (e.g. that can bypass even subsections of the panels). So these newer panels would take care of them problem as well.
I loved the commentary on "knowing too much." I work in product development and spent an entire team meeting discussing bizarre test results. Everyone had weird ideas to explain what we were seeing. I eventually just retested the prototypes myself (a technician did it the first time) and found that the data sheet must have just rotated all results by one ID (results for A were recorded on the sheet for B, and so on).
I was probably 2 years into my role, and it's funny that you put it like you did... That was the exact thought I had when I solved the riddle. "Dang it. I know too much." When you don't have the knowledge to invent these minuscule probability explanations, you check the simple ones first. That was a great lesson to learn.
I'm surprised you only have just discovered now that when your neighbors have solar feeding the grid it can over volt the street and reduce the amount of you're feed in power. It screws you're pay back models as you may not get the full feed in power as expected, and its impossible to know if your neighbors will get solar too in the future as its bad for you. Also the dramatic power loss on partly shaded series string panels is a issue too..
The funny thing is that I SAW that pole shadow in the time laps video. I though that this might be the problem and sure enough, to me surprise, it was the only problem. I guess that the benefit of watching the EEVBLOG video on a 40 inch screen. Even the small details are clearly visible.
Great explanation of bypass diodes on a solar panel - thanks.
Mains voltage going up/down would be correlated to peak and off-peak consumption of energy... lots of people using the grid around 5-7pm ;)
Super interesting! Thanks for sharing!
You can just bolt solar optimisers to those panels in the string. Essentially turns a string inverter setup in to a micro inverter setup without significant additional cost. I got them for my panels that get shade.
amazing. this video may explain why many consumers arent happy with the output of their expensive solar panel systems compared to what the suppliers promised. i have made a mental note of this for when i get solar panels
Nice observation! 253V is where it's mandatory for a inverter to shut off (or limit) here. So mains voltage theory wasn't that wild.
Amazing find, after watching this, i must go on the roof, and check my array. thank you.
If your mains voltage is out of spec, the inverter will usually shut down completely, or at least throw an error.
Had an issue with a customer whos inverter would just shut down production at certain times of the day. Measured mains voltage, and one of the phases was really low, like 200V maybe. Went to check the main fusebox for the incoming supply, and one of them was absolutely scorching hot, and crackeled when given a little twist. The fusebox was from like the 1940s, and pretty worn out this point.
So it turns out that everytime there was too high of a load on that phase the voltage would drop just enough to trip the inverter, and shut down until there was almost no load on that phase and it would work for a while.
WOW.... this video is amazing, crazy useful knowledge to keep in mind. I knew shadows caused power dips but never imagined something so small causing that huge of a power loss.
Wow...I totally wrote off that shadow when you first showed it. Crazy that much loss from cascade of issues.
Would be interesting to see a test where you create a thin shadow earlier in the day for experimental confirmation.
Thank You. I would not have believed that small shadow would do that.
First thing I could think of when I saw your setup was your antenna was casting a shadow on them.
Just goes to show that regular cleaning of your PV panels to get rid of the slightest amount of build up can have a significant improvement in generation capacity? Not many would expect that PV output deteriorates so significantly due to very light shadowing or film buildup.
A tiny single bird dropping can take down the production from a panel as it will create resistance across the circuit which will also create a hotspot in those shaded cells.
On a string setup, if you just had voltage monitoring across each cell (that could be done fairly cheaply) it could reveal things like this... I'd be curious to see you hook up a voltmeter to one cell in the string and start shading it
Well, he'd need a cheap source of computer logged voltmeters. Maybe he knows someone in the industry.
Start of the video my first reaction were the sight of a pole on the roof. I don't know the direction of the sun, but considering how the event clocked in at about the same time day after day, then it is most likely a shadow.
Thermal shutdown would be more sporadic and dependent on ambient temps.
Mains voltage is however logical given how many solar panels there is locally. So overvoltage protection kicking in wouldn't be strange. But the graph instantly killed that idea. Since no reason for it to drop so sharply a 20 to 10 in the morning, when it delivers just fine at 11.
Though, long series strings can be sensitive to small things like birds flying past.
I am though curious to the micro inverter solution. I have seen some other solutions using DC-DC converters instead and having a main high voltage DC bus going over to the inverter.
long line shadows over several sub-strings will also degrade power with microinverters.
I have never seen anything like that, that's insainly extreme. I do not experience the same effect on my array. The shadow of a chimney moves across one of mine and is still not that bad
Wow - glad you found this. I am just setting up a 12V system and I know that one panel is going to get some shade. I had been musing about serial vs parallel so I am going to wire the 4 panls as 2 x 2 parallel
Exactly, a great example of why panel level microinverter or panel level mppt optimization (Tigo etc.) is so important and advantageous to strings. Some shade indeed makes a big impact.
Round 1 to the Aussie Sundial!
I had tested shading in my solar experiments starting about 2013. I was trying different combinations of panels, bypassing diodes and various configurations trying to see how to maximize yield in less than optimal conditions. My system is DC as I charge batteries to provide power isolated from the mains.
My present test system has 6 x 350W panels in pairs on 3 masts that I rotate throughout the day (I'm retired and haven't put up linear actuators).
The single best way of connecting them is each pair in series and then the 3 pairs feeding a combiner box where they each have a Schottky blocking diode feeding the cable to the MPPT charge controller. In this way, any pair of panels that is shaded is simply isolated until such time as it becomes illuminated. I have some more industrial Schottky diodes picked up at some flea market that work quite well for this purpose. I tolerate the minimal series voltage drop going through the Schottky diode as simply being the price I pay for convenience.
The MPPT controllers that I've tested each have quirks about when they recompute and reset themselves to new input voltage and current conditions. One hopes that the controller will discover new operating points within a few minutes of things changing.
The horizontal antenna shadow is wide and solid in the video and spans an entire panel, 20%. The pole may also be a secondary cut-out source. The coax may be part of the wiggle. Have you tried masking with dowels of various width to see when cut-out occurs? How about testing various number of plastic layers to get a signal reduction for an entire panel of the minimum width to cause a drop out.
I like the idea and simplicity of microinverter designs. But being required to keep an internet (or any other type of) data connection from the microinverters to Enphase or other company's servers is non-negotiable deal breaker for me.
You don't need to have a constant connection. After installation you can cut it from the i-net. But your warranty will drop from 25y to 2y and its also not possible to update your system or troubleshoot. There are plenty systems out there without a constant connection. But it will improve your system a lot.
Good breakdown and interesting to see in real life how a small shadow is affecting the setup.
For the breakdown of the panel, (from 18:30), there is also a "half-half" in that the diodes are in he middle and there are 6 strings (3 on top and 3 bottom) allowing it to produce at lest 1/2 power when top or bottom is obstructed.
OMG I'm so happy you mentioned why the diodes were in reverse!! It was driving me crazy. I love this man.
I think it is more likely that the partial shading is not enough drop to trigger the bypass diodes. However the partially shaded cells can generate less current. Since your cells are in series, ALL of the cells are now limited to the current in the most shaded one. This is the major downside to series-connected panels. An interesting experiment would be to completely shade one or more cells, and see if the blocking diodes trigger and cause a lesser power loss.
At work we have seen the bypass diodes get overheated and fail also. With solid shadows on boats.
I was talking about almost exactly this with my boss who worked both as a solar install contractor and as a grid engineer. The voltage problem is a really common issue actually. They have to oversize new transformers because of solar output at this point because some houses will push out 250-ish where the inverters cut off, that's 230 and 10% error, 253, which your inverter exactly hovered over. So that could still be a problem even if it wasn't the root cause.
Thanks for explaining the (seemingly) reverse-biased diodes in the panel diagram. Definitely not used to thinking in terms of current sources. 👍
I know analogies aren't perfect but I was thinking about the bypass diodes like the spillway of a dam. It provides a safe channel for waterflow should the water level rise above some threshold which would be unsafe for the structure, for example if there was a unseasonable amount of rainfall upstream or if there was a mechanical problem with one or more sluice gates which prevents the dam from releasing water at the desired rate.
there is actually one brand that do put bypass diodes on each cell : sunpower
th-cam.com/video/sznZHSuZXrc/w-d-xo.html
Modern string inverters with shadow management take advantage of the bypass diodes, which allows them to short out different panels. So one shaded panel will not reduce the total production by more than its part of the production