EEVblog 1386 - 295W Inverter vs 370W Solar Panel - WTF?
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- Опубликовано: 11 апр 2021
- Why do Dave's new 370W LG solar panels use lower rated 295W Enphase microinverters?
What gives?
Inverter clipping, solar panel overrating, DC/AC ratio, solar irradiance, and microinverter underrating explained.
And a look at data from Dave's old 3kW system to predict how many days a year the new 5kW system will clip.
Solar irradiance map: solcast.com/solar-radiation-m...
LG 370W NEON2 panel: www.lgenergy.com.au/uploads/d...
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#Solar #MicroInverter #Rating 
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Follow up video on temperature effects: ruclips.net/video/BtQUuD6QRMw/видео.html
Still amazing how Solar isnt on every roof in Aus, not even talking about the paying back into the grid costs.
Another thing that is not considered is the actual energy received by the panels: because they are not tracking the sun, even is you reach 1000W/m2 the panel receives less because of the cos(angle) losses. Even in ideal conditions, a panel oriented at 90° just received the scattered light instead of direct illumination and produces almost nothing.
The dummies guide 1a. Ignore temperature as you have no control of the weather, do something useful and get on with your lives....sure analyse it to the end of time and then realise anyway you have no ability to influence temp, if it’s a hot day then it’s hot and your Arduino will tell you...run a sprinkler, that will help or put the panels in shade... now seriously 1. Get three phase. 2. If you don't have shading get two three phase inverters with 2 strings per inverter 3. Get inverters that automatically share or spread maximum export to the phase with lowest voltages as this makes you the most money. 4. Oversize the panel array to max specs of inverters.....see point 3 as this is way more important than anything else as being on a single phase with a high penetration of solar will result in high voltage on that phase and limit your ability to export. 5. Only get enphases if you have serious shading and even then 4 strings across two three phase inverters which maximise export through lower voltage phases will easily create more benefit.
Magic numbers are 12.6kW's of DC on Roof, 10kW's to mains across two three phase inverters, with a total of 4 Strings. Ohhh yeah and face two strings east or west and two north. The east will give you early morning charge and the west will give you late day energy offset and pre-peak charge. North is just a no brainer for at least half of your solar, assuming 3 phase and 10kW's to grid.
As for analysis.....haven't paid a power bill in 5 years, do no analysis as I can't be bothered as this stuff is high school maths and just choose the retailer with the highest Feed in Tariff (FiT). Am on no special Govt FiT....this ain't rocket science so maybe just go with what 40% of Queenslanders have already figured out.
See above...
ruclips.net/video/3Dc_cnj1PEc/видео.html
@@AndrewDeme yet we have to plan for it in our canadian winter as deep cold can cause overvolting of the charge controller, so we need to buy higher voltage rated ones ;)
Notice how your 3kW system only peaks on cloudy days right after cloud passed by. I believe it's due to overall cell temperature being lower. Clouds help to cool it down.
Currently we do extremely little with the waste heat from panels, they could easily heat a pool.
Yes they do, but I have seen perfect days close to 3kW, it's just a lot of data to sift through.
@@spikester or perhaps cover the belly side of the panel with heatsinks
@@EEVblog just checked Sydney summer temperatures 18.6 - 25.8°C. I did not realize you got such cold summer. I thought it's similar to what we got here in Phoenix 40C-50C.
There is also a cloud edge effect with scattered clouds which produces somewhat of a lens that concentrates more than 1000w/m2.
it would not keep me awake at night, there is no sun at night to loose ... but it would keep me awake during the day ... so I guess I could also save on coffee
I live in Europe, so it will apply for me: the sun shines while you are asleep!
😃
Belgian solar installer here, partial shading on an array of solar panels in a string should not drag down the complete output. There are 3 zones in every panel that get bridged by the built in diodes in case of partial shade on a panel.
For a string inverter, yes partial shade on any panel in a string will bring down the output of the entire string.
@@neomage2021 A microinverter can do nothing about this, either. So, there is no advantage to using them, at least from this point of view. All solar panels have bypass diodes so the entire argument for microinverters is a fail. There can be other reasons to use them, such as avoiding dangerous DC voltages, which is why I am using custom-made MPPT microinverters on automated articulated lower-efficiency and much much cheaper panels.
@@neomage2021 only if it cannot do full voltage sweep or when solar panels dont have bypass diodes. When inverter can do full voltage sweep and panels do have bypass diodes, then partial shading WILL NOT bring output of entire string.
19:50 If you want to get an accurate idea of the ratio of the areas under the curve, cut out the entire peak with scissors, weigh it, then cut off the tippy top and weigh it separately. The ratio of weights will give you the ratio of the areas under the curves.
Back in the day when integrators were not available in this part of the world, we would analyze our chromatograms like this to determine the content of chemical compounds in samples. It does require a sensitive balance though.
That's amazing!
“As an engineer I find that a bit offensive.” How many times have I said exactly that!
Yup. I just spent twice more on a UPS than I really needed because I couldn't stomach it having a lower rated output than the theoretical maximum power consumption of my PC (which I fully well know it will never hit).
In Europe there is less sun sure but it's also not as hot as in Australia. The hotter the panels get the fewer power they output. So I wonder how that all would count up in the end.
Just shot a video on my 2nd channel about this, uploading now.
many hot days are absolutely better than many overcast cold days. no two ways about that
I can get full power on sunny day, I'm in france.
@@ursodermatt8809 Except you're more likely to run A/C. Unless you have an extremely well insulated house.
@@chaos.corner
you are more likely to run A/C when it is cold too.
i repeat for you again. solar generation depends on solar insolation. no sun no generation. no matter what the temperature is. no matter what you use the solar generated electricity for.
Very interesting. Slap a IQ7a or two up there and measure it over time, for science!
Thought same. However, this is great work by Dave, since I never realized the details, along with that solar panels use "marketing speak" to sell (imagine buyin 20 of the 370W panels and never getting that "advertised" wattage because of the inverter clipping.
@@xoxo2008oxox q
@@xoxo2008oxox ]10¹11
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Solar designerer here. I did that experiment over a 3 year period with their older 215W and 250W emphases inverters. Over 3 years there was a 2kWh difference between the different modules. That's about 60c of savings per panel for a $10+ cost per inverter upgrade.
As an engineer myself, I really enjoyed your data-rich and technical video. Installers in the UK told me in string installations, they de-rate the inverter by 50% - 10kwh panels get a 5kwh inverter. Then if you have batteries, the charger has losses, batteries have 80% depth of discharge on top. Bearing in mind everything ages and degrades with time, so it seems actual usable energy is a lot less than 40% of panel rating and decreasing each passing year!
Here in the UK, inverter undersizing of 20-30% is the standard. Some string inverter manufacturers actually allow 50% undersizing. By undersizing, I mean the DC/AC power ratio is 130% or 150%. The reasoning behind this is that you want to keep the inverter operating as close as possible to the maximum of its efficiency curve. As Dave mentions, NOCT is different than STC so you can install more rated DC power to achieve "actual" power closer to that efficency curve point.
Great update video 👍
Thanks for sharing your experience with all of us 👍😀
Wow, your explanation is spot on for my system. It was just fully commissioned today. It has the same panels and inverters as your system and my system consists of 29 panels, which means the system size is 10.73 kW. The Enlighten software showed that I was producing 8.6 kW during the peak time of day, which is 295 watts times the 29 panels. Your explanation is much more useful and makes more sense than the one provided by the installer. Thank you from Plainfield, Indiana.
I think you might be missing out on generation capacity at the start and end of the day as well. The specs say it has a minimum start voltage of 33VDC. I presume this means you get zero output before this. If you had 14 panels in a string generating 33VDC each you would have 462VDC. A common string inverter would be generating a respectable output at 462VDC compared to the microinverters generating 0VDC. I imagine this effect would be greatest over the winter months.
Finished the rest of this video today and your organization and analysis makes me happy. I'm going to have to go through your channel and look at all your methods and tools. So far I have a turbine for which I need a new inverter and 3 280W panels on an off grid set up. 2 on my shed charging my lawn care and one is the roof on my golf cart keeping it charged.
I rent so I currently have no stake in solar, but learning all those little nuances was really interesting. So yes it'll clip, but it's not clipping every day, and the days it does clip it won't be clipping the whole day, and then the other microinverter benefits that may offset small losses anyway.... today on the internet people seem to join one camp or another so very easily and forget about all the small details. And these details can tip the scales in ways they haven't thought about. And from the comments already I see there are even more factors warranting consideration. Always refreshing to get this sort of overview on a topic, thanks.
With the solar system that I installed, we typically got 115-120% of the nominal rating during most of the day. Even after 15 years it's giving about 95% of nominal. So in my case if the inverter were only rated for 80% of the maximum, I'd estimate we would be missing 20% of the available energy over a given day on average. So depending on the cost per kilowatt it may be worth it.
I think the biggest thing is space limitations. If you are trying to extract the maximum available energy from limited space, then that's a different question if you can just throw up another panel.
I've been playing about with 4x340w panels, I only have room for 8 in total. Originally I had IQ7 inverters which clipped them to 250w.
Following convos in Dave's original video I swapped out one of the microinverters for an IQ7A, and have seen over 340w out of that panel here in the UK already, so when the last 4 panels go up I think I'll be using bigger microinverters for exactly the reasons you noted, very limited space!
@@juststeve5542 Yeah, regardless of what Enphase (and LG too, as they do a ton of LG/Enphase installs) claim, The IQ7A would be a better match (but still nto ideal of course). Although you'd have to do the amortisation costing over time.
I wonder if their Enphase IQ8 would have a higher output
@@PHamster at this point I'm starting to believe in fairies more than the IQ8!
When/if it finally appears it will probably come in a range of flavours like the IQ7,7+,7X,7A
IIRC, the higher capacity 7A is a later addition to the IQ7 range.
@@juststeve5542 have 20-300watt panels with IQ7 mico inverters should i Use the iQ7A. i need to get it up to a 9k system
When you said, “if you’re going to clip, it’s only going to be the tip,” I was reminded of that bit in a movie with Mel Brooks playing a mohel describing circumcisions saying, “just nip the tip!”
Once again, me too. I’ve encountered the same question with my 370 watt panels and my Enphase IQ7s. Appreciate the clarification.
Glad to see the follow up video on temperature effects as that is my first thought. Days with lots of cloud but sudden bursts of sun will get much higher efficiency of panels and thus higher peaks than full sun days. This is also why all my diy panels have white backing, not black.
Just installed a 6.6kw system with a 5kw inverter. Thanks for the cool info
TLDW: Loosing 10% per day on 38% days equals 3.8% total loss(on ideal days). Realistically probably less than half of that, say 1-2% total loss.
But you get same 1-2% back in improved inverted efficiency.
Dave, please note that the global solar irradiance which met stations measure is NOT the solar irradiance that your panels get, because the global solar irradiation is measured with a sensor (pyranometer) perfectly leveled horizontally. To get the exact irradiance value of your panels, you should get data from a pyranometer which is at the same azimuth and elevation angles as your panels! (This post somehow disappeared previously, so I posted it again without the link, maybe someone thought it was advertising, but it's not, I'm just happen to measure solar irradiation at work).
I assume that you'll get a performance boost from well tuned elevation angles?
@@CED99 Of course, but that's a given factor by the orientation and angle of the roof. Modern houses should be built with this in mind (the usually are). You can mount the panels at a different angle on taller framework, but that would look horrible, and it can be dangerous as well, because it would put higher wind load on the panels.
I dunno... What you're saying makes total sense. But, as a sound engineer, I have trouble with the idea of deliberately clipping an installed system. I guess I'm just the guy kept up at night on the thought of lost power. Someone will make a mint off of me when I go solar. 🤣👍
The thought of it is rather offensive!
Glad I wasn't the only one. In the audio world clipping = bad news.
Sounds like a intentionally ripping off customers to be honest.
@@HiragamaIkunai Not necessarily. Everything's a compromise. People who live in areas that don't see much strong sunlight might benefit from this configuration, for instance, because they can generate power at lower light levels.
Thanks for this, just looked at my Enphase system and sure enough it is clipping in San Diego on some days. I had seen this before but frankly hadn't looked close enough at it to notice. Like you, I have an older system I moved from a previous house that is a 4.5 kW Sunny Boy and then added new Enphase system with micro inverters. Now I've got to go make this a science project to see if it is worth upgrading my micro inverters. I was looking to add a few more panels so would have the inverters upgraded at the same time.
I had the same question when I received my panels (in the Netherlands) The explanation I got was that the high power inverters also have a higher loss (at 100% of the days) I checked and indeed the higher rated SMA inverter had a higher loss
I live in Switzerland; 18 Panels each with 330Wp with 18 Enphase IQ7+ Inverters (290/295 Wp). I had a clipping maybe 3 or 4 times in 2020(!) It makes really sense to slightly oversize your panels - compared to the cost of more expensive inverters.
Good advise. Thank you!
You have to also account for the lower efficency in non-shadowed state. Microinverters are overall less efficient in vastly most cases. String inverters are easyly 2% more efficient.
@@flipschwipp6572 Claims and stories from old times. Completely irrelevant. Every manufacturer and every study tells something different - and all like to embellish their own efficiency values. Just like with the consumption values of cars, I wouldn't put a damn on it. I would *_never_* buy a string inverter again, even if it were 5% more efficient - and that of course only on paper. And which PV system has a "non-shadowed" state over the whole year? Even then, there may always be times with snow, ice, frost, leaves, dust, dirt, sand, bird poop, a weakaning or faulty panel and much more. And even brandnew panels themselves always vary in efficiency within a few percent(!) - and _no_ string inverter can handle that, but the weakest panel determines the performance! (Except for such with SolarEdge DC optimizers.) Micro-Inverters always produce electricity immediately, even with the smallest amount of light in the twilight, while string inverters just kick in at a neccessary minimum input power (e.g. greater than 10, 20 or even more watts).
*Summary: your apparent "2% more efficiency" literally melts away like butter in the sun.*
And last but not least; the most efficient system is *_never_* that which simply has the most efficient inverter(s), but rather the system *_overall_* that is *the fastest to write a black zero (= reaching the profit zone).* This can only be determined after years or decades, after including all income and expenses - and here, too, Enphase Micro-Inverters are ahead with their 25-year guarantee. It is not unlikely that *_you_* will have to buy a new, second string inverter in the meantime ...
@@RomanKuechler What is the relevance of Guarantees in respect to energy efficiency? String inverters cant also have Guarantee? Marketing BS! Upfront cost of optimizers overwhelm any benefits. Once The Manufacturer goes down, like it was often happening in the PV market, you can wipe your ass with your warranty card and pay someone to rip the whole pv array apart, remove the inverters and re-wire everything. With a normal inverter, it is just replacing the Inverter, which ther will be 1:1 replacements in 25 Years, for Microinverters I highly doubt that.
@@flipschwipp6572 You have not read or understood any of my arguments. This makes the discussion pointless. And your answer lacks logic. Your 2% will be nullified by the tolerances of the panels alone, it's not that hard to understand right now, is it? If someone buys a string inverter because of 2% more efficiency - but not taking everything around it into account, what should I say? If someone really wants a string inverter then they should buy a string inverter. It's not my problem. I have nothing more to say about it, thank you.
The most common string system in Australia is actually 6.6 kWp on 5 kVA inverter.
Enphase micros have a longer warranty and life than most string inverters on the market, they don’t run hot internal temperatures as they run as extra low voltage (40 Voc generally).
cost difference is almost double now. Also if any of those inverters fail the warranty is there for them but not the labor to go up and pull solar panels off the roof to get to the inverter underneath and hope nothing else gets broken like tiles etc for those with tiles. Its not all green grass on that side. Also being up on the roof in summer, can't imagine even being under a panel they wouldnt be smoking hot.
I installed a similar system in 2015 with 32xLG 310 watt panels for a 9.9kw nominal system, using enphase M250 micro inverters, and so the system peaks at about 8kw. Up here in Canada I believe this is a fairly common type of system to install. And so yes, it does clip on a perfect full on sunny day, but overall it's a very small percentage of "lost" power as you outline. Eyeball estimation would be loosing about 2 or 3kWh generation on a perfect zero cloud full summer day where it currently generates 70kWh. Perfect days are pretty rare, and I'd guess I'm only loosing 50kWh or so generation due to clipping on a given year out of a total of ~12000kWh. So although the clipping "feels" wrong, it does have very little effect, and obviously doesn't make any financial sense to pay for larger micro inverters just to capture that little bit extra power.
This popped up in my feed again.
One thing I've noticed with my system is that total illuminance often goes up to 125% on partly cloudy days compared to direct sunlight.
This is backed up by a paper written decades ago by a research group in USA.
Amazing info Dave I'm an Enphase fan and have never heard anyone chat about this.
Some of the times where it has clipped the 3kw system may have just been momentarily due to the cloud edge effect. My system generally maxes out at 2,700w but the inverter will see 3,300w when clouds pass by.
My system is oversized for the inverter (5kW). When I got the system installed (and then later ugpraded -- panel wise) it was the most common thing that people here in Western Australia were doing.
The system clips a few times during the summer time, but then the Fronius Primo 5kW inverter is locked to 5kW, in other countries the inverter can go up to I believe 5.5kW.
For most of the year (except for winter), my inverter tends to sit around 4.5-5kW for most of the day.
I have limited knowledge on PV systems, but looks like de-rating is quite common here in Brazil. Since the string inverters are so expensive, adding more panels is cheaper. As a result, the inverter starts clipping earlier in the morning and stops later in the afternoon, so as to use the inverter for a higher % of the time. It's not only about the energy, but the system cost.
Boa! já ia pesquisar sobre e tu me respondeu!
Best video on the internet, I am looking at building a new system with 30 Solaria Power XT400 system and wasn't sure about going with SMA Sunnyboy or Enphase
Thanks so much for sharing. 😎👌🏼
Couple of things, the power over 5 minutes is average not peak.
Cooler solar panels = more energy.
Perfect days do not produce perfect solar power output. Reason is quite simple, the datasheet says: 1000W/m2 @25C this 25C does not happen. Even in the winter the modules will get hotter than that. However it can definitely peak if a cloud covers them and a cold wind blows over then the clouds go away. I have seen 3660W output from my 12x215W system.
If you don't use power from a solar panel the energy that is not used is lost as heat (or potentially emitted again as UV light). Worst case the clipping causes the panels to heat up causing efficiency losses later that day.
I would assume it’s taking a reading every 5 minutes, not calculating the average for the 5 minute period.
If it's clipping, upgrade the opamps to something which has better dynamic range!!! That'll fix it 😜
😁
@@ts757arse My nearly 20 year old "pure sine" Trace/Xantrex inverter causes audible buzzing and harmonics in audio circuits and some power supplies. If they had made one with "audiophile-grade" sine output, I would have been interested.
This could be a huge untapped pool of suckers, er, market of enthusiasts!
Another reason to underrate - because they use more and larger switching devices, a higher rated inverter is always going to be less efficient when running at a lower power. So there will be a point, even with the same panels, where you will get more overall energy from a smaller inverter that occasionally clips, because it is slightly more efficient at other times.
@OohBuntu That's kind of the point - that 0.5% efficiency gain at the common low load times can easily mean more than losing ~10% from clipping during the rare peak generation times.
My family has multiple PV arrays in south Germany. The older ones (about 19 years now) have undersized inverters, the newer one (about 10 years old) has oversized inverters.
As far as I know, currently the inverters are usually oversized on new systems. I don’t know the exact reason why it went from undersized to oversized inverters, but probably the efficiency got a lot better with all load-scenarios and the price difference isn’t much.
All our installations are still fully operational and there are no signs of significant degradation. Only the Inverters seem to reach the end of their lifespan after almost 20 years. On the old arrays, we swapped them for new ones, since they stated failing, and the new ones are more efficient anyway. I expect the oldest system to last at least 10 more years, probably even a lot more.
I’m not sold at all with the microinverters. They are under the solar panels, where it gets already pretty hot in the summer, obstructing airflow and adding even more heat, which decreases the effectiveness of the panels further. Also, they are fully potted, which makes them completely unrepairable. I guess they run bloody hot a lot of the time and I wouldn’t expect them to last nearly as long as normal inverters. Swapping them is also a bigger issue, because you need someone qualified to go onto the roof to do it and the faulty one is of course always the one in the middle of the array…
Partial shading isn’t as much of an issue as some people make you believe since even our oldest panels have bridging diodes in them to avoid limiting the current.
I always thought my system had been bodged. I’m in the uk, just north of london. I have a 3kw system and a 2.5 kw solis inverter, my peak is 2.7kw. Good to know its actually working as intended.
Hi Dave, great to see you come back to this.
My experiments with my 4 QCell Q8 340watt panels have been going well. Even here in the UK in April I've seen over 340watts out of the panel I installed the IQ7A microinverter on last week. Yes, exceeded rated panel output in the UK in April! WTF right?! The NMOT says 254watts for them, so I think I'd better start slip, slap, slopping over here too!
The other panels are limited to 250watts by the IQ7 microinverters.
In my case I am very restricted on space, and I'm clipping a larger chunk of the hump (250w from a 340w capable panel). So I think the next/last 4 panels that are due to go up are going to get 7A (or at least the 7+) microinverters. Not sure if I will upgrade the 3 remaining original IQ7 ones though, they're higher up and an a pain to get to!
April is time of the year you get peak instant power from PV in the UK -- clear skies and cool panels
In ireland, I've oversized my array I have 8.64kwp on a 6kw inverter.
I haven't had a perfect day yet. But on days with scattered cloud, it can peak at 6kw when the sun comes out and the panels are cold.
2 string NE/SW (low angle, agri shed) array 12 panels on each.
I have jinko 405 panels paired to iq7+ and iq7A inverters. It's a string of 12 panels. 3 panels in the middle are the A inverters. Here's the data from last week as an average per day
The value is in kwh.
2.62 +
2.65 +
2.58 +
2.62 +
2.59 +
2.55 +
2.68 A
2.67 A
2.63 A
2.50 +
2.51 +
2.53 +
Remember this is an average per day over a week the iq7a's do not significantly increase production.
The reason I went with the mix, was because my roof fit 12 panels perfectly. I could not run a string of 12 iq7A as the amps would be to high. So I ran as many A's as I could. Anyway hope this is valuable to someone.
If anyone has a question, I will answer.
@@deelarry2137 What area is this in and what time of year? I have a 30 panel Panasonic EverVolt 370W system with the IQ7+ inverters. This is an 11.1kW system and I max out at 8.8kW around 1pm. Each panel comes in at around 2.35kW each day and I produce about 70kW total each day. Based on your data and everything else I have read, the IQ7A would theoretically reach 11kW during the peak power time, but it seems like it will still produce the same overall amount of energy each day as compared to the IQ7+. I keep thinking I should have just purchased the IQ7A's but it probably would have been a waste of money.
@@alanhoman1810 west Texas in summer. The A's are a waste of money. Over a couple months(summer) the A's have produced about a kwh each extra.
@@alanhoman1810 but we are very hot. Maybe in cooler climates like Australia it might make sense to use the A's
For me it's simple...if you need power in winter, go for oversizing panes vs inverter (my case, I'm totally off-grid with 8kw). If you want to maximise power on the whole year cause you can sell power...or use it completely...do not oversize.
There are many low cost inverters, growatt is one of them.
A 5kw inverter with a 6kw mppt, including battery charger can cost 500$ us.
A 370w pc cost 130€ in my country.
Solar panels, Electric Cars, Office lighting, Cameras? Isn't this what happened to great, hardcore electronic magazines? Just saying.. (yes, still "gave a Dave" a thumbs up ;)
I've been doing solar related videos for over 7 years.
Good info. Oddly enough I believe the Neon2's are made about 20 minutes from my house. I haven't found a way to get them cheaper straight from the factory yet. :-/
Hi Dave, actually even regular inverters are downrated in Australia as well on most current installations. All the quotes I have been provided install 30% more panel capacity than the inverter nominal power. For example a 6.6kw system is fitted with a 5kw inverter.
That was probably not the case when you installed your original string system.
Yeah, that was never the case when I was looking.
I decided on 7.7kw of lg neon 2 panels with a 6kw sma sunnyboy based on your previous videos and my own thorough research. However I also added OPTOMISERS to each panel.
Optomisers are added to each panel same as micro inverters, but use a string inverter as normal. The optimiser allows individual panel monitoring and isolation. The benefits of micro inverters at a lower cost. Only exception is dc cables on your roof instead of ac.
Hi Dave, I'm from the Netherlands and for me it went the other way round with that Wp value. I didn't trusted it because I assumed the "low light condition performance" from different brands of solar panels would differ significantly, therefore I assumed the Wp value would be a useless number. But as it turned out it is quite closely related to total yearly production!
I live in Florida and i definitely get my full output also i have mono panels rated at 100w each they do 120w so yeah i don't go under
Florida Man builds his own solar roof
Hi Dave - I have a 4 KW system 16 x 250w panels and here in England I have never seen a higher reading then 3 KW since it was installed. most of the time its around 2 to 2.5 KW on good days. LOL.But it has paid for it's self 2 or 3 time over via the grid feed in tariff payments received. And I have to go clean the bird poo now. All the panels are on my shed flat roof, none on the house roof.
I have a 6.6kw peak system installed with a 7.6kw solaredge inverter. So I have 1kw more inverter capacity then peak panel output. I really like the way the solaredge system works, by boosting your string voltage up to 380 to 440 V dc your inverter can be built way more efficiently.
I originally had a 6kw inverter installed and would constantly clip in the the spring. I couldn't sleep on that! So I was able to get my installer to swap the out for the bigger inverter at cost ( about 300$? ) and just be done with it.
In the spring and fall when the temps are cool but the sun output is good I can CLIP! I push for about an hour on only a handful of days 7.6kw out of my 6.6kw panels.
Oversizing the solar panels is common in the US too. Im in Utah.
Everything with a switch mode power supply (which is most things these days) can work directly on DC ( a lot of led lighting included). So on a small rural of grid system, you can power most things straight from the series battery string. Have a small inverter for the AC only appliances. Your battery string can be between 170 to 325 volt DC (120 to 230 volt AC equivalent) and most appliances with switch mode power supplies will work across this voltage range. So the voltage won't have to be regulated.
Thank you!
Well explained Dave
Not sure I trust the logic that clipping prolongs their life. Just means they get hotter. And then hotter.
Where is that claim? I didn't say it did I?
@Sage What am I'm missing here, given the same inverter running at 300W or 400W output, the one running at 400W would be hotter. The panel would get hotter sure, but hopefully that is decoupled well enough from the inverter that it would have no significant impact on it.
@@jaro6985 you cannot compare inverters like that. 300W inverter @ 300W output + solar panel will produce more heat than 400W inverter @400W + solar panel (100W less heat to be exact, assuming the same solar panel under the same outside conditions). 300W inverter may waste less at full power (compared to 400W one), but you have around 100W more turning into heat within solar panel
@@EEVblog maybe you didn't commit to it but you did relay the notion of derating for longevity, did you not?
@@jaro6985 well you did edit your reply so maybe you caught what you were missing :) I assume it's panel longevity that's in question, not inverter. Panels are typically the cost intensive parts. Even though inverters are quite overpriced.
Great video. Can you please provide links to the Enphase Australia document you highlighted in the video? I couldn't find it online. Thanks.
NICE system!
For cold seasons what about heating an insulated tank of oil during the day with unused power, and then circulating that in the house through some form of heat exchanger or radiator when it cools off?
I love a good mystery teardown and a mailbag "Monday" ;) but this is video is the real stuff. Thanks a lot for doing this in depth analysis I didn't ask for...
I didn't read the comments to the undersized inverters, but I know it would have driven me crazy if I read it, or even came across this overrating of solar panels in person. So thanks again for explaining :)
Btw could we agree on either the term of "overrating (panels)" or "under-sizing (inverters)" so the average person doesn't get confused completely :D
You should be able to easily calculate % power clipped for each interval, then extrapolate that to your 5kw system, to determine energy lost per interval / day
In the cold north america we get our highest output solar days in the winter - on very cold clear days the PV will put out over their rating . What also helps is the cold sunny days there is not a lot of humidity in the air and if there is snow on the ground the reflection off that may help the output too. I am not grid tied - I put the power in batteries so no clipping from inverters - but you sort of get clipping from your controller since it throttles back the power as the batteries charge toward 100% full. But if you have something like Midnite Solar controller there is a Waste Not option on AUX contacts that will PWM the exact extra power not needed to keep batteries full - into a resistance load like hot water or space heater. Of course in the winter out days are short !
well i get the best results in spring here in NSW australia in the spring. weather still cold sun high up
Thanks mate...
It is't that difficult a calculation, Dave!
Just upload the minute-by-minute data from the 1980 days to a shared cloud, and let your YT-followers do the grunt-work ;)
Its actually really easy. The area under/over the line? Just cut it out and weigh the mass. Thats how they did it back in the day. Not to mention all the other (digital) options.
My system is 1:1 (10kW panels to a 10kW inverter). I can't stand the thought of clipping.
It's kinda offensive.
@@EEVblog I have a 10kW SolarEdge inverter with their per-panel optimizers. It's nice because if you have multiple roof faces the individual panels can output the full 370W (which would clip an Enphase inverter), but not clip the 10kW inverter since other roof faces might only be putting out 250W at that moment.
also better on the inverter it will not run so hot than when it is maxed out all the time
Calling this "de-rating" of the inverter system is backwards to my ears. "De-rating" is when we purposely use components with higher capability and purposely design to not use all of it. Is this not actually over-rating of the interter system? Or de-rating of the solar panel system?
Me too. Completely misusing the word to justify what is IMO just another scam.
I've come to expect that from the solar industry though.
I have IQ6 microinverters that took a grid hit and took out 16 units. I shaved off the top off of the area (with my table saw, ruined my shirt) just around where you lost small cube part that came off of the board.
I was able to solder in a 3.15A 300V fuse mouser part 504-SS-5H-3.15A-APH ($0.57) and a similarly located MOV mouser part number 871-B72214P2171K102 ($0.38) Soldered the leads onto the leads on the board (I carefully trimmed them). Hooked it up and it started working normally.
***I will be installing a MidNite Solar Surge Protection Device (MNSPD-300-AC Amazon $111) Close to the incoming AC power feed at the main breaker panel that should prevent this from happening again and as a bonus protect my home electronics.
On a side note the MOVs used are designed to take anywhere from 1 to 15 grid events depending on the severity. This means if you lost 1 to a grid event then the other ones have used up one of their "9 Lives" it would be a great idea to try and protect the ones that are still working.
Also have to take into consideration panel degradation over time. In 15-20 years you might have little to no clipping
I think I've only seen full out put from my solar system twice in the 3 years it's been up. But being in Eastern Washington at 47 deg north we don't get a very high solar angle. My system is over rated right now, but I plan to add more panels to so I can get a little bit more power over the winter months. I don't think I'll have to worry about clipping but for a month or two a year with the extra panels added.
data from your solar array will absolutely keep you up at night, especially when the system is new there’s so much to take in. generally the folk who install these systems are the type who really like sifting through the data on how each day went... it’s fun ;¬)
Thank you! I think you've just convinced me to buy IQ7+ inverters for my new 370W panels instead of the more expensive IQ7A!
Interesting. My panels are ground mounted and interestingly they are bifacial i.e. there are panels on the front and backside of the panels. The front side is rated at 375W but with the bifacial gain which is dependent on the albedo of the the ground under the panels (snow, grass, etc) I believe the claim is -425W- correction 488W per panel. I have 16 of them in one array. If you're interested they are Canadian Solar CS3U-375MB-AG.
Are they made in Canada?
Ah, no, made in China it seems.
@@EEVblog Yeah, I think they're manufactured in China. You can't tell these days. Thankfully it's not all bad. Went thru several crappy all in one inverters but settled on one of the more expensive UL listed units. It is also made in China (overseen by a US company) but it works flawlessly.
that is absolutely bananas.
They rely on the reflection from the ground underneath? Wouldn't it make more sense to have an internal reflector behind the panel, this way you could get much higher reflection.
Look at all those 'mostly cloudy' or worse days. Having lived in a n area all my life where we have more than 300 sunny days every year, it's amazing.
What you don’t know about the UK over the last few days is that one minute it was bright sunshine, the time it was a snowstorm several times 😂🙈 this is why we don’t rely too much on solar!
You're not wrong! I saw snow this morning, and then by lunch time I had over 330watts coming out of a 340watt panel which I'd upgraded to an IQ7A as a test last week!
There is a reason why people in the British Isles are notorious for talking about the weather - and in April doubly so.
I am from Mauritius in the Indian Ocean, the local power company does not allow us to over dimensioned the solar panels installed, if your inverter is 3.5KW you should not be having more than 3.5KW of panels installed. For 3.5KW of solar panels, I only got 22.5KWh on a few days since mid 2016. You are right 2017 was a good year for solar PV production.
There are a few other factors that make undersizing your inverter a more economical long term option.
Panel effeciency degrades over time. LG says their panels degrade 2% to 3% in the first year, and eventually stabilise around 0.7% to 0.5% loss per year. We can probably assume a 10% loss of effeciency over 10 years for an average solar panel, so you're 350 watt panel for example, will end up becoming a 315 watt panel.
Another factor is panel orientation. A good strategy for maximising the amount of solar electricity you actual use (rather than feed-in) is to face a portion of your panels east, and another portion of your panels west, say at a 15 to 22 degree angle (common roof pitch). In that situation, your panels are less likely to hit their maximum power output, and your system as a whole (for a non-microinverter system) would peak much less. In my system, I have 8 panels shooting directly up, and another 12 facing west at about a 30 degree angle. In far north queensland, I only get moderate clipping in the summer months, and due to most of my panels facing west, that clipping happens a little later in the day. I would never consume this extra power directly, so I'd only be getting 10 cents per kw/h for the extra power I may be generating without the clipping, which would probably equate to less than $10 a year at the most. Hardly worth paying the extra $500 for the next size up inverter as I'd never see a return on that investment.
The econmics of undersizing the inverter hold true in at least 90% of circumstances.
Today I'm getting my system upgraded, from a 10 panel 1.9Kw system to a 34 panel, 13.2Kw system / 10 Kw inverter, battery and optimisers on 18 of the 34 panels.
On a related note, do you have any issues with your micro inverters communicating with the Enphase Envoy module that connects to the web? Mine is connected to an outlet right off the distribution panel but still has trouble occasionally talking with some of the inverters.
In Poland you roughly get about 1MWh per year or slightly more per 1kW of installed PV power. Of course I'm talking about a static non tracking system facing close to south and with correct inclination (the all-year optimum is around 39-40 degrees but anything above 15 is close enough). Currently I'm running a 5.55kW system but with panels lying nearly flat (actually half of them are even having a "negative" inclination by few degrees) and I get about 4.6MWh per year so I loose around 18% or so.
Nice
The solar systems available in my country are way too expensive to make sense, since we got very cheap electricity from hydroelectric power plants it would take 10 to 15 years to pay back the cost in energy and most systems sold here have only 10 years of warranty.
Fair enough.
63% of our electricity comes from Hydro and it makes the overall production at 83% renewable energy. Only 1% is from solar.
@@thomasesr All the better hydro is probably better for the environment sine hydro plants last a long time and are mosly recyclable unlike solar panels.
@@adamdnewman yes indeed, too bad for the huge areas needed for the reservoir which displaces a lot of Fauna.
@@thomasesr Isn't that replacing one environment for fauna with another?
"inverter vs Dave sleeping at night." waiting for the update on eevblog2 XD
Great analysis. Your logic, however, may be coming from the wrong direction. Over here in Perth, WA, we are restricted to 5kW of "Production" if we want to connect to the grid and get paid the abysmal (8c) feed-in tariff. The inverter output is "Capped" @ 5kW, and we are allowed up to 4/3 (6.66kW) of panel peak overproduction. My inverter goes into 5kW "limit", 2-4 hours per day during the summer months. Regulations vary for battery storage and electric vehicles.
May I suggest some content for you to create:
~ Battery Storage - Hybrid DC vs AC (Tesla). I like that hybrid inverters use Panel DC upstream of the inverter . There may be some fun looking at the operation and losses of each of the inverters in the different typologies: MPPT, DC Battery (LG Chem), 240VAC Stage, AC Battery (Tesla)
~ How Panel Optimizers work : "Boost" - Distributed MPPT (Solar Edge) vs Buck - Constant Current (Tiago). It is an interesting exercise in cost, efficiency, complexity and reliability. I like that the Buck optimizers operate in bypass most of the time, Switching on during shade or obstruction.
~ Self consumption including Time of production. Like you said, plan when run your washing machine. If you use power in the afternoon, North-West facing panels are Great. This could sprawl into Smart Home network. Energy Production timed operation - Pool Pumps, Hot water, Fridges, HVAC etc.
The SolarEdge system's power optimizers (DC MPPT) can do up to 370 watts on the standard and 800 watts each on the big one, then you just size your main inverter as you wish. I got an inverter that can handle my full 9600 watts at 370 watts per panel (96 cell panel)
Im filing a class action lawsuit against the sun for insolation discrimination... hello from cold-ass sweden.
As legitimate as half the law suits out there.
Clipping makes sense in a place where you want to extend the lifetime of your system and up untill recently this would have made sense here in Belgium as well. About 6 months ago, however, our supreme court ruled that reverse counting in the kWh meter (soon to be a digital meter in every home) is somehow discriminative. It boils down to the fact that people with a digital meter (where what you take from the grid and what you put back are counted seperately) are paying about 25 eurocents per kWh for what they take from the grid (nighttime, cloudy days) and are getting 4 eurocents for every kWh they put back. Hundreds of thousands of people who recently invested in systems are pissed cause their ROI now skyrocketed. Some people (myself included) still have the old analogue meter which spins in reverse when you're producing more than you are consuming and some people are now refusing access by the power company when they want to place a new digital meter (which is somehow illegal). So the power company can take this cheap energy from one house with panels and sell it to the next house a few feet away for 600% more. Charging taxes and the "cost of all the infrastructure needed to transport this power a stonestrow away". In my case, before they come knocking at my door to replace my oldschool meter, I don't benefit from the derating as discussed here and I'm just gonna roll out a cable with a kill-a-watt meter to my neighbours house which they can use when it's sunny. I'll charge them half price of what the energy company charges so we both win and stick it to the electric company, the supreme court and policymakers... Even if it's just a few days a year, i'm pissed and every Wh counts...
Sounds like the easy way to test this with microinverters would be get another one that logs similar data, that does support the max, then track the number of days where that inverter produces more power than the panel that is directly next to it, and compare the total outputs
I oversized my array, but for very different reasons. Here in Victoria I was only allowed to have a 5kw inverter tied to the grid, but was allowed to oversize the array on that inverter by 33%, so I have 6.5kw of solar panels over a 5kw inverter to get as much electricity as possible within the legal limitations. Once I go off grid I will be able to have an inverter as big as want.
Maybe a stupid question.. but where does the power go when the inverter is "clipping" ? Is the solar panel cooking itself with the additional energy? Does it lower the lifespan of the panel if it can't dump its generated electricity ?
Running 14kW per 10kW inverter on my farm arrays. Panels are cheap now.
Pumped out 201kWh today. Cool weather helps with the 20% derating due to heat.
Is it possible to parallel the inverters on the DC side so that they can be switched in or out depending on the current coming from the panels?
I have 6.6kw of lg panels on a 5kw fronius in North Queensland and clip nearly daily I wish I got a bigger inverter seeing as it was only $500 more but the joy is I make more power earlier and later in the day.
thank you
% clipping published.. Is that of daylight/max sun time or per 24hrs?
There is another issue though : burnout.
I dont know the specific overload margin those micro-inverters can handle, but most systems out there are not designed to digest a lot of overload.
They tend to overheat and burn a mosfed or two.
And replacing a fried microinverter is costly. Even more if it's hard to get acces because it's on a roof.
If you clip 8% of the energy 38% of the days of the year then thats 3.04% energy loss over the whole year. I suspect that on those 38% of days the 8% figure is much less than that, so the figures on the data sheet are plausible "worst case" figures.
Hey, I have a question, why can't we use a single 5kw inverter & a single micro inverter and use something like A smart switch connected to each solar panel which switchs the solar panels from the inverter to a micro inverter when it's not giving a similar output compared to other panels??
most if not all panels rarely reach the quoted power simply because they drop output as they heat up (full summer sun ) can reduce o/p significantly , ps most grid panels have bypass diodes built in (not blocking) so if panel a panel is partly shaded it wont drag the hole string down , interesting to see if the inverters still work after several years on the roof.
Top of atmosphere TSI is around 1365W/m2. Attenuation through the sir is highly variable. Under clear skies, without dust, 1200W should reach the surface. Note that the angle of the panel to the sun is significant!
Panel temperature and current density make a substantial difference. They also define the panel life, other thing being equal.
Does running an inverter at peak power handling affect it's reliability and lifetime, and dies that matter compared to the MTBF and usable lifespan of the panels?
@19:30 the curve will be flatter yes because of clipping...but don’t forget wider too thanks to mppt and lower cell temps on the shoulders.
It's kind of funny how we take the DC output from solar panels, invert it to AC, feed it to a generic device with an AC-DC converter where it gets rectified, then inverted again at high frequency, then rectified again to supply the end load. Seems like there ought to be a better way.
then convert it back to DC to charge your cell phone!