EEVblog Electronics Community Forum

EEVblog => EEVblog Specific => Topic started by: EEVblog on April 03, 2021, 12:58:09 pm

Title: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 03, 2021, 12:58:09 pm
Dave explands his 3kW home solar power system to 8kW using new 370W LG NEON 2 panels and Enphase IQ7+ micro inverters!
The complete installation video. Time lapse videos and other analysis videos to come on the EEVblog2 channel.
Thanks to LG Australia, Enphase and Clenergy:
https://www.lg.com/us/business/solar-panels/lg-LG370N2W-G4 (https://www.lg.com/us/business/solar-panels/lg-LG370N2W-G4)
https://enphase.com/en-au/products-and-services/microinverters/family (https://enphase.com/en-au/products-and-services/microinverters/family)
Clenergy racking: https://www.clenergy.com.au/ (https://www.clenergy.com.au/)

https://www.youtube.com/watch?v=VTUZk7vY1ME (https://www.youtube.com/watch?v=VTUZk7vY1ME)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: coppercone2 on April 03, 2021, 03:55:35 pm
Added 1.2 kW recently to a 2.5 kW system. we take it slow

I recommend full machine crimps with the Rennsteig 624 1301 3 RT

I don't like those folded things on the roof.

I also got a type 2 surge protector installed next to the panel

After 1 year our solaredge failed but it got replaced by warranty, probably because the power grid here is on crack

Also, I recommend some high power loads if they start charging you for export, you can have luxuries like hosing your car with the best warm soap and air drying it with a 5kW blower every day
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 03, 2021, 11:59:03 pm
Everyone seems so invested in this microinverters, and I still dont get it. A few years ago we analyzed 7000 installations and the break even time to invest into microinverters was like 2 years longer than regular inverter.
The regular IQ7 is so weak, it cannot handle the average inverters today. The IQ7+ is better, but for a 350W panel, the output is limited to 295VA. The IQ7X can output 320W. And it costs 121 EUR this thing, that's the price of a full (Chinese) panel. And if your roof has shading problems, a solaredge system has those DC optimizers, that cost 45 EUR. Yes they need a separate inverter box, that costs money, but at 8 panels it is already cheaper than the micro inverters.
I can only see the benefit for installers. When the bloody under engineered things blows up, because it is installed on the back of a hot panel, they can just send you the money back, instead of going on site and fixing your installation under warranty.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Brumby on April 04, 2021, 12:20:55 am
Everyone seems so invested in this microinverters, and I still dont get it.
Start with this: "Single point of failure."

Quote
I can only see the benefit for installers. When the bloody under engineered things blows up
Evidence?  Or is this only conjecture?

Quote
, because it is installed on the back of a hot panel,
Not ideal - but I haven't studied the thermal design.

Quote
they can just send you the money back, instead of going on site and fixing your installation under warranty.
Not in Australia mate!  It'll get fixed - or there will be hell to pay

.... and then it'll get fixed.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 12:54:50 am
Everyone seems so invested in this microinverters, and I still dont get it.

Safety--no HVDC.  Every solar system fire I've ever heard of--and there have been a few--has been HVDC related.  You would have to work very hard to start a fire with a microinverter system.

Reliability--while earlier Enphase units had issues, they've been reliable for a decade now.  Mine are 8 years old and still working 100% with no failures.  And if one does fail, I lose 1/30 of my capacity.

Efficiency--while you can use SolarEdge equalizers with a regular central inverter, the microinverter does all that in one step.  I lose nothing due to partial shading.  The issue of 'clipping' or 'not being able to handle' a certain size panel is pretty much a non-issue because the amount of time that a panel has enough light to put out 90%+ of its rating is quite small, even here in SoCal.  In northern Europe, it's probably quite rare. 

Ease of installation and cost effectiveness--mine paid for themselves three years ago.  I'm not sure how you are 'analyzing' installations, but here there are real-world permitting and other issues that have to be accounted for when you consider costs.  For example, the 'clipping' issue can actually be a benefit, even though a small amount of energy is lost, because it lowers the size of the wiring and circuitry required.  Just as an example, using the old M215 inverters that I have, I can run 34 panels on a relatively standard electrical system.  Since I have 240 watt panels and could use bigger ones, at some point the system occasionally maxes out and I 'lose' some power.  However, if those inverters harvested ALL of that energy, I would not be allowed to connect 34 panels to my system because the maximum power would exceed a certain calculated metric (80% of 20% of 200 amperes if you want to know...). 

Newer larger panels and inverters will run into the same math issues.  For residential, redoing the base electrical service would be a huge expenditure that would eclipse any minor cost issues with the particular type of solar installation.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Kleinstein on April 04, 2021, 07:29:42 am
Even in not so ideal northern europe, short time the peak insolation  can go a bit over 100% - this happens with some clouds, getting direct sun plus some refleced off clouds.
Depending on the angle one may however never get the sun at the right angle. Dave's old panels would likely never see the full sun because of the orientation.

With now relatively low prices for the panels it makes absolute sense to have the inverter power lower than nominal panel power.  At peak times there is anyway the tendency to have too much PV power in the grid. From the grid side it would probably better to have the inverter only at some 50-70% of the panel power.  They may have to adjust the money they pay for PV sold to the grid - like lower at peak times and maybe higher at night  :-DD.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 04, 2021, 07:31:35 am
Everyone seems so invested in this microinverters, and I still dont get it.
Start with this: "Single point of failure."

Quote
I can only see the benefit for installers. When the bloody under engineered things blows up
Evidence?  Or is this only conjecture?

Quote
, because it is installed on the back of a hot panel,
Not ideal - but I haven't studied the thermal design.

Quote
they can just send you the money back, instead of going on site and fixing your installation under warranty.
Not in Australia mate!  It'll get fixed - or there will be hell to pay

.... and then it'll get fixed.
Here is the warranty site:
https://enphase.com/en-au/support/labor-reimbursement-warranty-service
 (https://enphase.com/en-au/support/labor-reimbursement-warranty-service)You have to judge for yourself, if 125 AUS is enough to drive to your place and 25 AUS is enough to get them to your roof.
If a SMA or Solaredge inverter dies, they come on site and replace the inverter under warranty, they have to.
If that happens after 20 years, well, you were lucky, You still only need to replace 1 inverter. If the same starts happening on your roof.. 20 years from now half your inverters dead. That is a lot more work to get fixed.


Ease of installation and cost effectiveness--mine paid for themselves three years ago.  I'm not sure how you are 'analyzing' installations, but here there are real-world permitting and other issues that have to be accounted for when you consider costs.
The way we "analyzed" the installations, was this: I was working at a company specializing in solar technology data collection. And dealing with so-called green certificates that were a government incentive. We had over a billion data points of 7000 solar installations, several experts, algorithm to detect partial shading, and very good understanding of the underlying costs. I was doing there the monitoring hardware, so not directly involved with the analysis, but the end result was clear.

We also had financial incentive to recommend the best possible system for customers, as when they generate more power, there was more income for the company. And still, we wouldn't recommend microinverters.
For example, the 'clipping' issue can actually be a benefit, even though a small amount of energy is lost, because it lowers the size of the wiring and circuitry required.  Just as an example, using the old M215 inverters that I have, I can run 34 panels on a relatively standard electrical system.  Since I have 240 watt panels and could use bigger ones, at some point the system occasionally maxes out and I 'lose' some power.  However, if those inverters harvested ALL of that energy, I would not be allowed to connect 34 panels to my system because the maximum power would exceed a certain calculated metric (80% of 20% of 200 amperes if you want to know...). 

Reliability--while earlier Enphase units had issues, they've been reliable for a decade now.  Mine are 8 years old and still working 100% with no failures.  And if one does fail, I lose 1/30 of my capacity.
So you are saying that it's better that they output less power due to some local regulation that you have.  :-//
The average panel size is 350W today.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: coppercone2 on April 04, 2021, 07:53:27 am
dave jones do you have surge protection for your system?

if I had that much I would think about a lightning rod even, but I don't really know much about them *until someone frees up those expensive IEC standards*
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: mikeselectricstuff on April 04, 2021, 10:24:48 am

Also, I recommend some high power loads if they start charging you for export,
Why would you not just disable export if they started charging for it ?
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 04, 2021, 10:28:43 am
The regular IQ7 is so weak, it cannot handle the average inverters today. The IQ7+ is better, but for a 350W panel, the output is limited to 295VA.

That indeed seems to be the case, very dissapointing.
I've got 370W panels, and I'm wasting 80W per panel, or 1.12kW total.
Although curiously the datasheet says it's designed for modules up to 385W, so  :-//
(https://www.eevblog.com/forum/blog/eevblog-1385-8kw-home-solar-power-system-expansion/?action=dlattach;attach=1208688;image)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 04, 2021, 10:33:11 am
Everyone seems so invested in this microinverters, and I still dont get it.

1) Safety, no HVDC.
2) Redundancy. If one panel or inverter goes down you only lose that one.
3) Shading, dirt, poop etc. You only lose that one panel, it doesn't impact the string.

If you want the cheapest system you wouldn't use microinverters.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 04, 2021, 10:36:39 am

Also, I recommend some high power loads if they start charging you for export,
Why would you not just disable export if they started charging for it ?

At that point you get a battery system.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 04, 2021, 10:37:31 am
dave jones do you have surge protection for your system?

Nope. Our entire suburb is underground wiring, so lightning surges usually don't make it as far as the house.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 04, 2021, 10:41:22 am
For those not following on twitter, they goofed up the install of both the new Enphase current clamps and the old Solar Analytics one too  :palm:
The system shows we are drawing power when we aren't home, and that power consumption just so happens to match the solar output of our old 3kW system  :-DD
This day was supposed to have only our two fidges (about 200W as you can see at night) consumption all day.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Brumby on April 04, 2021, 11:27:23 am
Quote
they can just send you the money back, instead of going on site and fixing your installation under warranty.
Not in Australia mate!  It'll get fixed - or there will be hell to pay

.... and then it'll get fixed.
Here is the warranty site:
https://enphase.com/en-au/support/labor-reimbursement-warranty-service
 (https://enphase.com/en-au/support/labor-reimbursement-warranty-service)You have to judge for yourself, if 125 AUS is enough to drive to your place and 25 AUS is enough to get them to your roof.
:palm:  Did you understand that page?  Did you even READ it?

Labor Reimbursement for Warranty Service
(Effective November 1, 2020)
Australia and New Zealand

The Enphase Energy, Inc. (“Enphase”) Labor Reimbursement Program (“Labor Reimbursement Program”) is designed to help solar-electric installation professionals (“Installers”) that do not have a product purchase (or similar) agreement with Enphase offset a portion of the service/labor costs related to replacing Eligible Products (defined below) that has been installed in a PV solar system located in Australia or New Zealand.

This Labor Reimbursement Program is separate from our standard limited product warranties. If your company has entered into a product purchase or other agreement with Enphase governing the purchase of Enphase products, this Program does not apply to you; please refer to the terms and conditions of such agreement with Enphase.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: ssander on April 04, 2021, 11:41:33 am
Dave, Thank you for the video. Looks like the microinverters might be the ones to use if I get panels above my place.

Any system would need to maximise the output with what little space I have available as none of my roof surfaces face North.

Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 02:14:33 pm
So you are saying that it's better that they output less power due to some local regulation that you have.  :-//
The average panel size is 350W today.

If 'local' means the United States, then yes.  And the panel size issue just scales, the concept is the same.  But even if there were no such issue, the loss of energy due to the panel max being more than the microinverter max is a very small issue.  If your inverter can only put out 90% of the panel max, you don't lose 10% of your production, it's more like 0.01%.  But if you analyzed 7000 systems, you ought to know that....
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 02:32:57 pm
That indeed seems to be the case, very dissapointing.
I've got 370W panels, and I'm wasting 80W per panel, or 1.12kW total.
Although curiously the datasheet says it's designed for modules up to 385W, so  :-//

There's no reason to be disappointed! This is perfectly sensible system optimization.  Both the inverters and the panels cost money, so why do we assume that the inverters need to be sized so as to use every last erg of energy from the panels and that anything less is 'waste'?  Wouldn't a smaller panel be 'wasting' the inverter's capacity most of the time? 

It's true that your system has a 20% mismatch while mine has about a 7%, but at 7% and a nearly ideal fixed SoCal installation, clipping is extremely rare--some years it never happens.  To get that 370 watts from your panels you need a day when the sun is nearly aligned perfectly (which can only happen 3-4 weeks per year), a perfectly clear day and the panels need to be....cold.  Since Enphase has per-panel monitoring, you can just review your power production graphs in Enlighten and you'll be able to see whenever the power production maxes out or 'clips'.  Figure out how much time each panel is clipped and assume that you are losing 40W per panel (which is likely an over-estimation) and see what you think.

I just did a quick check on mine as we are in that 3-4 week window where the sun is aligned with the panels.  80% for me would be 192 watts per panel.  Some of my panels are occasionally reaching that in the middle of the day, the highest one in the past 7 days was 196 watts, that panel stayed above 192 watts for about an hour.  A system that clipped at 80% would have cost me maybe 4 watt hours in a week on a panel that produced 8.08kWh in that same period.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: coppercone2 on April 04, 2021, 03:39:40 pm

Also, I recommend some high power loads if they start charging you for export,
Why would you not just disable export if they started charging for it ?

so there are plumes of expensive wasteful steam every afternoon

it might be impossible in australia though
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: David Hess on April 04, 2021, 04:01:56 pm
Regarding replacing copper with silver during World War 2 in the US, the power houses at the dams along the Columbia river also did that, and I assume it was done at other dams.  The copper bus bars were replaced with silver ones and armed guards were posted.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 04, 2021, 07:03:39 pm
:palm:  Did you understand that page?  Did you even READ it?
Not really, I have better things to do with my time, than figuring out what the warranty is somewhere else.

Everyone seems so invested in this microinverters, and I still dont get it.

1) Safety, no HVDC.
2) Redundancy. If one panel or inverter goes down you only lose that one.
3) Shading, dirt, poop etc. You only lose that one panel, it doesn't impact the string.

If you want the cheapest system you wouldn't use microinverters.
I'm familiar with the claimed benefits.
1) Solaredge and other DC optimizer,  have some communication that limits the voltage on a string in case a failure. So if a wire is broken for example, you have like 5V and minimal current through it. According to the new regulations, you dont even have to install DC isolators. This is only a benefit compared to regular string inverters.
2) I just dont see how this is relevant. I have a freezer at home, if it breaks, I loose maybe 2-300 EUR worth of food 10 hours later. Yet I dont have several small freezers at home. If an inverter breaks, I stop generating power, until the installer fixes it. Several heating systems. I have 1 mains power line coming from the street, what if that one breaks?
The microinverters have shared AC line. This redundance feels like marketing, and if you take one step backwards it doesnt really make sense.
3) Just like with DC optimizers. With half cut cells, they even reduce the panel area that gets effected by shading. I've read that they actually want to go to quarter cut cells in the future, that will reduce the benefits of microinvertes even more.

And this effect is over estimated. We had this nifty algorithm, that could tell a customer, when they had shading over their panels. It was comparing the generation of an installation against neighboring installations, and we sent an email when we found shading. And the average loss was something like 25 EUR a year ( as I remember, you know how memory is).

It was a much larger issue, that inverters shut down when there was too much generation. You have a street, with a transformer feeding it at one end. The AC line and the transformer was designed to convert from the 10KV to 235V. At the end of the street you have 225V due to the voltage drops. They install the system 30 years ago, nobody had solar.
In the meantime, Belgium became one of the most dense in solar installations, but the transformers are the same. So there is still 235 at the beginning of the street, but in the middle you have 240V and the inverters at the end of the street have to shut down, because the voltage is too high. Some people were loosing out as much as 150 EUR/year, because of this, and they cannot do anything about it. DSO doesn't care, because they have no financial incentive to spend money on the lines or the transformer.
They also
4) Cost more
5) Place electrolytic capacitors in heated areas. Regular inverters can be placed in the shade, or have a heatsink built in. Some of them even had fans.

That indeed seems to be the case, very dissapointing.
I've got 370W panels, and I'm wasting 80W per panel, or 1.12kW total.
Thats one of the issues that I'm seeing. Regular strings usually also have DC over provisioning. But that's 20% per panel, very different than 20% of an entire system.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Dread on April 04, 2021, 07:15:35 pm
I am in the process of ordering a 6KWh - 8Kw system for use abroad.
The country uses 115V/230V 50Hz and the solar guys I have been in contact with in Miami have suggested everything from Schneider to OutBack Radians to SMA.  Those same Panels that Dave got the LG360N1C-N5 along with a comparable Panasonic panel have been mentioned.

One thing that all three of the companies suggest I stayed away from was MicroInverters.  The reasoning was always the same, they said that the Inverter was the most likely part to burn out and it's better to deal with a single Inverter than 20 of them. They also said they get extremely hot and therefore have a short lifespan. I mentioned shading and one guy replied that the panels would be set in three per series and that should eliminate most of the problems but if they still encounter a problem they would use Optimizes on the affected panels.    I don't know enough about solar equipment to comment but when three different companies stare you away from something it's a done deal in my head.

They all agreed that the SMA system was the most reliable and also said the easiest to service as the new model has two sections, you can remove the Inverter section and leave the lower half with all the wiring in place.  Easiest to service and best warranty at 10 years plus optional 10 extra years for $400+

The wiring proposed was very strange to me.
 Since not much power will be used between 10am and 5pm which is the peak production hours I told them storage was a must.  The LG RES Battery pack was recommended but things got tricky with how to use the power at night.  The last wiring scenario I was told involved feeding a Sunny Boy 230V 50Hz model directly into a Sunny Island 230V unit and then Grid Tie the Sunny Island using an Autoinverter Transformer to split the 230V into two 115V lines. The system creates a Micro Grid during a power Outage and disconnects the mains so that the in the Daytime the Solar panels are still operating.
On a normal night with power the Sunny Island powers the house in Grid Tie mode. (This is the part that confuses me but he mentioned it can be done).  Daves video was great to watch and convinced me that the SMA products are the way to go.  You cannot complain when an Inverter gives you eight years of great service.

Any feedback or questions I should be asking these guys would be greatly appreciated.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: HattedSquirrel on April 04, 2021, 07:22:20 pm
Why does Dave keep calling it a 5 kW system if it can technically only supply 290 VA * 14 = 4060 VA max? What am I missing here?

Are the panels just called "370 W", but will never reach more than 290 W in any realistic scenario or what is the reason? I find it quite confusing I must say... especially if the system as a whole is labeled with a power rating that is technically impossible to achieve. Wouldn't that be as if I claimed my car could do 400km/h - with a different engine, enough fuel is in the tank, at least for 5minutes.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 07:40:02 pm
1) Solaredge and other DC optimizer

If we are comparing a Solaredge optimized system with an Enphase system I'd agree the performance seems similar, but so are the costs.  Those optimizers aren't free.  And I'm not sure how well that voltage protection works in the case of a high-resistance but not open connector--or worn insulation that could pose a shock hazard in some cases.  I'm not sure they totally mitigate the HVDC issue.  I know micros do.

And as far as redundancy/reliability issues go, there's a plenty of experience to rely on.  You can talk of heated capacitors all you like, but DC-string inverters have typically had a disturbingly high failure rate compared to even old micros.  Read the warranty terms of each if you want to know the manufacturers take on that. And with DC optimization, the optimizer is in same place as the micro, so where's your advantage?

Quote
Thats one of the issues that I'm seeing. Regular strings usually also have DC over provisioning. But that's 20% per panel, very different than 20% of an entire system.

Why is it very different and when does it matter?
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 07:50:15 pm
Why does Dave keep calling it a 5 kW system if it can technically only supply 290 VA * 14 = 4060 VA max? What am I missing here?

It is misleading, but solar systems are often referred to (and sold) in terms of the sum of the panel maximum ratings, which are measured at 1kW/m2 and 25C panel temperature, which rarely ever happens and never for long.  There are other rating schemes, such as NOCT, that would be more appropriate for determining how much power to expect, and how big of an inverter to use.

https://amsolar.com/diy-rv-solar-instructions/edpanelratings

If you look at the datasheet of the solar panels Dave got, you'll see that their NOCT PMAX rating is 273 watts.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Dread on April 04, 2021, 07:59:41 pm

And as far as redundancy/reliability issues go, there's a plenty of experience to rely on.  You can talk of heated capacitors all you like, but DC-string inverters have typically had a disturbingly high failure rate compared to even old micros.  Read the warranty terms of each if you want to know the manufacturers take on that. And with DC optimization, the optimizer is in same place as the micro, so where's your advantage?

Not when compared to SMA inverters!  As for warranty it's 5 years vs 10 Years with SMA.  Also they will ship you a new one right away if your on their monitoring system.  Keep in mind Dave got that Enphase systems as a promotional item.  I would imagine that after 8 years of great service from SMA if he had to have made a purchase out of pocket it might have been different.  I would not pass up the Enphase offer either but for us on the outside who have to spend lots of $$$ it's not so easy of a decision.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: nctnico on April 04, 2021, 08:19:22 pm
One thing that all three of the companies suggest I stayed away from was MicroInverters.  The reasoning was always the same, they said that the Inverter was the most likely part to burn out and it's better to deal with a single Inverter than 20 of them. They also said they get extremely hot and therefore have a short lifespan. I mentioned shading and one guy replied that the panels would be set in three per series and that should eliminate most of the problems but if they still encounter a problem they would use Optimizes on the affected panels.    I don't know enough about solar equipment to comment but when three different companies stare you away from something it's a done deal in my head.
It could be none of them has experience with them. But to me it seems micro-inverters don't bring much to the table. They are installed in the worst place (on a hot roof) and instead of high voltage DC you now need to bring high voltage AC to the roof running at higher currents as well. IIRC the typical voltage a DC system runs at is 300V to 400V per string and for a >2000W installation you end up with several strings which each run with relatively low corrents (couple of amps). With all the panels disconnected you bring the voltages on the wiring down to safe levels (unless ofcourse you have panels with very high voltages but I have not seen those myself).

In the end it is all about TCO / ROI. Getting a few % extra might not be worth the extra money. If you install a cheap inverter in a cool place then it is not likely do develop problems due to temperature related aging. Maybe it is even cheaper to have a spare inverter on hand compared to buying a very expensive one and pay for warranty on top.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 04, 2021, 08:55:19 pm
It could be none of them has experience with them.

Or maybe they do!  Enphase had an earlier model with pretty high failure rates and they didn't respond in the best way at first.  Eventually they came out with and replacement/upgrade program.  If I had to make dozens of warranty service calls and go up and replace those for little or no compensation, I might not be so happy either.  HVDC inverters had pretty high failure rates too, but typically only once or twice.

Quote
high voltage DC you now need to bring high voltage AC to the roof running at higher currents as well.

Not really a good comparison.  The AC is just standard wiring protected by a breaker and has no unusual hazards.  Older string systems had HVDC not so well protected, I'll leave it for others to argue that current string systems have reduced hazards.  DC currents are 8-10 amps per string, on Enphase the AC currents are 16 amps maximum per branch.  I've not seen or heard of a fire caused by an Enphase installation.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: nctnico on April 08, 2021, 07:57:38 am
high voltage DC you now need to bring high voltage AC to the roof running at higher currents as well.

Not really a good comparison.  The AC is just standard wiring protected by a breaker and has no unusual hazards.  Older string systems had HVDC not so well protected, I'll leave it for others to argue that current string systems have reduced hazards.
IMHO this is more of a lack of regulations issue for HVDC wiring in general. Lower current = less energy available = less chance of fire. AC power packs quite a punch due to the energy the grid can provide.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 08, 2021, 08:01:22 am
And as far as redundancy/reliability issues go, there's a plenty of experience to rely on.  You can talk of heated capacitors all you like, but DC-string inverters have typically had a disturbingly high failure rate compared to even old micros.  Read the warranty terms of each if you want to know the manufacturers take on that. And with DC optimization, the optimizer is in same place as the micro, so where's your advantage?

Solaredge optimizers dont have electrolytic capacitors in them, they are ceramic. I guess I dont have to go into the details, that electrolytic capacitors have a life expectancy on the datasheet. Also as I understand the marketing, its 1/3 the component count.

Why is it very different and when does it matter?
In summer, the sun is shining, there is shading on a panel. Say, you have 10 panels, 350W each. Say all systems will have 20% overprovision.
The DC system with optimizer will output 80% of its nominal (DC) nameplate capacity, the maximum of the system.
The Enphase will output about 74%, because 9 panel will output 80% and one 20%.
A regular inverter with two strings will output 60%, as 5 panels will be 100% and the other five 20%

Honestly, beyond the technical discussions, I dont like Enphase because of the bad moves they were pulling in the past. People report that they are charged a monthly fee per panel for the monitoring. And they were charged money, when they were transferring the warranty when selling the house. Even if this only happened in the past, I just dont want to deal with a company that des these things.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Brumby on April 08, 2021, 12:24:07 pm
:palm:  Did you understand that page?  Did you even READ it?
Not really, I have better things to do with my time, than figuring out what the warranty is somewhere else.
Then DON'T make statements from a position of ignorance!
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: floobydust on April 08, 2021, 09:27:41 pm
I don't know the exact installation details, but I started with my usual EE first question: "where's the fuse?"
Because the micro-inverters' outputs are all in parallel, I think on the Q-Cable 20A branch max., I wondered if this was covered.
What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.
Fault LED is a "DC Resistance Low, Power OFF" doesn't make sense on what that is. What power is off, grid or PV and who's got the ohmmeter lol.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: mikeselectricstuff on April 08, 2021, 09:36:32 pm

What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.

I would be highly surprised if they didn't have  an internal fuse as a last-ditch protection measure- as it's potted, any internal fault would be unrepairable so the fuse doesn't need to be replaceable. 
In normal operation they will be actively monitoring everything throughout the AC cycle, so will be able to shut down in the event of any abnormal situation.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: aqarwaen on April 08, 2021, 10:27:49 pm
DAVE have you actualy tested how much load your solar power system can produce in peak time,before you need to draw extra power from grid?
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 08, 2021, 11:29:02 pm
What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.
Fault LED is a "DC Resistance Low, Power OFF" doesn't make sense on what that is. What power is off, grid or PV and who's got the ohmmeter lol.

If the breaker blows, the inverters all stop working instantly because the grid power goes away.  This is an extremely reliable intrinsic function of the microinverter and is required for anti-islanding certification.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 08, 2021, 11:38:56 pm
In summer, the sun is shining, there is shading on a panel. Say, you have 10 panels, 350W each. Say all systems will have 20% overprovision.
The DC system with optimizer will output 80% of its nominal (DC) nameplate capacity, the maximum of the system.
The Enphase will output about 74%, because 9 panel will output 80% and one 20%.
A regular inverter with two strings will output 60%, as 5 panels will be 100% and the other five 20%

Honestly, beyond the technical discussions, I dont like Enphase because of the bad moves they were pulling in the past. People report that they are charged a monthly fee per panel for the monitoring. And they were charged money, when they were transferring the warranty when selling the house. Even if this only happened in the past, I just dont want to deal with a company that des these things.

OK, if you are comparing a Solaredge optimized system with microinverter system, I'll agree that they are similar in efficiency.  Your example pencils out, but it would be an unusual--but not unthinkable--circumstance.  The effect on overall system productivity would still be minimal because that situation will only last for as long a the non-shaded panels can put out near 90% of their rating. 

Your other point about Enphase is entirely true, unfortunately.  I use 'Enphase' and 'microinverter' interchangeably because they dominate the market now, but in the not-too-distant past they were struggling in many ways--high failure rate with a parts-replacement only warranty,  borderline deceptive advertising (I bought mine thinking they were US-made), various attempts at recurring revenue (monitoring, warranty, etc) and more.  I was worried they would go under and I'd have no warranty.  The company has greatly improved under new management, but if I was the one that had been burned by them, I'd not like them either.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: ssander on April 09, 2021, 03:57:17 am
After Dave's live stream last night. I was wondering about the specific microinverters used.

Enphase also makes an IQ7A inverter and I found this document on their website.

Technical Brief: https://enphase.com/sites/default/files/downloads/support/IQ7A_Vs_IQ7plus_in_Australia.pdf (https://enphase.com/sites/default/files/downloads/support/IQ7A_Vs_IQ7plus_in_Australia.pdf)

I'm no expert on the subject, but (there is always a but) it seems to me that the system is correctly spec'd. 
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 09, 2021, 05:48:11 am
After Dave's live stream last night. I was wondering about the specific microinverters used.

Enphase also makes an IQ7A inverter and I found this document on their website.

Technical Brief: https://enphase.com/sites/default/files/downloads/support/IQ7A_Vs_IQ7plus_in_Australia.pdf (https://enphase.com/sites/default/files/downloads/support/IQ7A_Vs_IQ7plus_in_Australia.pdf)

I'm no expert on the subject, but (there is always a but) it seems to me that the system is correctly spec'd.

According to them, yes. But they have also admitted that my system will clip on high solar insolation days. Even the 340W output IQ7A will also clip.
It's whether or no you are happy with that loss on those days. Enphase don't have  higher output option available, so they have to try and justify it.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 09, 2021, 05:59:21 am
DAVE have you actualy tested how much load your solar power system can produce in peak time,before you need to draw extra power from grid?

No because it's just insalled, but absolute peak with high soalr insolation I'd say about 4.13kW (max of the Enphase system) + maybe 2.8kW for the SMA system (was 3kW peak, but now not optimal) = approx 7kW. Maybe 6kW on an everage day.
Our consumption has peaked at about 8kW, but that's fairly rare.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 09, 2021, 06:00:51 am
What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.
I would be highly surprised if they didn't have  an internal fuse as a last-ditch protection measure- as it's potted, any internal fault would be unrepairable so the fuse doesn't need to be replaceable. 
In normal operation they will be actively monitoring everything throughout the AC cycle, so will be able to shut down in the event of any abnormal situation.

Yes, the IQ7 system has a measurment sample and processing time of 20us.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 09, 2021, 06:04:21 am
The Enphase consumption measurement problem got sorted today with an extra current transformer in parallel with the xisting one to compensate for the old SMA system production.
The SMA/Solar Analytics system is still giving wonky consumption results because it needs another CT as well to compensate for the production of the Enphase system!

The joys of having two different systems on the one circuit.
It's actually a rather interesting problem once you figure out what happening, will have to do a video on it.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 09, 2021, 04:19:59 pm
According to them, yes. But they have also admitted that my system will clip on high solar insolation days. Even the 340W output IQ7A will also clip.
It's whether or no you are happy with that loss on those days. Enphase don't have  higher output option available, so they have to try and justify it.

Why fixate on the clipping?  Go back and look at your own data and see how much total time your old system spent at more than 2.7kW.  Even a fairly small efficiency increase at other times, such as low light or partial shading, will make up for that. 

Also, even with 1kW/m2 insolation, it is unlikely your old panels actually produce their full STC-flash power.  You are basing your theory of solar production on your one example.  I can think of three possible explanations:

1) Your location has peak insolation well in excess of 1kW/m2 and/or it is actually quite cold in Sydney in December.  This seems unlikely, especially the latter.

2) Your power measurements are wrong.  I think this is unlikely as well, although 5% error wouldn't be unusual.

3) The accepted and published theories of solar panel energy production are wrong.  Or....

4) Your original panels had an STC flash power rating considerably higher than 250W.   I'm familiar with that line of panels because they came out right around the time I was shopping for panels.  I assume it was this one:

https://www.lg.com/us/business/solar-panels/lg-LG250S1C-G3 (https://www.lg.com/us/business/solar-panels/lg-LG250S1C-G3)

They made these, IIRC, in 250, 260 and 270W versions, which I presume were manufactured and then binned.  These ratings were not excessive or aggressive for a mono panel--I bought poly panels around the same time that were 240W.  Perhaps their process was better than anticipated and they down-binned some panels to meet orders for the 250W version.  Or perhaps they were worried about degradation and wanted to be conservative because of the production warranty.  Although I doubt you are likely to tear one off and send it for testing, I'd bet a small amount of money they would test well over 250W even now.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 11, 2021, 10:51:24 pm
According to them, yes. But they have also admitted that my system will clip on high solar insolation days. Even the 340W output IQ7A will also clip.
It's whether or no you are happy with that loss on those days. Enphase don't have  higher output option available, so they have to try and justify it.

Why fixate on the clipping?  Go back and look at your own data and see how much total time your old system spent at more than 2.7kW.

I plan on doing exactly that.
BTW, I recall looking at measured insolation data at one point and I saw over 1000W/sqm in Sydney.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 02:28:25 am
BTW, I recall looking at measured insolation data at one point and I saw over 1000W/sqm in Sydney.

It's entirely possible for that to happen on occasion, but keep in mind that unless it is cold, the -0.459%/K tempco of your panels will reduce the output by at least 10-12%.  One of the useful features of the Enphase system is that it gives you inverter temperature, which is a fairly decent proxy for panel temperature.

I think about 1050W/m2 is pretty much the absolute limit for clear sky--and that only under specific circumstances usually only found in northern climates.  However, if you have just the right combination of factors on a partly cloudy day, the limit is quite a bit higher.  Of course I don't own a pyranometer so I haven't measured anything directly myself, but published literature on this all seems to agree that 1kW/m2 is the normal maximum on clear days.

https://journals.ametsoc.org/view/journals/apme/47/11/2008jamc1861.1.xml

Edit:  I forgot to mention altitude as a factor, so there's that too.

Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 03:09:00 am
BTW, I recall looking at measured insolation data at one point and I saw over 1000W/sqm in Sydney.

It's entirely possible for that to happen on occasion, but keep in mind that unless it is cold, the -0.459%/K tempco of your panels will reduce the output by at least 10-12%.  One of the useful features of the Enphase system is that it gives you inverter temperature, which is a fairly decent proxy for panel temperature.

I think about 1050W/m2 is pretty much the absolute limit for clear sky--and that only under specific circumstances usually only found in northern climates.  However, if you have just the right combination of factors on a partly cloudy day, the limit is quite a bit higher.  Of course I don't own a pyranometer so I haven't measured anything directly myself, but published literature on this all seems to agree that 1kW/m2 is the normal maximum on clear days.

https://journals.ametsoc.org/view/journals/apme/47/11/2008jamc1861.1.xml (https://journals.ametsoc.org/view/journals/apme/47/11/2008jamc1861.1.xml)

Edit:  I forgot to mention altitude as a factor, so there's that too.

Here you go, the peak output power of the 3kW system histogramed over 1980 days.
My new 5kW system uses the same LG panels (but 370W vs 250W) in the exact same location. So I expect pretty close to the same peak output power of 5kW.
With 295W peak inverters, lets say 80% of the rated power at 1000W, so 4130W peak maximum possible, round to 80%.
Take the same 80% for old 3kW system (2400W) there are total of 769 days out of 1980 days where the peak output would exceed the inverters, or 38.8% of days. That's hardly "on occasion".
Data doesn't lie.
YMMV

(https://www.eevblog.com/forum/blog/eevblog-1385-8kw-home-solar-power-system-expansion/?action=dlattach;attach=1210306;image)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 04:14:51 am
Take the same 80% for old 3kW system (2400W) there are total of 769 days out of 1980 days where the peak output would exceed the inverters, or 38.8% of days. That's hardly "on occasion".

"On occasion" referred to exceeding 100%, not 80%.  I'm at a similar latitudinal situation as you (inverted of course) and I routinely exceed 80%.  Nobody is denying that clipping will occur when the threshold is 80%. The question isn't 'how often', it is 'for how much time, and by how much".  According to Enphase's data, it amounts to 0.075% of your total energy production.  Their paper that is linked above,  and in your YouTube video comments, lays it all out, complete with the amount 'lost' due to clipping.

Enphase actually recommends a threshold as low as 75% (133% over-provisioning) and that only because your CEC has mandated that as a limit for some reason.    They even explicitly recommend the IQ7+ for your panels over the IQ7A and they explain why.  There are, in fact, good reasons to have systems with even higher overprovisioning because maximizing the usage of all available panel power is not the only valid objective, especially since panels have become so cheap.  For example, I could replace my panels with new LG ones like yours and new IQ7 inverters that are custom-configured to replace my old ones with a 225W max power output.  If you only looked at all the peak power I was 'wasting' due to clipping, it would seem a terrible idea.  It would be 165% over-provisioned and my clipping threshold would be 60%, which would horrify some.  But when you look at the fact that it would be a simple, easy retrofit that requires no new permitting or infrastructure, it's a great idea and would increase my power production tremendously.  Everyone will have their own situation, but these issues are common.  Avoiding clipping would lead to poorer system design in many cases, not to mention that SoCal Edison (my power company) really doesn't need a bunch of peak power in the middle of the day.

Some may object to the fact that a system like yours is commonly sold as a '5kW system', when in fact it can never produce that.  Up until now I've more or less agreed, but actually I'm not so sure that it is an invalid or even deceptive descriptor.  The '5kW' is a sort of sensitivity rating that describes how large a net you have for catching the sun.  Whether that is 25m2 at 20% efficiency or 50m2 at 10%, it is a valid way of comparing and the peak power issue has such a small effect on total energy production that it really only serves to confuse the issue.  IMO, the question is how much your electric bill would change if those inverters were 350W as opposed to 290.  If Enphase has given you good data the answer is 'not much'.  Then ask what the difference would be if you used 290W panels--the answer to that is 'a lot'.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 05:19:39 am
Take the same 80% for old 3kW system (2400W) there are total of 769 days out of 1980 days where the peak output would exceed the inverters, or 38.8% of days. That's hardly "on occasion".
"On occasion" referred to exceeding 100%, not 80%.

In this case I am talking 100%, i.e. 14x295W=4.13kW
So 38% of days my inverters can be expected to clip.

As for the rest of your comments, yes, of course, and I've already shot a video on this, to be released shortly.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 05:59:42 am
In this case I am talking 100%, i.e. 14x295W=4.13kW
So 38% of days my inverters can be expected to clip.

OK, I was referring to exceeding 100% of the panel STC rating--that's an occasional event.  If you haven't read that link in my post, it refers to some interesting, and apparently not that rare, situations where irradiance can be much higher than 1kW/m2 for a short while--in one example they had 1832W/m2

Yes, I concur--according to your data, providing your new panels scale exactly as the nameplate rating (370:250), you will see some clipping on 38% of your days.  And with the Enphase monitoring system you'll be able to see it quite clearly.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 07:40:22 am
In this case I am talking 100%, i.e. 14x295W=4.13kW
So 38% of days my inverters can be expected to clip.
OK, I was referring to exceeding 100% of the panel STC rating--that's an occasional event.  If you haven't read that link in my post, it refers to some interesting, and apparently not that rare, situations where irradiance can be much higher than 1kW/m2 for a short while--in one example they had 1832W/m2

Yes, the sun is a pesky thing.
My old 3kW system clipped occasionally too due to that.

Quote
Yes, I concur--according to your data, providing your new panels scale exactly as the nameplate rating (370:250), you will see some clipping on 38% of your days.  And with the Enphase monitoring system you'll be able to see it quite clearly.

I've already seen it clip, although Enphase claim it technically didn't.
4.172kW is greater than 4.13kW (14 x 295W), so yeah, I'd say it clipped in April.
Unfortunately I won't see it easily because I've now changed the system to show the total production from both systems.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 11:50:06 am
https://www.youtube.com/watch?v=3bG6luzg6Rk (https://www.youtube.com/watch?v=3bG6luzg6Rk)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 11:56:32 am
Why does Dave keep calling it a 5 kW system if it can technically only supply 290 VA * 14 = 4060 VA max? What am I missing here?

Because it uses 5.1kW of rated panels. That's actually important even if you have an underratted inverter.
e.g. 5kW of panels with a 4kW inverter will give more output power on an 80% insolation day than 4kW of panels with a matched 4kW inverter due to the higher efficiency of the 5kW panel vs the 4kW panel. Yet both systems are capable of only 4kW peak.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 12:00:49 pm
One thing that all three of the companies suggest I stayed away from was MicroInverters.  The reasoning was always the same, they said that the Inverter was the most likely part to burn out and it's better to deal with a single Inverter than 20 of them. They also said they get extremely hot and therefore have a short lifespan. I mentioned shading and one guy replied that the panels would be set in three per series and that should eliminate most of the problems but if they still encounter a problem they would use Optimizes on the affected panels.    I don't know enough about solar equipment to comment but when three different companies stare you away from something it's a done deal in my head.

It's always a tradeoff. They aren't wrong that long term the microinverters on the roof are more likely to fail than a single string inverter in a shaded location.
But then again one failed microinverter isn't going to take down your entire system like a normal string inverter would. Plus you get the added benefit of any shading or other degredation on a single or multiple panels.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Robert Smith Eco Warrior on April 12, 2021, 12:39:16 pm
We are completely off grid running about 4kw (peak) panels.

The shading issue is quite staggering. I tried this some time ago and if you just shade one of the cells within a panel the output drops considerably.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 01:25:43 pm
We are completely off grid running about 4kw (peak) panels.

That's not much of a system for completey off grid. I presume you'd have to be pretty careful with consumption?
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 01:59:12 pm
I've already seen it clip, although Enphase claim it technically didn't.
4.172kW is greater than 4.13kW (14 x 295W), so yeah, I'd say it clipped in April.
Unfortunately I won't see it easily because I've now changed the system to show the total production from both systems.

You didn't get per-panel monitoring?  And is that monitoring at 15-minute intervals?  The 5-minute data from the inverters is more interesting.  You can browse my system here:

https://enlighten.enphaseenergy.com/public/systems/jRab149502 (https://enlighten.enphaseenergy.com/public/systems/jRab149502)

Edit: Never mind, the public view isn't any good either. 

With this display you would spot it without doubt:

(https://www.eevblog.com/forum/blog/eevblog-1385-8kw-home-solar-power-system-expansion/?action=dlattach;attach=1210435;image)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 12, 2021, 06:08:48 pm
Enphase actually recommends a threshold as low as 75% (133% over-provisioning) and that only because your CEC has mandated that as a limit for some reason.    They even explicitly recommend the IQ7+ for your panels over the IQ7A and they explain why.  There are, in fact, good reasons to have systems with even higher overprovisioning because maximizing the usage of all available panel power is not the only valid objective, especially since panels have become so cheap. 
But this is actually where Enpahse fails. Panels are cheap, and you can overprovision a DC system cheaper. Or you can get a larger DC inverter cheaper. Going from a IQ7 to an IQ7A is 50% increase in the inverter cost. The IQ7 is sold for 97 EUR here, IQ7A is 149 EUR. It more expensive than most panels. Going from a 2KW SMA to a 3KW SMA is an increase of 787/1051 = 25%. Upgrading to a 4KW inverter is only 11% more expensive than the 3KW system. Or to give you an even more extreme case, going from a 4KW Solaredge to a 27KW solaredge doesn't even double the price of the inverter. Microinverters don't scale properly, the more panels you have the less sense they make.

But let's say you want microinverters on the roof for reasons. There are microinverters with multiple inputs. Like APS QS1. 4 panel connected to it, individual MMPT, 1200W output power. And it costs only 2x the price than the Enpahse.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 06:32:27 pm
Microinverters don't scale properly, the more panels you have the less sense they make.

At some point that might be true and very large installations with no shading issues are less likely to use micros.  But it all depends on your actual pricing.  I just looked and the price of the IQ7+ is $99 if I buy them with panels.  The LG panels Mr. EEVBlog was gifted go for at least $300/panel, even a cheapo 370 watt mono is $215.   Yes you can get panels in the $150 range or even cheaper, but so what?  Thrifted systems and products always look better from a cost-effectiveness standpoint, at least at first.

Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: tszaboo on April 12, 2021, 06:50:15 pm
Microinverters don't scale properly, the more panels you have the less sense they make.

At some point that might be true and very large installations with no shading issues are less likely to use micros.  But it all depends on your actual pricing.  I just looked and the price of the IQ7+ is $99 if I buy them with panels.  The LG panels Mr. EEVBlog was gifted go for at least $300/panel, even a cheapo 370 watt mono is $215.   Yes you can get panels in the $150 range or even cheaper, but so what?  Thrifted systems and products always look better from a cost-effectiveness standpoint, at least at first.
Lol no. Longi solar for 110 EUR for a 370W half cut PERC panel.
120 for canadian solar.
For 135, made in Germany
LG... nobody sells LG, there is no market for it.
I think Dave bought the panels, and had the inverters gifted to him.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 11:11:33 pm
I think Dave bought the panels, and had the inverters gifted to him.

Both the panels and inverters fell off the back of a truck, I only paid for installation + cabling.
My old 3kW system I paid for everything and decided to get premium LG panels and top quality Sunnyboy inverter.
I would certainly have bought the LG panels again, not sure about the Enphase microinverters as I hadn't done the cost analysis. But Mrs EEVblog did like that they are safety, and I really like the data and associated system, so it's likely I would have even though it would have been more expensive. By my needs are different than most in that I get interesting video out of it, and microinverters are just more interetsting from that aspect.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 11:17:15 pm
Slightly updated video with extra bit added on why you would get hte biggest panels you can anyway.

https://www.youtube.com/watch?v=x4ER6I8Y9gA (https://www.youtube.com/watch?v=x4ER6I8Y9gA)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 12, 2021, 11:20:57 pm
But this is actually where Enpahse fails. Panels are cheap, and you can overprovision a DC system cheaper. Or you can get a larger DC inverter cheaper. Going from a IQ7 to an IQ7A is 50% increase in the inverter cost. The IQ7 is sold for 97 EUR here, IQ7A is 149 EUR. It more expensive than most panels. Going from a 2KW SMA to a 3KW SMA is an increase of 787/1051 = 25%. Upgrading to a 4KW inverter is only 11% more expensive than the 3KW system. Or to give you an even more extreme case, going from a 4KW Solaredge to a 27KW solaredge doesn't even double the price of the inverter. Microinverters don't scale properly, the more panels you have the less sense they make.

The debate of microinverters vs string is a different one that that of underrating inverters.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 12, 2021, 11:35:55 pm
Lol no. Longi solar for 110 EUR for a 370W half cut PERC panel.
120 for canadian solar.
For 135, made in Germany
LG... nobody sells LG, there is no market for it.

Are those prices VAT included?  Is there VAT on solar panels?  We have 20% import tariffs and LG panels are made in Alabama, so that's going to pencil out to a different result.  Obviously if the relative pricing changes, so will your calculations.  But if panels are that cheap and you have the space, it would indeed make sense to overprovision even more, regardless of what type of inverter system you use.  OTOH, if space is limited and you have shading issues, Enphase might still be worth the money. The details are just math.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: AmnevaR on April 14, 2021, 08:28:48 am
What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.
I would be highly surprised if they didn't have  an internal fuse as a last-ditch protection measure- as it's potted, any internal fault would be unrepairable so the fuse doesn't need to be replaceable. 
In normal operation they will be actively monitoring everything throughout the AC cycle, so will be able to shut down in the event of any abnormal situation.

Yes, the IQ7 system has a measurment sample and processing time of 20us.

Ok, I get that the microinverters analyze AC cycle really fast and all microinverters are in sync. Right?

But what is the source of AC signal? Existing grid? How all the microinverters will be in sync in an off-grid installation. Could someone enlighten me? Thanks.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: mikeselectricstuff on April 14, 2021, 09:27:51 am
What stops a bank of micro-inverters from roasting a failed one also on that AC bus? There's no local disconnect or fuse that I can see.
I would be highly surprised if they didn't have  an internal fuse as a last-ditch protection measure- as it's potted, any internal fault would be unrepairable so the fuse doesn't need to be replaceable. 
In normal operation they will be actively monitoring everything throughout the AC cycle, so will be able to shut down in the event of any abnormal situation.

Yes, the IQ7 system has a measurment sample and processing time of 20us.

Ok, I get that the microinverters analyze AC cycle really fast and all microinverters are in sync. Right?

But what is the source of AC signal? Existing grid? How all the microinverters will be in sync in an off-grid installation. Could someone enlighten me? Thanks.
Most domestic solar setups are not designed to work off-grid
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: BrianHG on April 14, 2021, 10:13:46 am
Truly affordable compact long term efficient home power storage needs to come about so you can truly say F-- to these stupid utility charges to send power back and go for the highest reasonable amount of power you can generate.

High efficiency electrolysis hydrogen fuel cells are hopefully coming with claims of 50% efficiency, but 20 years life span and huge kw storage.

https://youtu.be/0_bTjcjqN6c?t=269

I would like to see the tech improve and become much cheaper.  The size of those 4 storage canisters is small and can power your house for 2 days, if you can just increase the hydrogen canisters, I would like to have a week reserve power for my house.

Even with the 50% efficiency, the lifetime and storage and cycle specs @7:45 in the video are much more impressive than lithium cell like what's used in the Tesla Powerwall.  And it can run an average home for 2 days.

Another link:
https://youtu.be/Jz3Tn2Z-Sac?t=1

LOL, they are currently only available in Australia, maybe Dave can get a free demo unit.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 14, 2021, 02:23:09 pm
But what is the source of AC signal? Existing grid? How all the microinverters will be in sync in an off-grid installation. Could someone enlighten me? Thanks.

The grid presents a very low impedance AC signal.  An off-grid system with standard (intended for grid-tie) microinverters will typically present a simulated grid signal by both sourcing and sinking current as needed, and it will communicate with the microinverters directly.  The new IQ8 microinverters can be configured to run off-grid on their own somehow.  I'm not sure how they handle anti-islanding requirements in that case.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: BrianHG on April 14, 2021, 04:46:44 pm
But what is the source of AC signal? Existing grid? How all the microinverters will be in sync in an off-grid installation. Could someone enlighten me? Thanks.

The grid presents a very low impedance AC signal.  An off-grid system with standard (intended for grid-tie) microinverters will typically present a simulated grid signal by both sourcing and sinking current as needed, and it will communicate with the microinverters directly.  The new IQ8 microinverters can be configured to run off-grid on their own somehow.  I'm not sure how they handle anti-islanding requirements in that case.
I wonder if it is possible to trick any of these grid-tied inverter systems by disconnecting from the grid & feeding a low power sine wave inverter as a dummy emulated grid feed while the grid tied units sync up and handle the bulk of your household load.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: oPossum on April 14, 2021, 05:26:41 pm
I wonder if it is possible to trick any of these grid-tied inverter systems by disconnecting from the grid & feeding a low power sine wave inverter as a dummy emulated grid feed while the grid tied units sync up and handle the bulk of your household load.

Yes. It can be done with an inverter that is capable of bidirectional operation. Demonstrated in this video (and again in a later one that I could not find).

https://www.youtube.com/watch?v=8YGRsrEOs9I (https://www.youtube.com/watch?v=8YGRsrEOs9I)
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 14, 2021, 05:43:27 pm
I wonder if it is possible to trick any of these grid-tied inverter systems by disconnecting from the grid & feeding a low power sine wave inverter as a dummy emulated grid feed while the grid tied units sync up and handle the bulk of your household load.

If by 'trick' you mean use microinverters that are not specifically configured for off-grid use, then you need a battery-linked inverter/AC charger that can sink (to the battery) up to maximum output of  your array and can also source up your maximum consumption.  The sinking part is problematic in the long run because if the battery is full, there's nowhere sink the power.  You then need a way to dissipate the power or curtail the array without completely shutting down your microgrid. 
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: thm_w on April 14, 2021, 09:29:09 pm
If by 'trick' you mean use microinverters that are not specifically configured for off-grid use, then you need a battery-linked inverter/AC charger that can sink (to the battery) up to maximum output of  your array and can also source up your maximum consumption.  The sinking part is problematic in the long run because if the battery is full, there's nowhere sink the power.  You then need a way to dissipate the power or curtail the array without completely shutting down your microgrid.

You'd think the microinverter would be smart enough to regulate its output down if the line voltage gets too high no? then no max sink would be needed.
Or is it more like: line voltage high -> error shutdown, have to power cycle to recover.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: bdunham7 on April 14, 2021, 10:18:44 pm
You'd think the microinverter would be smart enough to regulate its output down if the line voltage gets too high no? then no max sink would be needed.
Or is it more like: line voltage high -> error shutdown, have to power cycle to recover.

Microinverters intended for islanding operation do regulate.  The grid-tie only ones shut down if voltage or frequency go out of range and then it is a 5 minute period before they try again--this is a requirement in order to use them without additional equipment. 
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: EEVblog on April 22, 2021, 01:46:01 am
Ok, I get that the microinverters analyze AC cycle really fast and all microinverters are in sync. Right?
But what is the source of AC signal? Existing grid? How all the microinverters will be in sync in an off-grid installation.

Most inverters will not work if the mains fails, this is called Anti-Islanding Protection and is a requiment by legislation in most countries that I am aware of.
It is designed to protect people working on the grid. You don't want rooftop solar systems pushing power back onto a grid you (as the line worker) think is denergised.
That mean that if your mains fails, your big arse solar power system is unusable.
If you want to work off-grid and/or have power backup when the mains fails then you need a specific battery/inverter system that generates mains power and/or set the inverters to not anti-island in some way if that's possible. It needs to be specifically designed and approved to do this if your house is connected ot the grid.

Of course if your property is completely off-grid then anything goes.
Title: Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
Post by: Robert Smith Eco Warrior on April 22, 2021, 06:51:02 pm
Yep,
We are completely off grid and..... Anything does go ...... I must do something about all the croc clips, exposed dangling buzz bars, twisted wires under plastic buckets outside and a mass of spaghetti inside.
It is atrocious and I am just in the process of doing it properly  :-+