Author Topic: EEVblog 1385 - 8kW Home Solar Power System EXPANSION  (Read 4284 times)

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Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #50 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.
 

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #51 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.
 

Offline Robert Smith Eco Warrior

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #52 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.
« Last Edit: April 12, 2021, 12:44:18 pm by Robert Smith Eco Warrior »
 

Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #53 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?
 

Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #54 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

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

With this display you would spot it without doubt:

« Last Edit: April 12, 2021, 02:09:47 pm by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline tszaboo

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #55 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.
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Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #56 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.

A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline tszaboo

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #57 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.
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Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #58 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.
« Last Edit: April 12, 2021, 11:14:58 pm by EEVblog »
 

Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #59 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.

 
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Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #60 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.
 

Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #61 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.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline AmnevaR

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #62 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.

Offline mikeselectricstuff

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #63 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
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Online BrianHG

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #64 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.
« Last Edit: April 14, 2021, 10:26:36 am by BrianHG »
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Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #65 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.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Online BrianHG

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #66 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.
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Online oPossum

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #67 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).


 

Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #68 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. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline thm_w

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #69 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.
 

Online bdunham7

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #70 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. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #71 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.
« Last Edit: April 22, 2021, 01:49:00 am by EEVblog »
 
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Offline Robert Smith Eco Warrior

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #72 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  :-+
 

Online EEVblog

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #73 on: July 10, 2021, 12:03:19 pm »
After looking at the output of the new system in winter time, it's clear that we still don't have nearly a big enough system for our basic needs given the electric car and Mrs EEVblog working a lot from home now.
I expect more than enough in summer using what I have, but it probably doesn't leave much value for getting a battery storage system.

I'm quoting up more 370W panels but with the 366VA IQ7A microinverters, just so I can do a comparison with the 295W IQ7+.
I can fit an extra 7 panels in a 2x4 arrangement (moving one of the existing panels down).
They said they have to run an extra isolator box and cable, as this would max out the existing 4mm cable.

Here is a summary email from my Enphase system. This doesn't include my old 3kW which is barely getting 900W at best in winter on the east side of the roof.
« Last Edit: July 10, 2021, 12:05:51 pm by EEVblog »
 

Offline IanJ

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Re: EEVblog 1385 - 8kW Home Solar Power System EXPANSION
« Reply #74 on: July 10, 2021, 02:21:21 pm »
For comparison,

Location: NE Scotland
System = 4kW (16 x 270W panels)

June 2021 (Summer) = 601.219kWh generated

Ian.
« Last Edit: July 10, 2021, 02:47:06 pm by IanJ »
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