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?
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.
high voltage DC you now need to bring high voltage AC to the roof running at higher currents as well.
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.
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?
Why is it very different and when does it matter?
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.
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.
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.
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.
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
I'm no expert on the subject, but (there is always a but) it seems to me that the system is correctly spec'd.
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?
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.
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.
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.
BTW, I recall looking at measured insolation data at one point and I saw over 1000W/sqm in Sydney.
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.
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".
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.
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.