Solar panels and Inverters - AC or DC?

For shade considerations - you want to wire them so the series group (the 3s in my case) areshaded together - e.g. you want the panels in the series to get ALL the shade rather than each series getting a little bit of shade. When series (of 3 panels) are shaded - the voltage remains pretty much the same as the ones (series of 3 panels) in the sun, but the power (amps) drop significantly - so its perfectly find to combine these sets in parallel. For example, 1 set might be 110v@3a then 4a then 6a ... and the ones in the sun are 115v@30a then 35a then 40a ... and they combine very well because the 110v vs 115v is very little inefficiency - so things settle at (I don't know exactly) at 114v @ Xa where X is the addition of the amps.

Here's a pic showing the shade moving across one of myarrays from left to right- and as an example, the 2 x right hand panels (on array) + 3rd on (on the far gazebo) are wired as a 3s set because of shading pattern - e.g. they don't get full sun till mid morning (9:30-11:30am depending on time of year).



When I first started - I obsessed over wire distance / loss of power but 10awg wire is cheap and then 6awg when combined and I'm running 150ft lengths (from array to controller) and its just doesn't seem to be a big issue as the charge controllers report full/expected power for the panel ratings.

Its a fundamental decision to go DC or AC from roof - and will affect all equipment downstream. I don't see evidence that either is 'the single best way' - so it might just be whatever you are more interested in ?

You started off saying off-grid (as apposed to grid-tie). I don't have any experience with micro-inverters - butI do have 45 'traditional' panels running to combiner boxes - and I don't find it that hard to arrange them for sun/shade. They are in 3 sets of 3s5p (or 3s15p overall). They are 3s because of the charge controllers I chose.For shade considerations - you want to wire them so the series group (the 3s in my case) areshaded together - e.g. you want the panels in the series to get ALL the shade rather than each series getting a little bit of shade. When series (of 3 panels) are shaded - the voltage remains pretty much the same as the ones (series of 3 panels) in the sun, but the power (amps) drop significantly - so its perfectly find to combine these sets in parallel. For example, 1 set might be 110v@3a then 4a then 6a ... and the ones in the sun are 115v@30a then 35a then 40a ... and they combine very well because the 110v vs 115v is very little inefficiency - so things settle at (I don't know exactly) at 114v @ Xa where X is the addition of the amps.Here's a pic showing the shade moving across one of myarrays from left to right- and as an example, the 2 x right hand panels (on array) + 3rd on (on the far gazebo) are wired as a 3s set because of shading pattern - e.g. they don't get full sun till mid morning (9:30-11:30am depending on time of year).When I first started - I obsessed over wire distance / loss of power but 10awg wire is cheap and then 6awg when combined and I'm running 150ft lengths (from array to controller) and its just doesn't seem to be a big issue as the charge controllers report full/expected power for the panel ratings.Its a fundamental decision to go DC or AC from roof - and will affect all equipment downstream. I don't see evidence that either is 'the single best way' - so it might just be whatever you are more interested in ?

If you are looking for more details, kindly visit Micro AC coupled inverter.

Everybody wants to sell me Grid-Tied.  The latest proposal is the subject of this post.  The proposed system is for an "off-grid" system that involves ..... an approximately 4500W Array with GT500 Microinverters AC Coupled to a Magnum 4448PAE, a 14kw LifePo4 Battery System, autobacked up by a 3kw or 7kw Honda Generator that is retrofitted to be powered by propane, fed by a 1000+ Gallon Propane reservoir.  Any excess power capacity would be fed to a Dump (an unused water heater most likely).

I know that tech has come a long way.  I know that these sort of AC Coupled "off-grid" systems have come about largely because "Grid-Tied" system sellers have increasingly met resistance from customers that want to use the generated Solar for Emergency Backup power, and don't understand that when the grid goes down on a traditional grid tied system - so does your solar power.  So this has emerged as an increasingly promoted solution..... for TEMPORARY emergency backup into an offgrid situation in the event of grid power outage.

I have done a LOT of reading and research on this, and this is generally what I have found to be concerns, concerns that might also be greatly exacerbated if I were to use this configuration for a 100% Fulltime PERMANENT Off-Grid system.....

1. It's overly complex and therefore increases the odds of system failure (including battery damage to overcharge).
2. Not only is it complex, it can involve very complicated variable settings, some which may require ongoing tweeking depending on how I am using the system at any given time. (I will have greatly variable use cases - sometimes as a weekender, sometimes full time, and quite possibly as a long term emergency situation if the grid goes down for a lengthy period due to bad actors)
   
3. The added cost is not a justifiable ROI (I also have a full sun roof with no shade issues ever except stray clouds)

I'm a bit frustrated. I want a totally off-grid system. I want simple and reliable. I want an auto-backup generator. But I am not an electrician, nor an exceptional DIY guy that can do this stuff myself. So I have now run through almost every Solar Installer in the North Georgia Mountain area - and still can't manage to find anyone willing to put together what I (ME) the Customer wants.Everybody wants to sell me Grid-Tied. The latest proposal is the subject of this post.an approximately 4500W Array with GT500 Microinverters AC Coupled to a Magnum 4448PAE, a 14kw LifePo4 Battery System, autobacked up by a 3kw or 7kw Honda Generator that is retrofitted to be powered by propane, fed by a 1000+ Gallon Propane reservoir. Any excess power capacity would be fed to a Dump (an unused water heater most likely).I know that tech has come a long way. I know that these sort of AC Coupled "off-grid" systems have come about largely because "Grid-Tied" system sellers have increasingly met resistance from customers that want to use the generated Solar for Emergency Backup power, and don't understand that when the grid goes down on a traditional grid tied system - so does your solar power. So this has emerged as an increasingly promoted solution..... for TEMPORARY emergency backup into an offgrid situation in the event of grid power outage.I have done a LOT of reading and research on this, and this is generally what I have found to be concerns, concerns that might also be greatly exacerbated if I were to use this configuration for a 100% Fulltime PERMANENT Off-Grid system.....

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I think I know the answer to my own question here, but I am really getting worn down in this process, and want to throw this out to a hopefully impartial group of users for feedback.  What are everyone's thoughts on combining AC Coupled Microinverters into a 100% OffGrid system???

PS... also, any separate issues with using it with the LifePo4 batteries?

FYI: my primary goal is to have a solid and reliable system in event of SHTF scenarios.  There won't be any technicians coming to the rescue etc.

Thanks in advance.

- david h

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