New off grid setup advice

TMMILAS

Hello all,
I am going to be using a offgrid setup and really would like advice on my setup
I am running 22 x 24v 300w ReneSola panels- 
Enphase Micro Inverters m250
Magnum ms4024PAE inverter/charger with ME-RTR
8 Full river DC400-6v
Junction box
Magnum Diversion ACLD-40
Enphase Router

I would love to run a 48v setup but not sure if thats possible with Micro Inverters

Because of the limited information available about Off-grid applications using Micro-inverters, I thought I would go to the pros and see if I can stir up some conversation.
1st question is- should I run the panels in 3 strings of 7 or 2 strings of 11?
I am working on adding a generator starter but havent done to much research in that area.
Is there anything important that I am missing??
Is there any links to information that might be useful? I am using a ground mounted system, elevation is 7700ft with high Snow in winter, temps range between 0-85 degrees. Great south facing lot with tons of sun in the Tahoe mountains. PGE is not an option so no grid tie

Any input would be great.


 

Estragon

My understanding of microinverters is that one goes on each panel, not a serial string like off-grid inverters, and they need an AC source to sync to. Off-grid, we obviously have no grid AC to reference.

There may be ways of using them off-grid by creating the AC reference, but they're really meant for grid-tie AFAIK.

Estragon

For the balance of the system you should generally start with loads and design from there.

At that elevation you should see good production, but with ground mounting and lots of snow you will want to take snow into consideration. You might want to build a sort of crib mount or something to raise the array racking up. Adjustable tilt helps too.

Photowhit

TMMILAS said:
Because of the limited information available about Off-grid applications using Micro-inverters, I thought I would go to

Micro-inverters produce AC current and need an AC source to sync with our they, by design, will not produce current. This is so they won't back feed the grid and create a dangerous situation. Since they don't produce DC current needed to charge a battery, nor can they be the sol source of energy to use an inverter/charger to charge with DC. I don't think it is reasonable to try this method.

Likely, if the panels are already in place, it would be easiest to bypass the micro inverters and wire the panels to a charge controller to charge batteries and the batteries to an inverter to provide power. If these were once hooked up to the grid and there is a dispute, it might be cheaper and more reasonable to settle the dispute.

BB.

There is a way to use the Micro Inverters + Off Grid. You need a pure sine wave AC inverter designed to be "back feed" with GT inverters--And it needs to be larger than the GT inverter output (i.e., if the GT inverter string can output 2,000 Watts, then the OG inverter need to be >2,000 Watts).

Basically, a typical high end Off Grid inverter is actually "bi-directional" regaurding power transfer. Raise the AC voltage on the 240 VAC output, and the energy starts flowing backwards through the inverter and it will recharge the battery bank.

A decade ago, when this was done, there was no off the shelf inverters that would regulate the battery bank voltage. The GT+OG inverter would overcharge the battery bank (possibly to destruction). The installer would have to install a dump controller+load on the battery bank and/or a voltage monitor that would open a relay to the GT inverter(s) to cut power until the battery was discharged enough to recharge again.

Today, there are Off Grid inverters that can vary the 60 Hz line frequency +/- a couple of Hz. The GT inverter sees this as a frequency violation and shuts down for 5 minutes before attempting to reconnect.

There are setups from SMA (Sunny Island) that have more precise integration between the GT and OG inverters (variable frequency gives variable output power from GT inverter)--But that is another story (you do not have SMA GT inverters).

Can you do it--Yea. Is it a good idea? Probably a bit over complex, but Schneider and Magnum (and others?) do have inverters that are "GT off grid" capable.

-Bill

Estragon

I thought this was something OP was thinking about doing, but rereading the post, maybe already has it? If so, wouldn't just getting a couple of charge controllers be cheaper and simpler?

Dave Angelini

Estragon said:

I thought this was something OP was thinking about doing, but rereading the post, maybe already has it? If so, wouldn't just getting a couple of charge controllers be cheaper and simpler?

Add on to your list better, as having electronics out in the sun is just a bad choice for Offgrid and the whole concept of Offgrid.
If he does do/have Micro inverters, add on the List Outback as well as Schneider for GT capable hybrid inverters.