Options for powerwall / generator

Options for powerwall / generator

I know that some similar discussions have popped up over the years, but I don't see one that's on-point and contemporary.

So I want to think about what happens in an extended power-outage.. say, after a Hurricane.

I've got an 11.7kw solar system going in. This *mostly* covers day-to-day needs; but there will be days in the year where production < need. Let's just assume that there's no way to reliably run more than a day or two on solar+battery.

My houses averages ~3kw/hr (a bit below that); but it *can* spike as high as 15kw or so.

Option 1
The most basic option is to put in a 20kw generator and not use solar during a power outage. In that case, I don't need any battery. It's the most expensive (in terms fuel, though perhaps not overall), and there's the concern that, if LNG for the generator becomes unavailable I have nothing.

Option 2
I can add a single battery to the mix and attach it to my most critical stuff. I can *maybe* cycle the generator off manually for hours at a time (like overnight when not cooking) and conserve fuel as well as put my solar generation to good use. I cannot power everything on my battery, not even briefly, because the draw is too high; and I may not even be able to reliably power "important" stuff like the AC without investing in multiple batteries and pushing costs up farther.

Option 3
I can abandon the generator, get 2-3 batteries and live on an energy-starvation diet to last out the outage.

Option 4 (this is the one I'd like to find solutions for).
I can get 1-2 batteries. This gives me 10-14kw of power. I can attach a 5kw generator upstream from the batteries.

The idea is that the batteries would power the house until they got to some low point (say 10%), then the generator would kick on to take over powering the house and also recharge (to what extent it could) the batteries. If there was a short load above 5kw, the batteries would kick in (like the do when running on solar) to deal with it then go back to charging.

Some problems.

1) For some reason, the powerwalls don't take DC? I have to (with solar or generator) do DC->AC->DC->Store/retrieve->AC?!?
2) My rep is not aware of a way to wire in the generator to get the powerwall to treat it the same way it treats a panel (which is to say: charge from it if supply>demand, support it if demand>supply).
3) Actually setting up triggers for the generator so it's not a manual process.

Has anyone tried this? Any ideas?

cwied | 27 marzo 2018

There are at least a couple of people experimenting with ways of integrating a generator who post in this discussion:

JerryLove | 27 marzo 2018


I originally made this having not looked in the proper sub-forum. Once I found this one, I tried deleting but to no avail so I moved here. My topic is contemporaneously duplicated in part via other discussions. Whoops.

Off-grid_power | 6 agosto 2019

"In an extended power outage" -- the scenario you are addressing is known as "off-grid." The key phrase in your posting was this one: "My rep is not aware of a way to wire in the generator to get the powerwall to treat it the same way it treats a panel." which exposes the key question: Where is the "traffic cop" in this system, which receives AC inputs from PV inverters (such as SMA Sunny Boy 5000s) or generators sets and then powers a load center as well as charging the batteries themselves (the PW2)? SMA's Sunny Island asynchronous inverter, as one example, performed this function in past generations of off-grid systems. It even started up the generator automatically when the battery discharge reached a prescribed floor limit. Where is the technology in, or in concert with, the PW2 that will perform this function? Sadly, the stellar Sunny Island inverter is compatible with other Lithium batteries or BMS's ..... but NOT the Powerwall 2.