What to do after 5pm til dawn?

[road glide]

Putting this out there for comments.........
From 5pm til dawn obviously no production.....AC battery backup??? 5kw SMA sunny boy....with 20 - 320w Jinko panels...6400 max (actual NOCT 225-250)
Usage would be heavy in Summer with A/C going til 9-10pm....
Sunny Island is a thought....Magnum? Schneider reviews are iffy

 

[svetz]

Presumably you're grid-tied since you're asking in the GT section... so, let the grid be your battery with a net-meter agreement.

 

[road glide]

I should have been clearer....we have many fires....and grid was down a few days this past Sunday, Monday and restored Tues nite....if this keeps up we will look harder at a backup system....
Just doing some homework...Solar Queen has a video on this subject (AC/DC coupling)....
Sunny Island would be my first choice in that it is an easier install and from what I've read is able to generate 60 cycles frequency to the Sunny Boy which could restore the battery bank if conditions are met.
I understand and agree an AC coupled system is not feasible $$ for one or two outages a year. (we have a LP/Gas 8k Generator if you're wondering for these short durations)..

 

[svetz]

You're on the right track! AC or DC coupling is what most with a system already installed do for battery backup. If your inverter is old/at end-of-life, another option would be to swap it with a hybrid like Sol-Arc and sell the old one on eBay. There's a lot of tech on Coupling and hybrids on the internet, but if you have questions we're here to help.

You might also look at the Tesla Powerwall, as batteries go they're one of the lowest non-DIY costs and they work with SMA inverters.

Although, batteries are expensive... if you have natural gas in your area (and they don't shut it off for natural disasters) a generator might be a better option (no fuel hauling with natural gas) until the price of batteries comes down more.

 

[Jmac786]

How much are you at your residence during the day? Could you blast the air conditioner during your PV collection hours so that the home is on the cold side and then slowly rises in the evening. It “might” make sense in your case depending on net metering availability and a bunch of other variables with your situation.

 

[Hedges]

Because you have Sunny Boy, Sunny Island is exactly what you want.
Alternative, Sunny Boy Storage.

Either of those will AC couple with your Sunny Boy and control its output to match loads and battery charging needs during grid outages. Changing a parameter in the inverter may be required to enable this function, but I think the new models recognize the battery inverter. Just need a data cable, possible add-on card for the interface.

For Sunny Island, either buy two SI6048 and connect for split-phase 120/240V,
or buy one Sunny Island and get a transformer. That could be a 6000VA isolation transformer, 120V to 120/240V, or a 3000VA 120/240V auto-transformer (two 120V windings connected in series.)
Each Sunny Island can pass up to 56A through its relays.

Connect:

Main panel <--> 2x SI6048 <--> PV breaker panel <--> "load shed" relay --> protected loads panel --> your circuits (refrigerator, computer, etc.)
Also, PV breaker panel <-- Sunny Boy

The "load shed relay" is a 48VDC coil, 2PST relay good for at least 50A, preferably 100A.
In the event battery gets run down to low voltage disconnect (70% DoD for my AGM batteries), loads are disconnected to prevent further discharge. Sunny Boy still gets AC so it can work when power comes up.

You can connect up to 4 Sunny Island, 2S2P, providing up to 23 kW continuous from battery, up to 44 kW surge to start motors, up to 112A 120/240V passed through from grid.
Supported 48V batteries are NiCD, FLA, VRLA, certain brands lithium with BMS that talks the right protocol. Some people here use DIY lithium; there is a BMS which works. From 100Ah up to 10,000 Ah, 5 kWh to 500 kWh.


Your other choice from SMA is Sunny Boy Storage.
It uses 400V lithium batteries of certain brands. I think about 4 kWh up to about 60 kWh are available.
An automatic transfer switch "Automatic Backup Unit" is required for off-grid backup operation. Otherwise, it is just an "AC battery", shifting time of use but shutting down during grid failure.

 

[svetz]

So, lot's of options! Please keep us in the loop!

 

[Trukinbear]

IMHO the Tesla Powerwall is a toy for rich people who want to think that they are acting green - the payback period for most situations is never. We're quite frugal with power living off the grid, but a single powerwall wouldn't get us thru a cold night, and would be totally recharged the next day by our 6Kw PV array by noon and would just be wasting the rest of the power made the rest of the day - I'd need three or four, and I believe by definition if I could afford three or four Tesla Powerwalls I'd be rich, not someone too poor to have a grid connection. Flooded Lead-acid will be the standard for many years to come - unless you are solar for some reason other than economics, and are rich. But I digress...

 

[svetz]

...- the payback period for most ...[energy storage] ... is never....

Energy storage doesn't typically have a positive payback period; but sometimes you don't have a choice (e.g., off-grid, or as in the case of the OP an unreliable grid). If you want LFP and don't want to DIY, the Tesla powerwall is 13.5 usable kWh and certainly isn't what I'd call a toy. It's worth considering as the price points ($7k for 13.5 kWh) is about half of something like a Kilovault ($1k for 1.2 kWh).

...Flooded Lead-acid will be the standard for many years to come - unless you are solar for some reason other than economics, and are rich.

In regards to FLA Vs. LiFePO4.... if you look at it as $/Ah, yes FLA wins. But, if you consider $/Ah/life-cycles... then it's not always so clear. Detailed math in the Battery FAQ.

 

[Trukinbear]

In 2019, the average annual electricity consumption for a U.S. residential utility customer was 10,649 kilowatthours (kWh), an average of about 877 kWh per month. That works out to just shy of 30KwH per day... most days won't be the average day, some will be less, some will be much more. I contend that 13KwH is little more than a toy as far as the average household consumer in the USA is concerned. My FLA is guaranteed to be at 80% in 10 years - I cycle maybe twice a day, so that's what 7300 cycles? If I was 20 (and I never ever ever wanted to move) and had that chunk of change in my pocket burning a hole in it, then you might be right LiFePO4 might eventually work out - but I'm old, poor, and fighting cancer - FLA wins hands down. True, I can never use every one of those 48.4KwH my $4995 bought me... but I sure can use more than 13!

 

[Trukinbear]

IDK, even if my battery was at like 50% in 20 years, that is still more than 13KwH... Ohhh, and I bet if you treated my 986Ah battery like it was the Tesla Powerwall and never withdrew more than 14KwH that it would last nearly forever!

Being fair the money for a Tesla Powerwall would buy a 1608Ah 48V industrial battery - I'd bet at the 14KwH limit imposed by $7000 of Tesla Powerwall that it would last just as long. I wish I was going to live long enough to prove that.

 

[Hedges]

Once you size a battery for 3 days without sunshine, your normal cycle is so shallow that lead-acid has a long enough life.
If you cycle it to 80% DoD every day, then the longer life of lithium may get used, so the higher cost is worth it.
With shallow cycle (16% DoD for a typical night), how long with lithium last? (assuming no mistakes, ever)
I'd rather wear the battery out in 5 or 10 years, get my money's worth sooner, instead of paying up front for a 20 to 30 year battery.
But, lithium is coming down to the same purchase price, which certainly changes the equation.
Just as PV has come down to where it is cheaper than fossil fuel, and cheaper than other power plants. (Can't replace them today, but certainly a competitive part of the mix.)

 

[Trukinbear]

I know, I'm just jealous I can't spend $28,000 for just batteries - I could have probably bribed the awficcials <sic> sufficiently to let me have my power connection back with that kinda change.

 

[Trukinbear]

Energy storage doesn't typically have a positive payback period;

I wholeheartedly disagree - when we found ourselves suddenly off the grid and living on a diesel generator running 24/7 - when we added the storage battery and inverter(s) our payback in reduced diesel fuel (at nearly $4/gal), maintenance costs and replacement cost factored in - the battery paid for itself in less than three years. We went from running the generator 24/7 to three hours every other day... you can see it is simple math.

 

[road glide]

How much are you at your residence during the day? Could you blast the air conditioner during your PV collection hours so that the home is on the cold side and then slowly rises in the evening. It “might” make sense in your case depending on net metering availability and a bunch of other variables with your situation.

We are retired so home most all day and inherited 2 grandsons both working thank God....but the usage is up from our original design.
That is why I was wondering if after the sun goes down and the Sunny Boy takes a nap...does the Sunny Island take over via the battery bank....
We have an energy analysis and we don't use much usage however I see usage from 5-6 till midnite....which I would like to reduce with more folks here.
That being said a Sunny Island and battery backup to accommodate the night time KW's would be pretty darn expensive.
Youngest grandson offered to catch some squirrels and put them on a wheel to generate more electricity at night....LOL

 

[Trukinbear]

Your generator would probably be your safest, and cheapest bet as long as your outages are few, and not of very great duration. A Sunny Island and battery system would seem to be an expensive option, I agree. We've graduated our way thru a dozen generators since we were forced off the grid, eventually settling on a pair of diesels. For backup LPG is the way to go! Can be stored for nearly ever, doesn't go bad, is cheap(ish), and can usually be delivered on-site. Plus storing large amounts of LPG doesn't require any permits, usually.

 

[Hedges]

Yes, Sunny Island would power the house with batteries at night. How many kWh do you estimate you would use in one night?
These days you can set up a pair of Sunny Island for 120/240V for about $5000 (Assuming you install them yourself.)
I spent more running rigid conduit and installed a lot of breaker boxes, but it can be kept simpler. Initially my Sunny Island was fed from the breaker panel, and backfed it with an interlocked breaker. So manual transfer switch after a power failure. I've since made it more automatic and expensive.

 

[road glide]

Yes, Sunny Island would power the house with batteries at night. How many kWh do you estimate you would use in one night?
These days you can set up a pair of Sunny Island for 120/240V for about $5000 (Assuming you install them yourself.)
I spent more running rigid conduit and installed a lot of breaker boxes, but it can be kept simpler. Initially my Sunny Island was fed from the breaker panel, and backfed it with an interlocked breaker. So manual transfer switch after a power failure. I've since made it more automatic and expensive.

I've been watching our meter (smart landis) very closely lately...I actually wonder if we are getting cheated....
I read it every morning and capture the #'s....We are getting hit overnight with around 10KWh...fridge is 785 watts and freezer is 350 watts. So I guess this is normal.. Just seems excessive.
From what I have viewed on the forums and google, amazon has lots of reviews and comments we are looking at lotsa $$ for backup...Right now grid tie is fine but where does it go from here. Rates per KWH will continue to rise. And now PG&E is moving peak time into the evenings starting next March...LOL (Everytime you try to get ahead the Uncle Sam, they pull the rug out)
PG &E is getting hammered by daytime production and no way to store it.. Selling to other states or paying other states to take the excess?
With fires year after year, and California moving to control PG&E or even take it over...Want to be proactive not reactive...
I want to be an optimist but wow ...what a mess coming our way...

 

[road glide]

Yes, Sunny Island would power the house with batteries at night. How many kWh do you estimate you would use in one night?
These days you can set up a pair of Sunny Island for 120/240V for about $5000 (Assuming you install them yourself.)
I spent more running rigid conduit and installed a lot of breaker boxes, but it can be kept simpler. Initially my Sunny Island was fed from the breaker panel, and backfed it with an interlocked breaker. So manual transfer switch after a power failure. I've since made it more automatic and expensive.

I would do one to get the 120 possibly 240 later or transformer....but how many Chevy volt batteries would I have to buy?...LOL

 

[Hedges]

785 watts and 350 watts includes heater for defroster, possibly ice maker. That would be 1100W and 10kW in 9 hours only if running constantly.
Try unplugging them for the night.

I'm trying to see if you can get under 3.5 kW from sundown to sunup. If so, 100 Ah 48V for $1200 (AGM) or less (golf cart) would take care of it.

I briefly saw a couple Sunny Island on eBay for $1200, now back to $2200.
I saw some bare toroid transformers between $250 and $500 which would work, but at the lower price Sunny Island I would buy two.

You do need a 240V solution for the Sunny Boy to work with Sunny Island and charge the battery.

Oh, 5 kW Sunny Boy into 240V is nominally 20A, uses at least 25A breaker.
Through a 240/120 transformer and single Sunny Island, it feeds one phase with nominally 40A, needs at least 50A breaker.
That may exceed what your code allows (40A PV breaker on panel with 200A main breaker and 200 A busbar.)
My panel happens to have 225A busbar so I'm allowed a 70A PV breaker. (not that I'm worried, if the PV breaker is at far end of busbar.)
Two Sunny Island for two relays on 120/240V avoids that.