System planning questions, first foray into solar addition

[pngaudioguy]

I've been reading for awhile now on this forum and other places trying to learn what I need to know for my upcoming project. Realistically, timeline is probably not until about a year from now. Timeline isn't super critical, so if budget requirements mean pushing the timeline back, that's ok too. I'd rather spend the money and do it right once and enjoy the benefits for 10+ years.

I'm planning to get the equipment, get it mounted, do low voltage wiring, then hire an electrician for tie in.

Project phases by importance if I have to spread it out:

1. Battery backup and inverter/charger
2. Solar panels
3. Generator

I have been watching my Sense energy monitor for the last year, and my heaviest use is the electric dryer. We average right around 900kWh per month, which is roughly 30kWh per day. With 6 mini-splits running on a 90 degree day and no dryer, usage floats 1-2.5kW with overnight down around 400-600W. I know that running the dryer will be a grid required function, at this point I have no plans of going completely off grid. That gives me a baseline of what to expect usage-wise daily.

I'm thinking that the LF280K type battery will be my storage, with a 48V target (16 cells). I understand they actually run around 51V, for about 14kWh of stored juice: ~4+ hours of backup of typical load. I'm pretty sure I want to use the Batrium BMS K9 system for management.

I can fit 10 of the REC Pure-RX 470 panels on the one roof surface I can use for solar, which would generate about 4kWh for the 4 or so hours of full sun that surface gets here in Northern MA.

Things I'm trying to decide on:
Inverter (Schneider XW Pro, Outback Radian, other?)

1. Needs to be able to send loads to my panel and the grid when solar output is greater than load during the day.
2. Either directly or through external MPPT need to charge batteries as well.
3. Would like to not have outage that requires setting clocks on microwave etc when grid drops - is the 50-100ms changeover on the Schneider units enough to drop the clock? Is there a better answer?
4. At night, as long as the batteries are above the discharge threshold, I'd like the system to power the house from the battery when possible, then recharge the next morning prioritizing solar, then grid if not back to 80-90% SOC by late afternoon. Otherwise, maintain charge and power the house from the grid. (Night power usage typically floats around 500W, so assuming 80% DoD that's easily more than 12 hours runtime.)
5. Eventually, I'd like to add a generator for battery charging when the sun and grid are both gone - we have winter storms and random outages and I don't want to be worrying about that when I'm older.

MPPT
Do I need a separate MPPT, or can I use the function from the inverter if I'm using a BMS like Batrium? I feel like it would depend whether I go with micro-inverters at each panel, or a string inverter.

Grid cutoff
What provides the full grid disconnect for safety when the grid is out while still powering the house from battery/solar/generator? I know Schneider makes a BCS, would I need something like that as well?

Will be mostly installed in the semi-finished side of the basement with dry walls and sealed concrete floor. Have wall space on the outside next to the main meter for the house as well, which is where the pad for the generator will eventually go.

I'm definitely interested in cost effective ways of doing the whole system, but don't want to cut corners so I'm looking forward to any and all suggestions for well known vendors, equipment combinations, etc. Thanks in advance!

 

[DIYrich]

Cost effective: eg4 18kpv, sol-ark 15k, or

New Growatt hybrid inverter SPH10000TL- HU-US split phase

Anyone have any info on this? 105lbs!!!

diysolarforum.com

18kpv and 15k have built in grid isolation for auto disconnect from grid (4ms for 15k, so no clock problem). Don't know about the growatt.

Outback is great, but expensive.

 

[pngaudioguy]

I like the form factor, features and price on that, but reviews for Growatt trend more negative than positive, though that's probably in part due to more people with complaints posting about things than those with no issues. A coworker just had one of those installed, so I'll see how his experience goes over this year as well.

I'll have to read more on the EG4 and Sol-ark. The latter in particular I've seen good reviews of but haven't fully investigated their products. I definitely don't want to be tied into manufacturer batteries only which I know some of them are.

Edit: Have been reading more this morning - both look quite capable but interesting that you're calling the Outback expensive but not the Sol-Ark. Looks to me like pricewise goes Growatt -> EG4 -> Outback -> Sol-Ark (Once MPPT's added Outback probably = to Sol-Ark). That said, price is not the main importance to me, features, stability and support are. I've read many things recommending low frequency vs high frequency for whole house - I do like that the EG4 and Sol-Ark appear to be all in one with MPPT's and everything, though that does create a single point of failure as well. I like that the EG4 and Sol-Ark specify 200A AC passthrough for the grid side - I do have an electric brewing rig that I don't ever anticipate trying to power on solar that pulls a good chunk of juice when I fire it up...

 

[pngaudioguy]

Additional thoughts after reading some of the battery fire threads: if I have to put the cells in the basement, what's the best way to completely contain them? Should I plan on building a buried enclosure for them outside instead?

 

[DIYrich]

Edit: Have been reading more this morning - both look quite capable but interesting that you're calling the Outback expensive but not the Sol-Ark. Looks to me like pricewise goes Growatt -> EG4 -> Outback -> Sol-Ark (Once MPPT's added Outback probably = to Sol-Ark). That said, price is not the main importance to me, features, stability and support are.

Sol-ark 25k is $7,000. Outback Radian 8kw GS8048A-AC system is $6,300. Add another 4kw for $2,700 to match the 15k output. $3,300 for 3 flexmax 100 charge controllers to match the 15k.

Don't know if the Outback can pass through grid, and transfer switch ($700?).

If you want stability, Outback is #1, and sol-ark #2. Eg4 18kpv has some growing pains (thread on 400v problem).

 

[DIYrich]

Additional thoughts after reading some of the battery fire threads: if I have to put the cells in the basement, what's the best way to completely contain them? Should I plan on building a buried enclosure for them outside instead?

Ignore the floor part:

Design for "ultimate" "fire-proof" 274kWh+ battery shed

I have been lurking on these forums (especially in the up-in-smoke and LifePO4 DIY forums) and been learning a lot and thinking about a design for an unconventional battery shed that will probably stir up a lot of controversy but I have specific design requirements that I will outline and would...

diysolarforum.com

 

[DIYrich]

I think with Growatt you have to know what you are buying. It is a basic system without some of the features of the 18kpv and 15k. Which is fine for off grid (where they started).

Off grid, pv supplies load, then charges battery. Battery supplements pv.
Turn on generator when battery gets low.

Doesn’t get any more basic than that. When you have the grid, more options are available, and your combination #27 may not be easily implemented.

 

[pngaudioguy]

Thanks for the continued thoughts. I'm leaning towards the Sol-Ark, though I really only need 8kW continuous with 12kW surge would be adequate - the Outback doesn't have a grid passthrough spec, lists 50A 240V as max AC input.

I'd love to have a detached battery shed, but 15 feet away from the house is my neighbor's property, except towards the back which would put it too close to one of their garages, unless I attach it to my existing tool shed. I'd rather a catastrophic failure take out garden tools than my house I guess. Then there's the matter of trenching the cables back to the house, but that may be ultimately the best option - lots to learn about where to put the inverter and how to get wires to/from batteries, panel, and house if I go that route.

The batteries below false floor may be what that one individual wants, but that's definitely not for me. I want them at serviceable height if at all possible!