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Houska
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# Posted: 29 Mar 2023 20:36
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We're in the exploratory stages of planning a 4 season off grid home to retire to, on the land where we now have our 3 season yurt.
Right now, we're just planning out space - what structures would go where. Does the following make sense?
Solar panels (demand not sized yet, but I expect 7-10 kW) will be ground mounted about 120' from the home. That's due to sun, plus ground mounting allows easier snow clearing (vs putting on home roof).
Seems the right battery technology to invest in now is LFP (safer and faster charge rate) over NMC. Lead acid has many disadvantages (discharge limits, off-gassing, etc.) other than lower cost.
Specificas to be sorted out later (and lots of great details on this board...) but now just checking this means battery/inverter room no longer needs to be in separate structure from living space for safety reasons, but probably makes sense to put them in a separate (heated above freezing) shed near the panels, rather than in the house, just since power losses and wiring over the 120' will be less for post-inverter AC than for 24 or 48V direct from the panels?
Do I have that right? We have all sorts of infrastructure/systems planning to do, of course, but now on an architectural design kick instead.
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gcrank1
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# Posted: 29 Mar 2023 22:37
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The voltage produced by the array(s) will define your wire gauge and length to the scc. 120' is a fair stretch but you might make it with the new-gen high output panels? It would be nice to have the scc, bats and inv in house.
The scc will need to be 'sized' for that input plus some overhead for cold weather voltage spikes and output voltage/amps for the battery bank. Given that you are talking 4 season home imo you need to be looking at 48volts.
The info provided by Steve_S previously on his build should be seriously considered. It works.
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Steve_S
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# Posted: 30 Mar 2023 10:11
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My personal suggestion is to build a Powerhouse as 120' long DC run will require serious wire (read copper $$$) trenching & more. Running AC 100' is easy unlike DC. Doing so with a well insulated structure that you can heat so it stays at 15C/60F over winter (at minimum 10C/50F) and this can be done cheaply & efficiently if planned at first. Because the structure is small (built for purpose) heating etc is quite simple... I use a propane RV Furnace (direct vent) from a 20' new (crashed) RV and it's perfect + cheap as snot!
Rules/Regs:
Depending on where you are there can be some ridiculous rules or really outdated ones... It's shockingly common and quite sad. Many of the rules will not allow for batteries within a habitable structure, others will not even allow inverters & such within. By using a powerhouse, that removes these issues and solves it. Extra Bonus as well "as such" should something go terribly wrong and a fire occurs, none of it would damage your home or array, being that the gear is separate.
My own powerhouse (14'L X 7'W) for example, it has a Frost Protected Slab Foundation with Radiant PEX within it as I will be using Solar Heating in tandem with the existing RV furnace. The building is also built with Thermally Broken walls (solid foam between studs & rafters, then a 1" layer of Foam on the exterior side and then the sheathing/wrap & finish) which is also a Huge Energy saver as it prevents thermal exchange which keeps the inside Cooler in summer (up to 40C/104F) and Warmer in winter when it is -30C/-22F outside.
A quick note on power-systems...
a General Rule is to NOT exceed pulling 250A from a Battery Bank. Of course this can be exceeded but that requires more planning & hardware.
12V @ 250A = 3000W
3000W÷120V=25A or 240V/12.5A
24V @ 250A = 6000W
6000W÷120V=50A or 240V/25A
48V@250A = 12,000W
12000W÷120V=100A or 240V/50A
* Values NOT corrected for losses / inneficiencies
BEWARE !
There is a HEAP of equipment out there from real crap to amazingly wonderful with everything in between. The marketing shmucks are also pretty wild & wooly. This is especially worse around AIO's (All In One) systems which incorporate the Solar Charger Controller, Inverter, Charger into one modular unit. There are several things at play with these... Running overhead tends to be higher, often you cannot disable "parts" like the Inverter so that only the SCC is left running (when away - PT res use) and quite often they require a LARGER ARRAY to accomplish the same task... Note that several of the Imported Asian have terrible MPPT (partial mppt) SCC's which are not so efficient. High End AIO's like those from Victron are far more efficient, manageable, stackable (expansion) and being Tier-1 & Certified the Inspectors like them. This of course comes at a cost...
Case in point, I run on 24V with 1300AH of LFP.
Solar Array 1: 8x260W (2080W) in 4S2P produces 200V and gives me 78A Charge via a Midnite Solar Classic-200 SCC
Solar Array 2: 6x395W (2370W) in 2S3P produces 150V and will provide 92A Charge via a Paralleled Midnite Classic-150 SCC
* Array 2 is being installed this spring
This can provide up to 170A Charge to my battery bank.
Some AIO's would require almost 600V DC to do similar and that also means a LOT more solar panels which adds up fast with racking etc...
IF I WAS BUILDING TODAY, I would go exclusively with Victron Component Gear, because it all works together is all fully manageable, configurable & monitorable + UL/CSA/ETL Certified. If properly planned this can be expanded over time as needed as Victron is very big on being compatible with all their gear. When I started my adventure into Offgrid Solar, Victron was not yet available in Canada...
Hope it helps & gives you a few more ideas & fills in some blanks. Good Luck
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Brettny
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# Posted: 30 Mar 2023 10:12
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There are charge controllers that can take 350v dc. I believe midnight classic is one of them. With a full time system and it being fairly big I would use at least doubles of things. 2 arrays and two charge controllers at minimum.
Lithium batteries need to be in a heated space so if it gets cold the best place to keep them is in your living space. How ever inverters and charge controllers can have fans that are loud and I wouldnt want in my living space.
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Houska
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# Posted: 31 Mar 2023 15:55 - Edited by: Houska
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Thanks all, esp @Steve_S whose other threads on his build I have flagged for a later read. For the moment, noting that a separate, heated cca 7x14 powerhouse (detail tbd), close to the panel arrays, then taking 120 VAC to the house, is a better default assumption. Then at house can have living space, garage, and utility room focused on the water/heating side of things (but just taking an AC power feed). Makes things quite a bit easier.
Hear loud and clear on watching carefully for exaggerated marketingspeak. Not interested in an all-in-one solution: I expect over the next few decades there will be considerable tech improvements in different areas, and different parts of the install will have different realistic time-to-replacement anyway. Want the flexibility (and resiliency) to fix and update different parts independently.
Fup question: I'm assuming 120VAC is good enough for residential applications, that stuff that commonly uses 240VAC (e.g. dryer, oven) is precisely the stuff it'll never be cost effective to run with off-grid electrical vs other energy sources (or patience) anyway?
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Steve_S
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# Posted: 1 Apr 2023 10:27
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I've mentioned this before but not in this thread. When I put my combo Pump/PowerHouse up, I placed it 50' from the house and ran 2X 4" Conduit underground to the house, 1 has the water line in it, the other with NMWU wires that can deliver 240/100A. Even though I run only 120V at present, I future proofed because as we all know things change.
I built my system in such a way that to switch from 120V to 240V involves swapping my inverter OR pairing it, to provide a 240V Split phase, and then a few small changes in the electrical panels and voila.
As for the cost effectiveness that really depends on A) the solar system you setup
B) your usage patterns and nasty habits too  We all got'em
A well designed & setup system can handle the loads it is designed for. You can start by building a robust 120VAC system "WITH" the advanced planning that you will upgrade it at some point. SO selecting Inverter/Charger that is Stackable and configurable to operate either in Single/Split Phase modes. A Solar Array which can also be increased in size by pre-planning for extra SCC's.
My system as an example, with the two controllers, a Midnite 200 & the Midnite 150 which takes 150VDC with 2370W of Panel (6x395W) provides my battery bank with 94A Charge. This of course is a Tier-1 product and not cheap, average sale $900. Similar to the higher end Victron Solar Controllers which can produce high amp charging with less panels as well. A Ground Mount solar array makes that a lot easier and if your "powerhouse" is close it that's best IMO. I would account for some kind of covered "generator shed" for a backup genny.
I do have to use the genny occasionally, this was the darkest winter in 80 years up here and I used it 7 or 8 times. It's a 4600W Inverter Generator and I only pull 120V/22.5A (2700W) via the L5:30 to charge my battery bank @ 24-27.5V/80A. I can be @ 20% & spend 8 hours charging it with generator to 100% and saturated which in turn provides me (with my usage) 10 days runtime on battery. Just as an example for our ponderings.
Regarding Victron.
They are indeed a quality company with excellent products, they are feature/function filled and do exactly as the label says. Their gear is also quite common and therefore readily available should you decide to add/upgrade at a later time and to stay "within the family". They also sell Victron Batteries but "holy macaroni sit down 1st"... There are several brands of batteries which ARE compatible with Victron equipment & software that are FAR less costly but still good quality.
Solar Panels & Racking
TBH, I am a firm believer in getting such from a reliable local vendor because if something is wrong, the fix is at hand... cracked panel etc... Also a heck of a lot easier later if adding more during an upgrade. Sure you can get cheaper online & ship it but there is trade-offs & risks... I am one who likes to know my panels are A Grade, not B or Blems or something I didn't ask for...
Hope it helps to pondering...
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travellerw
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# Posted: 1 Apr 2023 18:59
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Steve is %100 right about Victron! Excellent stuff and they support "tinkering" with whitepapers on most of their protocols. They even release the OS for the GX system that you can run on a Raspberry Pi.
If I was living on my system (again), it would be %100 Victron. For my cabin that I'm only at on weekends, I just couldn't swallow the price (and am a sucker for punishment). I ended up with a Growatt 3000 AIO. So far its doing everything I need, but it has high standby usage with the inverter on (50W). It drops to just 9W if you turn off the inverter (everything else keeps working including the WIFI module). Not a big deal as we will be wiring a switch in the cabin to turn off the inverter at night. For long term when we aren't at the cabin we are installing a Victron 375 inverter to just run our security and cameras. Even then, the cost savings are about 1/3 of full Victron gear.
Of course, that is if the Growatt actually lasts.
I really wished I could go LiFePO4, but I have no services to the cabin so heating the batteries is a deal breaker. The self heating batts draw too much power for my tastes and most do not support temps below -20C. So a good old oversized FLA bank for me!
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mj1angier
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# Posted: 3 Apr 2023 14:06
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I am a Victron fan boy too!! If/ when my no-name China charger/ inverter goes amps up, I will replace it with one of theirs to go with my solar controller
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redwolfguild
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# Posted: 4 Apr 2023 17:03
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This is an AMPs and Volts math problem easily solved. Your array is going to be large enough you can run the voltage needed to run it to the house. If you think about it, you put the battery by the panels you are only running 120 volts per conductor. If you run 150-200 volts from the panel to the house then convert it, much more efficient.
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travellerw
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# Posted: 4 Apr 2023 23:29 - Edited by: travellerw
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Quoting: redwolfguild If you run 150-200 volts from the panel to the house then convert it, much more efficient.
But harder to meet code.. Not to mention the safety factor. You need to be more careful with planning as 200VDC is definitely less safe than 120VAC. Not insurmountable, just more work and planning. Its one of the reasons why many residential based systems use micro inverters at the panels.
I have built both now and I have to say. I prefer the 120vac/220vac inverted over running DC. Everything just gets simple with a codebook that is easily accessible and inspectors that are comfortable with those codes. Sure, not as efficient, but a worthy trade off to me!
P.S. More efficient, yes.. Much more efficient, no! Ohms law can math this out over the distance. but 120VAC VS 200VDC is not going to be that big and can be easily compensated for with a bump in wire size!
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redwolfguild
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# Posted: 5 Apr 2023 11:32
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Sometimes doing it right cost more! Has more loss. You got to do what works for you.
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travellerw
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# Posted: 5 Apr 2023 22:15
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Hhhmmm.. I wasn't going to comment, but your last post really needed some clarification for future readers.
It was clear that you were implying running DC is more "right". That is simply not true. AC or DC each have their trade offs and neither is "right" or "wrong".
If you are doing a project like this, please do your research..but most importantly follow local codes in your area. Although inspectors seem mean, the reality is they don't want to fail you. MANY want you to call before you do your project to help and ensure you do pass!
There are at least 3 posters in this thread that have lived on solar for years.... and while I respect their advice (I'm one of those 3), I would not take it as gospel. Things are different everywhere and its important to follow the local codes (even if you have no intention of getting inspected). Not all codes make sense, but checks and balances ensure that codes are the safest way to build things! Efficiencies is just one factor.
For the OP or anyone else reading this, please spend the time and make sure you are building something safe (not just efficient!)
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gcrank1
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# Posted: 5 Apr 2023 22:23
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And there is a big diff between a 'spartan, basic' 12 or 24 volt setup and larger 'whole house' (and shed/shop, etc) higher voltage setup. The later is not only better done at code, but probably required, especially by one's insurance company.
Even the former should be done using 'best practices' (though often is not....) and then may not meet code but is at least done well.
All that to say that compromises should not be on the safety side. Often folks dont know what they dont know.
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redwolfguild
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# Posted: 7 Apr 2023 19:17
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I agree with all of you, and consulting your local Electrician should always be part of the planning process. Sometimes I assume that everyone knows that - Sorry if I ruffled some feathers.
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neckless
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# Posted: 17 Apr 2023 11:40
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seems to me uall are off topic lol..... where to put batterys .....me since i live in the far north, going to build a root seller and put them there so the - 40 is not a issue when not there
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gcrank1
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# Posted: 17 Apr 2023 11:51
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Off topic?, no...
OP's post says 'in the exploratory stages of planning' so all these considerations are pertinent.
But if you are wanting/needing a root cellar anyway that sounds like a good idea 
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NorthRick
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# Posted: 18 Apr 2023 17:29
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Quoting: neckless me since i live in the far north, going to build a root seller and put them there so the - 40 is not a issue when not there
If you are really far north you might have an issue with permafrost. The other consideration with a root cellar is humidity. High humidity can be heck on electronics.
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