delusional beginner looking for validation, off-grid setup

luckydraw

New Member
Joined
Dec 29, 2021
Messages
7
Happy holidays everyone. I found this forum from Will's excellent youtube videos. I am currently in the stage where I think I can wire an entire off-grid setup myself, and I'd like to ask all these questions while I'm still "delusional"


Jokes aside, I believe am capable, but have never done any projects like this before, however, have good basic electrical understanding.

Here's my setup. I have a main house which receives company from the grid, 100A.

Then I have a cabin in a hard to reach location on the property, behind a creek. After some research, I thought it might be possible to upgrade to 200A on the house, then run 2AWG URD underground cable (aluminum) for 100A from the breaker to the panel on the cabin.

Anyway, this is a solar forum so I'll get back to that : ) Either way, if I have cable running from main house to cabin or not, I still want a functioning off-grid system at the cabin.

I've calculated I have roof space at the cabin for about 3000W of solar panels.

At the cabin I need to be able to run:
- 1 HP well pump
- small tankless water heater (will have to get model #)
- small refrigerator (300W)
- induction stovetop (1200W?)
- under tile radiant heat mats (this is about 12W/ sq ft. So in the needed ~ 100 sq ft of heated floor space, 1200W or more). I can live without these if it pulls too much
- use of electronics/laptops/chargers ~ 500W

I do have the possibility to run some things off propane but I'd prefer to keep everything electric. The cabin will be heated by wood stove.



After a lot of research I still have a few questions:
- I have a small "utility" room where the well water pumps to, but it is not insulated. Does it need to be fully insulated? Can I modify this room so that I can run all the equipment there? (batteries, inverter, etc.). This is northeast US so the in winter can get into the teens. I understanding the issue is on the charging side at under freezing temperatures. I see that the BMS systems can come with low temperature sensors for cutoffs
- Purchasing batteries vs building your own, is it worth it? Seems very promising to save the $ and build your own if you're willing to take the time for it
- Is it possible to hook up a water turbine to the inverter in addition to the Solar PV array (not a deal breaker, but I would really like to be able to do this as I have a flowing creek on property)
- 120V split phase possibilities?



The possibilities:

1) All in one solutions
- At first I researched the Ecoflow Delta Pro and Mango Union Power. These were all in one solutions including inverters, BMS, breakers, etc. and considering all that, the price does seem reasonable.

To use in my circumstance, powering the whole panel, I would need to get their top package:

Mango Power Union x 2 + mPanel (https://www.indiegogo.com/projects/mango-power-super-capacity-home-backup-battery)

That is $7700 for 13.8kWH from batteries and 3800W from each inverter . Up to 4000W w/ MPPT from solar panels

The Delta Pro x 2 + panel would be similar cost and specs.

The issues I see with both of these is that I don't really need any of the features as I don't really need constant access to the battery. I just want it hooked up to my panel and be able to withstand the climate of the utility room.


2) Custom solutions

battery options

EG4 48v 100AH 5.1KWH (also have a waterproof version)

OR

build my own battery, add BMS and temp sensor cutoffs


inverter options (include BMS or support BMS input, MPPT solar inputs)

2 x Growatt 5kw w/ split phase transformer

1 x Growatt 8kw

2 x LV6548 in split phase configuration

1 x 16,000W low frequency inverter (ebay) w/ split phase
- maybe I'm crazy but this seems like an enormous deal



Final thoughts:
- what size battery capacity is enough for my needs, is 5KWH, 10, 15?
- what size should my inverter be in relation to my battery capacity
- things like the well pump will pound the inverter when turning on. I don't know how long this "surge" lasts. What does that mean for me, and do I need a frequency inverter absolutely?
- if I want to keep the inverters balanced (under load) with split phase, then perhaps the growatt separate transformer is best?
- I want to be able to bring 240V to my cabin's breaker panel, and then have some breakers @120V, and some @240V. I'll have to double check my appliances, maybe everything runs fine @ 120V but I am worried about the surge amperage at 120V



Thanks for bearing with me here. Appreciate anyones thoughts/input/advice or if there is a completely different solution for my needs, I'm open to hear that please!
 

Rednecktek

Photon Sorcerer
Joined
Sep 8, 2021
Messages
1,838
Location
On a boat usually.
Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the Uber-Sun-Hours calculator site to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later. The water heater, induction stove, and radiant heating are going to KILL your system. Good thing you're looking at $$stupid money right up front for this plan.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.
 
Last edited:

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
946
Location
Mallorca ES
Now, RNT explained it very well :·)
I'll just add my personal takes...
Personally, when working out a system, the way I'd go about it, first you try to estimate how much energy you're likely to use in 24h.
It never works, but at least it gives you an idea what ballpark you're in. :·)
Then you plan the battery(s). It's the core of the system, the really expensive part, the one that will give you the most joy or grief.
Then you try and work out how much you'd sensibly need to keep it charged. Panels, you can always add, and they're a lot cheaper than batteries - which you can always add, but it's not as simple to do. Charge controllers, you can also add, and it is quite simple.

Then you guesstimate the inverter. Then you multiply by (at least) five your estimate. Inverters can be added, but only if they have parallel operation capability. After the battery, it's your most important purchase. If you can find a good quality used one - not easy but possible - resale value in the event of second thoughts can be good.

Now, the creek. OK, charging is the easy part, panels nowadays are reasonably efficient and cheap, if you have the space, they're probably good enough. But the creek... hydro is the Holy Grail of renewable energy. It runs 24/7, once you set it up, maintenance boils down to... changing a few bearings every few years? If you can have at least 30 metres (90') of "head" (drop), it will give you 3 bars of water pressure.
A couple of micro-turbines on that, it buffers the system out so much that the batteries can be smaller, the panels can be less, consecutive cloudy days become a minor annoyance, unless you're planning to run AC units, electric cookers, and the like, the creek will make you whole :·)
 

luckydraw

New Member
Joined
Dec 29, 2021
Messages
7
@Don B. Cilly @Rednecktek thanks very much for your responses.

Ok, as for estimating, I can do that but I have no real comparison for this as it's a new setup. By my basic calculations, it seems that the biggest issue really is the WELL PUMP. That thing uses a massive amount of startup surge power.

Thats why I was wondering if anyone had any particular experience with the inverters I listed. Again, the one on ebay is tempting for the $ but I have no idea about the company! From my research it does seem like I need a low frequency inverter, so I can support big surges on appliance startups.


Another consideration is the well pump – maybe instead of a 1HP 240VAC pump, I can just get away with a 12VDC pump. It's a spring well not a deep well so I don't need a lot of power. If I run it DC off a dedicated battery and/or 200W solar panel, I figure I can have much more room to wiggle on the inverter specs.


Furthermore, unless I'm just using a 2 burner induction stovetop (which may be fine), I could also just go with a gas stove and put a 100lb. propane tank outside. I'm guessing with light use that would last several months minimum. If I put in an induction range, those can pull an enormous amount of watts if using multiple burners (10k or more)


I did some calculations, being very conservative on usage, and actually came out to much more power than I was expecting, even if I don't consider the well pump:
Screen Shot 2021-12-30 at 11.03.20 PM.png

Some of this stuff is seasonal, but still. This looks to me like it means, even if I have an inverter with enough to handle the starting surges of the appliances with motors, I'd still need between 20-30KWH of capacity to run everything for 1 day on the battery??

That seems like so much, unless I am doing something wrong here. To put it in perspective, this is about a 600 sq ft. cabin.


Of course this is all assuming absolutely no charge is incoming from the solar PV array. For that I would like to do at least 8x 455W panels. I like the Growatt inverter because it takes up to 450VDC input on the solar PV array. With each 455W panel open voltage at 49V, that means I could get 8 panels going to the one inverter.

The water turbine would be minimal. I have a nice flow on the creek but there isn't a lot of drop. If I did anything there it would need to be a run-of-river type setup. I'm not sure how much Watts I could generate - of course anything is better than nothing, 24/7 energy is great. I also don't want to put anything too large there to disturb the natural setting.
 

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
946
Location
Mallorca ES
Let's see.
- The pump. A 12/24V DC one should do just fine. I have one, 24V, uses some 600W, and runs... maybe 20 minutes in the day?

- The fridge. I have a decent one, 240V. Draws some 60W, about 15 minutes in the hour.

- Electronics. My laptop - a decent one, Dell Latitude E7440 - uses ~10W. The external monitor some 30. Phone chargers... irrelevant.

- Why you would have all 16 led light in use 8 hours a day, 10W each, and the fan 24h, I can't guess.

- Using electricity for heating is not a very good idea, IMO. Using it for cooking is definitely a very bad one.
- For one thing, you can't cook properly with it. For another, using it on batteries/panels is... absurd.
- I use 12 kg. gas bottles. The same one is for the gas cooker and the water heater. It lasts... months.

- Air conditioner, 24h? You must have a not-so-nice climate :·)

Here, it gets hot enough to warrant an air conditioner, say 40 days a year. My cabin is really well insulated so I just don't need it, but, I lived in a bus last summer - as I was building the cabin - half the day it was unbearable, I just set up an old computer outside, under awning, there's always a bit of a breeze, quite pleasant actually.

So, rather than having a massive energy system to supply what I personally find ludicrous energy usage, I would think about revising the usage itself. See if you can work out a more efficient way of doing things. Find an alternative to the floor mats. Better lights. Danfoss compressor for fridge. Creek water for air-conditioning... in the end, if you find a non-electric heat source, sort out the water pump, and revise air-conditioner use... you could get away with a lot less power.

Try to get into a "solar-powered, off-grid, energy-mindful" frame of mind. See what sort of revised energy needs you can come up with.
See if you can insulate your cabin better - it helps a lot.
 

luckydraw

New Member
Joined
Dec 29, 2021
Messages
7
@Don B. Cilly Absolutely agree, I need to cut the usage down a lot. A few thoughts:

- I agree, and was surprised how much the floor heater mats consume once you account for how often they'd need to run and the sq footage. I could live without them, but the thing is I'm thinking the tile/or stone (haven't decided) I put in the kitchen area and in the bathroom are going to really get cold. I don't have any standard heat on the cabin - the plan is to simply use a wood stove as necessary. Do you suggest any alternative ideas?

- pump, yes running DC 12 or 24V on its own system will save me a lot of headache needing room for massive startup watts of a 1HP unit. I already have a 1HP unit but I can sell it. The well is spring-fed and not very deep, so I think I can get away with a less powerful pump than I initially thought I needed.

- LEDS, yea... I just pulled that one out of thin air. It's a big overestimate but I will have some lights probably running at least a few hours every day.

- Stove: I didn't realize how much induction ranges actually use. Definitely deciding to go with gas. 12kg gas bottles sounds interesting but I wouldn't mind having a 100lb propane tank that I don't need to change as much. I like to cook!

- Air conditioner, yes probably 24/7 at times in July/August. It can get quite humid

- The cabin itself is insulated pretty well. The walls are really well insulated. The ceiling is vaulted and not insulated but because of the sunlight the cabin gets, it stays pretty warm. However I've never lived in there so I don't really know. I'm a new owner and this hasn't been in use for years.


The creek, well I have to do some tests on the creek flow. There is barely any head drop.. I've looked into run-of-river turbine setups. Basically it sits in the creek and directs/jets some water into an inlet on the same level as the outlet. Probably not a ton of power but even 100W 24/7 would be great.


For my specific inverter questions I'll post in the off-grid inverters section, I didn't realize there was a subtopic for that :)


I'll come up a diagram with my whole plan and then maybe it'll be easier to ask for help so one can easily see my master plan. I think it's easier to understand my whole scenario from a diagram. The property is, well, unique, for better and worse. Basically, a lot of my concerns are around winter time, a few come to mind:

- well pump (12 or 24VDC with dedicated solar panel) => holding tank. How do I keep the holding from freezing? What about the pipe going from tank to the house? Do I need pressurized or can it be gravity fed. I have a steep hill behind the cabin so its possible to put the tank high up, or into the hillside.
- if I install my whole setup (batteries, inverter, etc.) in the "utility room" behind the cabin, how "insulated" from elements does the room need to be? I understand the batteries should never charge below freezing. If it stays above 40 F all winter is that sufficient? Maybe put a little 300W heater in the room with a thermostat.



Happy new year!
 

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
946
Location
Mallorca ES
The plan is to simply use a wood stove as necessary. Do you suggest any alternative ideas?

See my signature :cool:
You could use the same method to heat the floor pads. Add a solar collector outside - not all that expensive - and heating should be easy.
The roof not being insulated is a problem, though. It's where the heat goes out. I just built my cabin, it's wood, I put 8 cm. (3") foam pads on the roof and 6 cm. ones on the walls. Covered with a thin layer of cement. Cheap enough, very effective. In December we had a few days below freezing (in the mornings). Kept the (wood) stove to a minimum.

If it stays above 40 F all winter is that sufficient?

Well, freezing (0ºC) is 32ºF, right? So, it should be :·)
I keep my batteries inside anyway. What I have outside is the inverter (it gets noisy). I also have a small generator, some way away from the house, under a little roof. I can barely hear it.
even 100W 24/7 would be great.

Yes. I wish I had a creek :·)
If you can make that 300 - maybe with multiple turbines - and manage to get your consumption to reasonable off-grid levels, you can make do with 2-300 Ah of (LFP) batteries, at 24V. I have 220 (at 24). I even have a washing machine - I just use it on sunny days :·)

The only thing that would be difficult to solve is the air conditioning. With 24h of that, you would need... more.
Maybe the creek can help with that. Talk to someone who understands A/C (I don't) and has an open mind. I'm almost sure there are interesting solutions there.
.
 
Top