Lots of questions about offgrid solar for cabin :)

[Liberty93]

Hello!?

To give you a little background, my husband and I recently purchased a 672 sq ft cabin on some land in northern Wyoming. The place is completely off-grid with only a generator for power. Although it’s way up in the mountains, the meadow it rests in gets great sun exposure, most days. I apologize in advance for all the questions, I’m just dipping my toe in solar and all the options out there are overwhelming lol ?

Is it better/more economical to build your own system or purchase a kit? Which kits/companies do you guys recommend?


Are lithium ion batteries really worth it in the long run? And does anyone know which batteries work best for cold temps? I’m talking -20 to -40 ? ?


Is it better to buy a huge kit that’s more energy than needed or buy small and build it up? I’m looking for something strong enough to power a tv/gaming system(for hubby), small water pump, and possibly a mini-split ac/heating unit...eventually. I’m thinking 800-1000 watts in panels or more idk???

I noticed most DIY videos out there are for RVs/tiny homes or grid-connected homes. Does anyone know of a video of how to connect an off-grid solar system properly to a small house? Circuit breakers for solar and the like...? Does the house need to be wired any differently? (I’m really trying to do everything by the book and want this house to be “up to code” as possible lol)

Thanks in advance!!!?

 

[dirk]

Hi Liberty,

It's always good to seek advice in advance. Let me first do some of the more simpler things.

1. Energy consumption, generation and storage.
A good thing to do is make a list of the appliances you want to run in the cabin. What kind of voltage are they running and what is their amp and watt count. Usually you can find this kind of information on the thing itself or online on the description of the appliance on the manufacturers website. A few things are power slurpers. Washing-machines, dryers, electric cooking appliances, fridges and freezers, heaters and AC's. And then you have a few apliances that take a big load for a short time. Blowdryers, Coffeemakers, Microwaves and alike. If you add the time per day you would be using those it helps to get a vision on how big your system needs to be. I.e. that is the generation and storage part of the equation.

2. Connectivity
You point out that you also want some internet access. At least if Hubby wants to game online, you wanna watch Netflix, Hulu etc. For that you will probably need Fixed wireless equipment that is on 24/7 and also needs to be fed. Take around 50W per hour or 1.2 KWh on a daily basis for that and add that to the list.

3. Batteries
Batteries are best stored between 5C and 35C (I am Dutch so I am bad at Imperial ). So above freezing. There are kits (sort of heating blankets) on the market, but a warm insulated indoor closet works best.

On the types and sizes of system there are better qualified people on this channel. But do your math, and that will bring you a step closer.
Love to see some pictures of the cabin in the future!

 

[svetz]

Are kits worth it?
That's probably like asking if someone is a republican or democrat. I suspect the kits like harbor freight sells are awful, but perhaps blue pacific is okay? It's like anything else I think... figure out what you need and then shop for bargains. But beware snake oil, if it's a great price and you haven't heard of the vendor just post it and someone will tell you if it's any good or not.

Are lithium ion batteries really worth it in the long run?
The way to compare batteries for the "long run" is to reduce it to a W cycle number/$. That is assume a lead acid batter is 1.4kW for $150 and it's good for 600 cycles at 50% depth of discharge. So, that means for $150 you can get half of 1400 watts 600 times = 1400 *.5 /150 *600 = 2800W/$

How does that compare to $1000 1.1 kW lithium battery good for 4,000 cycles at 80% discharge? 1100 * .8 / 1000 * 4000 = 3520W/$

So, if you're consuming a lot of cycles lithium is generally the way to go. If it's just for emergency power and you won't use 200 cycles in a decade, lead might be the way to go. You're offgrid, so you'll be using a lot of cycles. Lead doesn't like cold either, but trying to charge lithium when they're cold can hurt them. Will's got a post on the "hazards" page that talks about how to fix this (it's an item like a waterbed heater).

Should I buy Big now? Or start small and work up?
The nice thing about buying big now is the 30% tax credit until the end of the year (goes to 26% next year, so no real rush). Not any good if you can't take the credit (e.g., won't owe Uncle sam any money). Starting small can be problematic in that later components might not match up.

small water pump, and possibly a mini-split ac/heating unit
It's all about the power budget. For example, it would probably be cheaper to replace your well head with a solar well head (runs off DC rather than 240V AC) then to try and power it. A small mini split would still take around 1 kWh per hour (you could measure it with a meter to get the actual usage information, you might even find a super efficient one); So, to run it 24x7 would take 24 kWh/number of usable house (probably 5.5, but the link below will walk you through it) - so just for that you'd need ~6 kW of panels. That's just a rough guess, you'd have to figure out an actual power budget.

Does anyone know how to hook up a tiny off-grid house?
You might check out the tiny house/shed forum, I suspect a lot of those projects are exactly that. Will's certainly is and I think he's planning the exact same setup as you (e.g., AC).

Other Stuff
You might also find some of the information in this thread useful: https://www.diysolarforum.com/index.php?threads/frequently-asked-questions.70/

Hope that helps!

 

[dlofc]

Ok, I am going to just do a little math here, maybe help with some of the process. Let's talk size because it matters here.

One, Air Conditioner's are energy hogs. Like, major ones. Temperature control in a house is one of the most energy-intensive appliances that you can run. One of the reason's for this is, they will run, on and off, all day long. I can use my house for a very good example here. I run what I term an "isolated hybrid" solar system. The main reason for this is my house started as a pure solar house when grid-tie was not available. It is a 296 ft2 tiny house. The solar can run everything in it, with the exception of the AC, even the fridge in a pinch. My inverter might not like the load, but it can and has in the past. Our power company is not what you would like to term as reliable. But back to what is at hand, without the ac, in one day, our usage is only 1Kwh. Our power company allows you to track your usage online. Now if we add an AC on top of the 1Kwh we spike to 11Kwh. Ouch. 10KwH.

So in math terms, our 10000 BTU AC unit, which does not run all that much for our little place, to be able to be run on a battery bank is going to need a minimum of 1100 AH of lithium 12v or 550 AH of 24V and that does not accommodate ANYTHING for multiple cloudy days in the summer. I like to keep three days more than my usage, just in case those week-long stretches of clouds. These batteries need to be lithium, otherwise, that AH rating has to go WAY up. But in the long run, you will save money with the lithium running large appliances but being in Wyoming, the thing you will need to remember is temperature. Lithiums are picky about the temperature they are at, lead acids are more forgiving. So if you want to be realistic, for my AC, 3300 AH. That would see that I probably have a "no problem" system during the hot humid summers here in Tennessee.

Now, the panels that would be required to see them batteries recharged in any amount of time will be utterly ridiculous. 270w Panels from renogy come in at 8.76 amps and 31.4 volts. That is optimal conditions, meaning if you have them at the right angle for your latitude with no shade, this is what you can expect. If we pair this with a decent controller, here is one of the best 24v I could find.

Robot Check

Will, could probably find better, but working with this one @ 24V, we can bring in a wooping 3000W of panels. In one day, 4hrs of good sunlight, that is 12Kwh. So, what do we need to do to build this nice array? Series or Parallel? Will has some very nice videos on this, but generally series works out nicer for your run saving you money on the cost by reducing the gauge of wire needed to transfer the power safely. There are plenty of ways to do this, my favorite is the 2 series and the 2 parallel or 2s, 2p, now making a 4-panel unit.

The 2s will double your voltage, giving the new run 62.8 Volts and then when you combine 2 of these series together into a parallel to get the 2s, 2p it doubles the amps, giving you 17.52 amps. A(V)=W this equation is what you need to get used to when building a solar system, Amps(Volts)=Watts. So we have 1100 watts now, ( technically we need 10 panels hooked in whatever way you have preference). This is just to run a basic house, no washer, propane - heater, water heater, stove.

This is the prices I could find:

Renogy 270 panels - 249 per panel
Battleborne 100Ah LiFePO4 - 949 per battery
EPEVER MPPT controller -329

The Batteries will always be an investment, but it is worthwhile. I am not trying to discourage, but it was a shock to me when I went to build my own. I always want to be upfront with people when they have questions like these. I hope this helps.

 

[naelr]

for the inverter/MPPT charger you might consider something like this. My opinion only not always the best option.

Amazon.com: MPP SOLAR 5000w 48vdc 120v 208V 240V Split Phase Solar Inverter 80A 2X Dual MPPT Charger max PV input 145V : Patio, Lawn & Garden

Amazon.com: MPP SOLAR 5000w 48vdc 120v 208V 240V Split Phase Solar Inverter 80A 2X Dual MPPT Charger max PV input 145V : Patio, Lawn & Garden

www.amazon.com

It will take all your solar and charge your batteries and run your house. Supplying 240 volts to a standard breaker panel makes everything AC after that just standard house wiring. Doing something like this you will need to size and wire up your panels in a specific way to meet the max 148V DC input and also your batteries to meet the 48vdc charging and powering of the device.

Will has done some great videos on these types of systems. Search his you tube channel for "MPP" but here is one link

All other info before my post is spot on IMO. Your power needs are going to need to be calculated and figured in order to size properly. If you don't take into account everything before hand what you install might not perform as expected.