Off-Grid Solar Setups

[Got2BTru]

Starting a thread as I was unintention hi-jacking another (Grid-Tied Solar) and didn't want to do that!

We purchased 32 acres 2 years ago & would *like* to start building. While I'm still figuring out the house logistics (could that be another thread?) as to whether or not to build with SIPs or another method, I've run into an issue with getting electricity to the house. Our utility company in NY is National Grid and they've tentatively given me a $25k number for running electrical from the road, 1300 feet to where we'll put the house. They won't give me a FIRM number until I have some sort of structure built on the property (which seems kinda ***-backwards to me).

With Federal, State & Local rebates I was wondering about going off grid completely with a battery system. My initial findings was that the batteries weren't even lasting 10 years, which made the setup very cost-prohibitive if I had to replace the batteries every 7 years or so. The Tesla Power Wall came out & they guarantee nothing more than 8% loss at 10 years, which would *seem* to me to mean that it should last longer.

Our current temporary house is 120 years old and we use 13,000 kwh per year or 1083 kwh per month. But that's on an OLD home with very little insulation, etc. We're hoping to build with SIPs or closed cell spray foam at the very least, so figuring that along with LED lights energy efficient appliances, a propane stove and dryer, it should all add up to considerably less usage. I'm also looking at hydronic radiant floor heating. Cooling is my biggest concern, though in CNY, we're talking all of 3-4 months and it's not run constantly.

Thoughts, issues, concerns? Anyone already doing this or looking into this?

Here's our land in case anyone is curious...the black outline is ours. I don't have a current areal picture of the driveway we put in last year, sorry!

 

[Got2BTru]

From the other thread, I found this comment interesting:

25K for 1300 ft of feed line seems to be way high. You can rent ditch witch or excavator and install a conduit by yourself and let them only pull the cable. Isn't the utility is required to provide free hookup to certain length and you pay only for the extra distance? Our house required about 500 ft of power line and transformer. Installed for free by the utility.

I was wondering if I could rent the ditch witch and do the work myself, if that would lower the cost, but I'm just not ready for that conversation yet with the utility company.

 

[Got2BTru]

I'm curious..... what real world life-spans on battery banks are you seeing discussed ? I'm a few years away from setting up my bank, so haven't done the ton of reading needed to get an accurate picture....

To guarantee 92%, a company like Tesla will have some life-span margin built in, so those should perform well over time.

With a more conventional battery, it comes down to simple maintenance - clean/coat the terminals, check electrolyte levels. I typically get 10+ years out of car batteries doing that, while the average lifespan around here (zero maintenance) is more like 5 years. Any battery system will have reduced output if terminal corrosion sets in.

Given decent maintenance, I'd expect to get more than 10 years out a good quality industrial conventional battery in a stationary application. My preference would to have the batteries in higher voltage strings (say 48v), and maintain each string above a certain capacity - say 80% of original rating. That way you are not replacing the entire bank at once, and still retaining useful capacity.

Rgds, D.

I was reading other solar forums and they indicated that battery life span is the biggest (and most costly) issue / concern.

 

[Got2BTru]

Battery life depends on discharge depth . A bank of 1000amp hours of batteries discharged with 250amp hr load . Will last much longer than a 300amp hr battery bank discharged with 250amp hr of load.
Most of the time short battery bank life is due to chronic under charging and chronic over discharging .

This is where I have MUCH to learn!

 

[BitChin1]

I think the key is where you are heading - reduce total kwh usage and limit the peak usage.
My house in sc KS we average ~ 1500kwh/month in a SIP house (timber frame with SIP walls/roof). Our peak months have been 2025 kwh (July - Sept) and min months have been 1278 kwh. During the min months we used no electricity for heating or cooling, so this is a good indication of our power consumption for "other" purposes, cooking, lighting, well pump, DHW, etc. What I don't know is how much of this use is during hrs the sun does not shine - I expect that it is considerable %.

Our house is total electric - which around here has been good as I have a total yearly bill for electricity that is less than several neighbors winter propane bill! Also their electricity bills in winter is similar to mine even though they are not using electricity for heat - we get good solar gain, use combination of mini-split and GSHP (next house will be mini-split only)

As for SIP's, I like ours, but not sure this is what I will use on the next house (yes I like building and will do it again). Key factor is cost and a desire for higher levels of r-value than what is economically viable with SIP (but it was fun going from foundation to enclosed structure in 3 days!)

 

[Got2BTru]

OK, so I'll bite...what gives a higher r-value than a SIP?

 

[Tororider]

OK, so I'll bite...what gives a higher r-value than a SIP?

ICFs, insulated concrete forms. Plus you get the thermal mass of the concrete and it's literally bullet proof.

Could you put a 6'x6' hunting blind up and tell them you want to run power to it. It would be a structure so that you could get a hard estimate.

 

[BitChin1]

What I am working on is a wall that would use double stud with deep cavity between filled with cellulose or BIB fiberglass, or a more standard 2 x 5 wall with with several inches of foam on exterior - this can provide what ever r-value you want (climate zone dependent) but at lower cost than the SIP will.

In my case I am planning to do much of the work/labor myself so buying components comes out significantly lower cost than the SIP cost and the labor to instal the SIP along with crane.
That said I do like my SIPs, so this only works if I save significant $'s.

My current house has r24 walls and r40 roof. Goal for next house is >R30 walls and ~ R55 roof - this can be done with SIP's but very costly.

 

[Got2BTru]

Interesting...this is what I am looking at literally right now!

Superior Walls® Xi Wall - Simply Superiorâ„¢

 

[BitChin1]

I looked into that wall when building my current house - cost was a bit higher but not crazy so, but there is no near by distribution nor manufacturing site, so transport cost nixed it. I did talk with them and they do have abilities to support point loads that come from the timber frame above