neebie off-grid question

Started by Greatlab, October 23, 2019, 11:57:11 AM

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Greatlab

My wife and I will be moving to a dryer climate for her health. We purchased 80 acres in Arizona and we have been told the nearest grid tie is more than 6 miles "As the Crow flies" away. We have also been given two 12 panel solar trackers to mount our panels on. Our panels and other equipment have yet to be purchased. We will have no shade on this property. The building will be around 1100 sq. ft. with an estimated max 2500 kWh used per month with average 80 kw used each day. These numbers are so my wife doesn't have to give up any of her present equipment and comfort items. The power usage is using our present homes power usage over the past two years. The old house is a 2X4 construction with fiber glass insulation and around 1200 sq. ft. and the new house will be 2X6 construction with spray foam insulation and 1100 sq. ft.. All the companies we have contacted keep trying to quote grid tie equipment, which is out of the question for our property. What info I have been able to locate on the internet all suggest we will need a 48 volt system for continues power day and night. I haven't been able to locate information for panels or equipment needed to connect batteries to the power panel in the house. The breaker box I have for the house is a 200 amp service and I have a few hundred feet of 10/3 copper wire for the use in the house. I understand I will need to keep the panels as close to the batteries as possible to keep power loss to a minimum and A/C power line can be longer without loss of power. I'm thinking I will need 1/0 or 2/0 cable to connect from the inverter to the house power panel. I also understand I can have two 48 volt battery banks connected to extend power supply. I have seen drawings on how to connect both of these battery banks together so they can properly charge both banks but still remain a 48 volt power supply. My question is Solar panel size, battery charging equipment , and D/C to A/C inverter size. Would anyone be able to supply information and drawings to assist with my research and installation needs? I know there are other items I haven't taken into consideration and would like any input for items I need to consider throughout our transfer from grid power to off grid living. I also have some local people who have offered to assist with my installation but I have very little time to talk with them between now and when I start to build the new house, my wife and I are in south Louisiana and the off grid helpers are a few miles from our build site in Arizona. Our back up power will be a Generac 17,500 watt gas powered generator. It powered our present three bedroom home, including A/C, during the four days we went without power after hurricane Rita came through our area a few years back. I just had to have the A/C unit modified with a soft start on both inside and outside equipment. We just couldn't run the A/C, Stove/oven or cloths dryer at the same time. The three families that stayed with us during that time have equipped their home with the same setup we now have. Just remember to cut the power feed to the grid before starting up the generator to protect the linemen working on the grid. Best $3,000.00 we ever spent for hurricane prep. It does use a lot of fuel so make sure you have a good 30 or 40 gallons to spare for a couple of days of security power.

ClassicCrazy

I think you need to find a good off grid solar supplier to install your system or at least to evaluate and design it.
There are so many things that go into the design - impossible to give you a simple answer to all your questions. I have an excel spread sheet that you put in your loads and helps you evaluate some of the wiring and battery size etc. If I can dig it up I will attach a copy but it is on a different computer now so will have to look for it later.
What part of Arizona ?
You should contact Wind Sun in Flagstaff - they sell pre engineered systems or maybe have staff to help you design and probably can point you in right direction to an installer in your area.
https://www.solar-electric.com/
A few points - yes for a big solar system 48v is better since an inverter is more efficient to make the AC and DC wiring sizes are smaller too.  You need to have the proper PV to be able to charge that 48v battery voltage.
You may want to look in the owner built systems on this forum - some have great photos and system details.
SMidnite Classic Controllers  are a good choice because you will have good support and good monitoring capabilities .  Midnite also has prebuilt inverter power centers . You should be able to find out about all those things at Windsun linked above.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Vic

Hello Greatlab,  Welcome to this Forum,

And,  as CC Larry mentioned,   Wind-Sun is a very good and reputable   supplier,  they also have had an excellent Forum,  for many years,   here:
https://forum.solar-electric.com

The key to off-grid living,   is Conservation,   Construction,    knowing your loads,  and when they occur.

Your new home  will probably have very large A/C loads,   and might want to possibly consider construction with higher R-value insulation,   bermed construction,  etc.

Did not read either of the two above Posts,  entirely,   but there are good resources here and on the WInd-Sun Forum.

FWIW,   good luck,    Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

Greatlab

Hello CC Larry and Vic,
Great info from both of you. Thank you both for your quick response.
Vic, you mentioned, “The key to off-grid living,   is Conservation,   Construction,    knowing your loads,  and when they occur.” My present home is a mobile home with 2X4 walls, fiber glass insulation, dark roof, 12/3 wiring and twenty plus year old A/C unit. I’m upgrading the new house using items proven by a close friend over the last six years. He changed his roof from a dark gray to white sheet metal. Lowered his electrical cost by more than $50.00 in all four seasons of the year. Not much until you figure our electric company only charges $0.11 per kWh used. About a year later he had three feet of water in his house and upgraded from fiber glass insulation, ½ inch sheet rock and 12/3 wire to spray foam insulation, ¾ inch sheet rock and 10/3 wire. He used ¾ inch sheet rock due to it being the only thing available at the time and the wire upgrade because he received the wire free of charge. He added a vapor barrier because there wasn’t one when we removed the sheet rock. He has a 2X4 exterior wall on his 40 plus year old home. Lowered his bill by another $35.00 plus during all seasons. We went back a few years of billing just to verify his claim.
I plan to use his example of upgrades plus use 2X6 exterior framing. I have also discovered some new (to me) lights that are replacements for the old 2 ft. X 4 ft. fluorescent four bulb lights that are for drop down ceilings. These new lights only use .26 watts per hour (that’s point 26 watts). About ¼ watt per hour for the 2X4 panel and less for the 2X2 panel. Light output is equal to the old fluorescent style fixture and I have been told the company claims the same burn time as small LED light string bulbs. They are about ¾ inch thick and my local electrical supply house took time to hook a set up for me to inspect. Should be a bigger saving for my house since we still use the old style bulbs throughout our house. I plan to use a small 12vdc fan to remove warm air during the hotter months from the attic area. Hot water shouldn’t be a big deal during the warmer months and I have been researching this problem for the colder months. I really won't know how to address this until I have the chance to see what the climate has to offer. I know the lower humidity will make heating and cooling much easier from what I have learned from others who have moved from coastal areas to Arizona/New Mexico. One gentleman even said his heating and cooling cost went way down when he moved to a more northern state that’s less humid after hurricane Katrina.
I expect my next two or three years will be a big learning experience for my wife and I.
Thank you both again for the much needed info and I will use it to expand my knowledge of off-grid living. Anything else that anyone may think I need to think about, please feel free to pass on to me. My wife and I are two people that do use any knowledge we can acquire from more experienced people. Even though we are retirement age, we are never to old to learn something new.

Thanks all, Duane

ClassicCrazy

If you can ,send me info on the lights you are talking about that use one quarter of a watt . I have to say I don't think that is the case. An LED light giving equivalent light output of 2 bulb four foot fluorescent light would be more like 26 watts. That would equal 0.026 kilowatt.
I would want to see an actual meter reading  on anything claiming that kind of light output for only a quarter of a watt.

There are lots of youtube videos about insulation  and improving it .
One channel is Matt Risinger
https://www.youtube.com/user/MattRisinger/search?query=insulation+

Ask This Old House has lots of good tutorials too.

Larry



system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Greatlab

Larry,
I'll go by the next time I'm in town and get some info for you. I didn't actually check the label but relied on the salesman reading the label to me while he was connecting it. It did give excellent light output, better than the two strand LED four foot light I have in my small shop.

mike90045

80kwh daily is huge.    If you are moving off-grid, something will HAVE to change in your life style.

Mostly, your air conditioning will need to be set to 80'ish, not 70.   And insulate, insulate, and seal & weatherstrip.  Keep the air exchange/infiltration to a minimum.

Consider using a rinse gallon of marine or aviation gas in your old generator, store it dry and turn it into your spare genset.  Gasoline stored in desert heat does not last long. 

Look to a new generator, either propane or diesel, both fuels store better than gasoline.  Or convert your existing to propane, and get a small 7kw genset as emergency backup.  When you are using your backup generator, it is not life as normal, you don't use dishwasher, all the lights, all the Air Cond at 65F.  You are in "Prevent damage to the expensive batteries and loosing all the food in the freezer" mode.

How to deal with 80kwh usage and 3 day reserve.    I say cut it way back , at least half, to 40kwh daily.

You use high voltage DC strings  (cheap 12ga wire) from the solar panels to the 600v MPPT Charge controller (CC) and locate the CC close to the batteries.   Locate the inverter close to the batteries to save on the 48VDC losses.

For that large of a battery, maybe a reconditioned fork lift battery is your ticket, tough to move, but tough to kill too.

Assume the trackers will fail (mechanical parts) and your panels will end up "fixed".

Budget your energy usage, maybe use a sub-panel for Critical loads, and use a smallish transfer switch for it, but allow for running your water/sewage pump and bare bones air conditioner, couple lights and a fridge. 

Remain open to the possibility that installing Grid power, may be less expensive over a 20 year span of gear and battery replacements.

Attaching an old draft of my power scheme as an idea generator.

Look into a CAD or drawing package to document and plan things with

http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

Steve_S

Along with a few other comments, I'll also reiterate that conservation is far cheaper & more effective than generation & storage, I suggest that you really need to sit down and do a proper power usage assessment and consider what you can do to cut your power usage.    I'm offgrid in rural remote north eastern Ontario Canada with temperature swings from -30C/-22F in winter to +40C/104F) in summer heatwaves and use 3-5kwh a day.

Some suggestion of making the house more efficient to operate which really work.
A Cool Roof system instead of a regular conventional roof.   It works amazingly well and can save you 25% of your heating AND Cooling costs !   The thermal break and passive airflow venting provides a thermal break preventing the cool from being sucked out in summer or having the cold pull the heat out in winter.    A Commercial description with great "plain English" info on this is here:  http://www.houstoncoolmetalroofs.com/cool-roof-information/cool-roof-design-texas/    They also have several videos in YT as well. 

Rain Screen Siding installation,  There are variations on this but essentially, it also provides a thermal break from the outside to the inside structures and seriously improves efficiency and is passive meaning uses no power at all.   Basic info here but more on GreenBuilding Advisor and elsewhere as well. 
https://cabindiy.com/how-to/rainscreen-siding/ 
https://www.greenbuildingadvisor.com/article/all-about-rainscreens

Being an off-gridder, in rural rough country where the weather can be seriously problematic I factored in several things when I built my place to make it more efficient and comfy as well. so here is a snapshot view:

  • FPSF (Frost Protrected Slab Foundaytion) with 4", R20 XPS Foam insulation
  • Radiant Floor Heating (7/8 pex) designed & provided by http://www.radiantcompany.com/ fuelled by propane
  • 2x6 Advanced Framing construction  REF: https://www.buildingscience.com/documents/insights/bsi-030-advanced-framing
  • 5.25" (R31) High Density EPS-II foam within the stud walls (wiring & plumbing surface mounted)
  • 7.5" (R45) PolyISO between the roof rafters (Cathedral ceilings)
  • All Windows & Doors are installed within "Baily Boxes (as shown in GBA article above)
  • Composting Toilet System with WeePee Urine diverter to grey water system.  REF https://www.we-pee.com/
  • Grey Water system takes kitchen sink, shower/bath & urinal waters to a 50 gallon drywell which then feeds to x 50" underground draintiles within the sandy loams soils.
Foam insulation prices are crazy at retail level BUT I found that commercial roofer's can provide such as much less $.  In fact, I bought 4'x8'x4" thick ISO for $8 a sheet.  The EPS used in my walls came as 4'x4' for $10 a piece, the XPS (Dow Corning Roofmate) in 2'x4'x4" sheets cost me $10 ea.   I had to hunt and get it when I could and store it till I started building but it saved a massive amount of cash !   Check with commercial roofers (who do commercial buildings like office complexes & malls etc).   

Hope that helps somewhat, good luck.

ClassicCrazy

Mike ,
My neighbor has the old Zomeworks trackers and they never seem to fail. Not sure if those are even available any longer but they have refrigerant sealed in them that changes the balance and that is what moves the tracker. No motors or sensors involved.
But these days it is less expensive to just buy more PV than to invest in a tracker anyway. Might even be less cost than investing in concrete to hold a tracker up even if you already have the trackers .

Larry

system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable