Author Topic: Off the Grid - System Design Question  (Read 97 times)

offthegridintn

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Off the Grid - System Design Question
« on: October 08, 2017, 12:36:54 PM »
Hey All,

(Please note that I updated this post a few hours after I posted it)

I have read all through the forum here and I must say that level of expertise and the depth of the answers are amazing.  I am hoping you all could offer some advice and guidance.

My wife and I purchased 20 acres of land in Tennessee USA last year.  We are going to be completely off grid on "the farm".

Since all of the buildings and systems will be brand new, I have no way of measuring the current usage to design a new system.

Our overall plan is the build as we can afford it. Each of the structures below will be built in the order listed:

1. Barn 40' X 40' with shop and living quarters above. Currently being built. We will live here for a few years until we can save up for a house.
2. Aquaponics Green House.  Again about 40 x 40.  Probably will install a completely separate system for this building.
3. Finally a house one day.

I am designing everything for off grid usage the best I can.  Wood heat, Wood cooking, On demand propane water heater, But some things are what they are.  Like our stand up freezer.  A must for deer and hog meat.  Also, the lower barn area is my workshop where I will be restoring RV's and building Tiny Houses.  I currently do this during the day at work, but our shop is getting too busy so I am moving the custom projects to the land.  So I will need to be able to run some larger power tools.

Also, due to my 17 years of RV repair experience, I am fairly knowledgeable in Inverter/Battery/Solar subsystems as they pertain to the RV industry.

Here is my idea...

I purchased a military grade 10KW diesel generator that I have loaded tested to 14KW. Awesome generator.  This generator has the ability for 3 phase power output (i.e. L1, L2, L3).  I thought I would dedicate L1 and L2 to the Inverter/Charger and dedicate L3 to the Shop Tools so that I can monitor their requirements independent of the household needs.

I was thinking that since I can not properly document my current usage (we haven't completed the barn/shop with living quarters above) that I could create a working test system that we could use day to day while gathering proper load specs once we move in.

I was thinking about purchasing 3 - 48V battery strings and tying them to an 6-8KW Inverter/Charger with auto change over.
Each night I could start the generator when the batteries reach the desired point of dissipation and let it run until the batteries were fully charged again.
I am not worried about buying too many batteries at the beginning as I can always take one of the strings down to the greenhouse once it is built.

This way I could really get a feel for the power utilization of the off grid power requirements and size my solar array based on actual usage.

So, my questions are as follows:

1. Do you all think that my initial idea is a good one?  What would you do?
2. What Inverter/Charger would you recommend?
3. Would you recommend utilizing a separate Automatic Transfer Switch for the Generator and Inverter or rely on the internal transfer switch in the Inverter?
4. Electric Motors have a "start up" surge requirement that can be very taxing on Inverters and batteries.  In the RV world our Air Conditioners have "Startup Capacitors on the compressors to help with this surge and it really makes a difference.  I have not seen or heard of anyone using some sort of "A/C Surge Capacitance" in their systems.  It would seem to make sense to off load those momentary power surges to a fast acting capacitance bank.
5. My final question is what batteries would everyone recommend for this type of system.  In the RV industry we use mostly Flooded Batteries. Some AGM, but they don't really work well in RVs.  Too long of a Recharge Time based on the existing inverters/chargers installed in most RVs.  Money is always an issue, but I would rather spend 3k more and not have to deal with it again.

Thank you in advance for advice/guidance and help.

Respectfully,
Greg
Offthegrinintn
« Last Edit: October 08, 2017, 04:22:19 PM by offthegridintn »

ClassicCrazy

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Re: Off the Grid - System Design Question
« Reply #1 on: October 08, 2017, 06:58:36 PM »
Until Midnite comes out with their new inverter seems like Outback or some of the others like Schneider or Magnum would be the choices available now. Pretty sure you can set any of those up to turn the generator on and charge according to whatever you set it up for. I have no direct experience with that though. So you would not need any transfer switch .

There are Lithium battery choices out there now days and they deserve a close look and cost comparison to lead acid.
The big forklift type batteries in the steel case are what I have seen people use with good longevity . If you want lead acid to last a long time ( 10 to 15 years ) you size your system so you only use 20% or so of their capacity .

There are some other types of bigger sealed lead crystal batteries available now too but I haven't seen a lot of talk about them other than from my battery supplier who says they are good stuff and have good performance in cold weather.

Larry
system one
Classic 150 , 20 Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

offthegridintn

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Re: Off the Grid - System Design Question
« Reply #2 on: October 09, 2017, 09:12:59 PM »
Thank you so much for your reply.

Fork lift batteries was one of my major considerations. I would welcome your input on those.  Manufacturer/Type/ Sizes

I agree with your inverter suggestions.  I posted this on Outback and had several responses.

Thank you,

Greg
offthegridintn


ClassicCrazy

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Re: Off the Grid - System Design Question
« Reply #3 on: October 09, 2017, 09:33:20 PM »
The people I know out here use East Penn Deka batteries - local dealer has sold them for long time and he knows his batteries.  You would have to check with local East Penn dealer and see what they say - I know some of those big battery packs come with all the buss bars between cells bonded on terminals. But they have some that have studs so you can remove each cell which makes transporting to your location possible if you can't forklift in a huge battery pack. There are different size and volt packs. Find a dealer who sells them for industrial forklift applications or wharehouses - they deal with those battery packs all the time . Our local dealer even reconditions those forklift batteries - they will load test each cell and find performance and then if one of the cells has failed they remove it and replace with one that has similar specs. He said it is usually the center ones that get hotter. But with these you are talking about batteries that get used hard all the time for years .

Solar usage isn't as tough as they get being in a forklift .

Larry
system one
Classic 150 , 20 Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

Resthome

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Re: Off the Grid - System Design Question
« Reply #4 on: October 09, 2017, 10:01:26 PM »
Been using HP Solar One 2V cells for 6 years on a house boat. Only using the 840AH version because I can't take the weight of the larger AH sets. I went with them because they included shipping in price of cells. Each cell can be removed and they furnish a lift cable to remove from case and include metal buss bars. They also have a great warranty.
John

10 x Kyocera KC140, Classic 150 w/WBJr, Link10 Battery Monitor, 850 AH @ 12v Solar One 2v cells, Xantrex PROwatt SW2000
Off Grid on Houseboat Lake Don Pedro, CA