Getting Ready to Go Off-Grid

sgtB · July 2013

Hello everyone! My wife an I have been preparing to off-grid for about a year now. We'll be ready to order our solar system soon (in about a month) and have pretty much worked out what we want but I stumbled across this forum and thought I'd see what folks here have to say. We did load calculations and compared current electric use to what we'll be expecting in our new home and feel that this system is sufficient for our needs (and then some most of the time). We will have an 800ah battery bank. We're in northern MN. We'd like to work toward a system that requires no, or very little, generator use so I think we're going to add 12 more panels to the system. We'll be running the basics (small fridge, small chest freezer, well pump, radiant heat circ. pump, laundry with propane dryer, lights, minimal television and internet use) but use electricity sparingly. Any thoughts on this set up? Am I way too optimistic about the generator? Will my little Honda 2000 be enough? Is the 12 additional panels the right way to go or is a wind generator a better option? Any input would be appreciated. Thanks!

vtmaps · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

Any thoughts on this set up?

Welcome to the forum. What set up? You're going to add 12 panels to what? --vtMaps

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

Welcome to the forum.

Your post is shy on important details. For instance an 800 Amp hour battery bank, but at what Voltage? You say you've done load calculations (and I hope you mean measured power consumption of existing equipment with a Kill-A-Watt) but you don't give a daily Watt hour consumption. Twelve panels of what size, added to how many of what size?

The only thing I can tell you for sure is that judging by the battery bank even at 12 Volts the Honda 2000 would be stretched. So you really need to look at the consumption and actual stored capacity to know for sure.

mike95490 · July 2013

Re: Getting Ready to Go Off-Grid

Do you currently have grid power there now ? totally off-grid power costs you about 10x more than grid power. Additionally, if you are converting a current residence to "off-grid" there are some bureaucratic "gotchas" that sometimes bite you. Some cities will red-tag your house as unsuitable for habitation, since you don't have commercial power. Some power companies will charge you a fee for loss of their income (they win, because they ran the expensive power lines, and you are not using them) So Grid-Inter-Tie may be your option - if the PoCo allows it.

If you are building a new place, a great start is to check your current electric bill for your monthly KWh usage, and that will give you a basis for starting. Be aware that a well pump requires a beefy inverter to supply it's starting surge (about 3-8 x the running power) and the batteries and cables have to supply that surge without so much voltage drop the inverter shuts down. A Fridge and air conditioner compressor motor have the same issue, but smaller.

Any condition of "less then full sun", you get much less electric generation, my 3,000 w array drops to 400w on a cloudy day. Today, is foggy, and I'm going to have to run my 3KW generator for about an hour, to get some charge into the batteries before my pump kicks on for a 4 hour run - all my irrigation water comes from a pond, and I have to pump up to tanks (12,000 gal in storage) to get pressure.

Buy the most efficient appliances. Insulate the heck out of the house, consider solar hot water....... We built a Masonry Heater for our main heat source, and other than having to feed it wood, it's great.

Practice shifting loads to match your solar harvest, best to run gear off the sun, than batteries, at least 20% more efficient, to not have to waste power recharging batteries, and saves cycling the batteries.

Use PV Watts to verify your expected solar harvest www.nrel.gov/rredc/pvwatts/‎

Running generator in AM, to Bulk the batteries, will allow most efficient fuel usage - let the solar top them off

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

There is a hyperlink inserted. Click on the word "this." Otherwise you can navigate to wholesalesolar.com and look at the off-grid medium home system.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

Whoa. Lot's of stuff to answer already. Thanks! Ok here goes:

Carib - 48v system. 12 more panels identical to those I linked to. Total 27 250w panels. I didn't expect that the Honda would keep up. I was really hoping not to use it except to run power tools.

Mike - No power now. Building new. The cost of this system will be about 30% more than bringing grid power in. We are super insulating and building a masonry heater as well. Backup heat will be radiant floor heat with a propane boiler. We are planning to get the smallest well pump we can get by with and add a large pressure tank so pumping happens during the day.

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

There is a hyperlink inserted. Click on the word "this." Otherwise you can navigate to wholesalesolar.com and look at the off-grid medium home system.

No, there isn't because links to our host's competitors are not allowed. (None of the moderators are connected with the host Northern Arizona Wind and Sun.) Probably this one: http://www.wholesalesolar.com/solarpowersystems/American-made-medium-2-ac-home-off-grid-solar-power-system.html

BTW having evaluated similar systems from this retailer I can tell you to avoid it as it is a bunch of stuff they sell without any rhyme or reason to the "design". Without knowing your consumption any choice of equipment is meaningless.

Do it right, or pay twice.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

I did not realize that the link wouldn't work. Thanks. Our consumption is currently around 10-15 kwh per day on average. However, that's using an electric water heater, electric stove, not-so-efficient refrigerator, huge upright freezer, electric dryer, etc. So using our current consumption isn't going to give us a very accurate number. We've done load calculations based on the actual appliances we intend to use or at least close approximations and determined that we'd need a 3kw system. Is there something in particular about that system that is not good? I guess I assumed that basing the system size on my load calculation was the right way to start. Am I missing something?

solar_dave · July 2013

Re: Getting Ready to Go Off-Grid

Chris Olsen lives up in Northern Wisconsin and tells us that the solar production in winter is pretty much nill, with many days of full cloud cover. He supplements his needs with custom made wind which his site has quite a bit, but is not cheap and must be well planned. He also has no qualms about running the generator all he needs.

PS since this is a competitor site I think you link has been modded, you should just give us the facts for your system directly.

Try this site to for really good production estimates http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Minnesota/

BB. · July 2013

Re: Getting Ready to Go Off-Grid

Here is the basic equipment list (from link):

15 ET ET 250-watt black-framed solar panels
1 4 Star Mini-Magnum MS4448PAE Power Center
1 Midnite Classic Charge Controller
3 Surge Suppressors
1 Magnum BMK Battery Monitor
1 ME-ARC 50 Inverter Remote Control
1 Wiring Diagram
UL Listed cables, breakers and connectors
16 Surrette 6v, 400 Ah S530 including cables and hydrometer (2 strings = 800 AH)

I would go back to loads first... The Honda eu2000i is a nice little genset--But probably well undersized for primary support of this size battery bank...

So, what are your loads (kWH per day, WH or AH, Peak average watts, etc.). A Honda EM4000SX is a nice genset and could even be a bit on the small size depending on your actual loads.

And yes, for an 800 AH battery bank, you could just about double the size of the solar array for a well cycled battery bank...

I can "run the numbers" based on the above design (I would estimate the system performance/sizing based on the battery bank you have picked)--But that is sort of backwards. Normally, I like to size the system/suggest equipment based on your needs instead.

For example, an 800 AH battery bank with 2 days of backup power and 50% maximum discharge would supply:

800 AH * 48 volts * 0.85 inverter efficiency * 1/4 of bank capacity = 8,160 WH = 8.2 kWH per day (or ~246 kWH per month)

That is a "goodly" amount of power for a typical well insulated full size home using a pretty much "normal" about of electricity. Usually, not much in the way of Air Conditioning. Using propane or similar for cooking/hot water/heating.

Solar panel sizing--There are two things to check. One is the amount of current required to recharge a battery bank (based on 5-13% rule of thumb of bank AH capacity) and the second based on the amount of sun you receive.

First assuming 800 AH 48 volt battery bank, solar panels, and 5-13% rule of thumb:

800 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 3,065 watt minimum array
800 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 6,130 watt array nomimal
800 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 7,969 watt array "max cost effective"

Next, how much sun for your region... Using PV Watts for International Falls Mn, fixed array, tilted to latitude:

Month    Solar Radiation (kWh/m 2/day)
1      3.09     
2      4.45     
3      5.22     
4      5.42     
5      5.24     
6      5.39     
7      5.60     
8      5.32     
9      4.19     
10      3.33     
11      2.25     
12      2.29     
Year      4.31

Toss the bottom three months (assume generator support), we have October at 3.33 hours of sun per day as the "break even" month:

8,160 WH per day * 1/0.52 overall system efficiency * 1/3.33 hours of sun = 4,712 Watt solar array.

The recommended array size (based on my guesses) would be in the range of 4,712 to 7,969 watts with 6,130 Watt array being a "healthy" nominal size.

Divide by 250 watt panels, the array would be around 19/32/25 panels (of course, the exact number depends on series/parallel connections for your particular setup).

A start. Your questions/answer based on my assumptions?

-Bill

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

Thanks BB. I was just starting to type that out. We expect our load to be under 5 kwh/day (load calculations came out around 3). We are building very small (24 x 28 ), we won't have/use air conditioning (we don't use it now in our 2x6 stick built home), all heat will come from propane or wood. If I need to upgrade the generator I can (and it sounds like I will). I considered the generac ecogen as well as a bigger Honda.

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

I did not realize that the link wouldn't work. Thanks. Our consumption is currently around 10-15 kwh per day on average. However, that's using an electric water heater, electric stove, not-so-efficient refrigerator, huge upright freezer, electric dryer, etc. So using our current consumption isn't going to give us a very accurate number. We've done load calculations based on the actual appliances we intend to use or at least close approximations and determined that we'd need a 3kw system. Is there something in particular about that system that is not good? I guess I assumed that basing the system size on my load calculation was the right way to start. Am I missing something?

Okay in off-grid terms there is no such thing as a "3 kW system". Such a term can apply in grid-tie because they are sized by inverter & array capacity; the quantity of power produced is irrelevant because it all has someplace to go.

You need a Watt hours number, because that is what matters. For example your existing bill of 15 kW hours, which as you realize would be massive off-grid. Eliminating all those electric heating devices will help considerably. I'm leery of calculations for consumption because they tend to be based on manufacturers' supplied data (which is invariably faulty) and estimated use time.

So what you do then is you take your daily Watt hours number and calculate a battery bank size based on that and 25% depth of discharge. Then you calculate the amount of array you need to recharge that battery bank, figuring in your location. Northern MN is not a great one for Winter sun, so the right size generator is going to be critical too. And you can't know that without the previous numbers.

What I dislike about "kits" is that they pic equipment that they either make money on or whose rep will sell it and put it in a package without any regard to the actual power consumption needs of the customer. You can't really even say "this system will provide 'X' kW hours per day" because that would be dependent upon the location it's installed at.

And thus back to the Watt hours per day needed.

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

Let's look at some of it "sideways".

An 800 Amp hour 48 Volt battery bank would supply about 8 kW hours @ 25% DOD. This may be more than you need.

A Honda EU2000i is a 1600 Watt generator, and is not going to be able to recharge that battery bank and run loads. You're looking at the need for about 3kW of gen here.

3750 Watts of panel on 48 Volts through a MidNite Classic ... 60 Amps peak. Again low for that much battery even in Summer. In Winter in MN you'll have two problems: not enough sunlight for it to charge the bank and potential Voc input exceeding spec unless you go with the 200 or 250 (depending on how the array is wired).

Do you need a 4kW 240 Volt inverter? Maybe. Maybe not.

See what I mean about it being an almost random assortment of equipment?

BB. · July 2013

Re: Getting Ready to Go Off-Grid

I would stay away from the less expensive generators... In your neck of the woods, you are going to be running it a lot during the winter (again, guessing). You can get a "small" genset for "average" smaller loads, and a big noise maker for running power tools, deep well, and backup for your backup genset.

And, as Marc/Cariboocoot says, start with your loads. If you are talking about a 3 kWH (kilo watts * hours) per day, assuming you use power an average of 10 hours per day:

3,000 WH * 1/10 hours per day = 300 watt average load

Vs if you use 3,000 Watts for 10 hours per day:

3,000 watts * 10 hours per day = 30,000 WH per day = 30 kWH daily load

Huge difference between Watts (which is a rate like miles per hour) and Watt*Hours (which is an amount like Miles driven).

If you have a refrigerator, some CFL/LED lighting, a laptop, an efficient clothes washer, and some small electronics (laptop computer, efficient LED TV, cell phone/tool charger, some water pumping, etc.), you can get away with about 3.3 kWH per day (that is a very efficient full time home).

But, energy usage is a highly personal choice. We have folks here that live on 1,000 WH (1kWH) per day very happily. Me, in the city and not being so energy efficient (2 kids, lots of refrigerator/freezer + natural gas in a moderate climate) probably do around 8 kWH per day.

The "average" North American home is probably in the 15-33 kWH per day range.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

Thanks for clarification Cariboocoot. We did look at power consumption (Watt hours) and our calculations put us at 3kwh/day. We bumped it up to 5 due to our own misgivings about calculations. Not sure what else to do as far as load determination since we don't even own most of the appliances, pumps, etc. yet. With that as a minimal size we bumped it up to what we think we can afford over that size. Looking at what BB just provided (thanks so much for that! It would have taken me hours of head scratching.) it seems we're on the right track. I understand the concern about just buying a random kit off the internet. I think we've sized our system properly but if we haven't I'm open to advice for sure.

Back to the system. Is there something wrong with that setup in particular? Many of the components are the same as what we had found piecing a system together.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

Man, I can't keep up with you guys! I need to get some work done but will respond when I can. Thanks for everything thus far!

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

Let's say you can manage on 4kW hours per day. Using a 48 Volt system you could cut the battery bank down to half of what is in that system. Right away you save significant investment. Further you could use cheap, locally available GC2's to start with:

Two parallel strings of eight 6 Volt 220 Amp hour batteries giving 440 Amp hours @ 48 Volts. That's about 4.8 kW hours worth at 25% DOD.

Next, you'd plan to recharge that at at least 10% peak current, and it may be worthwhile to go higher than that where you will be at. So you get 44 Amps * 48 Volts = 2112 less derating factor: 2743 Watt array. (Round up to nearest available size). You could even go for 1.5 or 2 times that amount, and "current limit" the controller.

You would still want a gen bigger than the EU2000i.

BB. · July 2013

Re: Getting Ready to Go Off-Grid

Depending on your actual loads--You should probably get two generators--The Honda eu2000i type (1,600 watts max--around 400-800 watts typical loads) and a bigger genset... I will leave it to you if you want a $600 or $2,300 4kW genset (remote start, auto start, pull start, gasoline, diesel, propane, etc.)...

Note that the Honda is a EM4000SX (there are em4000s and others). The SX has full electronic engine controller can can be setup for autostart (auto mixture control, etc.).

Generators are a whole subject matter themselves.

Question about battery charger selection with EU2000 generator.

And from this thread with lots of sources/information about solar/conservation/etc..:

Poster ChrisOlson (and others) has some good advice here for "swimspam" :

Choosing a good generator
genset alternator failure (and if your generator is not generating AC? What to look for/do--Thread started by "Unicornio" from Spain)
Demonstration of Generator Support (A couple inverters that will share AC loads with the generator--smaller generator with large load support)

End result--you get what you pay for.

-Bill

Add 12/6/2012:

ChrisOlson wrote: »

BB. wrote: »

The smallest genset I have seen here so far that can be (more easily) configured to auto-start (automatic choke) is probably the Honda EM4000SX that Chris Olson is using. The choke/mixture is controlled by the electronic engine controller.

I'd like to point out that the little 46538/46539 Champion generators also have an auto-choke and I have mine configured for auto-start with the Trace/Xantrex GSM on the SW Plus inverter. When our Generac would fail to start in cold weather I used the Champion as a backup with the auto-start and it works fine.

It is basically a three-wire start generator and you only have to tap into the wires on the back of the Combination Switch to do it, which is quite easy to do.
--
Chris

My suggestion--Do not buy anything until you have done a couple paper designs. The "kit" may be the way for you to go--But you should have a really good idea of your needs and the basic components needed for your home. Then see if the kits fits those needs or not.

-Bill

ChrisOlson · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

I considered the generac ecogen as well as a bigger Honda.

If it was me, I'd consider the bigger Honda instead of the EcoGen. Already had a EcoGen and you can't get 'em started in the winter and the output is not near as clean and stable as the Honda EM-SX series. Both are about the same price. The Honda is definitely a better generator for the money. However, the EcoGen is a good choice if you intend to use propane fuel for your generator. Just plan for cold weather starting issues and some way to keep the pressure up on the propane tank when it gets down to 30 below or you'll be doing like we used to do - out there at 30 below and wind blowing 20 mph with charcoal in pans under the propane tank trying to get enough pressure to keep the generator running. It's not fun.

Northern Minnesota has terrible solar insolation in the winter time. If you live up in the pine forests (Brainerd and north International Falls) your wind conditions in the winter aren't all that great either. If you live in the Arrowhead (Iron Range) and have a fairly open site - then DEFINITELY consider wind power for winter. The Arrowhead region gets excellent wind year 'round.

Otherwise you may as well figure that better than 50% of your power will come from the generator in the dead of winter from Dec 1 to Jan 31. In that case, consider a diesel prime genset, as well as a gas unit that will start when it's 30-40 below.

We have all the above and all I can tell you is that off-grid in this part of the country is not cheap. But it sure is a beautiful place to live! There is no place else in the world that has the beautiful hardwood forests dotted with thousands of lakes with excellent fishing, and rolling farmland that stretches for almost 400 miles across our two states. So despite the expense, it's worth every penny if you enjoy the location.

Edit:
Forget to mention about the electric stuff - we got electric range (high efficiency unit with induction cooktop and convection oven), electric water heating, and we also got central A/C. You can do it with careful system design, selecting a different inverter that has Generator Support, a slightly bigger battery bank than what you got planned, and using (my latest theory) careful application of diesel prime power to carry heavy continuous loads (like the A/C system). We're pretty much living "high on the hog" here after almost a decade of learning what it takes to do it, and spending a LOT of money because we did it wrong about three or four times. And there is some expense involved because you have to learn to consider generators as your friend instead of the enemy, and don't be afraid to run 'em to support your lifestyle. But we do it and I think even with the expense of off-grid power, we still get by cheaper than folks that live in California do on grid power. So it's all relative

--
Chris

mike95490 · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

Am I way too optimistic about the generator? Will my little Honda 2000 be enough?

Maybe. If you PLAN on running it in 4 or 6 hour cycles, it will be fine. My house base load averages 200W (one of the 2 fridges running, ozone generator, laptop charger) What is your backup genset ? The backup to the backup ? I have 3 generators:
5KW 240V 3600 rpm screamer - simi-portable for welder and charging
3KW 240V 650 RPM Listeroid - fixed, main generator, wired to the inverters integral transfer switch (AC2) for loads and charging
2KW 120V vari-throttle inverter gen, wired to a 240V transformer to run the charger , or 120V to IOTA charger.

Eventually, (on a dark an stormy night) one generator will stop, you need a plan to switch right over to another one.

Cariboocoot · July 2013

Re: Getting Ready to Go Off-Grid

Another thing the OP should consider is using an inverter that will provide gen support. That way if the generator has to be running and the loads temporarily are too much the inverter can make up the difference until the loads go back down and the gen can return to battery charging/light loads. This can be a valuable function for year-round off-grid in more extreme climes.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

The purchase of a (rather expensive) generator and the fact that I may need to use it extensively in December and January might just be enough for me to rethink the off-grid option. The money I'll save on the generator, battery bank,and off-grid inverter might make a grid tied system more realistic. Crap. Back to the drawing board I guess. I'm going to meet with the power company and get an actual quote for bringing service in tomorrow. Thanks again for all the info.

ChrisOlson · July 2013

Re: Getting Ready to Go Off-Grid

sgtB wrote: »

The purchase of a (rather expensive) generator and the fact that I may need to use it extensively in December and January might just be enough for me to rethink the off-grid option.

Only the brave, adventurous (and mostly brain-dead) live off-grid in this part of the country

--
Chris

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

I think I fit that criteria! Especially the last part! I've been on the fence for a year about which way to go and I'm still undecided. Cost definitely isn't everything. Freedom is worth quite a bit. On the other hand the ethics of the decision get fuzzy. Enough thinking about it and I'll just switch the subject to "How many beers can I drink?"

BB. · July 2013

Re: Getting Ready to Go Off-Grid

You might still want to have a good quality backup genset and fuel supply for your "longest" emergency.

1-2 weeks is typically not too hard with a genset and on-site fuel storage--keep your power needs small/resonable.

Going for 1-multiple months--May not be as easy for on-site storage--and the whole question of fuel availability/deliveries during a "fuel emergency".

-Bill

ChrisOlson · July 2013

Re: Getting Ready to Go Off-Grid

The basic criteria is that if you like the location, want to be independent, don't mind putting up with some inconveniences getting started out (like getting up at 3:00 AM and trying to start a bone-frozen generator at 30 below because the batteries are dead - did that way too many times), and cost is not the main consideration - then go for it.

If you try to boil it down to dollar and sense, the dollars will win out and you'll never do it. Despite the fact that we could've brought two brand new diesel pickups, a couple new snowmobiles, a nice bass boat, and the fanciest four-wheelers you can find for what we've spent on being off-grid - we still don't regret it even for one instant.
--
Chris

BB. · July 2013

Re: Getting Ready to Go Off-Grid

By the way, Chris is the poster child for living 100% off grid in the far north (cold and snowy) with solar+wind+generator power and a full electric life style (A/C, induction stove, electric drier, etc.). A big help are the three (?) wind turbines that he designed/built/installed himself on >90 foot towers.

So it can be done--But it is a calling and a lot of work + $$$ to accomplish.

-Bill

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

The little Honda that could would run pretty much anything I'd need to run (individually at least) in a long emergency. We'll be set up to cook, heat, and even heat water with wood. It would mostly run refrigeration, lights, and a well pump. We'll also have a hand pump for water just in case and a large cellar.

sgtB · July 2013

Re: Getting Ready to Go Off-Grid

It's definitely not a pure dollars and sense issue. Otherwise we wouldn't be this far along. Lots to consider.

ChrisOlson · July 2013

Re: Getting Ready to Go Off-Grid

BB. wrote: »

A big help are the three (?) wind turbines that he designed/built/installed himself on >90 foot towers.

Although, if MidNite Solar had never invented the Classic 150 controller so I can design wind turbines that run at high voltage and actually produce real power, wind power is more of an experiment than actually being useful. The problem with wind turbines on battery systems is getting the power to the house without losing all of it on low voltage battery systems. Turbines usually have a 90 foot run just to get to the ground, and then you have to have the towers placed someplace where you can raise and lower them (meaning more wire because that's usually a long ways from the batteries). By the time you got all done you needed a copper mine to make your own wire because you sure couldn't afford to buy it.

MidNite came along and fixed that problem with a reliable controller that actually WORKS with wind power on battery-based systems. The very first of its kind. And nobody yet has duplicated it.
--
Chris

westbranch · July 2013

Re: Getting Ready to Go Off-Grid

For more info I suggest you read, and try to digest some of the lengthy discussions about generators ad other issues Chris has spoken on.. just do an 'advanced search' upper right corner of the page) for his user name.

BTW set aside a few days for reading, it will be worth it...:cool:

Getting Ready to Go Off-Grid

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