Wanting to build a scalable off-grid system

phalynx

I have been reading about solar for years and have learned quite a bit. Now I am looking for those that have or those that know best to help me plan my system. My ultimate end goal is to take my existing on grid tied house with no solar to 100% off grid. I need to do this over time and that 1 thing is what causes the biggest design questions.

I do not want to be grid tied. I intend to build up a "small" system that can expand easily. I want to purchase about 1000 or so a month in gear to expand. I do not wish to just save up the 1000 until I have the perfect amount and then buy it all. I have about $5000 to start. I know I will want 240v capability so one of the 4000+ watt inverters with 120/240 seems logical.

Here is what I think I should be looking at. I think I should stick with 24V battery side power. Reason is there are appliances that can run from 24V and the expansion of batteries would be cheaper (in chunks) to upgrade. Meaning buying 4 - 6V batteries to expand to the next capacity instead of 8 - 6V for 48V.

Inverter I think one of the Xantrex 4024 or the Magnum 4024 inverter. Since, I believe I can stack these for more power, they would expand.

PV panels - I think the Kyocera 315 is the right fit because they are popular and should be around for a while so I can buy them in small quantities as I expand monthly.

Charge controller - I really am not sure what makes the most sense here or which is the better choice.

Electricity needs - well, I fully understand about reducing loads and work on that all the time. What I intend is to rewire circuits in my house to run from this system as the capacity can handle. So, I intend to build a system that can run X watts and then supply the load to it that will equal X. I would continue to do this as my system expands.

As for technical capability, I am familiar with electricity in the home. I built my entire home from the ground up and wired every single circuit, breaker, panel, sub-panel, etc, in the house. I have a healthy fear of electricity that keeps me reasonably safe and don't get over -confident). Where I live, we don't have inspections and such so I can easily rewire as required. I don't have all of the red tape that exists in many places.

So, overall, I would love input and suggestions as to how I should proceed. If I am completely nuts and this won't work, feel free to tell me. I am a big boy. I do believe it is workable though. Ask any questions and I'll provide the answer to the best that I can.

Rules of my system... absolutely NO grid-tied. Expandable in smaller chunks. 240V capable.

Thoughts?

Cariboocoot

Re: Wanting to build a scalable off-grid system

Welcome to the forum.

I guess we'll skip the obvious question of "Why do you want to do this?" and the usual explanation that grid power is a lot cheaper than off-grid. Economically it makes no sense. Enough said.

You're going about it the wrong way, though. If you want to plan any type of off-grid system you have to start by measuring your actual loads, and then reducing them as much as possible. No one ever complained about reducing their power consumption, on or off grid. But unless you have that target number you will be guessing at equipment needs and probably wasting money and/or running out of power.

Doing it in stages is problematic too. But if you plan ahead you can alleviate much of the problem. You need to know what the eventual consumption will be, and plan for that. Then you can take "sections" of your loads off at a time. You may end up with multiple systems, which is not always a bad thing: redundancy provides a certain amount of security if something should fail in one of the sections.

Some aspects of expansion don't work well no matter what. Mixing old batteries with new, for instance. If you need to up the battery bank capacity it should be a total replacement all at once, or the previously mentioned redundant secondary system. Likewise you can't add batteries without adding charging capacity.

Picking the right system Voltage in the first place is essential. 24 Volts will run most things, but if your loads are large enough then the advantage is with 48. A bit about system Voltages: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

You can, in fact, use the grid to your advantage while you're expanding if you want to bite the bullet and buy the big inverter capacity to begin with: the grid can then become your "back-up generator" to supply power if the battery bank can't until you can build up enough capacity to handle loads all the time.

But the essential ingredient to planning this will be measuring loads.

We're here to help.

niel

Re: Wanting to build a scalable off-grid system

may not be able to be done as the batteries will need to be purchased well within a year of each other by manufacture date and the rest of the system will need to already be in place to charge them. the pvs, controllers, inverters, etc.can all be bought piecemeal over time, but the batteries cannot be. if you buy the batteries first then they will die from not being charged or charged properly. to get them last after the other items are purchased would mean to have the batteries all bought within the year or nearly all at once as you don't know how the manufacturer date will be on the batteries no matter when you've made the actual battery purchases so that means you can buy them in a 6 month period of time to only have the manufacture dates exceed a year.

maybe save some of the initial $ you have as the reserve for the battery bank and start monthly piecemealing of the other components and then the reserve can be made to buy the battery bank.

this is broad speak of course and some variations can occur that could make it work out better, but the biggest obstacle is the battery bank and it is costly in a short time period that is limited in its ability to be spread out.

imho, if you have a need for 4kw or more then go with a 48v battery system to keep wire sizes and losses lower and to also keep battery inequalities from getting excessive with the advent of too many paralleled strings. do make a more definitive determination on what you will maximally need for wattage at any one time and also the kwh over the course of a typical or, better yet, worst case day.

BB.

Re: Wanting to build a scalable off-grid system

If your goal is 100% off grid (check with your local laws--In some locations it may be illegal to disconnect the utility and/or you may have pay the utility to go off grid--generation capacity stranding charges).

To do it in stages--My plan would be:

1. Measure all your loads with a Kill-a-Watt type meter and/or Whole Home type Meter. You have utility power, use it to get data for your new system.
2. Conservation--It is almost always cheaper to conserve a watt than to generate a watt (insulation, energy star appliances, high efficiency heat pump systems for heating/cooling/hot water--can be operated from solar in some cases, laptop vs desk top computers, put appliances on switches/power strips to kill standby loads, etc.).
3. Remeasure your loads and come up with a kWH per day power usage, peak watts, seasonal variations (winter/summer usage), etc.
4. Define the Battery Bank
5. Define the AC battery charger
6. Define the AC Backup genset (fuel, size, how much you want to operate, etc.)
7. Define the Solar Array based on battery size, daily power usage, seasonal sun, backup generator support needed (typically 9+ months a year without generator is a good goal, perhaps generator during a few weeks of hot weather for A/C, etc.).
8. Repeat 3-7 several times with several options (type of batteries, inverter options, etc.)
9. Install battery bank with AC Charge Controller--Start with less expensive AC inverter for smaller loads (if you want to multi-stage this--very good inverters are not very cheap).
10. Install backup genset and fuel supply
11. Install solar charge controller
12. Install solar array (in stages, as money permits)
13. Disconnect Utility Power

The key is that battery banks are very hard to "expand" in a cost effective manner. Also, inverter's DC input bus voltage is fixed--So if you start with a "small" system (12 or 24) then eventually grow into a 48 volt class system--The battery bank, inverter, and some support stuff will need to be changed out.

Another option is to build a smaller system (say 1-3.3 kWH per day)--Get experience and have backup power for emergencies--Then build out a "full sized" system as time and money permits. Either keep the smaller system for backup/guest house/remote cabin/etc. use, or sell it on Ebay/Craig's List and get some of your money back.

-Bill

phalynx

Re: Wanting to build a scalable off-grid system

The why... yes, that is an obvious question. It has nothing to do with "I want to save money". I know very well that solar is not a savings anywhere. My reason is simple, I wish to live almost exclusively off grid. I want to change my life to become more sustainable. Not for the Earth, but for me. I am tired of "services" that others provide that I must "subscribe" to forever. I will absolutely get rid of a lot of stuff that consumes. I have my own water, my own waste. I live in the country with plenty of land. That is my reason. May not make sense to some, may make sense to others.

48V does make sense for larger than 4K, which I believe I will eventually be at, for wire sizing and such. I had thought I could make it in smaller chunks and be able to expand but you are right, I did not think about the batteries being "Aged". That would create problems in charging and usage, as well as capacity.

So, that makes perfect sense and makes me a little sad that I can't. But, I am not defeated. I do like the idea of multiple systems. Part of the desire to grow was to learn the care and feeding of the system and how usage works around here.

All that being what it is, should I build a small system first to play with and then buy the large system in pieces with the batteries saved for 1 last large purchase?

Cariboocoot

Re: Wanting to build a scalable off-grid system

I'll suggest you plan out the "end system" first, and then see how practical it is to divide it up. For example if you're going to need four stacked 240 Volt inverters, then going with one at a time is practical to some extent. Likewise you could build a "small" system that would be dedicated to lighting (hard wired - no outlets) to begin with. If it doesn't work out you just switch back to grid power until you figure out how to fix it. Next you could put in a bigger system to take care of the refrigerator and a few outlets, for example. Then finally flip the switch on whatever size is needed to power everything else.

This is all predicated on what you will need to power. Our off-grid cabin is <3kW hours per day, but it could stand more as much load management is required. Also it can not work in Winter up here (6 hour days, often totally overcast). So again we're back to load analysis. Do you really need 240 VAC? That usually indicates some large power user which you would be better off without (except possibly a well pump).

As far as the inverters go, Magnum, Outback, and Xantrex are all "stackable". I would not go for the Xantrex as they have GT capability you won't be using, cost more, and are somewhat "buggy" with not the best customer service (in my opinion).

Eric L

Re: Wanting to build a scalable off-grid system

All that being what it is, should I build a small system first to play with and then buy the large system in pieces with the batteries saved for 1 last large purchase?

There are a few things you could "oversize" now and use in a small, starter system while also likely being able to use in a larger system. The charge controller is one; a big modern MPPT type charge controller will still work in a smaller system and a larger one, even if the battery voltage in the larger one is higher. Heavier wiring, larger combiner boxes, and bigger "e-panels" or distribution panels could be bought and used with a small system now and a larger one later, provided you designed around the larger one. Combined, these things add up to a considerable part of the cost, so if you planned well now you could do some of what you hope to do.

Panels and panel mounting might also be used in the larger system later, but you'd have to choose panels carefully since you'd want to have the same, or very electrically similar, panels available later.

As noted above, the battery bank and inverter are almost impossible to 'upsize' without replacing them altogether, although some inverters can be stacked.

To do this well you'd really have to plan it carefully though; perhaps starting by following the first steps from BB's list, reading about various systems, and reading lots of equipment manuals (usually available online) to figure out what you'd eventually need and want.

Don't be tempted into buying equipment, even if it seems like a great deal, until you know exactly what you need. For this to work, you must be very careful with your equipment selection.

niel

Re: Wanting to build a scalable off-grid system

hmmm. after thinking for a bit you may be able to purchase the batteries and a inverter/charger. this will facilitate a backups type of operational capability until you could implement the solar aspect. you could also make dry runs at periods of no power to see how the system will fair with your needs and would allow some time to add batteries or another inverter if needed, should what you went with initially proves to be insufficient.

after that all equipment for solar could be gotten piecemeal. this may be very doable depending on the inverter and batteries chosen in order to fit your $5k budget.

maybe go with a magnum 4448pae inverter charger and i'd recommend he remote even though not always a necessity. this could be half of your budget right here.

you will need to invest in the wiring, fusing or circuit breakers, etc. this could also be the addition of an epanel which would add considerable cost to the budget, but makes wiring, circuit breakers, etc. much easier, but lets hold off on the epanel until you know the score better and you can see how your backups is working for you. you'd also eventually want to have some surge protection devices, but i'd recommend at least 1 initially adding another $100 or so. the cost of the wires and fuses can vary depending on many factors, but i'll take a stab at another $350-$400 minimum as a good rough guess.

you will now be in the area of about $3k and could allow for the costs of some batteries at about $2k. remember i recommended a 48v battery bank so this sets a minimum number of batteries being 4 for 12v batteries and 8 for 6v batteries, but we also recommend about 100ah of capacity per kw of inverter capacity at 48v minimally as a ripple voltage could be set up that would be counter to the proper operation of the system. maybe, get 6v golf cart batteries (about 200ah and good starter batters) and have 8 in series paralleled to another 8 in series. that's 16 batteries and is probably cutting it close on your budget depending where you buy and what brand. the guys can advise about these batteries better than i, but if you opt for these 2 strings of 8 batteries remember to keep the wires heavy and as short as possible all while staying equal in length. a battery bank of batteries that already have 400ah+ capacity in each would allow the preferred single string of batteries to be used and would mean less heavy gauge interconnecting wires. if you can afford the single string it is the preferred method, but makes expansions of the battery bank more expensive so some manipulating and robbing peter to pay paul in the meantime may be necessary.

icarus

Re: Wanting to build a scalable off-grid system

Just to put a point on your reasons, you may not wish to have to Perennially "subscribe" to the utility,, but for a bunch more money per kwh, you are going to, in essence subscribe to the battery supplier instead. Persoanlly, I don't think it a wise choice, either financially or environmentally but that is just me.

Tony

vtmaps

Re: Wanting to build a scalable off-grid system

You have been advised not to add a parallel string of new batteries to an older string of batteries. Its even worse than that... you should try to avoid parallel strings of batteries, even if they are all new.
read more: http://forum.solar-electric.com/showthread.php?14674

BB. gave you some good advice about expanding a system... build multiple systems. Perhaps a 240 volt system and a separate 120 volt system. Two 24 volt systems can often do the work of a single 48 volt system.

--vtMaps

stephendv

Re: Wanting to build a scalable off-grid system

About the only thing you can add gradually are the solar panels. Better to buy the other components exactly the size you need with no later additions. You could still do it in stages though, e.g.:
1. Buy inverter/charger and battery bank, 48V and preferably as 24 x 2V cells. You can now use the grid to charge the batts and run the whole house off the inverter/charger
2. Buy charge controller and solar panels as funds become available, don't need the whole array because you still have the grid for backup
3. Buy generator and disconnect from grid if you have enough panels.

You could switch 2 and 3 around if you don't mind spending a lot on fuel and have a reliable generator.

hillbilly

Re: Wanting to build a scalable off-grid system

You never did mention what your actual loads are now, or what you realistically expect them to be. Lots of solid advice has been given already, but ultimately your loads would pretty much answer your questions a lot more definitively. For instance what you're describing could well be possible, although challenging, IF you are talking about a fairly smallish load (and system). On the other hand if you have a more typical home and lifestyle it's quite possible that you'd be looking at a very large ($$$) battery bank to adequately handle your needs/wants, which would be very tricky to try and grow in stages. A lot also depends a bit on how reliant you want to be on a fuel driven generator, as that can reduce the size of battery bank needed. I think most folks who live off grid have a goal to be as free as possible from generator usage, but almost everyone I know of has at least one generator as a pretty key component of the whole system. We have 2, and while we happily don't need to run them a lot on average throughout the year, we certainly DO need to use them from time to time in the dead of winter.

I think if it were me, I'd probably look to buy a smallish set of cheaper batteries and plan on replacing them with a bigger more robust set in a few years. That's if you think that you'd be able to have the rest of the system up to be able to handle the larger battery bank at that time, and that you'd have the funds left over from all that other upgrading to buy the battery bank that would fit your needs. As others have already pointed out, the batteries are both the heart of an off grid system, and they certainly can be the "achilles heel" as well. Cost wise they are a big liability for sure.

I can understand the desire for "independence" but I also tend to agree with others that you might want to really think this one through carefully before totally jumping ship. Do take a close look at your energy consumption right away, that's the number one thing that will guide you on whether or not you'll want to go through with this plan, as well as give you some better ideas of what some of the other steps might look like.

Best of luck,
HB

RandomJoe

Re: Wanting to build a scalable off-grid system

As the others said, scaling up a system over time can be problematic. It is certainly quite difficult, if not impossible, to go from a small "testing / learning" setup to a whole-house off-grid system. However, within certain limitations it can be done without too much waste.

I started out with just a set of Harbor Freight panels and a 12V AGM battery. Certainly nothing highly useful overall, but it let me run my scanners and ham rigs (long as I didn't use them *too* much, the HF panels don't provide a lot of charging). I still use the AGM battery for the ham bench, but went to a larger panel and better charge controller. The HF panels are still around, though not used a whole lot.

Next was a "large" 12V system. My original intent was - as you mentioned - to run things straight off 12V when possible (I had a whole ham shack of things ready for that) and that worked well enough. The problem with using 12V or even 24V to power anything of any consequence is the high currents involved. You have to run some BIG wire if you want to use them anywhere away from the battery bank. I ran into that when I wanted to relocate the ham shack across the house.

At this point my system consisted of an Outback FM-80 charge controller, Iota 12V battery charger for charging from grid or generator, 1500W 12V Samlex inverter for the fridge and other things if/when I wanted/needed (I manually plugged things in) and 100W in panels on the roof. Also six T105 6V batteries wired in three 12V strings.

When I realized I wasn't going to easily keep using 12V directly, I decided to make a big step up. Realized that DC lighting and appliances were just too doggone expensive for what I was getting (120 VAC items are so much cheaper, easier to come by, often better quality) and inverters weren't that bad efficiency-wise anyway. So I bought two more T105s, rewired to 48V battery bank, and bought an Outback VFX-3648. At this point I kept all my "backup" circuits separate. I mounted a small breaker panel beside the inverter, and started running dedicated outlets to various parts of the house.

Of course here I had my first few items going unused. The Iota charger and Samlex inverter are no longer used. I could sell them, just haven't! But everything else I had at the time is still in use.

Eventually I decided I wasn't going to get all the dedicated circuits I wanted run (getting down exterior walls in this house is a PAIN!) so I moved the subpanel back beside the main breaker panel and pulled off several house circuits. SO much more convenient now!

I have also since added another 1000W of solar panels, tied to the same Outback CC since it has plenty of capacity.

So my system has grown bit by bit, with very little "wasted" items, but it also isn't terribly large. I'm nowhere near being completely off-grid, I don't even run the circuits I do have on it 24x7 off-grid, though that's mostly because I have my computer network on it and the servers do add a measurable load. If I didn't have those going I probably could keep the rest off-grid. That doesn't account for the other circuits still on my main panel, though. I use way more power than I could generate with my system, especially in summer with the A/C running!

In theory I could go off-grid, but the cost would be substantial. However, even the system I have offers me considerable independence from the power company. If the grid goes down, I still have all my "critical" loads going - the lights don't even blink, the inverter switches that fast. (Only reason I even know about many of the shorter bumps and outages is my microwave clock is blinking - its outlet isn't on the inverter.) I am able to offset the electric bill somewhat by running off the solar panels as much as possible during the day. (Won't ever pay me back, but it does help.) In a pinch, I can even run the (natural gas) furnace off the inverter for heat in a winter outage, although it would draw my T105 bank down pretty quick. (800W total draw once fully operating.)

The next "upgrade" I'm considering would be to go with L16s instead of the T105s - but only when this bank has worn out. I'm not sure I'll even do that, as that would drop my charge rate back down to "barely enough" (the reason I added the second half of my solar array). Perhaps by then I could instead go LiFePO4 instead - that'd be sweet, more capacity in less footprint than I use now!

westbranch

Re: Wanting to build a scalable off-grid system

If I were on grid, I would start with some GC's, a three stage 12v charger and a TSW inverter and start to experiment with it, see just how much it will run, next step is to get some PV panels and a mid line to top line CC, no go top line as you can reuse it later on a larger system.

YMMV

solar_dave

Re: Wanting to build a scalable off-grid system

Just as an FYI the grid with net metering is the cheapest and most efficent battery out there. Nothing to maintain or water, no losses from charging and discharging, 100% of the generated power goes to your loads, just something an off grid system can't do. If your utility has a decent net metering plan look it over and you can make your solar go much farther per dollar invested.

I do understand the want to go Independent however financially grid tie is a better deal

Photowhit

Re: Wanting to build a scalable off-grid system

OK, Where in the world are you? Lots of land, so possibly US...

I'm with the Hillbilly here, You have a very reasonably starting budget of $5,000. I wouldn't want you to spend a load on batteries with out having a 'starter set' golf cart batteries are cheap and reliable (if your some where they play golf).

What does your current electric bill look like? Planning on air conditioning? Heating is pretty much out, less sun when you need it the most. So do you heat with wood? Might start with a wood boiler or furnace or just a wood stove...

On the solar side of things, with $5000 you could go with a 4448PAE inverter and 8 - 6V golf cart batteries, a midnite classic charge controller (the only CC that will talk with each other as far as I know, and very large capacity and latest design) a some racking, I think I shot most of your budget there, and I would buy panels by the pallet, but if you hunt around you should be able to find panels at <$1 a watt and buy a pallet for @5K so 5 months later... but if you live in the US you want to do this in the same year and take the 30% tax credit off your tax liability (until the end of 2016)

With this setup you can set the Classic to only charge to the rate the batteries can handle and set the Aux function to come on when the batteries reach float to run auxiliary loads like a water heating element. When you get your tax credit on your first years $10-12,000 investment, look into buying a fork lift or traction battery that will meet your needs.

I'm doing much this same thing, with no budget and a lot of enthusiasm. I had built my cabin for off grid and found a mobile home and some land cheap so my system is pretty much set for 24 volt, all I would need at the cabin, but really would have prefered 48 volt, but had bought a good sized forklift battery (after receiving my tax credit from added array) I lived with 4 golf cart batteries for 4 years until they died running an A/C in the summer time (tiny cabin with 6" walls) The fork lift battery should last 15+ years.

ggunn

Re: Wanting to build a scalable off-grid system

phalynx wrote: »

The why... yes, that is an obvious question. It has nothing to do with "I want to save money". I know very well that solar is not a savings anywhere. My reason is simple, I wish to live almost exclusively off grid. I want to change my life to become more sustainable. Not for the Earth, but for me. I am tired of "services" that others provide that I must "subscribe" to forever. I will absolutely get rid of a lot of stuff that consumes. I have my own water, my own waste. I live in the country with plenty of land. That is my reason. May not make sense to some, may make sense to others.

My advice to you is to decide now what your end system will look like and price it out, factoring in the periodic replacement of batteries and the eventual replacement of inverters (along with the rising prices of these items) and then decide if this is truly what you want to do. It's not a matter of saving money or not, it's about spending a whole lot more of it.

BB.

Re: Wanting to build a scalable off-grid system

Once you size/cost out your system... It is very easy to add up all the costs (initial and maintenance--Batteries typically last 5-8 years, electronics around 10+ years, panels hopefully 20+ years) and divide by the kWH per year * life of system (in years) to get a $/kWH cost...

Every time I have run the numbers, it comes out to around $1 to $2+ per kWH (a few folks here that have been very careful on their power usage and getting the best prices for their equipment can get a bit under $1 per kWH)--And like energy costs, the costs of replacement parts/batteries/etc. will both go up over time via inflation (because of government policies).

If you have existing grid tied power with reasonable prices (in California it runs from $0.09 to $0.50 per kWH for Time of Use billing with tiered rates).

In terms of saving money, extreme conservation is almost always a better investment (vs generating your own power).

For survival after a storm/earthquake/etc..., A (small) generator (or several generators, small one to power lights/fridge most of the time, a larger genset to pump water for a limited time per day, etc.) with stored fuel, a small battery backed/generator (and solar if it makes sense for you) is usually the next cost effective level of backup power. If your backup power needs are over a couple weeks, then solar makes more sense as backup power support (still not cheap).

-Bill

Photowhit

Re: Wanting to build a scalable off-grid system

I do think at todays prices and doing the work your self you can get down in the 50-60 cents a Kwh.

While I'm an extreme case, if you want to spend years bargain hunting and have no backup power supply, and only a 24 hour backup battery storage(during the summer) and understand this implies a willingness to reduce your use and take the tax credit into account, you might get down to the 25-30 cents a Kwh. I did spend a hundred or so dollars more on array expendetures, I'll some day do a finalized accounting.

niel

Re: Wanting to build a scalable off-grid system

solar_dave wrote: »

Just as an FYI the grid with net metering is the cheapest and most efficent battery out there. Nothing to maintain or water, no losses from charging and discharging, 100% of the generated power goes to your loads, just something an off grid system can't do. If your utility has a decent net metering plan look it over and you can make your solar go much farther per dollar invested.

I do understand the want to go Independent however financially grid tie is a better deal

in addition to what dave has said here there are also hybrid systems that combine both options so you can sell to the grid or go off grid.

TnAndy

Re: Wanting to build a scalable off-grid system

icarus wrote: »

Just to put a point on your reasons, you may not wish to have to Perennially "subscribe" to the utility,, but for a bunch more money per kwh, you are going to, in essence subscribe to the battery supplier instead. Personally, I don't think it a wise choice, either financially or environmentally but that is just me.

Tony

THAT right there. You're simply trading one outfit you're dependent on for another.

And believe me, I DO understand your desire to be independent......we have our own water, septic, raise most of our own food, cut firewood off our place for all our heat and so on. And I have a 6kw GRID TIED, battery backup system ( so when the grid goes down, we don't ). The grid is a nice, big, cheap battery.....don't be so quick to dismiss it or cut your nose off to spite your face .

icarus

Re: Wanting to build a scalable off-grid system

And to add the post script... Not only will you have to continue to subscribe,, but at a price of ~4 times a much money our kwh as grid tie.

T.