100% Off Grid Shop - Maybe small cabin in future

[hermanr]

Hello, I'm new to solar and been doing HEAVY research but still getting stuck and ran across this forum. I have read and tried some searches to try and get me over the hump but still feel like I'm missing something.

Here is what I'm trying to do: 32x40 shop 100% off grid. Want a good starter system to grow over the next 1-2 years to handle most of my "light" loads fully via solar. So here is where I have made it and where I am stuck.

I plan to keep as much direct DC 12v as possible, so all lighting will be LED 12v running from a buck converter.

I plan to use min. 24v maybe 48v, this is part of the area I get lost in where you move from 24 to 48, is there a particular kwh that it makes more sense or if you know you want to grow just start with 48v?

I have a spreadsheet and I have it broke down by DC load, Inverter load and generator loads - when I need the compressor, welder - any large load I will run the generator. I also would like a setup that will allow the generator to auto start if for any reason the battery bank drops to X, not so much to charge but to stop the draw from the battery bank. I read the sticky regarding running a generator in order to keep cycles on the batteries down, this is the concept I want to deploy. It would be nice that if/when I need the compressor this function of the generator kicking in would be automatic (nice to have but not critical at all)

Here is a quick high level of where I believe my load(s) will be (shop is not built yet, hopefully by end of Sept. 2016)
12v DC via buck converter = 1600 w/hrs per day (calculated on the high side)
AC inverter load is roughly 8050 w/h a day. (some loads I am using internet avg.)
Remainder Generator - still TBD size based on solar design and capacity - goal would be to slowly reduce my generator load as I learn and grow my "starter" system.

I am mid Missouri so 4.5 sun hours a day, Shop roof is just off from facing directly south so still contemplating doing roof mount or top of pole (leaning top of pole so I can adjust it the 4 times per year manually) - since shop is not up yet can't get a solid degree reading but estimating about 15 degrees to 20 degrees off facing more southeast - no shade all day.

I believe the 260 watt panels is the min. I want to go with or even higher per panel wattage based on feedback.

battery box, generator etc would be on the outside of the shop and purpose built.

Hopefully this all makes sense so far. Now where I have got with regards to the parts for my "starter" system.

Equipment	QTY
60 amp MPPT Charge controller (24 volt)	1
260 watt solar panels	4
Top of pole mount	1
Wiring
24 volt inverter - 3000 pure sine wave	1
6 volt batteries (min 200 AH ea) - or 12v ??	?

Thanks for any guidance, help, clarification etc. Solar is definitely not an easy design task so many factors to consider.

Rueben

[organic farmer]

It is incredibly difficult to design a system that can be easily 'grown' later.

[hermanr]

Maybe that is my problem So maybe some simple questions, can you "stack" charge controllers as you grow your array and batteries? Can you "stack" DC to AC inverters?

[Wy_White_Wolf]

The 2 main things you can't grow are the batteries and inverter. You're pretty much stuck with what you have or completely replace them. Also 4.5 hours insolation sounds like the yearly average for your location. Need to recalculate using the lowest monthly average which would be about 2.5 for your location.

WWW

[organic farmer]

There are hundreds of different ways to customize a system. 'most' systems across the nation seem to be fairly standardized.

Here in my town we do not have any two systems alike.

My charge-controller is designed to be stackable. Though I do not have any experience in doing so.

[Logan5]

If you purchase the correct equipment, you should not have to stack anything. Before you spend any money, read, and study, depending on your electrical experience, it could take weeks to months to have the knowledge need to reduce mistakes and make your off grid shop a reality. Less = more when running on battery, Reduce your needs and save thousands on battery.

[organic farmer]

One home in my town has a 12vdc system from the 1980s. All of his batteries are in parallel. His charge-controller is a Chevy voltage regulator, the cheapest charge-controller I have ever seen among home systems. His house is wired for 12vdc.

Any appliance that needs 120vac gets it's own individual $100 invertor. Located next to the appliance.

His system is very simple, and it is very easily expanded.

That is an option.

[hermanr]

Looking for that Chevy voltage regulator now in my spare parts box... LOL, thanks for the response's, I understand 12v and 120 VAC well, its the mixing of the two that cause's so much confusion and then the information that is out there is a lot of times conflicting.

I like the ideal of just using smaller invertor's at the appliance or maybe combine like loads E.G. one invertor for garage door openers. One for the Blower on the Wood stove, etc.

Sounds like I just need to take a step back look at my initial design, base it on my own knowledge of AC/DC and what I have learnt. Then maybe bring that back for a sanity check here.

[ButchDeal]

Maybe that is my problem So maybe some simple questions, can you "stack" charge controllers as you grow your array and batteries? Can you "stack" DC to AC inverters?

Yes some of the are designed to stack like outback inverters and CC. Batteries are difficult to grow though. You invariably get a mix of old and new with the old sucking the life from the new.
I would stay away form anything 12V or even 24V if you want to grow. Stick to 48V and and central inverters with some efficiency and safety.

[Mike90250]

My suggestion. (rationale follows)

48V system & full size 48V inverter that will also charge batteries via generator (cloudy weather)
your existing PV array
48V charge controller
48V battery bank, 8ea, 6V 200ah golf cart batteries.

This should last you 2 years, and power most of the big shop tools
In 2 years, to "grow" the system, you replace the nearly dead golf cart batteries, with larger 400ah solar batteries
and add charge controllers, each with their own PV array, as needed to keep the system charged.

Avoid parallel battery banks, but 2 parallel strings can be acceptable when wired properly

[hermanr]

Thanks everyone! I've started to re-calc with a 48v battery bank. All shop tools will be ran from generator. Just so no confusion, my solar loads are more of the day to day items (Lights, two ceiling fans, garage door openers, my largest load being a blower on a small wood stove, which I hope I can convert to a DC motor in the near future). This will be the main loads for at least the next two years outside adding a load here and there like a cordless drill battery charger.

As a sanity check as to where I'm at (with the help here). I estimated about 1.8 kw per day usage on inventor and about 1kw for DC LED lighting. (I factored in the blower year round, it will be of course winter only and that is when I typically work in the shop with any big shop tools and the generator I am accounting to help offset the cloudy days in winter and less PV efficiency)

60 amp MPPT controller (48v) with ability to charge and auto start generator if needed
4 -6 - 260 watt panels (started to compare cost of higher watt panels per Kwh and space) preferred option is top of pole mount, 2nd is roof
48 volt invertor - 3000 watt (AC load today is just under 2k watts with a max surge of largest device not more than 1k watts)
I used a calc and it gave me 16 - 6v batteries 200 ah each so a series/Parallel setup.

Wiring, I would like to bring my generator into a typical 120 amp breaker box with a transfer switch.
Solar to its own DC fuse box. Most solar loads will all be on one side of shop so runs from invertor to appliances will be min. Only long runs will be lights and garage door openers and of those garage doors only thing on AC invertor. Lights will all be DC 12v LED
Outlets will be color coded - Generator vs Solar

2 - Questions - I read by using 48v that you can wire your PV array in series to take advantage of the higher Voltage and keep the wire size requirements down. If I can go top of pole my battery bank will be within 15-25 feet of PV array and inventor will be maybe 6 feet from battery bank also. Is there any good diagrams or calculators for wiring PV arrays and wire sizing?

other questions, I've been looking at a complete system but when I start pricing buying the components individually it seems to be a large cost difference. would you consider these all in one systems or just design and buy separately?

system looking at: http://www.wholesalesolar.com/189070...d-solar-system

Thanks again!

[Mike90250]

so, just a couple things:
Loads you are saying 2kw is that the current load, or are you meaning to say 2kwh consumed per day ?
Fan You can order brushless DC fans that run on 48V, may have to search some to find one that is good for 45-70V which is the range the charge controller may put the system through during EQ cycles. Otherwise, you get a DC-DC converter to power a 12 or 24VDC fan, and run that off the 48V battery bus, or just run the fan off the inverter
Complete System vs self designed kit Whoa. I don't think you are ready to buy anything yet, still many questions to be asked and answered first -Kw vs KWh being primary.
Then we need to know the winter sun hours, winter loads, summer sun hours, summer loads and how your generator will tie to a battery charger to keep things going in winter

[hermanr]

Don't worry I know I'm way away from buying anything. Sorry I did have a typo and it is 2kwh per day, with that said my challenge is I travel during the week for work so in reality my loads during the week will be about 250 watt hours per day for some exterior lighting and phantom loads from the garage door openers etc. But when I am in the shop and winter I will hit the 2kwh per day.

So I am 4.5 hours zone in summer, I have not found a site that breaks down summer and winter so I went off a 2.5 hr winter. As mentioned above my winter load unfortunately is my highest load due to the blower on the wood stove (the reason I'm looking to move it to a DC to help with efficiency from the inverter loss)

Here would be my goal with the generator, I would like the design to be more of when battery drain = X% (say 80%) I get a warning and I can move all loads to the generator rather than using the generator to charge and continue to draw power from the battery bank which increases my cycles on the battery's. I still expect to have some type of charge controller that will accept the generator feed to charge should for any reason need to. I believe the alerting is no problem with the correct charge controller etc. and then the switching will have to be a manual transfer switch, one way I thought about is to put my inverter feed into a standard AC breaker box which is also feed by the generator, of course have to have disconnects and protections to not have both on at the same time. If this would work then I would have my light DC direct loads only and could easily move my "AC" loads between generator and inverter. I have not had the time yet to put this into Visio for a wiring diagram and then I will have to take into account wire diameter distance etc.

Thanks again for the insight, knowledge and gotchas.

[J.P.M.]

So I am 4.5 hours zone in summer, I have not found a site that breaks down summer and winter so I went off a 2.5 hr winter. As mentioned above my winter load unfortunately is my highest load due to the blower on the wood stove (the reason I'm looking to move it to a DC to help with efficiency from the inverter loss)

For more detailed and useful information,check out PVWatts on the net. It will give a better estimate of resource availability and estimates of system output. Spend 20 min. or so with the help/info screens, particularly about how the input and output is calc'd/origins, and estimate limitations. The learning curve is steep but you will learn a lot, quickly. Much more useful than "sun hours" for the few minutes spent. Use the monthly estimates for a start, or, for more detail, including weather data and irradiance input estimates, use the hourly output option. You'll probably discover other useful ways to use the data than the designers didn't write about.

[Logan5]

you can create an adjustable alert system with a LVD module, a relay and a buzzer. You can also add a relay to assist in the transfer of loads automatically when set point is reached.

[hermanr]

Thanks, I will go check out that site and start reading and playing with the calculators.

I know they make the relays that can be configured to kick the generator on, my fear is I have read stories during my research of people burning their generator up because of not servicing it. E.G. Low oil. I would like to start with manual and as I learn move to more automation. One thing I would like automated is a relay to cut off the loads should my battery voltage drop to X% I know this won't necessarily stop discharge but in the case of bad weather while I'm out of town it may spare my batteries.

Thanks again everyone!