Suggestions for off-grid island home in Maine

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Island Mon
Island Mon Solar Expert Posts: 29
Hello all,

I am new to the forum. Glad to have found this wealth of information.
This is the first off-grid system that I have designed so I am looking for input/criticism.

Background info:
My current project is a barn/house located on an island in Maine at 44.13 N latitude. The barn is going to be used as a vacation home in the summer months of June-August.

The barn roof is south facing, has a dormer structure with a 17 degree pitch which is 10' x 20'. (this is where I have decided to install the panels)

I have calculated that 17 degrees is near optimal for the angle of the PV panels during the summer months at this latitude.

Maine has an average 4.3 usable sun hours/day.
July is around 6 hrs/day. (june and august being slightly lower).

There are no obstructions that would shade the panels.

Loads (120vac):

Dishwasher - 1200 watts - 4 days a week @ 1hr- ~686 avg watt hrs/day
Clothes Washer - 512 watts - 4 days a week @ 1hr- ~293 " "
Well pump - 1000 watts - 7 days a week @ 4hrs - ~4000 " "
(10) lights - 50 watts - 7 days a week @ 6hrs - ~3000 " "
Refrig. - 1800 watts - 7 days a week - ~ 1800 " "

The minimum inverter priority wattage would be ~2850 watts
-refrig
-well pump
-lighting

Note: there will be flat panel collectors for solar HW.


based on the background info and loads....

9778 avg watt hours/day or 9.78 avg KWH/day

divided by 5 hrs usable sun/day = 1.95 kW array size.

I would use 10x 200 watt panel.

Batteries:

The batteries and inverter are going to be stored 20-30 feet away from the building in a shed.

I am looking for 3 days of storage.

9.78 kWh/day x 3 days storage = 29.34 kWh of storage needed.

I would use 6V 350 AH batteries = 2.1 kWh

29.34kWh / 2.1 kWh = 14 batteries = 4900 Amp Hrs



I was thinking about going with an outback inverter
trojan batteries and sanyo 200 watt 48 volt panels in parallel.

Please reply with any input. forgive me if I have left anything out, I appreciate any help I can get.

Island Mon
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Comments

  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
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    Re: Suggestions for off-grid island home in Maine

    You are fogetting efficiency losses of wiring, charge controller, batteries and inverter. With your setup, total efficiency should be about 55%. Solar panels will not deliver their advertised output for 5 hours per day. I get about 82% of my panel's advertised power at peak noon sun in South Florida. That only lasts 2 hours or less.

    So, taking that into account, you are looking at 2KW / (55% * 82%) = 4.42 KW of "advertised" power solar panels.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Even though Neil admonishes me for it I like to use a 50% of name plate rating times the number of hours of expected good sun,, usually ~4,, although coastal Maine might be less on an annual basis.

    A couple of observations. First,,,most newbies underestimate their loads,,, and over estimate their solar input. Looking at your numbers,,, I think you are under estimating your loads at quick glance. I see no radio/tv/computer/tools use etc. Perhaps you are that monastic but that would be rare. I also think you may be too light on lighting loads,, your ten lights burning only 50 watts sounds like 5 watts per light,,, not very much. (I personally would lose the Dishwasher,,, why do I need to spend the $$ for the kwh used?)

    The other truth that seems to emerge is that loads can and most like due increase over time. The luxury of having 24/7 power makes it real easy to use more!

    Good luck, welcome to the forum. There are some pretty sharp folks here who have spent the better part of their lifetimes inventing the wheel so that we don't have to.

    Tony
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine
    (I personally would lose the Dishwasher,,, why do I need to spend the $$ for the kwh used?)

    Yikes, that's one thing I'm insisting on. As I watched my Great Aunt & Grandparents age, their dishwashing skills got worse and worse. (bad eyesight ?) And the machines use much less water. I figure about noon, as batteries come off bulk, and the solar water heat is good...
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Dish washers may indeed be a more efficient use of water, and even hot water,, but unless you run it chock-a-block full, you loose that advantage. With just two of us,, it would take us several days to use enough dishes to fill it. We wash and rinse in between 1-2 gallons of water,,, if that. I rinse in hot enough water that by the time I'm done, the dishes have dried themselves.

    Island Mon's ~680 wh/day add up to MORE than we use in total on an average day. (we use ~3-600wh/day net/net. We could probably use twice that much on average and not have to increase the Pv capacity.)

    Tony
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    You need 2X the panels minimum

    Forget the Sanyo panels, they can't charge 48V battery's ( single ) and most charge controllers can't handle two in series

    Good news is Evergreens panels are much lower cost ( can be had for near half the cost of Sanyos ) and excellent performer

    A Single Outback won't be able to handle the loads either, most of the loads listed are inductive and you push over 10kW for start up easy .. also looks like you'll need 240V for the well pump so consider a split-phase setup, either a pair of FX's or a single XW-6048
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Suggestions for off-grid island home in Maine
    Island Mon wrote: »
    I am looking for 3 days of storage.

    9.78 kWh/day x 3 days storage = 29.34 kWh of storage needed.

    I would use 6V 350 AH batteries = 2.1 kWh

    29.34kWh / 2.1 kWh = 14 batteries = 4900 Amp Hrs

    That's assuming you discharge the batteries 100%. Doing so will destroy them. They should only be discharged to 50% of their capacity. Since your system is on the large side, it may be a good idea to go for a 48V battery bank. So thats:
    9.78kWh x 3 days x 2 (for 50% discharge) = 58.68kWh
    With a 48V bank = 1222Ah
    Finger-in-the-air efficiency loss of 20% = 1467Ah

    You're looking at an expensive set of batteries :D
    Consider shortening the 3 days and using an additional energy source such as a good quality generator or wind turbine (if it's windy when you need it).
  • peterako
    peterako Solar Expert Posts: 144 ✭✭
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    Re: Suggestions for off-grid island home in Maine

    If i understand this is only a holiday home. if so you are setting up a expensive setup and it will not provide the power on the way you want it.

    I think that if you use a generator to run all the big loads once a day and a smaller 12 v charger inverter plus battery for the daily use lights and radio tv.

    Also use a storage tank for your water use and a smaller booster pump running from 12 v.

    From there on you can build up using solar panels.

    Greetings from Greece8)
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Peterako makes a great point.

    Consider over sizing your water tank for example. Run the generator in the morning and pump 24 hours + of water from the generator,,, eliminating the need for that much PV. Also take that opportunity to run the aforementioned dishwasher, and do you daily load or two of laundry. You could also bulk charge the battery bank at the same time, assuming your generator is big enough to run all the expected loads at the same time. As SG suggest,, you need a huge inverter just to start the inductive loads. By running them off the genny,, you can down size the inverter as well,,, making the system much smaller,,, as well as it's cost.

    Do a calculation regarding fridges. In many cases, for seasonal/weekend type use, propane fridges will, net/net be much cheaper and easier to run, assuming you don't have to pay a huge premium for propane.

    I my case, we used to use gasoline for pumping water (from the lake), we still use a gasoline washing machine,, and we use the generator(s) for shop tools, and LP for the fridge(s).

    We now use solar for the water pump, but we are only pumping ~30 gpd, from 10' or so into 50 psi tank,,, 12vdc pump runs ~15 minutes/day. As I have said before,, if I were to do it over,, I would up size the solar to run a energy star fridge rather than the LP but it is sort of too late. (The fridge equation changes, the more you use it on an annual basis,, the more reason to go with a compressor,,, you have to run some cost calcs to find your own numbers.)

    The point here is that you will need a generator and charger anyway,, so planning it's use to run efficiently can dramatically reduce the size and cost of a Pv array.

    Just for the record,, we have ~300 watts of panel,, and we use ~300-600 wh/day for all uses,,, including water pumping,, lighting, radio, 2 lap tops and charging, satellite modem, (no TV) paddle fan, fridge ignitor etc. Additionally we use ~10 gallons of propane per month for water heating, cookstove/oven, and fridge. (The fridge burns ~1/8 gallon/day) We get fully charged almost every day,, winter and summer,, certainly in one day of full sun after two days of snow or rain. We have the advantage of having our panels get big reflection off of snow/ice for 6 months a year,, and water the other 6 months, as well as cool temps.


    Tony
  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine

    Thank you all for your replies.

    First off, I have looked at Evergreen panels and have found that they have an excellent reputation, and I can get a pallet of them for a great price (28 for $17K).

    I have considered using an LP fridge instead of an energy star 1800 wattHr/day, which should bring down my energy/storage demand.

    I like the idea of running a generator for doing laundry and dishes, as well as boosting the battery bank.

    I have a few more questions.

    My panels will be up on the roof (roughly 30 feet of wiring to the ground) and will be connected to a battery bank in a shed (30 feet from the house). I am planning on running the evergreen 200 watt 24V panels in series of 2 and in parallel (probably around 24 panels).

    My question is, how do I determine the appropriate wire sizing for this voltage(48V) to my 48v battery bank 50-60 feet away?

    Also, if I am interested in making the system scaleable, what does this entail?

    Thanks.

    Island Mon
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    The 200 watt Evergreens are 12V panels not 24V ... run 4 in series and then home run to a fused combiner.

    On my 4000 watt arrays, I have 4 in series, 5 strings of the 200 watt panels, outstanding performance.
  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
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    Re: Suggestions for off-grid island home in Maine
    Island Mon wrote: »
    My panels will be up on the roof (roughly 30 feet of wiring to the ground) and will be connected to a battery bank in a shed (30 feet from the house). I am planning on running the evergreen 200 watt 24V panels in series of 2 and in parallel (probably around 24 panels).

    My question is, how do I determine the appropriate wire sizing for this voltage(48V) to my 48v battery bank 50-60 feet away?

    If you will run 48V battery bank, you will need to string 3 of those panes in series for MPPT process to work, assuming each panel is 24V. You will have about 7A at peak power running from each series string of panels. Using 60 feet of 10 AWG copper wire for each string, you will lose 1.4%, or 98.6% of solar power will make it to your charge controller.

    You want 24 panels, then 24/3 = 8 parallel sets, or 8 pairs of 10AWG wire going to the roof. 60' * 8 * 2 = 960' of wire will be needed.

    Or if you want to combine your series strings of panels on the roof, you will need 1 AWG pair of wires to have identical loss of 1.4%, or if you are OK with the loss of 4.5% then 6 AWG will do, but not smaller.

    Edit: I use this wire loss calculator: http://www.csgnetwork.com/voltagedropcalc.html
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Evergreen has never produced a 24V panel to my knowledge, the only current 200 watt panels are 12V nominal ( actually the vmp is more like 18.3V a bit higher than the typical 17.2 )

    In a cool climate like Maine, there will be NO issues running 4 in s series, I run 4 in series here in Florida for my test arrays and the VMP is still in the 59-60V range at the charge controllers even when the panels are 150F ( 90F ambient ) and that includes all wire losses.

    In Maine, it never gets that hot and will be typically 20-30F cooler at a minimum
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Suggestions for off-grid island home in Maine
    Evergreen has never produced a 24V panel to my knowledge, the only current 200 watt panels are 12V nominal ( actually the vmp is more like 18.3V a bit higher than the typical 17.2 )

    In a cool climate like Maine, there will be NO issues running 4 in s series, I run 4 in series here in Florida for my test arrays and the VMP is still in the 59-60V range at the charge controllers even when the panels are 150F ( 90F ambient ) and that includes all wire losses.

    In Maine, it never gets that hot and will be typically 20-30F cooler at a minimum

    I thought that as the temperature goes down array voltage goes up?

    Had a problem with that here in the Great White North: 72 volt array exceeded charge controller's max. input voltage in cold winter months. Might have the same trouble in Maine.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: Suggestions for off-grid island home in Maine

    Using any of the "popular" MPPT controllers (Xantrex, Outback) and such--they are typically 140-150 VDC maximum solar array input voltage..

    Using a 72 volt maximum controller on a 48 vdc array is just too close (battery voltage + controller drop would exceed 62 volts on a "standard" day). Not near enough "margin of safety" for a 48 volt bank.

    From just playing around with the numbers--The ratio between Voc (very cold) and Vmp (very hot) is almost 2:1... So, to be able to properly charge a 48 volt battery bank in any condition--the controller+panels would need to work over ~124v:62v range.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,781 ✭✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Tony,
    We do the same except use the 1.5 gallons that are in the sink after dishes to rinse all our bottles and recyclables. That allows us to store the recyclables in the garage for months and it keeps the Bears where they belong. We have a dishwasher and used it once about 5 years ago. It is just about useless! A nice little touch that my better half came up with was a workbench that is high enough that the recycleables can be stored in garbage cans underneath. Saves space and very funtional. With a plan like this 2 people have a 1 gallon ziplock of trash every 2 or 3 days and get paid 25 dollars four times a year for recycling. Whatever works in the big city is often the way not to do things offgrid.......
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,781 ✭✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Sorry about my last post.... I did not intend it to go here! But since I am here I have 2 Sanyo systems up at 5,000 feet that hit 141V the last three winters with temps near 18 degrees. For $500 and 15 minutes to change controller it is worth the risk INMHO.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine
    The 200 watt Evergreens are 12V panels not 24V ... run 4 in series and then home run to a fused combiner.


    I have looked at my loads, attempted to decrease by using energy star appliances, and scaled my system up a bit.

    Now I am looking at having 18 Evergreen 210 panels. 6 strings of 3 in series.

    The nominal array voltage will be 36v. the battery bank will be 16 L-16s in series of 8 and in parallel @ 700AH 48VDC.

    Am I correct in believing that the array voltage will be above 48vdc and able to charge the battery bank?
    I would like to have 2 flexmax 80 charge controllers.
    2 strings will be on a roof with different tilt so I will run them to the second charge controller in order to maintain efficiency.

    I appreciate all of the help.
  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine

    I have revised once again, please give me any feedback you want.

    I have chosen energy star appliances and found out that a well pump won't be necessary due to a 200 foot well hole with no water.
    Instead of a well pump I will be collecting rainwater from the roof and storing it in a cistern, much like I do down in the Virgin Islands.

    The loads now are:
    Refrigerator.....Energy star....403 kWh/yr...or 1104 watt hrs/day
    Dishwasher......Energy Star...190 kWh/yr....or 520 watt hrs/day
    Washing Machine...Energy star...140 kWh/yr...or 385 watt hrs/day
    12VDC lighting...10 LED's at 5w each.............250 watt/hrs/day

    Before I go any further, I want to say that wattages for the appliances were not listed, I was on the phone with Bosch for an hour trying to get a figure out of them... I am using the estimate, and for 7 days a week, which will be unlikely for everything but fridge and lights.

    With those loads, I am at about 6200 watt hrs/day. I rounded up to 6500 watt hrs/day.

    Divided by an average 5 hours of insolation for june-september = 1.3 kW PV array

    1.3 kW PV array / (55%* 82%) = 2.88 kW of advertised solar panels

    2888.88 watts of panels / 210 watt evergreen = 13.75 panels

    I will use 16 panels, mounted on a 17 degree pitch roof, in series of 4, in 4 parallel sets.

    For batteries I am planning on using 16 trojan L-16HC's in two series of 8. For 790 AH of storage.

    My loads will require 772 AH of storage based on 2.5 days of storage and 50% discharge.

    I am planning on running this on a XW-6048 inverter and an outback flexmax 80 charge controller.

    Let me know what you think!
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    No TV, Sat, Computer or radio ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine
    mike90045 wrote: »
    No TV, Sat, Computer or radio ?

    No, the people I am designing for are insisting on not having any of that.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    And yet they "need" a dishwasher? go figure.

    Tony
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Suggestions for off-grid island home in Maine

    I'm not a solar installer, just an interested newbie, so with that disclaimer out of the way a few random observations:
    Island Mon wrote: »
    The loads now are:
    Refrigerator.....Energy star....403 kWh/yr...or 1104 watt hrs/day

    IMO you need to go beyond Energy Star for off-grid. Here's an example of a fridge that uses 197kWh/year: http://www.liebherr.com/hg/en/products_hg.asp?menuID=101405!332118-0_26502-0
    Island Mon wrote: »

    1.3 kW PV array / (55%* 82%) = 2.88 kW of advertised solar panels
    2888.88 watts of panels / 210 watt evergreen = 13.75 panels

    I will use 16 panels, mounted on a 17 degree pitch roof, in series of 4, in 4 parallel sets.

    Out of interest where does the 55% and 82% come from?
    Island Mon wrote: »
    For batteries I am planning on using 16 trojan L-16HC's in two series of 8. For 790 AH of storage.

    My loads will require 772 AH of storage based on 2.5 days of storage and 50% discharge.

    Why are choosing to connect them in parallel? Since it's a new installation, why not go series with large capacity cells?
    Capacity wise, it looks good although those cells are rated as 420Ah @ C20, since you've sized them for 2.5 days, they'll probably be drawn off closer to the C100 rate which will mean the capacity will be slightly higher.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,781 ✭✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Seems really crazy to use an an Outback CC for a XW inverter/charger. OK, it seems worse than crazy!

    Trojan has 2V cells in L16 size now which are tempting. If it were for a customer that I had to keep happy 10 years from now I would use Surrette period!

    Make sure you have your numbers correct for your panel wiring to drive summer temperatures into a 48V nominal. You will need 62Vdc plus the loss from the array and conversion.

    And my standard whining about how nutty it is to not track the sun offgrid if you have a desire not to run generators. Up in Maine your cards are probably already dealt and, it is great for the roofing business.........Good Luck!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine
    stephendv wrote: »

    Out of interest where does the 55% and 82% come from?

    The 55% is my estimated overall efficiency and the 82% is the power that the panels will produce at peak noon sun.
    stephendv wrote: »

    Why are choosing to connect them in parallel? Since it's a new installation, why not go series with large capacity cells?
    Capacity wise, it looks good although those cells are rated as 420Ah @ C20, since you've sized them for 2.5 days, they'll probably be drawn off closer to the C100 rate which will mean the capacity will be slightly higher.

    I am connecting them in parallel because I would like to use 6V cells. I have been taught to avoid 12V batteries, have also heard that suggestion from people offgrid as well.

    Seems really crazy to use an an Outback CC for a XW inverter/charger. OK, it seems worse than crazy!

    So would I be fine with just the XW inverter charger?
    Make sure you have your numbers correct for your panel wiring to drive summer temperatures into a 48V nominal. You will need 62Vdc plus the loss from the array and conversion.

    4x 210 watt 12V panels in series will give me 48 Vdc nominal, summer avg high is 77F.
    Does this mean I would have to wire 5 in series to arrive at 60Vdc?
    I am unclear on this, if you could explain I would appreciate.

    Does anyone have experience with the 6V trojan L16 HC's?

    How about 6V surrettes?

    Thanks again.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    I've used Trojan l-16 6 volts,, wired in series parallel array to 12 vdc. One set is still running fairly strong after 10 years,,, still on a seasonal bank. We lost one in year 7, another in year 8,, four are still going pretty well. The original string was on a full time off grid house,,, after year 7 they went to seasonal use.


    Tony
  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    I like Stephendv's link to the Liebherr fridges. at 242 litre capacity that's only what north americans would consider a bar fridge, too bad.:cry:

    Ralph
  • Island Mon
    Island Mon Solar Expert Posts: 29
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    Re: Suggestions for off-grid island home in Maine

    Hello everyone,

    I have taken many of your suggestions into mind and have scaled back the system a bit.

    I got rid of clothes washer and dishwasher, and increased the Ah capacity of my battery bank to allow for shallower discharging.

    I am going to repost the background info for anyone viewing this thread for the first time.

    Background info:
    My current project is a barn/house located on an island in Maine at 44.13 N latitude. The barn is going to be used as a vacation home in the summer months of June-August.

    The barn roof is south facing, has a dormer structure with a 17 degree pitch which is 10' x 20'. (this is where I have decided to install the panels)

    I have calculated that 17 degrees is near optimal for the angle of the PV panels during the summer months at this latitude.

    Maine has an average 4.3 usable sun hours/day.
    July is around 6 hrs/day. (june and august being slightly lower).

    I am using 5 hrs as my figure for avg summer insolation.

    There are no obstructions that would shade the panels.

    Loads: 5000 Kwhr/day

    21 cu ft energy star refrig
    240 V 1/2 hp soft start well pump
    15x 10 watt 120Vac lights
    400 watt hrs/day random plug loads.

    Starting from the top...
    Panels:
    12x Evergreen 210 watt 12V In 3 strings of 4 in series. 48Vdc.

    All 3 strings to a combiner box with 3x 20A fuses.

    Charge Controller:
    FM80

    Battery Bank:
    24Vdc 12x Trojan L-16H, 420Ah (20hr)
    3 strings of 4 in series, total of 24V 1260Ah

    I will have the positive(+) and negative(-) cables from each string attached to two bus bars.

    I will be discharging no more than 25% of total capacity. Estimated storage of roughly 2 days.

    Inverter:
    24V 4000watt Magnum inverter 120/240Vac split phase.

    -or-

    two outback FX2524T's 24V stacked. Providing 120/240Vac

    I will also have an Ah meter using a shunt.

    Let me know what you think.

    I appreciate everyone's responses, I am learning more everyday!

    -Island Mon
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    dump the 24V system,
    > 3 strings of 4 in series, total of 24V 1260Ah
    too many parallel strings for my likeing, if starting fresh, go with 48V, less system loss.
    Will you have a backup generator ? Consider an inverter/charger for when the genset runs.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    Island Mon,

    My view is that a 17 degree array tilt (from horizontal) would be too low, even in the summer. “Latitude – 15 degrees” usually works pretty well in the summer, so something around 30 degrees should work. The steeper angle will also help the panels self-clean.

    Make sure you leave a large air gap (at least six inches) between the roof and the modules. This will help keep the modules cool and result in higher output (both voltage and power)

    Here’s another source for insolation data: http://rredc.nrel.gov/solar/pubs/redbook/PDFs/ME.PDF

    12 x 210 W = 2,520 W STC. This value pushes the FM80 beyond its spec limit. Reconfiguring the array from “48 V” ( 4 modules in series x three parallel strings) to “36 V” (3 modules in series x 4 parallel strings) will improve the FM80’s operating efficiency and therefore reduce waste heat. The “36 V” array’s summer voltage will still be high enough to achieve battery voltage targets for a 24 V system.

    See: http://www.outbackpower.com/pdf/specs/flexmax.pdf
    And: http://www.evergreensolar.com/upload/011108%20Datasheets%20(SR)/ES-A_200_205_210_US_011108.pdf

    Finally, pay close attention to the specs for the various Evergreen modules. There's a BIG difference between the "ES" modules (aka "Spruce") and the "ES-A" or "ES-B" modules.

    See: http://www.evergreensolar.com/upload/010408%20revA%20Datasheets/ES-195_US_010408_RevA.pdf

    HTH,
    Jim / crewzer
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,781 ✭✭✭✭✭✭
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    Re: Suggestions for off-grid island home in Maine

    No matter what voltage you use for the battery 24 vs 48v I would use the newer Surrette or Trojan L16 2V cells. They are near your capacity and so much simpler to deal with. You will have 36 cells to check with your choice. My suggestion will have 12 cells for a 24 Volt system. It is a no brainer for maintenance, intelligent design, and just plain lifting more batteries.

    These new 2V L16's are the way to go if you can make them work for your plan. If you really want to reduce shallower discharges a tracked array is way to take the load off the battery early and float the battery into the evening in summer.
    There are too many folks including our hosts here who still think the world is flat and can't see the forest though the trees with offgrid tracking. Up in Maine I guess it might take some data that I don't have to make the case, but in Arizona???
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net