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Rooster6968Rooster6968 Registered Users Posts: 1
have a cabin two miles from main road,all need to power right now are a small deep freezer,small fridge,microwave,two fans&two lights.Was wanting to find out how many solar panels&size&what size inverter

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  • BB.BB. Super Moderators, Administrators Posts: 30,037 admin
    Welcome to the forum Rooster.

    Your idea to build a "small" off grid solar system sort up got "medium" size once you mention a fridge, freezer, microwave, and several fans.

    All of those items draw a fair amount of energy (mechanical, moving air, moving water, etc.). Have you picked/installed/measured the amount of energy they use with a Kill-a-Watt or DC Watt*Hour/Amp*Hour meter? Basically for a typical small fridge, that is around 300 kWH per year or:
    • 300,000 WH per year * 1/365 days per year = 822 WH per day... The small freezer may use a similar amount. And the fans can draw a similar amount of energy if they are not very energy efficient/and depending on how many hours per day you run them (i.e., 5 hours in the evening, 10 hours at night, 24 hours per day, etc.). If you are in a hot climate, the refrigeration systems will use more power... If cool/cold climate, less.
    Need to know:
    • What major city you are near (hours of sun per day by season)
    • Weekend/summer cabin or 9+ month per year
    • Backup genset available? (i.e., during bad weather, use genset to bulk up battery bank)
    • Watt*hours per day (by season, if variable)
    • Peak Watts (a refrigerator can take 600 to 1,000+ watts just starting, and 100-500 Watts running (if self defrosting closer to 500 Watts for 1-2 hours), etc.
    • Do you have access to open sky from at least 9am to 3pm all year round. Any trees, builtings, vent pipes, etc. that cast a shadow on your solar array can dramatically reduce the harvest (by 50% or more).
    • If you have local weather conditions (coastal/marine layer, summer T-storms, etc.) which can also reduce harvest.
    All of these devices add up to a fairly stiff load for a "cabin" off grid solar power system... If you are in the USA southwest, generally good amounts of sun all year round. If you are in the North West, Canadian Border, northwest, much less sun (especially during winter).

    Just to give you an idea what a suggested cabin size system would look like (one energy star full size fridge, LED lighting, Laptop, possible well pump and clothes washer):
    • ~650 AH @ 24 volt battery bank (flooded cell lead acid deep cycle batteries)
    • ~1,500 to 3,000 Watt AC inverter
    • ~2,450-3,200+ Watt solar array
    • ~85+ Amp MPPT solar charge controller
    The above is a guess... WIthout knowing much about your energy needs or where the system will be located... But it does give you a pretty capable off grid power system--If you run power in the winter in poor solar conditions, a larger solar array and/or using a backup genset a 2-3x times a week (winter/stormy weather).

    Your thoughts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,451 ✭✭✭✭✭
    Lots of missing details, but I'll bite.  Fridge + freezer =3kwh/day.  A good sized off-grid system already.  No mention of water source, but lets call it $25-30,000 for openers, plus you need to understand all the stuff involved in being the utility.

    Bottom line, if you want simple answers and grid power is less than ~$40-50,000 to install, get grid power.

    More complicated answers need more details (location, daily and peak loads, etc).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • HorseflyHorsefly Registered Users Posts: 369 ✭✭✭✭
    have a cabin two miles from main road,all need to power right now are a small deep freezer,small fridge,microwave,two fans&two lights.Was wanting to find out how many solar panels&size&what size inverter
    If you can, the fridge / freezer are good candidates to run off propane. Much better solution than electric if you are doing solar.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • mike95490mike95490 Solar Expert Posts: 8,606 ✭✭✭✭✭
    have a cabin two miles from main road,all need to power right now are a small deep freezer,small fridge,microwave,two fans&two lights.Was wanting to find out how many solar panels&size&what size inverter
    What sort of time frame are you talking about ?  All summer.  Weekends summer?  Year round?

    The last number I heard kicked around, was that after 3 years, solar PV and electric fridge had the cost advantage over lugging tanks of propane.   So i'd build the "small system" and use 24 or 48v, so you could easily expand it with more panels and batteries when you want the electric fridge
    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 ,

  • HorseflyHorsefly Registered Users Posts: 369 ✭✭✭✭
    mike95490 said:
    The last number I heard kicked around, was that after 3 years, solar PV and electric fridge had the cost advantage over lugging tanks of propane.   So i'd build the "small system" and use 24 or 48v, so you could easily expand it with more panels and batteries when you want the electric fridge
    Hey Mike - I'd be interested if you can remember where you found that. The devil is in the details, and I'd like to pour over the details they used.

    I think for a fridge and freezer to be useful at all, you have to assume they are on all the time, at least during the months the cabin *MAY* be used. You can't really fire it up when you come in for the weekend. In our case we leave the fridge stocked with butter, mayo, mustard, beer, and sports drinks. Everyone using the cabin hauls in their meats and such, and they know the fridge is cold when they get there.

    Just FYI, we don't actually "lug" tanks of propane. We have a 500 gal tank, and we use around 100-125 gal every year. We pay the local propane company to come up and fill it (to about 80%) every year or two. It's about an hour drive on dirt / gravel roads each way, but I don't think they charge all that much. The propane runs the fridge, the four-burner cooktop / oven, and a couple of wall-mounted lamps which don't get much use since putting in the solar. We used to have a second fridge in the basement, but it wasn't getting enough use to justify keeping it.  We clean out the fridge every fall, prop the door open, and shut off the supply at the tank was part of the "winterizing" the cabin.

    I can't imagine using solar generated electricity to run a fridge in a cabin that is used anything less than full time. That would mean leaving the inverter up and running, and hoping the system gets enough sun to keep the system going between visits. Otherwise, the inverter shuts down due to LVCO, and everything in the fridge goes bad.

    Just my opinion, and based only on our cabin. Your mileage may vary.  :)  
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • mike95490mike95490 Solar Expert Posts: 8,606 ✭✭✭✭✭
    I think the details were - the cost of 3 years of propane, vs buying 600w more of PV panels.   And you don't "have" to leave the fridge and inverter on over the winter, just the charge controller, to keep the batteries topped off.
    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 ,

  • HorseflyHorsefly Registered Users Posts: 369 ✭✭✭✭
    edited July 2019 #8
    mike95490 said:
    I think the details were - the cost of 3 years of propane, vs buying 600w more of PV panels.   And you don't "have" to leave the fridge and inverter on over the winter, just the charge controller, to keep the batteries topped off.
    Well, I'd still be curious about the numbers, like the assumed cost of propane, cost of panels, etc.  Seems like there would be more details behind the statement, but I can try to find the source.

    I think you mis-read what I said. We shut down the fridge over the winter, and the inverter, leaving the CC going. The issue is during non-winter months, between visits. The fridge runs, no matter if there is sun or not. I guess with it all in mind, I like propane for such a situation.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • 706jim706jim Solar Expert Posts: 298 ✭✭✭
    Propane gets a lot less attractive when the tanks have to be carried to the cabin on a boat. And over time, it costs a lot. With bottled gas over $1.00/day for an 8 cubic foot fridge/freezer.
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
  • NANOcontrolNANOcontrol Registered Users Posts: 169 ✭✭✭
    I think cabins and camps are a real specialty that has been ignored because the market is so small. It takes a total different way of thinking and living habits. Conventional systems are just a bunch of black boxes connected together without much thought.  Big always works. I have just a chest freezer converted to a fridge which only runs in the day and I am at camp for 5 months with just a car battery. I also have PV hot water, all the usual stuff, and even a dishwasher with heated dry. Wife wouldn't come without that. I have a lot of panels because I want to have things run even in the rain and they are all under trees.  I have 2500W of grid tie panels which is hardly any cost and can only get about 600W out of them. It is all about automatically controlling your loads. When I get home I am a gigantic energy waster
  • HorseflyHorsefly Registered Users Posts: 369 ✭✭✭✭
    706jim said:
    Propane gets a lot less attractive when the tanks have to be carried to the cabin on a boat. And over time, it costs a lot. With bottled gas over $1.00/day for an 8 cubic foot fridge/freezer.
    This gets to the heart of my comment that the devil is in the details. I don't doubt you are paying $1/day for an 8 cf fridge, but we are paying closer to $0.70 per day for a 10 cf fridge / freezer.

    It's really like everything else that is discussed for an off-grid home: Do the math, calculate the cost of alternatives, and choose the best combination of alternatives. Periodically, revisit the situation knowing that the math has changed in any number of ways.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • EstragonEstragon Registered Users Posts: 4,451 ✭✭✭✭✭
    Off-grid I'd be reluctant to leave either an AC fridge or a propane one unattended for any length of time.  If gone for more than a few hours, I shut down all AC, propane, and water.  Maybe I'm just a worry-wart but... stuff happens.

    I do have to haul propane across the lake, and 100# tanks seem to get heavier every year.  If I was just at the cabin on summer weekends (maybe 30-40 days/year), a propane fridge might make sense.  Even with the PITA getting the propane here is, $40/year would likely be way cheaper than the battery & solar gear needed for an AC fridge.  In my case, I'm here much more than weekends, so propane makes less sense.

    Like horsefly says, do the math and to each their own.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • 706jim706jim Solar Expert Posts: 298 ✭✭✭
    In Canada all new propane fridges must be vented through an external wall. This makes them susceptible to blow out in windy conditions. However they will happily run on rainy days if not so windy. And yes, my cost was at least $1/day to run the fridge. Propane is sold in Canada by the pound and a 20# costs over $20 to fill. For reasons known only to propane suppliers, it is sold by the gallon in the US making comparisons of costs tricky. 
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
  • BB.BB. Super Moderators, Administrators Posts: 30,037 admin
    I gallon of propane weighs around 4.23 lbs. (US gallon, not imperial gallon and density of propane is fairly temperature dependent).  A 20 lb tank should be around 4.2 gallons with room for expansion.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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