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Thread: Solar to run a fridge.

  1. #1
    Join Date
    Oct 2012
    Location
    Ontario, Canada
    Posts
    172

    Default Solar to run a fridge.

    hello all.

    I bought 3 - 110 watt solar panels, mounted them on top of a 20' hydro pole in lots of sunlight (no tracker), then I found out that both the solar panels and the small 300 watt grid intertie inverter that I bought - I cannot use. Since they are not CSA certified, or do not have ANY Canadian content, I am not allowed to hook them to the grid (or my house) here in Ontario Canada.
    I did find out, that I can set up a stand alone power system with batteries to run off grid. I already have a 20 amp morningstar charge controller now I would like to get a battery bank, inverter and battery state of charge meter.
    I hope that when all is said and done, I will be able to run my fridge off of this system. I purchase a brand new fridge - don't have the square footage with me here - and then wrapped it in 2 inches of white styrofaom - front - back - sides and top. Using a Kill-o-watt meter, without the foam, it used about 1.6 killowatts over 24 hours, with the foam it uses .65 of a killowatt hour a day - 650 watts day ? That is from 11 pm to 11 pm, according to the meter...
    Using the meter, the fridge draws 700 watts for a few seconds at start up (start up surge), and I do have a 700 watt square wave inverter, but I am worried about heating up and frying the fridge motor using this type of inverter. . .
    I would like to just start firing all the usual questions at you guys, but I think I will take some time to read the forums, as there is ALOT of info here.

    Thats it so far.

  2. #2

    Default Re: Solar to run a fridge.

    Welcome to the forum.

    First some terminology; your refrigerator is using 650 Watt hours per day, not just Watts. That is about half normal. A caution about covering it with insulation; over time this could backfire as you may be covering the areas that radiate heat. You can check this by simply putting your hand on the surface when it's running and see if it gets warm.

    You are right that the 'frige will have quite a start-up surge. It is doubtful that a 700 Watt inverter will handle it, especially an MSW type. You are also right that the 'frige will not like MSW; although it would work it will not work well.

    You have three 110 Watt panels or 330 Watts total. Over the course of a day you could expect 686 Watt hours AC from them; just enough to run the refrigerator (based on good insolation and 4 hours of equivalent good sun). That's also just enough panel for a couple of 220 Amp hour 6 Volt batteries in series which would also just provide the power necessary to run the 'frige. The panels are probably about 6 Imp, so the MS 20 Amp controller should do.

    It is possible for this to work, but it's a bit on the edge. When you add the power consumption of the inverter necessary to run the refrigerator you may not have enough power.
    Four 175 Watt panels, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #3
    Join Date
    Jun 2003
    Location
    pittsburgh, pa
    Posts
    10,083

    Default Re: Solar to run a fridge.

    to add to your standalone system to make it operational it may cost as much as buying new pvs and throwing small gt inverters on them, all certified.

    i know you don't want to have what you already bought to be useless to you so you could use it for lights being they aren't as critical of the modsine inverter. the batteries will need to be sized for your loads no matter what loads you opt for. keep in mind that you don't want to draw off more than 50% of the battery capacity over 24hrs to preserve battery life. they aren't meant to be drained dead.
    NIEL

  4. #4
    Join Date
    Oct 2010
    Location
    Nova Scotia canada
    Posts
    2,505

    Default Re: Solar to run a fridge.

    Further to Carriboocoot's note on totally insulating all sides of the fridge - - - where does your fridge get rid of the heat it extracts from within? Many have coils just under the outer metal skin that do that, others have separate "coils" mounted on the outside of the back. The former will not operate properly if it can't get rid of the extracted heat, the latter will work fine IF you put the insulation under those external coils, between the coils and the actual cabinet.
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

  5. #5

    Default Re: Solar to run a fridge.

    Quote Originally Posted by waynefromnscanada View Post
    Further to Carriboocoot's note on totally insulating all sides of the fridge - - - where does your fridge get rid of the heat it extracts from within? Many have coils just under the outer metal skin that do that, others have separate "coils" mounted on the outside of the back. The former will not operate properly if it can't get rid of the extracted heat, the latter will work fine IF you put the insulation under those external coils, between the coils and the actual cabinet.
    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.
    24V system. 8x BPSX170 and 4x Suntech 170 on Redrok trackers through Midnite Classic200. 250W of fixed homebrew panels though C40. DanB 10' Piggot axial style wind turbine through Classic 150 and Ryan-copied clipper. HuP Solar One, 845Ahr@24V Outback VFX3524. Generac 7550EXL.

  6. #6
    Join Date
    Oct 2010
    Location
    Nova Scotia canada
    Posts
    2,505

    Default Re: Solar to run a fridge.

    Quote Originally Posted by Volvo Farmer View Post
    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.
    Not so fast. I had a Sanyo fridge with the coils under the skin, and a local organization I belong to, has a Maytag fridge with under-skin coils, I know because I moved it by myself to another room this past Saturday. And three feet from me at this very moment, I have a Sears upright freezer which I use as a fridge, and it has external coils. I also used to sell fridges that had neither. They used a fan cooled condenser down under, beside the compressor. So it depends on the design the manufacturers decide to use.
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

  7. #7

    Default Re: Solar to run a fridge.

    Sorry about my trite response, my original post did not go through. You are correct. However 95% of USA domestic refrigerator freezer combos have the coils underneath and are fan cooled. I would be curious to get a model number of that Maytag, because I have never seen one that was not static air cooled from the back or fan cooled from underneath. Almost every USA sold freezer built in the last 15 years, either upright or chest has the coils under the skin like you describe. My understanding was that the OP had a brand new refrigerator/freezer combo, and I have never seen that configuration with the coils wrapped under the skin. I have been repairing appliances for twenty years now and have seen a lot of refrigerators, but I'm always interested in learning something new.
    24V system. 8x BPSX170 and 4x Suntech 170 on Redrok trackers through Midnite Classic200. 250W of fixed homebrew panels though C40. DanB 10' Piggot axial style wind turbine through Classic 150 and Ryan-copied clipper. HuP Solar One, 845Ahr@24V Outback VFX3524. Generac 7550EXL.

  8. #8

    Default Re: Solar to run a fridge.

    I think I have the same Maytag in my kitchen. It has the freezer on the bottom. The model is MBB1954GEW. And yes the sides get warm when it is cycling in Summer.
    Four 175 Watt panels, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  9. #9

    Default Re: Solar to run a fridge.

    Quote Originally Posted by Volvo Farmer View Post
    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.
    My almost new Maytag refrigerator has the coils under the skin.
    Northern Arizona Wind & Sun Forum & Website Administrator

  10. #10
    Join Date
    Apr 2009
    Location
    Northern NH
    Posts
    272

    Default Re: Solar to run a fridge.

    I have a kenmore 5.5 cubic foot chest freezer. It has a grill on its side and vents hot air through the grill. I am in the process of adding insulation. It was quite noticible that by laying a piece of 4" iso board foam on the top cover that when I removed the foam, the top cover was a lot colder. I have also done this with the sides and noticed the same effect so I guess it depends on the design.

    I think in the "old days" the manufactureres were cheap on the insulation so the cases would be cold enough to condense vapor int he air leading to puddling, by putting the coils in the outer layer of the case it kept it warm so water didnt condense. Generally old freezers were energy hogs.

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