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  • Hi, Wayne from South Africa

    Came across Solarpaneltalk whilst doing research into a DC solution (lights and Freezer) for my fishing lodge and looking forward to the learning/advise I will receive from this forum. Biggest challenge I'm finding with all the info out there, is to get to the most functional solution without under or over specking on a system to suite my needs. Perhaps I can kick off right away with recommendations on the ideal system setup for my freezer. Bought a 254L solar chest freezer that runs off 12 or 24 volts, with a power consumption of 1800 wh a day. The area that my lodge is allocated in also has abt 5-6hrs of sunshine hrs a day. Would greatly appreciate your expert opinion/input.

  • #2
    Welcome Wayne.
    If you go right to the stickies at the head of the Off Grid sub categories you can get a TON of valuable info. That should keep you busy for a while and help you to come up with more, to the point questions.

    BTW 1800 wh seems like a lot of power for a low voltage freezer. Have you measured this yourself? Is this from the label on the freezer?
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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    • #3
      Hi, thanks for your response. Time is an issue hence the requested feedback from the Pro's. The Power consumption rating of 1800wh is the manufacturers (DEFY) spec specified on the label and confirmed verbally. This freezer was specifically manufactured to function as a DC system running (12/24 volts). The proposed solar system design by the manufacturer does not seem to be correct and a proposal given by one of the local solar companies was 2 x 200w panels (paralleled), 2 x 105AH 12volt batteries connected in series, 30w (PWM) charge controller.

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      • #4
        1800 wh. just seems high. likely worst case scenario. These type of freezers are usually very efficient using Danfoss compressors. Maybe yours isn't that efficient
        105 ah. @ 24 volts is 2520 watt hours. If your freezer actually uses 1800 wh. a day you will kill your batteries real fast. You only want to use 20% of your batteries a day and need to more than replace it daily.
        400 watts into a pwm controller will more than likely yield 250 watts x 5 sun hours = 1250 wh. a day, on a good day.
        Methinks you need to verify the actual consumption of the freezer on a typical warm day and adjust your array and battery bank accordingly. Hint; Think MPPT controller.

        Refrigerators & Freezers

        Efficient Refrigerators & Freezers

        Efficient refrigerators for living off the grid using solar panels for your home should be the most efficient, lowest energy consumption available. Super-efficient electric refrigerators and freezers designed with 3 to 5 inches of insulation use only one third the energy of most standard units. This catalog shows the best of those solar designed refrigerators. They are the very best choice for smaller power systems.
        Standard freezers and refrigerators can use 3000 watt hours each day. A few better models like Maytag MTB1956 18 cu ft can be found that use under 1500 watt hours a day, and cost around $900. You need to add about 500 watts of solar modules in the best year round sunny weather to operate; more panels needed in less sunny areas. Total cost $900 refrigerator + $3,000 solar = $3,900 to use the best conventional units.
        Refrigerators that are specially designed for off-grid homes require fewer solar modules and less generator run time. All our refrigerators are rated in watt-hours power used per day. Watt-hours compare equally whether 12, 24, or 120 volt units. Divide watt-hours/day by your battery voltage, 12 or 24, to get amp-hours per day consumed.
        Sunfrost

        Sunfrost products have 4 to 6 inch insulation, and the compressor is on top where it can't put heat back into the box. The RF-16 model uses a total of 750 watt hours a day, about 300-400 watts of solar modules, depending on the climate.
        Novakool

        Novakool products are smaller DC powered refrigerators made for RV & marine markets. With the same Danfoss compressor as the Sunfrost, these are smaller refrigerators but use about the same power. Adding 2 extra inches foam insulation to all surfaces except the door cuts that power use in half.
        Sundanzer

        Sundanzer DC powered chest freezers are as well insulated and energy efficient as any available, using 200 to 800 watt hours/day, at better prices.





        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          Thanks for the feedback and advice. Regards

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          • #6
            OK here you go. I am in a hurry and do not have time to explain it to you

            24 volt battery size = 375 AH
            MPPT controller = 40 amps
            Panel wattage = 900 watts
            Last edited by SunEagle; 06-15-2018, 10:59 AM.
            MSEE, PE

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