Question about emergency refrigeration with solar

LeehamrickLeehamrick Posts: 17Registered Users
Hi,
I have a small off grid system (300 watt) the main reason for it is because where I live we lose the electric
On a regular basis. Using this system to power it I have a water system out of a camper with a propane water
heater. So when the grid goes down I have lights in every room and running water hot & cold. Everything is 12
volts. But the one thing I don't have is any refrigeration. I don't need much maybe enough room for a gallon of
milk and some eggs. I have been looking at the 12 volt coolers people use for camping. They don't look like they
use much electric would this be a good choice for getting by in a pinch?
I have 4 batteries that are 12 volt [email protected] and I don't seem to have a problem keeping them fully charged even
when I using the lights a lot.

Comments

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Question about emergency refrigeration with solar

    You mean the ones with the Peltier/Seebeck devices: solid state "refrigeration"?
    They draw their power constantly. Not terribly efficient, but easier to operate than a compressor (no start surge of course). Look at the specs on one that you think would suit your size requirements, and calculate its power consumption over a 24 hour period. See if your battery capacity can handle that.
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: Question about emergency refrigeration with solar

    Go to a auto wrecking yard, and find a Rv fridge. (I have even found them in the dump!). If you already have propane, your set. The downside is that they take a while to get cold, so unexpected power outage would require moving your cold stuff into it quickly to help cool it down quickly. If you keep a block of ice in your freezer, it will help while the fridge cools down.

    Tony
  • techntrektechntrek Posts: 1,366Solar Expert ✭✭✭
    Re: Question about emergency refrigeration with solar

    I second the RV fridge. Peltier coolers suck down the amps, I've experimented with Peltiers and they are very cool (pun intended) but not practical off-grid. Older RV fridges work w/o any DC input, but newer ones all require 12 volts to run their "brains". They don't have a dumb fallback mode if the 12 volts is lost, unfortunately.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • TecnodaveTecnodave Posts: 7Registered Users ✭✭
    Re: Question about emergency refrigeration with solar

    Hi,
    I am using an RV fridge in a very unusual way: I have two Dometic brand Automatic Energy Selector Refrigerator/Freezers that I use on my solar system. They run on the solar 12 volt system and automatically switch to propane when solar is low voltage (less than 12.6volts) and at night. The low voltage part is done by the logic board on the Dometic and night switching is done by the auxiliary output of the solar charge controller. These refrigerators require 12 volts dc to run the logic board and the gas igniter no matter what source of refrigeration power, this is 12 volts dc @ 100 ma. Even when running on AC Power. The heating elements are 120 Volts AC 250 Watts. AND 12 volts dc 250 Watts. Only one of the heating elements will be used. The DC connections to the refrigerator are DC 12 volts positive and negative and ignition. When the RV engine is running and alternator is charging the refrigerator will run of the battery. When ignition is shut off the ignition signal will be lost and the refrigerator will automatically switch to propane. I have connected the ignition terminal of the Dometic to the auxiliary timer on my solar controller. This will also work if you use AC power as your primary and solar as backup. The Dometic logic priority is use AC if available, then DC Battery power, then propane. Hope this helps you fellow off girders .


    System one: 8 Seimens 55 watt monocrystaline panels wired in 2 strings. Bejing EP Solar Tracer 3215RN MPPT Controller
    System two: same as above
    System three: 10 Seimens 55 watt monocrystaline panels wired in two series strings. Bejing EP Solar Tracer 4215RN controller
    System four: 2 Suntech 280 watt polycrystalline panels in series, Bejing EP Solar Tracer 4215RN MPPT Controller
    Batteries. 4 ea Interstate L-16 Renewable energy. 375 amp hour 6 volt. Wired as two strings. 12 volt system
    No inverter
    Onan Emerald 3 Generator 4500 watt 120 volt
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: Question about emergency refrigeration with solar

    Techno,

    That is a pretty good solution.

    It should be noted however that running a absorption fridge on electricity is terribly inefficient, especially compared to running a comparable fridge of the same size. That said, if you re. Running it on PV and have excess capacity then it really doesn't really matter. I used to have mine run on 12vdc when the batteries were full, but for the few hours a week I could do it, i simply wasn't worth the effort, so they simply run on L/P. If I added a bunch of PV I could run the fridge more on PV.

    Tony
  • TecnodaveTecnodave Posts: 7Registered Users ✭✭
    Re: Question about emergency refrigeration with solar

    Tony,

    You are absolutely correct, adsorption refrigeration is very inefficient, but I have 1990 watts of solar on my 12 volt system. I am using excess capacity. It would not be worth it if you paid regular prices but I purchased my Seimens panels used for .19/watt and my Suntech 280 watt panels for $60.00 each. This is why I have the LO-voltage lockout and burn propane at night.

    Tecno
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