Is a Sunfrost Fridge worth it?

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  • softdownsoftdown Solar Expert Posts: 3,481 ✭✭✭✭
    edited January 2019 #32
    FWIW - one could freeze a gallon of milk and use it in lieu of a block of ice in a cooler. In the shade, that would last quite awhile. I buy milk every couple weeks and immediately freeze it. Works great for keeping a cooler cool on extended trips. But then, I'm a milk guy at least once/day. One could do the same thing with water jugs. Indentations on the side indicate that the jug is made to handle the expansion of freezing. 

    Takes a lot of energy to bring a refrigerator down from room temp to ~36F or so. 

    Energy Star refrigerators make Sunfrost etc. significantly less needed. Propane is a good refrigerant but needs a little periodic maintenance I hear. 

    What happened to $400 refrigerators anyway? About all I see anymore are giant stainless steel behemoths that often cost well over $2000. Yet it is still hard to buy a used Energy Star refrigerator. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    mcgivor said:
    The energy guide numbers are fairly accurate under normal temperatures, right now it's the coolest part of the year here, April is the hottest, so I'm going to log useage until at least May to see the trend. The energy guide for my Panasonic is 324Kwh per year, I suspect it will be higher because ambient temperatures will be >30°C, the screen shot shows normal running, the one shot value is useage since 7am. the power is transferred to another system for four hours per day. Note the power factor, the actual power taken from the batteries is 114W, the power recording can also displayed as a daily list or graph.
       

    Wow.  With a pf that low, would it make any sense at all to attempt correction?
    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
  • mcgivormcgivor Solar Expert Posts: 3,563 ✭✭✭✭✭✭
    At one stage I ran the entire house through the power monitor for a month, the power factor then, with all loads connected was never that low, usually 0.8 to 0 depending on what was running at the time. Attempting correction to a single circuit would have an effect on the entire system as it's not a constant load, kind of like a moving target.  When the refrigerator is the only load in a system or on an inverter, perhaps then correction may make sense, though I'm unsure how the inverter in the refrigerator will react to additional capacitance as well as the DC -AC inverter. This PF dose however demonstrate that some things are not what they appear when looking at nameplates or Energy Guide fifures, particularly when off grid where the owner is the utility and has to account for these losses.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 31,090 admin
    That power factor is not good... Either they have a very simple rectifier and high voltage capacitor on the AC input (series of pulsed current) or something is broken.

    https://en.wikipedia.org/wiki/Power_supply#AC-to-DC_supply

    It is not that hard or costly to make digital power supplies that have nearly 0.95 PF (power factor corrected supply). In Europe, they require PFC...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭
    Will  plug in the power thingy next up at holiday home ... and check the power factor for the Samsung and lg fridge/ freezer.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • stmoloudstmoloud Registered Users Posts: 111 ✭✭
    You can see from my sig that 269 kWh per year fridge freezer might theoretically be a challenge but in real life l do have more energy on tap than I can use.
    I do get up at least three times per night and not ever have I seen resting battery voltage at less then 12.5.
    I  live in a temperate zone, no real extremes. And I do have < 6 month  batteries.


    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcgivormcgivor Solar Expert Posts: 3,563 ✭✭✭✭✭✭
    Will  plug in the power thingy next up at holiday home ... and check the power factor for the Samsung and lg fridge/ freezer.
    That will be interesting please do report 

    BB. said:
    That power factor is not good... Either they have a very simple rectifier and high voltage capacitor on the AC input (series of pulsed current) or something is broken.

    https://en.wikipedia.org/wiki/Power_supply#AC-to-DC_supply

    It is not that hard or costly to make digital power supplies that have nearly 0.95 PF (power factor corrected supply). In Europe, they require PFC...

    -Bill
    Agreed it is rather poor, actually came as a bit of a suprise, that PF was using a generic DC-AC inverter, when it transferred to the Schneider the PF is slightly better at 0.6 but still pretty dismal, perhaps testing on other refrigerator models at a store will provide more information, they do have > than 30 inverter refrigerator models from various manufacturers. One interesting thing is, when logging for a month the Kwh out from the inverter  (just a single inverter for test purposes) revealed that the difference between the solar input/AC output were very close, 83Kwh in 81wh out, taking into consideration inverter tare load, so 2 Kwh loss in 30 days, that would be less than the poor PF would indicate. The LFP battery is efficient though not 100% so there must be some losses there as well, now I have more questions than answers

    stmoloud said:
    You can see from my sig that 269 kWh per year fridge freezer might theoretically be a challenge but in real life l do have more energy on tap than I can use.
    I do get up at least three times per night and not ever have I seen resting battery voltage at less then 12.5.
    I  live in a temperate zone, no real extremes. And I do have < 6 month  batteries.



    Battery capacity is not really a concern in my case they could support ~5 days with no input, which is very rare. As state of charge is not an isue with LFP it's easy to recoup losses over a few days, or just charge with the generator, if need be. The  days of living close to the edge are gone, in 5 months the only reason to run the generator is to exercise it, or to do some welding. The data supplied is raise the question, are inverter refrigerators actually a good fit in off grid applications, however I too am questioning what I'm seeing.
    .
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭

    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭
    Both lg and samsung show powerfactor 100 .  . Photo is the samsung running .. suspect that the $29  Power meter could be lies ...  
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • mcgivormcgivor Solar Expert Posts: 3,563 ✭✭✭✭✭✭
    Some power factor meters use a percentage scale, 100 being both voltage and current are 100% in phase, which would be perfect.

    Did some research into battery based systems as there were some seemingly strange results whilst logging my entire house over the course of a month. The amount of energy produced over 30 days, 83Kwh was 2Kwh more than was used, naturally there would be some losses  in batteries, wiring and so forth, however the poor power factor of the refrigerator didn't reflect this, losses should have been higher, but they weren't. Turns out power factor has no negative impact on the batteries themselves, 1Kwh used, even with a power factor of 0.5, is still 1Kwh taken from the battery, the Arcillies heel is however the source suppling the energy, be it a generator or inverter, that is where power factor becomes an issue. 

    The DC /AC  inverter in my case can handle the PF of such a small load, but I am still curious as to why the PF is so low, I will test some other models in the near future to see what they are.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • SurfpathSurfpath Solar Expert Posts: 400 ✭✭✭

    We installed a 14.9 cu ft LG inverter Fridge (looks very like this model: LT44SGP) about 6 months ago. Advertised Kwh/month on the energy saver sticker is 23.5 (it's atill on the fridge), actual usage over the past 6 months (my meter is still on it), is around 28 kwh/month. Still, better than any conventional fridge I've ever measured.

    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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