What happens if the panel produces less power than required?

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  • dave_ryman
    Junior Member
    • May 2009
    • 1
    #1

    What happens if the panel produces less power than required?

    Hi there from a newbie.

    I'm wanting to chill some medication whilst camping. We have a small portable (12vdc) fridge. During the night, the insulating properties of the fridge will probably keep the medication cool enough. During the day, we will need to provide additional cooling. Solar seems the way, since cooling is most critical when the sun's out.

    The fridge is rated 12v/40W. A 40W solar panel would be rather expensive for this project, and I was thinking more along the lines of a panel that can (in the brightest weather) produce 2 to 5W.

    I'm familiar with what happens when a battery (eg: AA) goes flat: The powered bulb goes dim, or the DC motor slows down. I also understand that it's not a good idea to use a DC power supply (plugged into the mains) that is rated at fewer Amps than the powered device will draw.

    So which of these is a Solar panel most analagous to? If I use a small panel to power the fridge, will I get the (desired) result that the Fridge will run on reduced power and not get as cold as it might at full blast, or will something hideous happen to the solar panel?

    Regards
    Dave
    Tags: panel, power, refrigeration, solar, wattage
    • greenguy
      Junior Member
      • Apr 2009
      • 3
      #2
      It would depend on how the portable fridge works. Does it operate like a conventional refrigerator, with a compressor, evaporator and a refrigerant like Freon? Or is it one of the ones that uses Peltier coolers (no compressor, and no moving parts at all except for a small fan to exhaust the heat from the cooler)?

      If the fridge uses Peltier coolers, a 2-5W solar panel will likely operate it, but the cooling capacity is going to be *drastically* reduced - probably not enough to keep the fridge from warming up during the day. If the fridge uses a conventional compressor motor, the solar panel probably won't operate it at all.

        Comment

        • Sharon_Hart
          Junior Member
          • Dec 2008
          • 26
          #3
          We have 2 relatively small solar setups to use for our laptops while camping, but frankly, have been disappointed with our lack of success keeping them powered up. If you use a too small panel to power the fridge, from our experiences, the fridge won't run at all. We haven't had disastrous results to either of the panel setups (one is an almost $500. multiple panel unit in a suitcase, and the other is a single panel.) Both of our setups work by charging a battery, and then the battery powers the device. I'd recommend dragging along an old fashioned cooler with ice and put your meds in a sealed plastic container to keep them dry-that's what I did when traveling with my diabetic cat for years. You can replenish ice most anywhere, and if the weather is good, and your solar setup works properly, you can start using the cooler for extra storage... Good luck! We all need to keep experimenting...

            Comment

            • lamar5292
              Junior Member
              • May 2009
              • 10
              #4
              You should run the panel through a controller and store power in a deep cycle battery. I suggest a 45 watt panel or larger as the 12 volt fridge you describe is probably similar to the one I have and these will drain a deep cycle in about 3-4 hours.

              They make very small 12 volt can coolers that use less power that may be more effective for your use. Look at auto 12 volt appliance websites and on amazon.com

              A small propane fridge may also be better suited to your use.

              LaMar
              https://www.simplesolarhomesteading.com

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