Announcement

Collapse
No announcement yet.

Off Grid house with Dish TV. Power off or leave on?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by J.P.M. View Post

    FWIW, if that fridge has a freezer, or if you have access to ice, loading some ice in the fridge will help keep it cool. I'll cost some space, but the ice will also increase the cycle times and reduce their number.
    A fridge that is packed, especially with thermal mass items like meat and liquids use less energy. An empty fridge will use more power than full fridge. Take away is keep the fridge packed with water bottles. If you do loose power buys you an extra day before spoilage.

    MSEE, PE

    Comment


    • #17
      Originally posted by Sunking View Post
      A fridge that is packed, especially with thermal mass items like meat and liquids use less energy. An empty fridge will use more power than full fridge. Take away is keep the fridge packed with water bottles. If you do loose power buys you an extra day before spoilage.
      I suggested ice because of the heat of fusion of H2O, liquid to ice and reversibly the other way around being about 80 times that of the energy required to raise the H2O's temp. 1 degree, meaning the volume of ice can be about 80 times less or a bit more after ice/liquid volume adjustment and thus have the same temp. retention as 80 times the same volume of liquid H2O with the added advantage of lower fridge temps., leaving more room for food storage.

      The drawback to using ice, if it can be called that, is probably no real energy use reduction except that from longer and fewer fridge compressor cycles, with that relatively small amount of energy savings being largely offset by a fridge temp. closer to C., instead of maybe something like 4 or 5 C.
      Last edited by J.P.M.; 01-04-2018, 08:31 PM.

      Comment


      • #18
        Originally posted by J.P.M. View Post

        I suggested ice because of the heat of fusion of H2O, liquid to ice and reversibly the other way around being about 80 times that of the energy required to raise the H2O's temp. 1 degree, meaning the volume of ice can be about 80 times less or a bit more after ice/liquid volume adjustment and thus have the same temp. retention as 80 times the same volume of liquid H2O with the added advantage of lower fridge temps., leaving more room for food storage.

        The drawback to using ice, if it can be called that, is probably no real energy use reduction except that from longer and fewer fridge compressor cycles, with that relatively small amount of energy savings being largely offset by a fridge temp. closer to C., instead of maybe something like 4 or 5 C.
        I am referring more to fridge not freezer section. But hey when it comes to Thermal Dynamics I am mostly IGNORANT, and leave that subject to you. .
        Last edited by Sunking; 01-04-2018, 11:40 PM.
        MSEE, PE

        Comment


        • #19
          Originally posted by Sunking View Post

          I am referring more to fridge not freezer section. But hey when it comes to Thermal Dynamics I am mostly IGNORANT, and leave that subject to you. .
          Ice in the freezer is a good idea. Ice in the fridge will help with energy, but then you have the make that ice and put it in the fridge every day.

          Comment


          • #20
            Originally posted by Sunking View Post

            I am referring more to fridge not freezer section. But hey when it comes to Thermal Dynamics I am mostly IGNORANT, and leave that subject to you. .
            Well that's a good thing because it seems to me (and lots of others who I call friends) that I have an obvious abundance of that quality (ignorance, that is), and seemingly getting more of it every day, with all that making me more familiar with ignorance than most from the inside out, to the point of being an expert.

            As for fridge/freezers and discussions discussions here about the rate of change of temp. difference between the inside of a cold(er) space and its surroundings, it makes no difference if the space is a fridge or a (colder) freezer or, say, a warmer oven for that matter. A simple and therefore incomplete but still useful model that uses a lumped mass system and the idea of a thermal time constant can be informative. Without a lot of math, the lumped thermal mass system is analogous to an RC electrical circuit where the thermal capacity ( the lumped mass) is analogous to a circuit capacitor, and the inverse of the rate of overall heat loss in the thermal model is analogous to the circuit resistance.

            The gross thermal mass (sometimes called thermal capacitance) divided by the overall heat loss rate per degree of temp. diff. between (the lumped mass system = the fridge and it's contents) and its surroundings is called the thermal time constant of the lumped mass system and has the dimension of time.

            So, the larger the thermal mass of a system OR, the lower the heat loss rate (or both) the greater (longer) will be the fridge time constant, and the slower the lumped mass temp. change will be, meaning in our fridge example here, the box will stay cooler longer when it has more stuff in it (or ice as discussed below).

            More thermal mass will allow the fridge to cycle less, with each cycle being longer, meaning longer run times but also longer off times - with the longer off times seeming to be the goal here.

            FWIW, the same longer cycle times can theoretically and actually be obtained by insulating the crap out of the box which will not only increase the time constant by reducing the overall heat loss rate,. but also reduce the electrical use as well. That ploy however, is fraught with lots of potential and practical problems and I'd not recommend it to the point of saying don't do it.

            As for ice in the fridge vs. other things (like beer for example) that don't change phase, ice in the fridge has the advantage of a large latent heat of fusion. So, a kg of ice @ 0 C. will absorb the same amount of heat as 80 times as much liquid H2O at 0 C. and remain at 0 C. until all the ice turns into liquid. That has obvious space saving opportunities. There are some disadvantages of ice in terms of perhaps too cold temps. in a fridge, but a little experimentation with ice quantity and location in the box usually solves that problem. I used plastic gal. jugs filled about 90 -95 % with loose tops. Worked great. Long, boring story.

            SK: not a knock, and if you're meaning some (self deprecating ?) humor, please accept my apologies for my slow uptake on the joke, but the proper term (since the mid 19th century anyway) for the branch of science that deals with the relation(s) between heat and other forms of energy, including work, is "thermodynamics" (with, and in light of recent discussions, it ought to be noted, is sometimes first letter capitalized by some). Referring to it as "Thermal Dynamics" is, as you seem to imply, ignorant. Your meaning probably remains clear to most, but, and I'm guessing you care not a whit here, its use doesn't do much to help folks knowledgeable in that area take you as seriously. Analogously to your actions around here, I try to keep my mouth mostly shut about stuff I'm ignorant about, but I know its not called "Elect Ronics".

            Respectfully,
            Last edited by J.P.M.; 01-05-2018, 02:30 PM.

            Comment


            • #21
              Originally posted by J.P.M. View Post
              SK: not a knock, and if you're meaning some (self deprecating ?) humor, please accept my apologies for my slow uptake on the joke, but the proper term (since the mid 19th century anyway) for the branch of science that deals with the relation(s) between heat and other forms of energy, including work, is "thermodynamics" (with, and in light of recent discussions, it ought to be noted, is sometimes first letter capitalized by some). Referring to it as "Thermal Dynamics" is, as you seem to imply, ignorant. Your meaning probably remains clear to most, but, and I'm guessing you care not a whit here, its use doesn't do much to help folks knowledgeable in that area take you as seriously. Analogously to your actions around here, I try to keep my mouth mostly shut about stuff I'm ignorant about, but I know its not called "Elect Ronics".
              No apology needed, it was a joke as indicated by the font I think you caught. Just like my biz, I hired ME's to do HVAC and building mechanical systems. I don't tell them what to do, they just tell me what they need for power requirements. I actually understood most of what you said with relationship to time constants and capacitance. Just not something I do everyday. I can size a heat pump for a house, but I always had someone double check my work. I would never Stamp drawings unless the other disciplines signed off. That is why they get paid the big bucks.
              MSEE, PE

              Comment


              • #22
                Originally posted by Sunking View Post
                No apology needed, it was a joke as indicated by the font I think you caught. Just like my biz, I hired ME's to do HVAC and building mechanical systems. I don't tell them what to do, they just tell me what they need for power requirements. I actually understood most of what you said with relationship to time constants and capacitance. Just not something I do everyday. I can size a heat pump for a house, but I always had someone double check my work. I would never Stamp drawings unless the other disciplines signed off. That is why they get paid the big bucks.
                RUA and agreed. I supervised a few EE's over the years but didn't question their decisions, design or judgment too much. I'm quite certain you understood all of it and more.

                Info was more for others like Cult, with respect to the 2d para. of his 1104 hers. post.

                FWIW, the same thermal time constant concept is applicable to time shifting of A/C loads to game a T.O.U. billing system. Sort of like a thermal battery. Or, as a minor advantage,. to increase HVAC cycle times and in so doing reduce startup transient losses and system wear a bit.

                Off topic, but the sunspace I added to the first house I owned in Buffalo had about 7,000 lbm of dyed black water contained in translucent 24" dia. 6' long vertical tubes that, along with rather effective and operable thermal shutters, would keep the temp. of the attached space about 30-40 deg. F. above the outside ambient temp. at night with no addition of aux. heat. The water also helped prevent daytime overheating for the ~ 50 - 60hrs./winter month when the solar disk appeared.

                Comment


                • #23
                  Originally posted by J.P.M. View Post
                  Off topic, but the sunspace I added to the first house I owned in Buffalo had about 7,000 lbm of dyed black water contained in translucent 24" dia. 6' long vertical tubes that, along with rather effective and operable thermal shutters, would keep the temp. of the attached space about 30-40 deg. F. above the outside ambient temp. at night with no addition of aux. heat. The water also helped prevent daytime overheating for the ~ 50 - 60hrs./winter month when the solar disk appeared.
                  Come on down to Panama and see true Southern engineering. Down here there are only a couple of cities that even have water and sewer plants. Water and Hot Water are almost free down here with an inexhaustible supply. Electricity is dirt cheap with unlimited supply. Depending on what part of the country you live in receives 200 to 400 inches of rain per year. You do not need wells, just a cistern or storage tank to collect rain water. Hot water is super easy just takes some black pipe and a salvaged 55 gal drum for all the hot water you want. So hot it has to be mixed with cold water to take a shower. During wet season with several days of clouds may mean some cool showers. Where I live showers are outside and some days a cool shower is refreshing. I live at altitude so temps are moderate all year, but once you get below 2000 feet, especially on the Caribbean side of the divide, you are soaking wet from humidity 24 hours a day and a cold shower is relief. Think Miami FL except with higher humidity and warmer temps and you know what Panama City is like. In the Jungle, it is unbearable even at altitude because there is no breeze or wind.

                  MSEE, PE

                  Comment


                  • #24
                    The thing stopping you from a lot of that stuff here is the gov't. They don't want anyone living "self-sustaining". They want to steal from all of us here. They fine people here for capturing rain water and now they have these stupid laws or some crap making it so your entire house in Miami cannot be off the grid. They force everyone to be connected to FPL.

                    Comment

                    Working...
                    X