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  • Thermostat placement

    Solar heater.jpg

    Apologies if this is an extremely basic question but I am trying to work out a simple 12V system using a woodchip pile to heat part of my greenhouse by pumping water via a solar-powered water pump. I have attached a drawing of how I envisage the layout but I am not sure if I can add a thermostat in the way I have shown. Any pointers would be appreciated as this my first venture in to solar power. Thank you.

  • #2
    Yes, you can.
    But normally the thermostat just needs to go in the red wire or in the black wire, not both wires.
    But your schematic is OK.

    Note: Keep those inter-connect wires identical and fat on the 3 - parallel battery bank.
    Last edited by NEOH; 09-22-2017, 05:30 PM.

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    • #3
      Originally posted by NEOH View Post
      Yes, you can.
      But normally the thermostat just needs to go in the red wire or in the black wire, not both wires.
      But your schematic is OK.

      Note: Keep those inter-connect wires identical and fat on the 3 - parallel battery bank.
      Thank you NEOH. I will indeed keep the battery interconnects identical and fat! I will now look into the best components for the job in question.
      kind regards.

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      • #4
        When you say wood chip pile, are you collecting heat given off by decomposition? Have you taken temperature measurements? is the wood chip pile outside of the greenhouse? You could achieve similar heat gains by simply painting concrete floors and tables black. You could consider employing old pavers, bricks, blocks as a thermal ballast.

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        • #5
          Hello Logan

          Thank you for your reply. I have experimented at my work with woodchip and grass piles which were just happily composting away and took temp readings of 70

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          • #6
            Originally posted by David G View Post
            Hello Logan

            Thank you for your reply. I have experimented at my work with woodchip and grass piles which were just happily composting away and took temp readings of 70
            Sorry. I don't know what happened there. Only a fraction of my reply got posted from my iphone!

            What i was going to say was that I managed to get 70degreesC from the compost pile at work just from decomposition. I would envisage a similar pile close to my greenhouse, coiled water filled pipe inside it which would be pumped into the greenhouse using the solar powered pump. It would be good to have control over when this heat is introduced to the greenhouse which is why I wanted it thermostatically controlled.

            I like your idea of the storage heaters and perhaps I could incorporate this by placing some concrete blocks or bricks under the benching which could then hold on to the heat a little longer. I think that would be a great thing to try.

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            • #7
              Special Characters. Mostly, they cause problems with the Forum software, which is configured to be spam resistant, and Special Characters are used in a lot of spam. So apostrophes and degree symbols are often stripped out or just plain truncated posts.
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

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              • #8
                Stagnant 70 degrees C is nice, but this is caused by 'slow but steady' action of bacterial decay, which at the rate of temperature/btus/calories are produced will be diminished quickly not only by the circulated water's extraction of this heat but will also be reduced at nearby pipe/coil due to cooling of the enviroment of this bacterial process which then defeats more continued heat to be produced. This will result in rapidly diminished returns or output.

                This does not even take in the considerations of the poor conduction of heat to allow it to migrate through the cellulose/wood...which is a soggy porous insulator.

                Heat Out will only equal the Heat In...you'll need acres of a massive pile and very lenghtly pipe/coil system and all else that goes with it...and/or a little tiny greenhouse.

                Food for Thought: Maybe try burying a garden hose coil to see proof of concept before spending any money here.

                Comment


                • #9
                  Originally posted by neweclipse View Post
                  Stagnant 70 degrees C is nice, but this is caused by 'slow but steady' action of bacterial decay, which at the rate of temperature/btus/calories are produced will be diminished quickly not only by the circulated water's extraction of this heat but will also be reduced at nearby pipe/coil due to cooling of the enviroment of this bacterial process which then defeats more continued heat to be produced. This will result in rapidly diminished returns or output.

                  This does not even take in the considerations of the poor conduction of heat to allow it to migrate through the cellulose/wood...which is a soggy porous insulator.

                  Heat Out will only equal the Heat In...you'll need acres of a massive pile and very lenghtly pipe/coil system and all else that goes with it...and/or a little tiny greenhouse.

                  Food for Thought: Maybe try burying a garden hose coil to see proof of concept before spending any money here.
                  Pretty much as you write.

                  To the OP: The decay process generates heat. How much heat is one question. How steady, or were the heat is generated within the pile, how that may change as f(time), and also how the thermal conduction properties of the compost might affect the rates of output to a set of coils, the design of which is itself contingent on the same questions.

                  Overall, while getting heat out of a compost pile is possible, I'd wonder if the uncertainly of the steadiness/reliability of the heating rate, and the PITA that goes with limited ability to get necessary answers to unknown questions of the type mentioned might make the otherwise possible concept, maybe not such a good idea to rely upon as a way to protect something from freezing.

                  Take what you want of the above. Scrap the rest.

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                  • #10
                    Thank you neweclipse and J.P.M. for your replies. This is all new territory for me so I appreciate all of your input. I think the intricacies of this subject go way over my head and I now realise I may be expecting miracles. I agree neweclipse that a proof of concept would be a very sensible thing to try and a garden hose idea would be worth pursuing.

                    At the end of the day i am not expecting to heat a greenhouse to tropical levels, just a gentle heat to ward off frosts essentially, so even a marginally successful setup to see me through a few of the colder periods would be satisfactory.
                    I intend to try out these ideas as my curiosity demands that I give it a go.

                    Comment


                    • #11
                      Originally posted by David G View Post
                      Thank you neweclipse and J.P.M. for your replies. This is all new territory for me so I appreciate all of your input. I think the intricacies of this subject go way over my head and I now realise I may be expecting miracles. I agree neweclipse that a proof of concept would be a very sensible thing to try and a garden hose idea would be worth pursuing.

                      At the end of the day i am not expecting to heat a greenhouse to tropical levels, just a gentle heat to ward off frosts essentially, so even a marginally successful setup to see me through a few of the colder periods would be satisfactory.
                      I intend to try out these ideas as my curiosity demands that I give it a go.
                      Do it for the fun of acquiring knowledge. Been there and done that lots. Still at it., But, book knowledge is a cheaper and easier way to get the fundamentals under your belt before a lot of $$ and toil. It'll also make the work more productive. BTW, don't forget to vent the compost. CO2 production in unventilated spaces isn't too healthy.

                      Comment


                      • #12
                        I use an old school kerosene lantern in my greenhouse to ward off frost, works pretty well.
                        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                        solar: http://tinyurl.com/LMR-Solar
                        gen: http://tinyurl.com/LMR-Lister

                        Comment


                        • #13
                          Originally posted by J.P.M. View Post

                          Do it for the fun of acquiring knowledge. Been there and done that lots. Still at it., But, book knowledge is a cheaper and easier way to get the fundamentals under your belt before a lot of $$ and toil. It'll also make the work more productive. BTW, don't forget to vent the compost. CO2 production in unventilated spaces isn't too healthy.
                          I will continue reading but at some point I get itchy feet and have to get my hands dirty too but will do so as cheaply as possible to start with.
                          Yes I will also bear in mind the CO2 aspect of the composting process although in my plan my woodchip pile will be based outside the greenhouse.

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                          • #14
                            Originally posted by Mike90250 View Post
                            I use an old school kerosene lantern in my greenhouse to ward off frost, works pretty well.
                            I know this is a tried and trusted method of greenhouse heating but if possible I would like to produce heat in a cleaner, more renewable way if I can. If all else fails I think I would use an electric heater (but not if I can help it).

                            Comment


                            • #15
                              Originally posted by David G View Post

                              I will continue reading but at some point I get itchy feet and have to get my hands dirty too but will do so as cheaply as possible to start with.
                              Yes I will also bear in mind the CO2 aspect of the composting process although in my plan my woodchip pile will be based outside the greenhouse.
                              Try foot powder and hand cleaner.

                              Every so often a mushroom farm around here starts a fire via spontaneous combustion in the mushroom beds which are somewhat similar to compost bins/heaps. Use to be welding /metal fab. shop housekeeping, or auto repair shops, etc. highlighted not throwing oil/solvent soaked rags in out of the way places for the much same reasons. FWIW, if you need dominion over your environment, think safety first and always. That's also a good place to start the book learning. Tends to keep insurance premiums low(er) as well.

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