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Hot Water by Solar Electric direct via MPPT ?

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  • #91
    Having a quick list of available elements is handy. Selecting the ideal resistance only guarantees that the resistance is not way less than the panel can support in the best two hours of the day. A slightly higher resistance may perform overall better daily in a direct connect without some power point control. In a half light condition the current is half, but the power is 1/4 and rapidly going down hill from there. For most of the day your heating will be in the toilet with direct connect. Panels are cheap. Solar is the only thing I know where the people are so happy if it even works at all. David will soon be demonstrating MPPT heating.

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    • #92
      David Poz does demonstrate the kind of results that can be expected when things are thrown together without any
      careful design. All you need are a few basic equations, like ohms law, P = Vsquared /R, etc. and your 4 function
      calculator. Get a better visual on it with a load line like this.

      So now enlightened Dave will solve your problem with his spreadsheet? Am I to just TRUST this so recent
      improvement, to do it all? Can nobody actually do, or is too lazy to do, or is too impatient for gratification, to do
      the most simple design and calculations for themselves any more? I did that phase with a slide rule.

      Anyway Dave has ignored the fuse requirements for 3 paralleled panels, and there is
      no mention of the type thermostat capable of DC operation. good luck, Bruce Roe

      PVLdLn.jpg

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      • #93

        Originally posted by cretch View Post
        Yes, because I'm not allowed to export to the grid. The power company will not accept any. I been trying to figure out what to do without going to a large battery packs. I've looked into the Outback Radian but on Gridzero that constantly cycles the batteries, does not a good solution to me. Any suggestion?
        I do exactly this by 'load diversion'. I have 200 gallon of DHW storage between 2 separate tanks. So far, on a good sunny day I can max them both out at 125*F. I am currently looking at a means to 'dump' any excess PV production beyond my storage capacity, as a last resort.

        Using standard factory tank electric immersion elements and thermo-switches, only mod to DHW heater for me was to make elements independent circuits, others may find that unnecessary in their situation.

        Using this 'load diverter' , popular in Europe, can literally holds the electric meter at a 'dead stand still' while diverting and can self-regulate even with moment by moment changing household loads.
        Control is by an electronic PCB with Atmega328 8-bit microcontroller running a SSR or triac switching at zero-crossing referenced to surplus load available as measured 60 times per second.

        All this is easily found at 'openenergymonitor.org'...that's how I got all my info. Cheers
        Note: Europe does use 230 VAC @ 50Hz, so that needs factored in to make this work for NA 240 VAC @ 60Hz
        Sorry, No, does Not work off-grid and batteries...Only Grid-Tied.
        Last edited by neweclipse; 04-25-2019, 04:44 PM.

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