help with solar panel plumbing

Discussion in 'Alternative Energy' started by ericjeeper, Jun 25, 2006.

  1. ericjeeper

    ericjeeper Well-Known Member

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    I have six panels.. what is the most efficient way to tie them into the heat exchanger? as for running them all in series? splitting them up ? Help need to know so I can set them next weekend
     
  2. rambler

    rambler Well-Known Member Supporter

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    I'll guess _much_ more info is needed to give you a serious answer that will mean anything.....

    What temp rise does each give, at your flow rate?

    Are you needing a large temp rise, or a large volume of low-rise heat?

    You would be looking at series, parallel, or a combo of those (2 or 3 in series, ganged into a parallel setup)?

    --->Paul
     

  3. JAK

    JAK Well-Known Member

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    I would run two large diameter pipe and have each panel connected to these in parallel, with one pipe as a supply manifold and one as a return manifold. With six panels I would make the large pipe at least 2.5 times the diameter of whatever diameter pipe or tube is in your panels, but I would also consider what pipe and insulation is available cheap. If the panels already happen to be of a design where they have a large diameter tube on the top and bottom, then you should be able to just hook the panels up in series, or a combination as rambler suggested. I think it is good to keep the flow rate in feet per second more or less slow and uniform, or if anything even slower in the supply and return than in the panels themselves, where a somewhat faster flow rate can increase heat transfer. It is good to keep distances short because pipe cost and insulation cost and friction loss and heat loss all add up pretty quick, and if it works well it can extend your season, perhaps even into winter. You don't want to be heating the water with your pump motor instead of the sun, but you don't want to spend to much on large diameter pipe and insulation either.
     
  4. ericjeeper

    ericjeeper Well-Known Member

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    there are no fittings on the bottom. all on the top.. as to flow rates I think Panle Mfg. calls for 2 gpm as stated on the tag. They are suncatcher (older panels) but have never been filled with water. had an oil of some sort in em. Thanks for the input
     
  5. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    Was hoping SolarGary would answer you. So here goes from my reading.

    I would plumb all the panels parallel. Plumbing any of them in series will give you hotter water but at the expense of efficiency. I can only speak in generalities, but in series each panel will only warm the water up by about 1/3 to 1/2 of what the panel before it did. So if the first panel heated the water up by 20 degrees, a second panel would heat it up about 6 to 10 degrees more and a third panel would only add 2 to 5 degrees.

    If a warmer temperature is needed out of the water when plumbed in series you can cut down the flow through the panels. It would also be nice to valve each one seperately so you can use them to Balance the flow through the panels.
     
  6. SolarGary

    SolarGary Well-Known Member

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    Hi,

    I think JAK and Wolf are on the right track.

    It will be more efficient if you hook them all in parallel.
    If you hook them in series, the last panels will be operating a higher temperatures and will have higher losses and lower efficiency.

    As JAK says, a supply manifold and a return manifold that have enough diamater so that the pressure drop in the manifold itself is low, and each panel gets nearly the same supply pressure. Most panels have headers along the top and along the bottom that can be connected to form the manifold, but sounds like you will need an external manifolds that are both along one end -- maybe that end shoud be the bottom?

    A manifold size of 1 inch is probably fine -- some people use 3/4 inch, but 1 inch is better. Copper is best, as temperatures of the fluid when the panels stagnate can be high.

    Your intake side manifold should be fed into one end of the bank of panels, and the the return manifold to the other end. That is, the first panel connected to supply manfold is panel 1, and the first panel connected to return manifold is panel 6. This results in each panel having nearly the same pressure drop. You are probably using antifreeze(?) -- if not, you need to slope the whole bank of panels a bit for drainage (and confirm that the panel internal plumbing will actually drain).

    If you had more than 6 panels, they would recommend dividing them into two banks with the banks in parallel.

    How big are the panels?
    Can you tell what the internal plumbing is like on the panels? -- i.e. is it one serpentine length of pipe the zig-zags back and forth, or is it a top and bottom manifold with parallel risers connected to each?
    There were some panels made that did no use tubes internally at all, but were fromed from two welded sheets -- if its this type (unlikely), you would have to be careful about overpressurizing them, and be careful of what material they are made from for corrosion reasons.

    You might find some helpful stuff here (used panels etc.):
    http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm#Maintenance

    --
    Just got back from the MREA fair -- quite a show!

    Gary
     
  7. ericjeeper

    ericjeeper Well-Known Member

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    I will post some pics as soon as I get home before dark,, Been working a lot of hours lately.. I am waiting on two pieces of glass before I can do any plumbing work..
    Yes I will be using 1 inch copper , from what I have been told.. I will feed the first panel first and it will be the last one returning to the heat exchanger.
    The panels are several top to bottom loops of fin tube basically.
    surely this weekend I will have some free time to take and edit and post some pics..
    Solar.. about the only thing free left in this world.
    The panels are 13 feet by 3 feet wide.. I have provisions for them setting at 65 degrees. aimed due south, hoping for the best winter position.,
    Thanks to everyone for their support.
     
  8. Kevingr

    Kevingr East Central MN

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    Eric, how has this been working for you since it's been a couple of years now? I'm in the middle of a similar project, 7 panels and about twice the cost of your setup.
     
  9. clovis

    clovis Well-Known Member

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    Eric...
    Glad to hear about your project. I have wondered about it many times. I described your project to a guy just a few weeks ago.

    Are you going to have a fall get together at your place this year?

    Clove