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Elegantly Simple Heat Pipe Design

Kevin_in_Denver_2
Kevin_in_Denver_2 Member Posts: 588
in Solar
Does anyone have any first hand experience with "all glass heat pipe evacuated tube collectors"?



Since there is no copper, these must be very low cost.



I would expect some thermal shock problems... but...



Usually they are inserted into an unpressurized storage tank.

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Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Would that be a Wet Vac design ;-)

    If it works the way I am seeing it in my minds eye, and it has a wetted glass surface, I'd be VERY wary of the water quality to be used in circulation, as well as the need to properly clean and flush the system prior to final fill.



    Please explain "Usually they are inserted into an unpressurized storage tank." Is this like a roof mounted bread box heater?



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    The working fluid is hermetically sealed inside

    The tube has a partial vacuum inside with a few milliliters of pure water as the working fluid. The clear part is the single-walled condenser bulb. The black part of the tube is double walled, with a vacuum between the walls. The black selective surface absorber is sputtered onto the outside of the inner tube. That's it. The price per tube has already reached as low as $2.00 - $3.00.



    I would think this design is more immune to scaling and corrosion than any design with copper parts.



    The condenser sits inside the storage tank of a "tank on roof" design:

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    SImplicity...

    is limited to where it can be used.



    Other than using evac tubes as the heat source, this reminds me of the old bread box heaters that were available a long time ago. Every one of those that I saw in Denver had to be cut out and eliminated because the homeowners insurance company refused to allow any more water damage claims. It falls under the same category as drain down systems. Appropriate for a very limited climate (never freezes) condition.



    Kudos to you for your continued efforts to bring the cost of solar hot water heating down, but as experience has shown, certain systems should be confined to areas where freezing is not an issue.



    See you at the ASES conference. What, when and where will you be presenting?



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited May 2012
    Low Cost Solar at ASES / WREF

    WREF this Monday May 14: http://ases.org/conference/



    "FORUM - Advancements in RE Technology: Radically Reducing the Cost of Solar Water Heaters - 5/14/2012 4:15pm - 5:30pm"

    I get eight minutes.





    In 1982-83 I was an engineer at Solaron. We were trying to develop a rooftop breadbox.

    We gave up, then went out of business.



    More recently, Jay Burch at NREL and others have developed a reliable low cost way to freeze protect this type of system. ( I tried it and it worked for me down to -10F) Of course, something like this needs widespread field testing! Lots of unknowns, and lots of bugs to find and squash. Again, it's FMEA.



    Note: breadbox heaters are no good for cold climates. They lose most of their heat overnight, just in time for the morning shower. However, the system shown above is not a breadbox collector, and will only lose around 10% more per day than if the tank were in the basement.



    I can't post the paper on how to easily freeze protect a tank on your roof. I'll email it to you.

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited May 2012
    Natural convection for freeze protection

    Still having trouble posting....

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Hope you can talk fast...

    Sound like an IGNITE presentation.....



    BTW, none of your links worked.



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited May 2012
    NCL for freeze protection

    still trying...

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited May 2012
    sketch of pipe couplet

    ......

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    the NREL paper....

    ???

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  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Nada...

    Nada dang thing ;-)



    Ever done a screen shot?



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    Finally Found it

    http://www.nrel.gov/docs/fy06osti/39664.pdf

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  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    ?

    why does that have to be a tank on the roof? can't it just be a fat pipe with a tank in the basement? am I missing something?
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited May 2012
    Looking for a Header

    Rob,



    You're right, it's just that no one manufactures a header for this type of tube yet. (That I have found, anyway)



    A dry header that was suddenly filled might be pretty exciting, whereas a tank smooths out the temperature changes

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  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    sure

    I'm not saying drainback it... though if you can, cool... but it could just be a fat pipe with water, it doesn't have to be the sum total of your storage on the roof.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    tanks on rooftops lose too much heat in cold climates

    Rob, I agree. The tank should be inside the house if possible. In most cases, that means you need a pump and controller.

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  • Karl_Northwind
    Karl_Northwind Member Posts: 139
    source?

    Where can I get those tubes?  I'm interested in experimenting with a bunch (say 30?) building my own array.  if they're that cheap, I'm game.



    karl
  • SWEI
    SWEI Member Posts: 7,356
    frozen PEX

    Interesting paper, though they seem to have somehow associated Wirsbo with silane cross-linking (Wirsbo is PEX-A, which uses the Engel process.)
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Good eye...

    Bad government employees, most of who really DON'T know what they are talking about (obviously)...



    ME

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  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    edited September 2012
    All glass heat pipes

    That's the spirit, Karl.



    Chinese manufacturers don't know our market well enough to design systems for North America. So we have to test their products ourselves and see if there is a fit.



    Here's what I've gotten from a Canadian importer:





    "Got in touch with China and got my calculator out. The cost per square meter ($150) is the same as for the fully SRCC(&CSA&Europe) certified high pressure copper heat pipe panels as for the all glass heat pipe panels.



    12 tube, 1.2 square meter, all glass heat pipe, same as 170 liter system tubes, $179 No SRCC, no pressure, same cost as copper, but no corrosion, and can be shipped without breakage.http://www.seabirdsolar.com/scripts/gravity_system_photos.php



    The condenser bulb ends of our copper heat pipe panels have chrome on them, so that largely negates the corrosion advantage. That leaves the single shining advantage that the all glass heat pipes are tough, they can ship without breaking."



    But Jay Burch, the NREL researcher, has been quoted $50/m2 for this type of tube. That's for a container direct from the manufacturer.



    So you can get them through Seabird Solar, but the price isn't that compelling yet

    http://www.seabirdsolar.com/scripts/gravity_system.php

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