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Massive failure of Heatpipe ST collectors

  • 07-09-2011 11:56am
    #1
    heinbloed
    Registered Users, Registered Users 2 Posts: 1,632 ✭✭✭


    The German ST test facility TUV has changed the test parameters for heat pipe collectors.
    The reason for this was a massive shortcoming of ST energy harvested in a very large collector field, the actual thermal harvest being much lower than what was predicted and guaranteed.

    The official test regime for heat pipe collectors demand a half an hour frost resistance. For the collector. But not for the individual heat pipe.
    So the half an hour test is easily passed. Most manufacturers ad the term " to be used in combination with glycol ".

    But the heat pipes themself are bursting, the inner copper tube holding the fluid, the thermal carrier.

    And these tubes aren't tested.

    The frost damage done is NOT VISIBLE, the bursted copper tube not visible since it is build-in.
    The vacuum between single glas pipe and evaporator (the copper tube) is not damaged during frost exposure. So no visible demage.

    Here a blogger on the issue:

    http://robertkyriakides.wordpress.com/2011/07/27/frost-damage-in-heat-pipes/

    Here the TUV in English language about the changed test regime:

    http://www.tuv.com/news/en/corporate/about_us_1/press/news_2/newscontent_cw_61760.jsp/Solar%20heat:%20T%C3%9CV%20Rheinland%20to%20develop%20new%20test%20procedure%20for%20freeze%20resistance%20of%20vacuum%20collectors%20with%20heat%20pipes


    Here the TUV report in German language on the official desaster, mind the pictures showing the damage at page 4/4:

    http://www.tuv.com/media/germany/10_industrialservices/downloadsi06/Frostpruefung_Heatpipe_Info_20110725.pdf

    The left bottom picture shows swollen copper tubes, titled after three cycles of 10 hours orig " Nach 10 EN Zyklen (a 10 h)"
    The right bottom picture shows the tubes bursted, titled after 10 cycles of 10 hours, orig. "Nach 10 EN Zyklen (a 10 h)"

    The fluid in the heat pipes freezes, expands and blasts the copper.


    In the actual case which has lead to the TUVs change of it's test regime 5 manufacturers had supplied HPs to the observed and metered, large commercial ST installation. ALL failed during the more strict freeze test.

    So check the clutter on your roof.
    There is no cure which can be done. Only an exchange of the heat pipes containing a frost proof thermal carrier liquid can be done.

    Note that the toy installations (standard household sizes) will hardly be spotted as failures since there are in most cases no calorie meters installed (thermal energy meters). The failed installation looks allright from the outside but hardly delivers any usefull energy.

    Ask your sales men for a certificate how frost proof the purchased HPs actually are. Don't be satisfied with an outdated collector test, demand the official heat pipe test report. And expect a massive closure of seller and installer companies. First come first go.


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