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Thread: EVA questions

  1. #1
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    Default EVA questions

    I'm looking to encapslate my panels and see syl-guard and areomarine as being to expensive.
    How does the cost of EVA compare?
    If you only do the backside do you need to use a vaccume?
    Can I place a plastic sheet like the wall covering they sell at Lowes on after?
    Do I need to have the frame in place before using the EVA?
    Since EVA is heat activated how does it stand up, doesn't it melt when the panel is in use?

    Larry

  2. #2
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    EVA is a hot melt glue. It does not provide any "weather protection".

    It works best with glass on the front, and Tedlar on the back:

    layer of glass
    layer of EVA
    PV cells
    layer of EVA
    layer of tedlar

    Fieldlines board has a great post/tutorial on how to do it right:
    Oztules' series (at Fieldlines):

    http://fieldlines.com/board/index.ph...,144982.0.html

    http://fieldlines.com/board/index.ph...,144995.0.html

    http://fieldlines.com/board/index.ph...,145004.0.html
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    Default

    Thanks Mike,

    I saw that thread, they were very good but I still have questions.
    I found through e-bay that EVA would be about $15 to do two sides of my 36 cell panel so it IS cheaper.
    But can I do just one side and a backing like teldar or tyvek?
    From the posts and vids I've seen I take it that the frame does not have to be on the panel, am I right?
    I don't understand using Tyvek as it is "breathable".

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    TEDLAR is not the same thing as
    TYVEK

    One is a sealing sheet (tedlar) other is a breathable house wrap (tyvek)

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    Mike,
    I know well what tyvek is, I'm a contractor, hence my question.
    If as you have said EVA is not the sealant and the Teldar is then why is it ok to use tyvek , as in the sticky post on it, which is beathable?
    As for me right now I'm going with taping the cells to the glass (100% coverage), framing the glass and then filling the back side with fiberglass resin. I figure the tape will act as a release agent from the resin and the resin will give me the moisture seal I need. I know the resin will probobly yellow but ti shouldn't matter since it will be kept from the front of the cells. The resin aging will be reduced by the fact that it's on the rear and not dirctly exposed. Tell me if you see a problem with this method I haven't thought of, I am a newbie after all.

    thanks,
    Larry

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    Default

    I could potentially see a cell cracking problem due to the hardness of the resin and different expansion rate.
    Resin is also not 100% vapor tight.
    The reason EVA is used with tedlar is to allow some flexibility in the laminate, will bond all the pieces together and with vacuum bagging will remove all the air.

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    Quote Originally Posted by Larry L View Post
    Mike,
    I know well what tyvek is, I'm a contractor, hence my question.
    If as you have said EVA is not the sealant and the Teldar is then why is it ok to use tyvek , as in the sticky post on it, which is beathable? ...
    I'll have to go re-visit the stickie. TYVEK does not belong in PV panels. That is an error.

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    Naptown.
    My hope is that the tape will act as some what of a release agent and keep that from happening. I guess we'll see.

    Mike ,
    That was what was confusing me. all the talk of sealing the panel then finishing off with a product made to let vapor move. Of course Tyvek is SUPPOSED to be uni-directional and let the vapor pressure only move one way.

    BTW it was in the feildlines post you sited earlier.

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    Quote Originally Posted by Larry L View Post
    .....Tyvek is SUPPOSED to be uni-directional and let the vapor pressure only move one way.

    BTW it was in the feildlines post you sited earlier.
    Then I believe it was a typo there. I don't think anyone really endorses tyvek as a PV barrier seal. Tedlar is supposed to withstand weather and some UV, tyvek has no UV resistance, and will break down quickly.

  10. #10
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    Mike,
    I agree with you Tyvek is designed to let water vapor move. In building sciences we design walls to let the moisture out and prevent condencation which would otherwise cuase mold to grow, not the same thing here.
    But it's no typo look at his pics. He even comments on the Tyvek logo runing the look.

    http://fieldlines.com/board/index.ph...,144982.0.html

    http://fieldlines.com/board/index.ph...,144995.0.html

    http://fieldlines.com/board/index.ph...,145004.0.html

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