Solar Wax Melter - 1 or 2 Panes of Glass and Why?
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  1. #1
    Join Date
    Oct 2012
    Location
    Prior Lake, MN, USA
    Posts
    16

    Default Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    Hi All,

    I built the solar melter from the front page this summer with some minor modifications. I'm in Minnesota at 44 degrees North latitude so I increased the window angle to 20 degrees. Exterior depth in the melting section is about 8 inches and it's insulated all around with closed cell foam and painted flat black. I've been using it now for about 3 weeks and it has worked very well. Just in the last week it has been melting wax, albeit slowly, even with partly overcast days.

    Now here's my question. The plans called for 2 panes of glass in the window which is how I built it. When sunlight contacts a glass pane some light passes through while some of the light is reflected away. Wouldn't the box collect more solar gain with a single pane of glass whereas the second pane would reflect light away? I've seen comments that the purpose of the second pane is to create an insulating 'air space'. Is the insulating effect greater than the light lost by the second pane?

    Thanks for your thoughts everyone.
    Chad

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  3. #2
    Join Date
    Mar 2015
    Location
    Derry, New Hampshire
    Posts
    2,295

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    i used 1 pane for this reason. used old storm window. 2 panes stop heat better then 1. most home windows are at least 3 for this reason. not sure what another pane would do that was helpful.
    Terrence

  4. #3
    Join Date
    Aug 2014
    Location
    England, UK
    Posts
    1,450

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    Quote Originally Posted by HatTrick View Post
    I've seen comments that the purpose of the second pane is to create an insulating 'air space'. Is the insulating effect greater than the light lost by the second pane?
    Hi Chad.

    Yes. With a double-glazed solar collector you may lose a small amount of energy from slightly reduced light transmission, but the major benefit is seen in the reduced thermal loss from the insulating properties of the trapped air between those panes of glass (which of course conduct heat) - hence the greater the distance between the panes, the more effective becomes that insulation.

    Double glazed panels may not be necessary in Texas or California, but make a helluva lot of difference for those of us who are less fortunate with our climate.
    LJ
    A Heretics Guide to Beekeeping http://heretics-guide.atwebpages.com/

  5. #4
    Join Date
    Feb 2012
    Location
    Earlysville, Virginia USA
    Posts
    135

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    What really blocks solar heat game is all the new window coatings that are put on modern glass windows. And old Double pane windows is great as it provides some insulation without blocking the sun's rays. I also lined the inside of my solar wax melter with blue xps foam. Boy was I surprised to find it melted which I believe means my box got up to 210 degrees. I replaced it with rockwool and it really melts great in our Virginia sun

  6. #5
    Join Date
    Oct 2012
    Location
    Prior Lake, MN, USA
    Posts
    16

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    Thanks for the replies!

    The windows I used were old ones and predate the coatings found on newer windows so they won't reflect or block any more than plain glass.

    @Ryan Williamson, I'll have to keep an eye on my insulation. I used the foil faced and plain xps foam board behind plywood lining. I did not expect its melting point to be so low.

    Would love to hear others' input, especially if you've had experience with both.

  7. #6
    Join Date
    Feb 2012
    Location
    Earlysville, Virginia USA
    Posts
    135

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    Oh I also tried foil-faced eps and it melted as well. I just looked it up and it melts at 212degrees. If I recall correctly a sheet roughly 6" by 16" turned I to a little curled up hard plastic thing I could hold in my hand.
    It's hot in there!

  8. #7
    Join Date
    Jan 2005
    Location
    Hamilton, Alabama
    Posts
    2,998

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    There is a fundamental design problem with the solar melters I've seen plans for and have built and used over the years. The wax drips into a pan or collector that can't reach or stay near temperatures hot enough to liquefy the wax. The result is a conglomeration of wax that accumulates and has to be re-melted to get a reasonably good cake of wax. To avoid this problem, the melter has to be about 6 inches deeper than most plans call for so the collector pan can be in the high temperatures.
    NW Alabama, 50 years, 20 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest

  9. #8
    Join Date
    Oct 2012
    Location
    Prior Lake, MN, USA
    Posts
    16

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    @Fusion, I noticed that as soon as I started using it. The drop down space for the bucked does not get hot enough, so the wax hardens quickly. Since the sun's not that high here anymore I actually get 'wax-cicles' off the pan into the bucket and I have to pick it off. Not a big deal, but it does back up the melting pan some.

  10. #9
    Join Date
    Mar 2018
    Location
    George County, MS
    Posts
    34

    Default Re: Solar Wax Melter - 1 or 2 Panes of Glass and Why?

    Quote Originally Posted by HatTrick View Post
    Hi All,
    Now here's my question. The plans called for 2 panes of glass in the window which is how I built it. When sunlight contacts a glass pane some light passes through while some of the light is reflected away. Wouldn't the box collect more solar gain with a single pane of glass whereas the second pane would reflect light away? I've seen comments that the purpose of the second pane is to create an insulating 'air space'. Is the insulating effect greater than the light lost by the second pane?

    Thanks for your thoughts everyone.
    Chad
    Chad,
    Double or triple pane windows would not be sold if the result was not more effective than single pane.
    In addition to thermal gap between the panes, a transparent sheet of polyester (think "saran-wrap") is included to reflect more infrared radiation; glass is very transparent to infrared radiation (heat). In most new windows, argon gas is injected into the gap to reduce conductive heat transmission.

    In the warmer parts of the country, the extra glazing also helps in the summer, keeping the heat out.

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