Evacuated Tubes [RE-wrenches]

Bill Loesch solar1online at charter.net
Sun Nov 18 02:29:11 PST 2007



Hi Todd et al,

You might be interested in Bob Ramlow's comments in his "Solar Water
Heating" that, "...evacuated tube collectors vary widely in their
construction and operation." [Different manufacturers build evacuated tubes
in entirely different ways.]

Bob is also not a fan of the evacuated tubes (except for high temperature
(160oF) applications) and references Tom's book, "Lessons Learned 1977 to
Today" for additional current information.

Happy Thanksgiving
Bill Loesch
Solar 1 - Saint Louis Solar


----- Original Message ----- 
From: "Todd Cory, Mt. Shasta Energy Services" <toddcory at finestplanet.com>
To: <RE-wrenches at topica.com>
Sent: Saturday, November 17, 2007 6:09 PM
Subject: Re: Evacuated Tubes [RE-wrenches]


>
> A local contractor also loves these. He claimed there was a 40 degree
> delta T on a sunny day with the panel under 3' of snow. I **seriously**
> doubt that is anywhere close to being accurate.
>
> The evacuated tube marketing folks are evidently doing a good job, but I
> prefer the trusted flat plate technology. Been around forever, very
> robust and long lived.
>
> The last time this thread went around here, the consensus was to steer
> clear of them. Perhaps the folks at AAA or Tom Lane might have more hard
> data, which I would also love to see.
>
> Todd
>
>
> Howie Michaelson wrote:
>
> >Hi All,
> >
> >I'm looking for experiential as well as "non-biased" info on Evacuated
> >tubes.  I have installed them a few times in the past, but have pretty
> >much steered clear of them since for several reasons:
> >
> >1. Here in snow country, I've seen them not shed snow for significant
> >periods of time, and have also seen them break from ice/snow movement
down
> >the roof.
> >
> >2. From what I've seen/heard their output is in most cases not any better
> >than flat plate collectors, and due to lack of snow shedding
capabilities,
> >sometimes substantially worse.
> >
> >3.  They are more expensive than flat plates, and are rated lower by SRCC
> >so in Vermont are given less incentive money (which is based on the
> >ratings).
> >
> >A client saw the Solar Decathlon and noticed that almost all the
> >competitors used evacuated tubes (ET's).  He also said that one
> >manufacturer was whacking a tube very vigorously against hard objects
with
> >no damage resulting.  He wants to put in the reasonably best collectors
he
> >can with an eye toward Return on Investment, but is now enamored with
> >Evacuated tubes since they would fit well on the south wall of his home
at
> >a very steep angle (near vertical), and was told that there is virtually
> >no output penalty for doing so.  Placing them near vertical probably goes
> >a long way toward answering the snow shedding issue, but I'm mostly
> >ignorant about the rest of these issues.
> >
> >Any info about any of these concerns or leads to a place where I can get
> >good comparative info on ET's vs. flat plate collectors would be much
> >appreciated.
> >
> >Thanks,
> >Howie
> >
> >
>
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>
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