[RE-wrenches] Heat dump or Stagnate?
Bill Loesch
solar1online at charter.net
Thu Apr 30 05:22:08 PDT 2009
Hi Carl,
Thanks for the explanation.
Any reason why the same technique would not work with the US manufactured thermal collectors?
TIA,
Bill Loesch
Solar 1 - Saint Louis Solar
Sorry for the itchy trigger finger previous post.
----- Original Message -----
From: Carl Emerson
To: 'RE-wrenches'
Sent: Thursday, April 30, 2009 4:54 AM
Subject: Re: [RE-wrenches] Heat dump or Stagnate?
Hi Gang,
We are installing our first "steam back" system with a German roof integrated array 51 SqM (flat plate) from the Wagner Company. http://www.wagner-solar.com
The system is pressured to approx 2 to 2.2 bar.
At approx 120 to 125 degrees the glycol/water fluid starts to go from liquid to gas and the pressure increases.
An expansion vessel starts to compensate for the pressure.
The temperature increases up around 155 to 160C until all the fluid is in gas form.
The right volume of expansion vessel, and a larger 'pre vessel' and right pressures are critical to guarantee that the medium is not going to crack (become acidic) and safely transition back to its original state on cooling.
The Wagner company stands behind this approach and we no longer need a backup UPS as for a standard closed loop system to keep things running safely during a power failure. Nor do we need to worry about the pH of the medium.
Hope this helps,
Carl Emerson
Free Power Ltd.
Auckland NZ
-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of August Goers
Sent: 25 April 2009 6:47 a.m.
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Heat dump or Stagnate?
Hi Troy -
We've installed a good deal of Schuco systems with Slim V collectors which
are supposed to utilize steam back. Being a mechanical engineer, I still
have my doubts about the steam back principle but I don't have any real
world data proving it does or doesn't work. I can't say anything bad about
it, however.
Our installed systems are all relatively new so it is hard to say how
they'll hold up in the long term. Our first Schuco systems were installed in
2006. We routinely check the glycol ph and haven't found it going acidic yet
although I've noticed the color (Schuco's glycol is pink) is turning a bit
brown. We've also revamped a large system where we disassembled the copper
piping and found quite a bit of dark pink sediment in the rooftop pipes.
The bottom line is that the more times the system overheats the faster the
glycol inhibitor is going to degrade in any system. Since all these systems
are so new it is hard to say how long this will take. The danger I see is
that it is easy to forget older systems and before you know it they start
failing.
On another note, Heliodyne is also packaging closed loop glycol systems and
they aren't touting the steam back principle. Their system operates at
higher pressures and use Dowfrost HD. Dow's website indicates that HD is
good up to 325 deg F which is cooking - I doubt flat plate collector
stagnation temps will reach that high at least in our area. See spec sheet
here:
http://www.dow.com/PublishedLiterature/dh_0040/0901b80380040bd2.pdf?filepath
=heattrans/pdfs/noreg/180-01315.pdf&fromPage=GetDoc
I guess I better get back to work... Anyone else have experience with
degrading systems?
Best,
August
August Goers
Luminalt Energy Corporation
O: 415.564.7652
M: 415.559.1525
F: 650.244.9167
www.luminalt.com
august at luminalt.com
-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Troy Harvey
Sent: Thursday, April 23, 2009 11:10 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Heat dump or Stagnate?
Apparently this is the "modern" design method used in many european
systems. It scares me too. But from several sources, this seems to be
considered one of the most reliable design methods for closed loop
systems (ie. it works even without electronic controls working, power
outages, etc).
Standard glycol. The main point seems to be the design of the pipes
and collectors need to facilitate collector draining from the steam
pushing the fluid back into the expansion tank, so the collectors
empty themselves. Its closed loop, but effectively becomes a
"pressurized drainback" in over heating conditions.
Here is a couple of links:
http://www.aee-intec.at/0uploads/dateien48.pdf
http://www.suterconsulting.com/CISBAT.pdf
I'm hoping to find someone with experience with this kind of system to
overcome my fears
Troy Harvey
---------------------
Heliocentric
801-453-9434
taharvey at heliocentric.org
On Apr 23, 2009, at 11:04 AM, Dana wrote:
> I have only seen boiled glycol turn to a cola like syrup that had to
> be
> purged and removed.
>
> What kind of system & glycol is this?
> Where would you expand that much?
>
> Can you provide a link to this paper?
>
> We use heat dumps.
>
>
>
>
> Dana Orzel
>
> Great Solar Works, Inc
> www.solarwork.com
> E - dana at solarwork.com
> V - 970.626.5253
> F - 970.626.4140
> C - 970.209.4076
> "I'd put my money on solar energy. I hope we don't have to wait 'til
> oil and
> coal run out before we tackle that."
> -Thomas Edison, in conversation with Henry Ford and Harvey
> Firestone, March
> 1931
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Troy
> Harvey
> Sent: Thursday, April 23, 2009 10:43 AM
> To: RE-wrenches
> Subject: [RE-wrenches] Solar Combi-systems: Heat dump or Stagnate?
>
> I'm wondering how many of you out there have installed medium sized
> solar hot water systems (6-8 panel) that were designed to stagnate
> during summertime over production as opposed to diverting to a heat
> dump or radiator? The International solar agency has a couple of
> papers that show a properly designed system should be able to stagnate
> in a way that the boiling glycol mix vapors in the panels, purge the
> panels of fluid, turning off the system without degrading the glycol.
>
> That doesn't seem to be a typical way to design systems in the U.S. ,
> we've usually gone to a heat dump. Does anyone have experience with
> this?
>
>
> Troy Harvey
> ---------------------
> Heliocentric
> 801-453-9434
> taharvey at heliocentric.org
>
>
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