solar thermal pumps [RE-wrenches]

Thu Aug 23 12:37:39 PDT 2001

Hi Jay,

We basically do the same thing, but we don't believe it's water tight for 
the long-term. Underground piping experiences tremendous stresses from 
ground movement (earthquakes to frost to traffic to construction). We've 
seen a lot of "waterproof" systems that were not waterproof over the long 
term. The ones with a 20 year guarantee carry a very hefty price, thus our 
statement.

So even though we use a "waterproof" outer carrier, we don't ever think 
that it's waterproof for long, so we design ways to get the water out.

Jeff

----------
From: 	jay peltz[SMTP:jay at asis.com]
Reply To: 	RE-wrenches at topica.com
Sent: 	Wednesday, August 22, 2001 2:58 PM
To: 	RE-wrenches at topica.com
Subject: 	Re: solar thermal pumps [RE-wrenches]

Hi Jeffrey,

In regards to insulating the pipe.  I have used a pipe in a pipe system in 
the
past.

If you are using say PEX pipe, then install the insulation around the pipe,
then install a second ( usually PVC) pipe around this, glue up then install 
in
the ground.  The biggest heat loss is due to moisture pulling the heat 
away.

If you have other ideas I'd like to hear them,

jay

Peltz power

"Jeffrey Wolfe, Global Resources" wrote:

> Our experience with glycol (we've standardized on DowFrost / DowTherm at
> 60%) is that is DOES slush, but that the March pumps we've been using 
will
> pump it when the day warms up. The hardest part to get moving can be the
> underground piping (no sunshine on it), but the underground in our 
systems
> has always received heat from the house basement, so the worst pipes are 
in
> the spaces behind the collectors.
>
> I believe that pushing this cold slush does wear the brushes faster,
> resulting in more maintenance.
>
> If a DC pump must be used, seriously look at Windy's. If you must go
> brushless (and I understand...) then you really must go AC.
>
> The advantage of PV direct seems to fad on the larger systems. As the 
size
> increases, having one controller doesn't seem like a big added 
complexity.
>
> Pipe all the collectors in parallel as Smitty says. They'll give you more
> BTU. Otherwise you're heating progressively hotter water in each 
collector,
> cutting efficiency in each one.
>
> Provide some means to balance the system. Parallel piping loops can 
create
> sections that get no flow. Arrange the collectors in say two banks of 3
> collectors, with globe valves on the return from each section. Set these
> return valves so that you get equal temperatures from each collector set
> (therefore equal flow).
>
> The piping should be minimum 1". The 3/4" would be good up to MAYBE 3
> gallons per minute, but that's high with glycol. The bigger pipe does 
have
> the disadvantage of more fluid, longer travel time, etc., but that can be
> overcome with a little extra insulation. (Insulation is cheap, collectors
> are expensive.) So run 1" out to the panel location, then feed each bank 
of
> 3 collectors with 3/4".
>
> Bury the pipes in an oversized smooth wall drain pipe. Pitch this pipe 
back
> to an open drain. Buried piping either costs about $200 PER FOOT, or it
> gets water in it. Since ours always costs less than $200 per foot, we 
give
> the water some place to go, rather than sitting in the pipe and 
insulation.
>
> Good luck.
>
> Jeff
> ----------
> From:   Smitty[SMTP:smitty at aaasolar.com]
> Reply To:       RE-wrenches at topica.com
> Sent:   Tuesday, August 21, 2001 11:38 AM
> To:     RE-wrenches at topica.com
> Subject:        Re: solar thermal pumps [RE-wrenches]
>
> Kurt, for what it's worth, Richard Lane and I have conducted some tests
> of various pumps moving glycol and water at the large Packerland system
> (R.I.P.) in Green Bay. I am assuming this system is going to be in
> northern Wisconsin. What we found is that in the dead of winter, with
> very low temps, the glycol will start slushing and even become a
> semisolid ice plug, but not enough to pop anything. At daylight the
> panels tend to thaw out, but the glycol in the insulated above ground
> plumbing remains semi frozen or very thick. The DC pumps we tested had a
> very tough time with this. Sorry Dan, but the El Cid just didn't cut it
> with semi frozen glycol. The Hartell did a bit better but in the final
> analysis I would use an AC pump and a differential controller if
> possible. A few days of the year, we would even have problems with the
> Packerland system, and that was with 6"-14" pipes and many 10 hp pumps
> (5000 collectors). If you go DC, I would oversize the PV panel to
> accommodate morning incident angle, so it at least it has chance of
> getting the glycol moving.
>
> The panels should be plumbed in parallel.
>
> The smaller a pipe is, the more frictional wall loss there is. 3/4" is
> the smallest I would use. Hope this helps. Smitty.
>
> Kurt Nelson wrote:
>
> > Greetings all (and Smitty?), I'm doing a solar thermal system/in-slab
> > hydronics, and though I have done a number of SDHW systems, I'm new to
> > moving fluid through larger arrays. The collector is 5  (possibly
> > six), 4x8 Solar Kings ground mounted about forty feet from the house.
> > I would like to run the pump(s) PV direct and it would seem that there
> > is a shortage of pumps to choose from here.  I was thinking two Hartel
> > HEH-10's (did I get the model numer right) and would welcome other
> > suggestions.  Also, .... 1 - Is it best to plumb (pipes) them in
> > series, or parallel?2- Is it best to wire them each to individual
> > 18-22 watt panels (my guess) or both to a single 38 to 44 watt panel.3
> > - The burried and insulated piping from the array to the house....  go
> > with 3/4 inch pipe (or even larger) to accomidate flow, or 1/2 inch to
> > reduce heat loss from piping surface area AND the increased time the
> > heat transfer fluid spends in the pipe? Thanks in advance for thoughts
> > and suggestions.Kurt NelsonSOLutions
> >
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