Hello Kelly,
I saw your website photos (nice work). Do you think that tubes oriented (1)
east-west would and (2) flat would perform as well as your tilted
north-south tubes?
Joel Davidson
----- Original Message -----
From: "Kelly Keilwitz, Whidbey Sun & Wind" <ke...@whidbeysunwind.com>
To: "RE Wrenches listserve" <re-wrenches@lists.re-wrenches.org>
Sent: Monday, July 20, 2009 12:12 AM
Subject: Re: [RE-wrenches] Tube solar collectors
All,
Apricus ET's have a cylindrical absorber surface, which are significantly
better at capturing low angle of incidence energy. I have both a Thermomax
(with flat collector plate internal to the tube) and Apricus collector in
parallel on my own home and see significantly better temperatures early and
late in the day on the Apricus collector.
IMO, ET's have a distinct advantage in our cool, windy, and low-snow
environment (northern Puget Sound).
Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd,
Coupeville, WA 98239
PH & FAX 360-678-7131
sunw...@whidbeysunwind.com
On 7/19/09 7:29 PM, "Darryl Thayer" <daryl_so...@yahoo.com> wrote:
HI Joel
I have done ev tube and flat plat, I am amazed that the flat plate is
almost
as good to better than the ev tube.
As to PV it is true that the output goes as the angle, (cosine function)
but
if you have a wavey surface it is very slightly better than a flat
surface.
the cosine effect is there for the entire array, and the modern modules
with
antireflective coating compensate for much of the reflected energy. So I
doubt that the tubes are any better.
Daryl
--- On Sun, 7/19/09, Michael Welch <michael.we...@re-wrenches.org> wrote:
From: Michael Welch <michael.we...@re-wrenches.org>
Subject: Re: [RE-wrenches] Tube solar collectors
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Sunday, July 19, 2009, 12:27 PM
Hi Joel. No experience here, but I
did talk to one of their installers (I think it was Carlisle
Energy Services) at Intersol last week, displaying one of
the modules with its mounting system. Some additional info
to consider:
E-T thermal collectors do have a "flat plate" in each tube,
so angle of incidence is still critical.
Solyndra's have wrap-around PV materials inside their
tubes, so E-W angle of incidence stays the same throughout
the day.
They recommend reflective (like white) roof coating which
picks up more bounced sunlight from the bottom side.
But it seems to me the main advantage is that they do not
require roof penetrations or even ballast, making them a
potentially quicker and cheaper install. The claim is that
wind underneath will not lift them, and if wind load
requirements are higher than normal (not sure where they
draw the lines), merely putting skirting around the outside
edge of the array keeps the wind out from underneath the
modules.
All that said, I also look forward to hearing about field
experience and performance.
Joel Davidson wrote at 07:15 PM 7/18/2009:
Wrenches,
Solyndra claims that their tube collectors "perform
optimally when mounted horizontally and packed closely
together, thereby covering significantly more of the
available roof area and producing more electricity per
rooftop on an annual basis than a conventional panel
installation." See
http://www.solyndra.com/Products/Greater-Rooftop-Coverage
It is my understanding that a solar thermal or PV tube
or flat plate collector's performance is based on the angle
of incidence and that curved collector performance decreases
as the angle of incidence moves away from perpendicular.
Does anyone have any field experience with solar
thermal evacuated tube collectors or Solyndra PV to show
that tubes perform better than flat plate collectors?
Joel Davidson
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