[RE-wrenches] Tube solar collectors

[Kelly Keilwitz, Whidbey Sun & Wind]

Joel,

We frequently will orient tube collectors on east or west facing roofs with
very good results. However, pointing a solar collector toward the south will
always produce more energy, as we all know that the greatest solar energy is
concentrated around noon.

The choice of whether to tilt comes down to efficiency, cost, and aesthetics
- and sometimes overheating issues. With a tube system care must be taken
not to oversize the collector in proportion to the tank. If a customer wants
to maximize heating throughout the year I recommend a larger collector
tilted steeply toward the winter sun angle. This not only maximizes winter
production but, more importantly, attenuates summer heat gain.

It's interesting to note that, as Apricus tubes have the collector surface
circumferentially, they will collect heat from the backside (a significant
factor during northern summers).

Another design factor is that the heat pipes must always maintain a slope
for heat transfer. Thus, tilting up on the east or west-facing roof is
necessary if the tubes are to be oriented N-S.

-Kelly
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
sunwind at whidbeysunwind.com


On 7/20/09 8:09 AM, "Joel  Davidson" <joel.davidson at sbcglobal.net> wrote:

> 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" <kelly at whidbeysunwind.com>
> To: "RE Wrenches listserve" <re-wrenches at 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
> sunwind at whidbeysunwind.com
> 
>