On 3/25/09 7:40 AM, Peter Parrish wrote:
could we start a thread?
My principal reason for looking into this technology is for
space-limited applications. Right now we are looking at trying to find
space on a crowded roof for about 100-120 sq-ft of conventional flat
plate collectors (e.g. SunEarth Empire 4’x8’ or 4’x10’), and
skylights, parapet walls and a PV array are getting in the way.
Climate is southern California coastal.
I asked for evacuated tube experiences on this list and have
subsequently queried a number of installers and manufacturers over the
past 2-3 years. There were some facts, a lot of bad experiences early
on, and plenty of opinions. What I have distilled from all of this so
far is:
ETs make sense when ∆T is high and when the location has a lot of
overcast days.
ETs do not make sense when ∆T is low to moderate and when the location
has few overcast days.
ETs cost more per square foot of aperture.
ETs present much lower wind loads than flat plates (potentially allowing
installation using ballasted racking on low slope roofs.)
Stagnation and scale present bigger risks with high fluid temps.
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