[RE-wrenches] Evacuated Tube-based SDHW

[Dana]

Add one more benefit. The ETs ability to create a higher stored temperature in the tank [ I start to divert to the heat dissipater @ 185° and it is in full diversion at 195°] t, this allows me to install the next size smaller tank [Super store , Crown Tri Tube etc], so it can save $ too.

 

Dana Orzel

 

Great Solar Works, Inc

www.solarwork.com

E - dana at solarwork.com

V - 970.626.5253

F - 970.626.4140

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“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

 

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kurt Albershardt
Sent: Wednesday, March 25, 2009 11:28 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Evacuated Tube-based SDHW

 

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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