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Posted by SJC on March 9, 2006, 5:04 am
 



  Last time I looked at 20 tube collectors they ran more than $,000 =
each.
If you need 10 of these to get a reasonable heat gain for a radiant =
floor system
in a large house, then you are not using $0,000 worth of collectors =
more than
half the year. One of the advantages to PV, you can use them year =
around.

Tube collectors have come down quite a bit in price since I looked years =

ago. Here is a 20 tube system for $95. It would not be such a big deal =
to
me to let those sit idle for the summer.

http://www.siliconsolar.com/shop/catalog/Evacuated-Tube-Solar-Collectors-=
p-16145.html

Posted by Solar Flare on March 10, 2006, 2:56 am
 
It is much cheaper to let the house absorb it's own solar thermal
energy. Good design is much cheaper.


"  Last time I looked at 20 tube collectors they ran more than $,000
each.
If you need 10 of these to get a reasonable heat gain for a radiant
floor system
in a large house, then you are not using $0,000 worth of collectors
more than
half the year. One of the advantages to PV, you can use them year
around.

Tube collectors have come down quite a bit in price since I looked
years
ago. Here is a 20 tube system for $95. It would not be such a big
deal to
me to let those sit idle for the summer.

http://www.siliconsolar.com/shop/catalog/Evacuated-Tube-Solar-Collectors-p-16145.html



Posted by Iain McClatchie on March 11, 2006, 12:50 am
 SF> Here is a 20 tube system for $95.

Wow, that cheap.

What's the aperture on one of those things? And, where's
the SRCC rating (which would say which manufacturer
they come from).

Here's a comparison against two 4'x8' flat plate
collectors.  I believe the Sunearths cost about what
those 20-tube collectors cost, and the Gobis are a
bit more.  It's pretty amazing to see the tube system
price competitive at all at the low end of the range.

Category  20-tube  Gobi-408  Sunearth
A             46            46            42
B             44            43            40
C             31            37            33
D             24            23            22
E             15            10            12

Unfortunately, my needs are probably in category "C"
(input temp - ambient = 36 F), right where the tube
collectors appear to have a relative dip in performance.

Still, the tube system seems nice because you lose less
aperture taking out a few tubes to get by projections through the
roof than taking out 4'x8' panels.


Posted by SJC on March 11, 2006, 1:06 am
 

  You would have to contact them to find out. I would imagine
that they are made in China and have less than 20 sq. ft. of aperture.
But considering that the Thermomax were going for about $000,
this was interesting.
   Who knows what the rating or field reliability is. As people on here
have pointed out, the design and construction of these types of =
collectors
is an important consideration, to insure long life of the collector. It =
would
not be much of a bargain if they stopped working after a short while.

Posted by Ecnerwal on March 11, 2006, 2:01 am
 

I asked this supplier that question last week, and have had no reply.
Without an SRCC rating, there's no Federal tax break, so it's rather
significant.

Going to the SRCC website and downloading all the collector ratings,
there are some _large_ differences in performance between otherwise
similar-appearing vacuum-insulated tubular collectors. So that part is
rather significant as well.

Some of the poorer tubes are actually worse than some flat plates over
the whole range. Note that the ratings are a bit confusing, as they do
not have a rating section for tubular collectors, and in fact, lump them
in with "flat plates" in the ratings. Look for "vacuum" (as in vacuum
insulation) to find them in the PDF document.

--
Cats, coffee, chocolate...vices to live by

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