[Greenbuilding] Evacuated tube collectors?

[Speireag Alden]

Sgrìobh Corwyn:

>Why not put the panels in parallel rather then the pumps?

     I don't know what his reasoning was.  I'll have to make an 
appointment to go check his system out.

>Sounds like you are getting close to flat panels here.  Why not just 
>get flat panel collectors?  All the dealers talk about efficiency, 
>by which they mean BTU/ft^2.  I tell them I couldn't care less how 
>efficient they are.  I care about BTU/$, as I have plenty of room on 
>the roof.

     I wanted winter-time production, and better freeze-protection. 
But, now that I've been to the local solar supply store and actually 
handled things and shared a waving-hands-in-the-air session with 
Local Solar Guy Mitch, I'm 99% sure that it would be best to 
segregate the systems, and use evacuated tubes for eventual hot tap 
water, but use a flat panel for summertime collection for under the 
house.  I have some stuff I need to check out, but it's looking that 
way.

>The EOS people I spoke to did not claim their tubes gathered much 
>more BTUs than a comparable flat panel.  They talked about more even 
>heating (which since we both are heating a large store, doesn't 
>matter).   Any references on how much better tubes are in marginal 
>conditions?

     A lot, apparently.  Most of the ratings are done in Florida, 
where ambient heat loss is much less.  Mitch was telling me that he 
has seen Sunda evacuated tubes put out heat in the 100°F range even 
with almost an inch of snow on them.  The winter-time trough for 
production is much shallower with evacuated tubes.

     Having handled both Thermomax tubes and Sunda tubes, I can now 
say that between the two, I would opt for Sunda, which are less 
expensive and, I think, have a better sealing design.

     However, I'm still checking out the double-glass-wall units like 
Apricus (which he didn't have any of).  They're not as efficient per 
ft^2, but they might very well be better per dollar.  Like you, I 
have plenty of space.

-Speireag.

-- 
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Sit with singing summer frogs.
Think on Jack's wedding.