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Solar Thermal Design For Historic Home - Page 7

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Posted by nicksanspam on August 24, 2006, 10:28 am

Something like a 4' deep x 12' diameter swimming pool in a basement, with
264 ft^2 of R30 surface that loses 880 Btu/h or 21K Btu/day, which would
end up in the house on an average day. It could supply more house heat
on a cooler or cloudier day. A new house might need less than 5 therms.

We might put a "collector" inside a sunspace, with its own glazing surrounded
by warm sunspace air, air which also heats the house on an average day.

Where's the nearest NREL weather station?

A house designed to be 100% solar-heated on an average day wouldn't need any
backup fuel if every day were average :-) The cloudy-day storage requirement
for 100% solar heating over a year in a TMY2 hourly simulation usually turns
out to be less than 5 cloudy days at the average temp in the worst-case month
(the one with the lowest ratio of sun on a south wall to the indoor-outdoor
temp diff.) Rochester NY has 560 Btu/ft^2 on an average 29.1 F December day...
560/(68-29.1) = 14.4, vs 28.0 in Phila and 54.2 in Albuquerque.

My Rochester TMY2 simulation for a 1600 ft^2 house with R34 walls and ceiling
and R3 windows and 240 ft^2 of U0.58 twinwall polycarbonate sunspace glazing
with 80% solar transmission and a 957 gallon cloudy tank (4' tall x 7' diam)
showed a min tank temp of 91 F in December, with no backup fuel. The tank
will be heated with 64' of fin tube near the top of 144 ft^2 of R1 polycarb
Dynaglas air heater glazing with 90% solar transmission inside the sunspace.
The $200 STSS tank will also preheat water for showers, via a copper coil
heat exchanger, after a 100' greywater heat exchanger.


Posted by Ed on August 19, 2006, 4:00 am

nicksanspam@ece.villanova.edu wrote:

Yes, the pictures I seen of the Crystal Palace show that it was a real
work of art.  I travelled and worked in Europe for a few years and my
French, German, and Swiss counterparts used to use the slang expression
"Orangie" or "Orangee" when discussing British Greenhouses and the
antique tropical setup at Versailles.  I guess the slang kinda stuck.
My British friends never commented on the slang version of the formal
name Orangerie, but then of course what does a crude American know
about the English language.


Posted by SJC on August 19, 2006, 4:03 am

  It was once said that the British and Americans are separated by a common

Posted by Ed on August 20, 2006, 5:23 am

Thanks for the numbers.  I usually think of my heat losses in terms of
percentages of square footage or cubic feet, but maybe I should think
of the losses in terms of individual components (e.g. windows, walls,
ceilings, floors) and air exchange.  For planning purposes I've been
guesstimating about 8%-10% losses for components and 15%-20% for air

If I understand your numbers correctly, perhaps I should add another
solar panel in order to reach a daily average requirement of 100K BTUs
or one therm.  Yes?  No?


Jeff wrote:

Posted by Jeff on August 21, 2006, 5:40 am
 Ed wrote:

   I can't really say, but would think so. I would defer to Nick's
advice as he has been at this for some time. Remember not all days will
be clear and your actual gain will depend on the tilt of the collector
and any obstructions, note Nicks arctan formula.

   Questions I would be thinking of would be what do I do with this heat
stored in this body of water? You'll want to know the minimum
temperature that your heat store can go to (and that depends on what
temp your heat source needs), then you'll have a better idea of what
your losses will be and what size heat store you'll want. Since you are
already heating your house you can look more towards offsetting your
heating bills rather than replacing your furnace.

BTW, you can check, I think its nrel.gov for historical data. Where I
am, it's rare to have more than two or three cloudy days in a row.



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