Simpler solar attics

Laren Corie writes:

Maybe no windows at all, just plastic film glazing.

Historically, most people tire of moving insulation twice a day. Twice a year seems OK. Or automatically filling a glazing cavity with soap bubble foam at night. My favorite "movable insulation" is a big fan with 2 thermostats in an insulated wall between a sunspace and a living space.

We might rethink how we use spaces. People seldom look out windows at night. They cover black holes with curtains. A living space might only have 1-2% of the floorspace as windows for small views. Picture a core living space behind enclosed porches, or "viewspaces" with lots of glazing for large views. During the day, move into a viewspace and steal some heat or AC from the living space with an occupancy sensor and a thermostat and a fan.
A 32x32x8' tall living space with 16'-deep SE and SW viewspaces and a 48'x48' footprint might have 24ft^2 of R4 windows with 6 Btu/h-F. An R40 ceiling and R30 walls would add 32x32/40 = 26 and 33, with 30 more for 30 cfm of air leaks, if it's tight, for a total conductance of 95 Btu/h-F.
With 4 American Craftsman 6068-2 6'x80" U0.48 sliding glass doors ($269 each at Home Depot) or 320 ft^2 of R4 windows, a 16'x48' SE viewspace would have a 123 Btu/h-F conductance. Two more doors would give a 16'x32' SW space 61 Btu/h-F. The glazing might have overhangs to reduce summer sun and dark mesh curtains to reduce light levels for people, eg 80% greenhouse shadecloth, which preserves views, like a dark window screen.
If the average living space temp is 65 F and we spend 4 hours per day in each 70 F viewspace (Henry Mercer built bonfires on the roof and moved from desk to desk as the sun moved in his 6-story concrete castle in Doylestown PA) on an average 30 F January day in Phila, the house needs 24h(65-30)95 + 4h(70-34)123 + 4h(70-34)61 = 79.8K + 17.7K + 8.8K = 106K Btu/day of heat. With 34.1K from 300 kWh/mo of frugal indoor electrical use, we need 72K more solar heat, which might come from a solar attic.
The solar attics of Soldiers Grove (see http://www.ece.villanova.edu/~nick ) can be improved. They blow warm air down into a building during the day, with a motorized damper to let the attic stay cool at night. Some have rock bed or hypocaust stores, but few store heat for more than 1 day.
A new attic might have a $1/ft^2 corrugated R1 Dynaglas polycarbonate 20-year south roof with a 60 degree slope and 90% solar transmission. NREL says 620 Btu/ft^2 falls on the ground and 1000 falls on a south wall on an average January day in Phila, so 1 ft^2 of roof would collect 0.9(1000sin(60)+620cos(60)) = 1058 Btu/day.
Nathan Hurst's "Low-cost active heat storage" story in the July-September 2007 Issue 100 of ReNew (http:www.ata.org.au) shows how to collect solar heat with a Mazda car radiator and its 16 watt electric fan. (I have a $35 1984 Dodge Omni radiator below my living room floor) With an 800 Btu/h-F air-water thermal conductance like MagicAire's 2'x2' SHW2347 duct heat exchanger, we could store 0.75x72K/6h = 9K Btu in 140 F water in 6 hours on an average day with a 140+9K/800 = 151 F attic air temp. A radiator in a box below an attic floor can both store and distribute heat, like this, viewed in a fixed font: upper g attic l | | a | | z ~ ~ i south --> | | n | vertical | motorized / g | duct | damper / | | / | | day / | | / | | / | | / night attic floor ---| -------------............---------------------------------- | . r . | . d room a d. | . a air d f a. f | . m out i m. | ==> . p a a ==> p. a <== room air in | . e t e. | . r o n r. n | . r . ------------------------------------- | | | duct to | | room floor | | | | | ~ ~
To collect heat, open the motorized damper and run the radiator fan. They typically last 3-4K hours at 225 F. If the fan lifetime doubles with every 10 C decrease, it might last 70K hours at 150 F. To distribute heat, close the motorized damper and run the room fan. The passive dampers could be plastic film over hardware cloth, aka "the 7-cent solution" invented by Doug Kelbaugh (now Dean of the UMich Architecture school) in Princeton in 1973. The motorized damper could be polyiso foamboard with an auto windshield wiper motor and limit switches or Honeywell's $50 6161B1000 damper actuator, which only uses 2 watts as it moves up to 45 in-lb. The room air outlet would also have a passive damper that opens out of the page into another vertical duct or closet to move warm air down into the room. The floor might have more motorized dampers over polycarbonate film to bounce light and heat down into rooms during the day.
If 1 ft^2 of glazing gains 1058 Btu/day and loses 6h(151-34)1ft^2/R1, the net gain is 356, so we might need 50.4K/356 = 142 ft^2 of glazing. A 4'x48' strip would do. At 140 F, we could make hot water for showers with a $60 1"x300' piece of pressurized black PE pipe in a heat storage tank and a simple graywater heat exchanger (eg 2 uninsulated 55 gallon plastic drums) to add heat to the house.
On an average day, with an 800 Btu/h-F radiator conductance, we can heat the living space with 70 + (70-30)95/800 = 75 F water. If the viewspace use patterns don't change on cloudy days, we can store 5x72K = 360K Btu for 5 cloudy days in a row in 360K/(140-75) = 5538 pounds of water, ie 665 gallons, in an STSS tank or a 4'x8'x3'-tall plywood box lined with a single folded 10'x16' piece of EPDM rubber.
Nick
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On Aug 21, 10:31 am, snipped-for-privacy@ece.villanova.edu wrote:

Name anybody you know that moves insulation twice a day or twice a year for that matter, Soap bubbles, I think you have had to many bubbles nick, we need more math to confirm this idea of yours.
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On Tue, 21 Aug 2007 11:07:52 -0700

    That would be anybody who closes curtains at night.
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On Aug 21, 10:31 am, snipped-for-privacy@ece.villanova.edu wrote:

Wow, thank you for the posting. Really enjoyed it.
Ken
Opportunities are never lost. The other fellow takes those you miss.
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We did a bit recently on storing energy at the phase change of Glauber's Salt (Sodium sulfate decahydrate) which melts at 90*F and when it cools releases a tremendous amount of energy as Heat of Fusion as it solidifies. It is less than $1/lb, and a barrel of it (dry) in a 55 gallon drum with water circulating around it will be a major component of my new system.
wrote:

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snipped-for-privacy@ece.villanova.edu wrote:

Historically, most people never move insulation, unless they're some kind of nut.
The only math anyone needs to know is, if someone wrote what you wrote just one time, they shouldn't be allowed out in public without the proper supervision.
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Maybe he's not allowed out in public. Reminds me of the episode of the Simpson's where Homer winds up in the psychiatric hospital. In the day room, while he's making a phone call, you could see all the speed dial buttons on the phone: Opra, Geraldo, Jerry Springer, etc. Welcome to Nick's world. LOL
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Wayne's world comes to mind.

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They are letting me out on 9/22/2007 to lecture again at the Pennsylvania Renewable Energy Festival :-)
http://www.paenergyfest.com
Nick
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Short of money again? or you were the only one that would do it for nothing?

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snipped-for-privacy@ece.villanova.edu wrote:

I applied to give a seminar entitled: "Whale Oil - The Renewable Resource" and the nay-sayers at the festival turned me down.
They do have a lecture on the Wind Depletion Allowance so tree-huggers can save on their taxes.
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HeyBub wrote:

Perhaps you should give a lecture on Vivoleum. http://www.dailykos.com/story/2007/6/14/214445/536 : "We need something like whales, but infinitely more abundant,"
Anthony
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