Simultaneous solar hot water and air collection


After 300 years of simple heatflow physics, most people still doubt that a house can be close to 100% solar heated outside of the Southwest, inexpensively. We might move 8' D-cubes into regional Infestations of Doubt, with 2" double-foil foamboard walls and ceiling and polycarbonate over the south wall and an EPDM-rubber-lined heat storage tank under the floor, which also serves as a ballast foundation. We might deploy these devices near churches and schools and green building conferences and Renewable Energy Festivals...
We might warm a small low-mass house with sunspace air for 6 hours on an average January day in Phila with 250 Btu/h-ft^2 of direct sun and a 34 F average daytime temp and simultaneously store 18 hours of overnight heat in hot water, using a low-power PV pump in a slow draindown system...
If we collect 200 Btu/h of 170 F overnight heat in B ft^2 of Rich Komp's homemade Big Fins (a 1/2" copper pipe pounded into a groove in a strip of brown-painted aluminum coil stock) behind A ft^2 of R1 glazing with 90% solar transmission (eg $1/ft^2 Dynaglas) and we also collect 50 Btu/h of T (F) air and 200 = 225B-(170-T)1.5B = 1.5TB-30B for the Fins, T = (200+30B)/(1.5B).
If A=B and 225B%0+(T-34)B, B=1.6 ft^2 and T3 F, with a 250/(1.6x250) = 0.625 collection efficiency. We could move 50 Btu/h in a 50/(103-70) = 1.5 cfm airstream.
If the Fins cost more than the Dynaglas, which is likely, with more labor and rising aluminum coil stock (60 cents/ft^2) and copper pipe prices, we could make B smaller and A larger, with a lower cost and a higher temp and a lower collection efficiency, but easier hot air thermosyphoning.
For instance, A = 2 ft^2 makes 450 = 250+(T-43)2, so T = 143 F, and 200 = 225B-(170-143)B makes B = 1 ft^2. Scaling this up to A = 4'x8', we could move 16x50/(143-70) = 11 cfm with an 8' height difference through upper and lower sunspace vents, each having an area Av = 11cfm/(16.6sqrt(8'(143F-70F)) = 0.0273 ft^2, ie 4 in^2.
Scaling up more, 2 $12 8"x16" automatic foundation vents might handle 16.6x8x16/144sqrt(8)(143-70)^1.5/(16x50) = 32 4'x8' glazing panels, collecting 25.6K Btu/h of 143 F air and 102.4K Btu/h of 170 F water (or more, with an average Fin temp less than 170 F) with about $1K of Dynaglas and $1K of Fins, and this can be dry in full sun as a draindown system with no damage. What's the equivalent evacuated tube system cost?
Leslie Locke's AF1B foundation vent has aluminum louvers and a bimetallic coil spring which opens the louvers when the air temp near the spring rises to about 60 F, but that soft threshold temp can be changed by turning the spring mounting screw, and the spring can be removed and reversed to make the louvers close vs open as the air temp rises, so it can work as a crude room air temp thermostat in a thermosyphoning sunspace system. For more accurate room temp control, we might add a $20 thermostat and a $50 2-watt Honeywell 6161B1000 damper motor.
Nick
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They are correct.

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Solar Flaire wrote:

No, they're not. It can work in Nova Scotia and it has worked in Germany.
--
derek

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If it works so well and inexpensively as claimed, then perhaps you can tell us why it,s not widely implemented. Are all builders and consumers stupid? Don't they want homes that our only heated by the sun? Has the free market broken down in this case? Or could it be that they know more about the real world, heating, construction and costs than those spouting a bunch of equations trying to impress folks?
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snipped-for-privacy@optonline.net wrote:
|| Solar Flaire wrote: ||| They are correct. ||
||| |||| After 300 years of simple heatflow physics, most people still |||| doubt that a house can be close to 100% solar heated outside of |||| the Southwest, inexpensively. || || No, they're not. It can work in Nova Scotia and it has worked in || Germany. | | If it works so well and inexpensively as claimed, then perhaps you | can tell us why it,s not widely implemented. Are all builders and | consumers stupid? Don't they want homes that our only heated by the | sun? Has the free market broken down in this case? Or could it | be that they know more about the real world, heating, construction | and costs than those spouting a bunch of equations trying to | impress folks?
No - they're not stupid, and the free market hasn't broken down.
People, in general, don't change from something they know has worked well in the past unless/until their pain threshold has been exceeded by a sufficient margin to motivate change.
In case you hadn't noticed, most people /don't/ know much about designing and constructing a home - just like they don't know much about how their vehicle was designed and built. Both products rely heavily on design folks working with equations.
If you think they do that just to "impress folks" you might want to think again.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto /
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Complete BS. Pay attention to how fast consumers are adopting new technology. Products come out and within a few years, they are everywhere. There are lots of people who would jump on a home that could be 100% solar and built inexpensively, if it were really possible and practical.

Well, Duh! I guess that's why we have cell phones and Ipods. Funny though I don't see these close to 100% solar energy inexpensive homes being built in NJ or anywhere else. If it's such a damn fine idea, why don't you and Nick go do it and get rich?

No, I just think a certain clown that posts here from time to time with loads of equations and no practical common sense does it to impress. I guess that point went over your head.

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On 16 Apr 2007 06:41:07 -0700, snipped-for-privacy@optonline.net wrote:

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snipped-for-privacy@optonline.net wrote:

It isn't widely done, because (a) while inexpensive, it isn't _without_ cost. People buy cheap. Never mind if they can save money in just a couple of years, they won't pay the cost up front. (b) where's the free market? I have a friend who has been building homes getting 50-70% solar heating (for the same price as similar sized homes in the area) for 30 years now. He's an engineer and an architect, and he _still_ has to fight building inspectors at every turn who tell him that his systems won't work, can't work and are illegal besides. Another architect I know is trying to get a development approved for St. Margaret's Bay, Nova Scotia, which will involve homes with no fossil-fuel heating systems - solar heat & waste heat from appliances with deep-rock storage, with a target of making them _less_ than market price. She's been at it for years, but is blocked by people like you who say it can't be done.
--
derek

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Many projects of this style have been attempted over the years all with failure as a result.
SO far, it hasn't been fesible with reasonable costs and no resistance by building standard people.
I remember a big green home built in Mississaga, Ontario back in the late 70s having an open house. One of the audience asked where the vertical axis windmill in the artists's conception drawing was. The reply?..It cost more than it would generate in a human's lifetime and was left out.
Even today PV is totally impractical where grid power is available. In Canada, my system cost me under $20K and I got most at a discount. I will break even, at today's rate, in 70-80 years. verdict? A fun toy. This is not "inexpensively". Logically it is a waste of money.
BTW: "Inexpensively" is a relative term and has no absolute value. Thanx Nick...LOL

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Solar Flaire wrote:

Many times "green" homes are over-hyped and under-designed. This doesn't mean that solar heating doesn't work but rather that there are a lot of dishonest salesmen and poor home "Designers" out there in the world and the give the rest a bad name.

If the building site didn't have very good wind resources then any kind of wind turbine would be uneconomical. Most people don't like to build in places that are exceptionally windy so few homes have good wind resources.

Today PV is practical where grid power is not available. This means you can build a house places where you couldn't before without the noise and cost of a generator. Besides, I've seen people spend more than $20K on sports cars, off-road trucks and the like. I can think of a lot worse ways to spend $20K than to buy 50+ years of power.
Anthony
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Anthony Matonak wrote:

Right. Then you go on to talk about projects that have no relationship at all to what we're talking about.

As in my home.
However, the subject was homes that could be heated almost entirely with solar. Slab-on-grade building, with passive solar heating, and in-slab heat storage costs _no_ more than standard building techniques, and can net you 50-70% of your heating (that's typical of the homes built by my friend). Super-insulation can increase that significantly (admittedly for some small cost - but still "inexpensive" when designed into the home in the first place.
--
derek

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Well, everybody has had their chance to twist the words to suit their fancy and defend against their imagined enemies. Let's go back to the OP's statement.
"After 300 years of simple heatflow physics, most people still doubt that a house can be close to 100% solar heated outside of the Southwest, inexpensively."
Now he did state "close to 100%". This has been proven to be true for decades, depending how you define "close to". If he stated 50%, I would agree it is false. I read "close to" as more like 98-99.9%.
Not happenning and it hasn't yet. We are talking sufficient heat storage for upwards to a month with temps down to -10c with no sun last December and January in the location I have my solar toys. The other word he stated is "inexpensively".
Not happenning and it hasn't yet.

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