I will believe the Saudis don't see any upcoming problems with Ghawar when they cancel one of their projects due to low oil prices. If they continue to be full steam ahead with increasing their capacity then I think they are aware that Ghawar may not be as robust in 5 years time as they would like us to believe.
Posted: Wed Jul 23, 2008 11:15 am Post subject: Re: Passive solar heat - true or not true?
Quote:
The dormer was a collector box about 4x4x8 with a glass cover that was slante about 30 degrees and faced predominantly south.
Seems unlikely that, at 12 below freezing, you could heat a normal house with 128 square feet of window.
Very unlikely. _________________ Massive Human Dieoff must occur as a result of Peak Oil. Many more than half will die. It will occur everywhere, including where you live. If you fail to recognize this, then your odds of living move toward the "going to die" group.
Posted: Wed Jul 23, 2008 1:40 pm Post subject: Re: Passive solar heat - true or not true?
Here in NM, the sun is a mean sumvitch. A 128 square foot solar collector could easily heat a house.
My neighbor has 4 2' X 6' air panels from the 1970's, and heats his 2500 sqft house with them, and leaves doors and windows open all the time because he smokes.
Heating through windows, maybe. Depends on the windows and how well insulated the house is. In this area, 128 sq.ft of windows could theoretically collect 128,000+ watts of insolation 6-8 hours a day in the dead of winter. If someone did that, they better have a plan for the summer, or else the house would unihabitable 6 months out of the year.
I have some 2X4' velux skylights. In the middle of winter, if you step on the patch of sunlight on the wood floor, it hurts your foot it's so hot.
SO to answere the questions: Overheating a house on a 20 degree day? Not likely, but I wouldn't rule it out.
Heating a house at 12 below with 128 square feet of window? Absolutely, I could find a dozen houses in Santa Fe and Taos that do that. Of course, they couldn't do that in a white-out snowstorm.
Posted: Wed Jul 23, 2008 1:57 pm Post subject: Re: Passive solar heat - true or not true?
Here in Nova Scotia, Canada there is a local architect/builder (Don Roscoe) who has been designing and building custom passive solar homes for over 25 years. He also teaches a course on passive solar construction a couple of times per year. I took the course and it was very useful and informative.
Basically what you need to get about 80-90% of your heat in the winter from the sun is about 12% of the square footage of your house in double-glazed, south-facing windows (so 120sqft area windows per 1000sqft floor space), an airtight, a super-insulated home (at least R-19 in the walls which can be achieved by retrofitting 2x4 construction with 2" rigid insulation on the exterior and residing the house, and an R-50 attic), a storage system to store the heat, and a fan to circulate the air through the storage system.
Don's houses are designed to use the poured foundation slab as the storage mechanism. They insulate the ground first with rigid insulation, put ductwork through the area where the slab will be poured, and then pour the foundation on top. After the house is built, the hot air is circulated through the slab and it stores the heat, for days if needed. This is how you deal with the 'superhot when the sun is out, freezing when it's not' problem that many passive solar homes have because of too much glazing (20% of the floor area or more) and inadequate insulation. The slab maintains the house at about room temperature all year round and it only costs the electricity to run the circulating fan year-round. For cold stretches with no sun for more than 2 days or so, these houses have a fireplace for backup and use about 1/2 cord (2' by 4' x 8') of wood for the whole winter. There is also a single 500W electric baseboard heater in the house for 'backup' to meet local building codes (solar is not widespread enough to be covered in the codes very well yet).
The other way to store the heat (for folks retrofitting) is to do it the way they did it in the 70's after the OPEC embargos....use big tanks of water or rocks to store the heat in the basement. Not nearly as elegant as the poured foundation, but still very doable.
So no, I think it is very possible to get that much heat if the system was designed correctly. You don't even need solar collectors etc, you can just use the windows which you would be installing in a new house anyways. Retrofits are always much harder than new construction, because we have been left with a legacy of houses that totally ignored passive solar design principles while heating fuel was cheap for the past 100 years. We are going to see all kinds of motley attempts to 'solarize' existing construction over the next 20 years. Remember, 30 years from now, 90% of the buildings will be buildings that exist today!
Could be, depends.. Clouds don't absorb UV AFAIK, so as long as the medium underneath the glass emits enough heat and doesn't just reflect the UV right out the glass, the house could heat up in the same way a car would heat up on a cloudy day. Whether or not the house got too hot depends on the amount of energy trapped as heat, the size of the house, as well as how well insulated it was. _________________
Certainly possible. That's a condition called "overglazing". If you have too much glazing (i.e. south facing glass) for the amount of thermal storage you have, then they'll tend to overheat in the day and get cold at night. _________________ "So while you sit and whistle Dixie with your money and your power.
I can hear the flowers a-growin in the rubble of the towers.
I hear leaders quit their lying
I hear babies quit their crying.
I hear soldiers quit their dying, one and all." - OCMS
Posted: Wed Jul 23, 2008 4:54 pm Post subject: Re: Passive solar heat - true or not true?
Quote:
Here in Nova Scotia, Canada there is a local architect/builder (Don Roscoe) who has been designing and building custom passive solar homes for over 25 years. He also teaches a course on passive solar construction a couple of times per year. I took the course and it was very useful and informative.
Basically what you need to get about 80-90% of your heat in the winter from the sun is about 12% of the square footage of your house in double-glazed, south-facing windows (so 120sqft area windows per 1000sqft floor space), an airtight, a super-insulated home (at least R-19 in the walls which can be achieved by retrofitting 2x4 construction with 2" rigid insulation on the exterior and residing the house, and an R-50 attic), a storage system to store the heat, and a fan to circulate the air through the storage system.
Can you please provide a link to something that verifies this?
These numbers in Nova Scotia are, in my experience, impossible. But I'd love to be wrong on this one.
Of course, if you define room temperature as 55 degrees, in which case, never mind. _________________ Massive Human Dieoff must occur as a result of Peak Oil. Many more than half will die. It will occur everywhere, including where you live. If you fail to recognize this, then your odds of living move toward the "going to die" group.
Posted: Thu Jul 24, 2008 9:34 am Post subject: Re: Passive solar heat - true or not true?
You can contact Don via the Solar Nova Scotia website for more details. Solar Nova Scotia is a non-profit organization promoting solar technologies in Nova Scotia. Here's an article by Don:
Posted: Fri Jul 25, 2008 7:55 am Post subject: Re: Passive solar heat - true or not true?
Thanks for ALL the replies.
Applying this tech to run of the mill homes such as mine. Could passive solar successfully be my only heat source in a NE winter? Or is it just a supplemental heat source at best?
Posted: Fri Jul 25, 2008 7:58 am Post subject: Re: Passive solar heat - true or not true?
allenwrench wrote:
Thanks for ALL the replies.
Applying this tech to run of the mill homes such as mine. Could passive solar successfully be my only heat source in a NE winter? Or is it just a supplemental heat source at best?
You'd need something like a wood stove as a supplement for when you go weeks with no sun. But depending on how you insulate and scale the passive heat design (along with a lot of thermal mass), it should be able to provide the majority of your heating requirements. _________________ All that we are is the result of what we have thought. The mind is everything. What we think we become. - Buddha
Posted: Fri Jul 25, 2008 8:32 am Post subject: Re: Passive solar heat - true or not true?
aflatoxin wrote:
Heating through windows, maybe. Depends on the windows and how well insulated the house is. In this area, 128 sq.ft of windows could theoretically collect 128,000+ watts of insolation 6-8 hours a day in the dead of winter. If someone did that, they better have a plan for the summer, or else the house would unihabitable 6 months out of the year.
It appears you took the solar constant, multiplied by 8 and
converted to watts. So I'm wondering how many miles above
sea level your post is referring to? 30?
Posted: Fri Jul 25, 2008 1:22 pm Post subject: Re: Passive solar heat - true or not true?
No thanks on contacting anybody about solar houses.
If this is verifiable, post a link here.
Otherwise, for the purposes of this thread, a failure to support your point should be viewed, IMO, as a failure of the point made.
Here's my contention . . .
Windows leach heat.
If you design a small, extremely well insulated house set up to acquire as much solar heat gain as possible, you will be able to supply some portion of your required heat.
I disagree that is possible in Nova Scotia to heat your house more than a fraction with sunlight just using windows and a fan.
If you had a massive solar collector array, then maybe.
But with a few windows?
Come on people, this is not difficult physics.
When it's 5 degrees outside and cloudy for 2 days, you aren't going to be drawing "stored heat" from a cement slab that was heated indirectly by forced air that was passed in front of a small set of windows 3 days earlier.
Love to be proven wrong.
In fact, if proven wrong, I'll consider building such a house, on a small scale, soon. _________________ Massive Human Dieoff must occur as a result of Peak Oil. Many more than half will die. It will occur everywhere, including where you live. If you fail to recognize this, then your odds of living move toward the "going to die" group.
Posted: Fri Jul 25, 2008 2:28 pm Post subject: Re: Passive solar heat - true or not true?
Even when it's overcast there should still be about a third of the energy that we would normally see when it's sunny out, or ~100Wh/m^2.
Wikipedia wrote:
Hence the average incoming Solar radiation (sometimes called the Solar irradiance), taking into account the angle at which the rays strike and that at any one moment half the planet does not receive any solar radiation, is one-fourth the Solar constant (approximately 342 W/m˛
Assuming the glass allows 85% of that through, and 80% of that is absorbed and let off as heat by an opaque surface, that's ~70Wh/m^2. W/ 12m^2 of that, ~5 hours/day, we would see ~4200Wh/day. Apparently...
Quote:
it takes about 1 kWh to heat 1 m^3 of water or 3,000 m^3 of air 1 C
So if a kWh will raise ~106,000ft^3 of air one degree centigrade, then it should raise the temperature of a 1,000ft^2 house with 10ft high walls, or ~10,000ft^3 of air ~10.6C. So, 4+kWh could raise a house with an average R-value of 40 in 20F weather from ~60F to ~120F if input all at once. Granted, this will be spread out over 5 hours, and the owner will loose some of that head gradually, so they probably won't see 100+F, but I think they could see 85-90+F. _________________
- http://www.amazon.fr/gp/product/2914717210 _________________ All that we are is the result of what we have thought. The mind is everything. What we think we become. - Buddha
Joined: Nov 01, 2005 Posts: 842 Location: Euro high horse bastard on the run
Posted: Sat Jul 26, 2008 10:34 am Post subject: Re: Passive solar heat - true or not true?
some_math_guy wrote:
You can contact Don via the Solar Nova Scotia website for more details. Solar Nova Scotia is a non-profit organization promoting solar technologies in Nova Scotia. Here's an article by Don:
Many interesting diy heating concepts in their gallery:
http://bonmot.ca/ship/photogallery.cgi _________________ DOOMerotron: at all-time high [8.1] out of 10..
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