Solar Heating During Winter?

[Nitack]

So, my wife and I are closing on our new house next week. For the first time I am going to have a large back yard that I can start putting some of my mad scientist notions to work. For those of you who who have not seen my Passive Electrical Generation thread, I am quite enamored with the possibilities presented by the behaviors of liquids and gasses at different temperatures/densities. So here is what I am kind of thinking and wondering if it is feasible.

Would a solar heat collector actually be able to supplement the heating of a house during a winter in Virginia, where the temperature does get into the 10-20 degree Fahrenheit range?

I actually thought about trying to create a universal system that could be switched based on the season from power generation to home heating, but have decided that it would require retooling the system each season. One system is being designed to shed heat at every possible point save the input, the other will have to be designed to retain as much heat as possible outside the collection point.

For my power generation project I decided to use a solar collector design that I saw at www.IWillTry.org, design here. I think the same design has similar potential for this project. The main question is, will my solar heat collector be able to collect enough heat during winter to actually make this feasible? The collector is going to be painted with a flat black paint, and then put into a greenhouse casing to get as much heat generation as possible. All other points in the system outside the house will be as insulated as possible. Before the winter I will be taking my caulking gun and insulation foam cans and seal up the house tight. One way valves will be used in the system to ensure that cold air is not feeding back into the system, and covers will be used during night time hours.

Perhaps this will just take some experimentation. Just wanted to get some impressions on the idea and if it is an unrealistic expectation that the solar collector could get reasonably hot enough during the winter.

[freeztar]

Sounds like a fun project.

If they can do it in Canada, you can do it in Virginia:
http://www.cansia.ca/Content/Documen...hx?DocId=12271

Here's a great resource from the Dept. of Energy:
EERE Consumer's Guide: Solar Water Heaters

And this is awesome, build a solar water heater for $5:
Make a Solar Water Heater for Under $5 : TreeHugger

[Nitack]

I just re-read my whole post and think I completely missed in the whole thing to specify that I wanted to adapt my design for the ambient heating needs of the house. Air, not water.

Thermosiphon - Appropedia: The sustainability wiki

[Zythryn]

Yes, the strength of the sun in winter is truly impressive. You should have no issues with power generation in the winter.
Our system in Minnesota works great in the winter (although it is a standard system as I am definately NOT a 'handy' person).
The solar cells themselves are actually much more efficient in the cold, although it doesn't sound like that will necessarily affect your setup.
I look forward to hearing more as your project progresses.

[freeztar]

Well, the hot water heater could double as a radiant air heater as well, with some modifications and some duct work.

The two most common designs for space heating seem to be roof structures that collect heat and distribute it throughout the house and radiant floor heating. There are lots of designs to be found here:
Solar space heating -- active and passive solar projects for space heating

[Nitack]

Originally Posted by freeztar

Well, the hot water heater could double as a radiant air heater as well, with some modifications and some duct work.

The two most common designs for space heating seem to be roof structures that collect heat and distribute it throughout the house and radiant floor heating. There are lots of designs to be found here:
Solar space heating -- active and passive solar projects for space heating

Why radiate? Why not just directly heat the air from the house and return it?

[freeztar]

Originally Posted by Nitack

Why radiate? Why not just directly heat the air from the house and return it?

Sure, but if this is a passive design, then how will you get the cold air to rise?

[Nitack]

air pressure

Hotter air leaving will rise given the design, as it leaves and goes back into the house air will have to be drawn from the other end of the system to equalize the pressure. I just make sure that the intake is at the lowest point in the house.

[freeztar]

Originally Posted by Nitack

air pressure

Hotter air leaving will rise given the design, as it leaves and goes back into the house air will have to be drawn from the other end of the system to equalize the pressure. I just make sure that the intake is at the lowest point in the house.

Yeah, it seems like that would work. The diagram threw me off as it seems to show the cold input up near the top.

[freeztar]

I was thinking about this more on the way home from work.

I think using water (or some liquid that holds heat well) is a better way to go all around. Water can retain heat much longer than air. With your design, it would get really cold at night. With radiant floors, it would stay warmer longer (possibly through the night?). I saw a design once in Colorado where they had built these window box type structures along the wall of the south facing side of the house. The tops of the boxes were clear (plexiglass maybe?) and the sides were wood. Inside the "window boxes", they placed very large drums of water, painted black of course. The side of the box facing the house was left open. The tubs would heat up through the day and slowly release the heat into the ambient air. Just another idea.

It would be nice to see the breakdown of efficiencies with these different systems. Perhaps one of the physics wiz-kids will come along and help out with the equations and such. I'll try to look around a bit, but it usually takes me a long time to calculate these things.