Brainstorming A Passive/active Solar Heating Project, Want Opinions, Please! - Green Home Improvement - DIY Chatroom Home Improvement Forum

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Old 09-24-2012, 02:23 PM   #1
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Brainstorming a passive/active solar heating project, want opinions, please!

OK, here's the scenario:

I own a home in a small town in extreme SW KS, which seems to enjoy one of the best climates in the United States for solar energy, according to the maps I see online.

The house is almost 100 years old and the furnace is gas fired...but, I had a bit of a dispute with the gas company and so I converted to all electric. That works fine for cooking and for the electric HWOD unit I have, but I haven't done anything about the heating system yet.

I spend about 90 days a year there....usually 60 in the spring and 30 in the fall, but this calendar year it amounted to 90 in the spring and NONE in the fall. Whenever I leave the home, I prepare it as if I were not coming back again before freezing weather, which means putting RV antifreeze down all the drains and also draining the supply plumbing to the lowest point in the basement.

However, I would like to address the heating issue in a manner that will allow me to leave the plumbing filled with water when I leave. Every time I leave it dry the inside of the old galvanized pipes rust and that plugs up the faucets and supply lines to the toilet, that sort of thing, every time I turn the water back on.

Here's what my brainstorm involves so far....a friend gave me nine 3'X7' solar panels, but they are unusable in their current condition. All that I can use is the glass (VERY nice double strength glass panels) and the black sheet metal that the sun shines on and creates the heat. I would like to devise some sort of "passive" solar heating device involving hot water with the pieces I have left, using the solar-heated hot water in a large tank in the basement to transfer heat to a closed-loop underfloor radiant heat system. I have access to the joist-bays from the basement under the main floor.

The house sits unheated all winter at present and the only plumbing that is below the bottom of the floor joists is the supply lines leading to and from the electric HWOD unit....and that has never been compromised, so I don't think the basement ever gets cold enough to freeze water.

So....I heat a water/antifreeze mixture with solar panels on the flat roof, and since I want it to be working when I am not there I don't want to have to deal with the complexities of a drain-back system, so I want it to be self-siphoning. I can imagine the tank being one of those plastic containers that farmers use to carry water back and forth to their livestock or a self-made, fiberglass lined tank made of plywood and 2"X4" frames...enough to probably hold as much as 250 gallons of that water/antifreeze solution which would be recirculated through the solar panels. The tank would be "stuffed" with as much coiled PEX as I could get in it and the fluid in the PEX (probably the same water/antifreeze solution as the fluid in the solar-heated tank) would absorb heat from the solar-heated water in the tank and carry the heated solution to the underfloor radiant system. I know that the system would need a pump to move the water through the underfloor tubing, so I would use a small PV panel to charge a few deep-cycle batteries, which would keep a 12V RV-style water pump in constant action, thereby providing heat to keep the ground floor (as well as the joist bay through which all the supply plumbing courses from the south side of the house to the north side of the house) warm...I don't really care if it is "livable" warm, just above freezing warm.

So, about your ideas? I know the PV panel will be non-productive on cloudy days, but in SW KS the cloudy days aren't very many and the sunny days are MUCH more common.

What I want to be able to do is get the underfloor radiant tubing installed and use the "passive" system until I decide to reside in the house full time, at which point I will discontinue use of the 12V RV pump and install a 120V pump and a small, low rise 240-volt electric HWOD unit to provide adequately high temperature fluid in the radiant floor tubing to make the house "livable" warm. The solar heated water tank/tubing will then be re-purposed and used to pre-heat the potable water that supplies the main-house HWOD unit, which will reduce electrical usage for that appliance.

Any suggestions would be most certainly welcome. Keep in mind that I turn the electricity off at the pole in the alley when I leave, so there will be no electrical service to the house, no gas service to the house, and no water service to the house while I am gone, the solar system will be totally stand-alone.

Thanks in advance for whatever illumination you can provide!




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Old 12-19-2012, 09:05 PM   #2
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If the sun don't shine, you don't get heat. And with a hydronic solar system, you may be asking for trouble in the freeze season.

Passive solar air sounds like your best bet. If you've got the glass and absorber plate you can finish the panels off pretty easy. Make sure you have dampers to prevent reverse flows. Get electric heating baseboards or wall heaters and set the thermostats for 50 degrees. If sized correctly, the passive solar will supply enough heat on standard days, and for those gloomy (low sunshine) days, the electric heat will provide a safety net. Also, for when you're there and want a little heat boost.


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Old 12-20-2012, 08:30 PM   #3
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Passive air is your only recourse. And those 3 panels won't give you much at all. And it won't be enough to guarantee against freezing.
Do you want it your way or the right way?
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Old 01-02-2013, 07:56 PM   #4
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Do a google search for pop can solar heater. They are connected soda cans in a case with a glass lid with a duct on top that goes in the house. Its really cheap to do.
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Old 07-13-2013, 06:29 PM   #5
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I made a "solar window heater" back in the 70's from plans in was just enough to raise the temperature of a small workshop to 20* above the ambient outdoor temperature.

I have thought about the popcan solar heater, could certainly rivet some soda cans (or Altoids tins) to the absorber plate...but the square footage requirements for keeping the house warm will require more windows than I have available on the south side of the house. There are only two normal size windows I can use...and one is blocked with a 240V window A/C unit, so....

The main structure of the house is 30' X 30' and the roof is a flat would be ideal for installation of a large solar array along the northern edge of the roof (would require some sort of welded framework).

I really think the only answer is a radiant floor system...sadly, I took a new job and have not been back to the house's been over a year. I have enough leave time built up for a two-week journey in October, but that is filled with quite a few repair/maintenance jobs already, so there can be no time for this project.

I do thank everyone who has taken time to will be a fairly simple job once I get everything plumbed in if I want to leave the electricity on while I am gone...which I think will always be the winter months.

Onward through the fog.....

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