Anyone built a solar power/heating system @ home?

Discussion in 'Homesteading Questions' started by Kung, Dec 5, 2004.

  1. Kung

    Kung Administrator Staff Member Supporter

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    All of a sudden I have this overwhelming urge to research/construct a solar power/heating system. Anyone else done this that can give me information, pitfalls, costs, etc.?
     
  2. DreamingBig

    DreamingBig Well-Known Member

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    I can't answer your questions, but I looked at a house for sale that had a solar hot water/radiant heat system with conventional backup. The water cycled through the water heater under the floor and back. The owners loved it and it was a big selling point to me. You should find lots of info on Google. Good luck!

    Chris
     

  3. Cygnet

    Cygnet Well-Known Member Supporter

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    My grandfather had a setup that heated two houses.

    He had a large bank of concave mirrors that concentrated sunlight on pipes of hot water. The water was circulated into a very large (2,000 gallon at a guess) concrete cistern that was insulated and underground. The water from the cistern was then circulated through radiant heat pipes through the house walls, plus provided all the hot water you'd ever want, at scalding-hot temps. I don't know how hot the water got, only that you could brew tea with water straight from the tap.

    Only problem I recall was the occasional leak. It worked nicely year round, and held enough heat that it kept things warm even after a few days of overcast, but this was in Phoenix, where there was ample sunlight.

    My grandmother ended up renting the houses out and at that point, they shut the system down and sealed the cistern out of liability concerns because the hot water was excessively hot (scalding temp) and the cistern was a hazard if anyone fell in (they'd be boiled like a lobster before they drowned!)

    Leva
     
  4. Windy in Kansas

    Windy in Kansas In Remembrance

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    While I have not built anything to date, there are a couple of solar application books that I highly recommend. They are the best I've read on the subject.
    Both were published by Rodale Press, although some time ago.

    "The Complete Handbook of Solar Air Heating Systems" by Steve Kornher with Andy Zaugg covers air heating units.

    "The Homeowner's Handbook of Solar Water Heating Systems" by Bill Keisling applies to the heating of water. There are plans for a batch heater that is tried and true according to information within the book. I plan on building this unit during the coming summer when I have a little more money for materials. The tank will be the biggest cost for me.

    I would also be amiss if I didn't recommend that you study up on super insulating homes. Loss of what heat you do produce is the first step.

    While the library I work at owns both of these books, I opted to purchase them so that I would have fingertip reference as needed. I might mention that the library copies are about worn out indicating that they are used heavily.
     
  5. Brad

    Brad Active Member

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    Wow!! Any more details like where he got the mirrors and who designed this system would be appreciated. Thanks.
     
  6. SouthernThunder

    SouthernThunder Well-Known Member

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    Have you looked into the passive ground tube heating/cooling systems? This system has about fifty different names but what it ammounts to is burried pipe that uses constant ground temps to regulat indoor temps. Its been discussed on here before. I am seriously considering this setup for my house I'm putting up this summer.
     
  7. gobug

    gobug Well-Known Member Supporter

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    It is fairly easy and inexpensive to make a parabolic reflector of ferrocement and run a pipe through the focal point.

    I have read detailed descriptions and will try to regurgitate them here.

    First you draw the parabola shape on a piece of plywood. Cut out the shape and use it as a form to bend pencil rod into the parabolic shape.

    Bend numerous rods. Plan on 2 parabola rods per foot of trough.

    Line them up to form a trough. Use straight rod and tie wire to connect them an even intervals. Put the straight rod outside the trough. I think 5 or maybe 6 straight rods would be adequate. Every cross section should be tied. Make a 2x4 support system to hold the trough shape during assembly. Design it to mount and position the trough after completion.

    Attach expanded metal fabric to the inside of the trough shape and tie it to the framework every 6 inches. (It would be an advantage to have the size of the curve equal the width of the fabric so no cutting is required) One layer will be adequate.

    Mix the ferrocement and parge it onto the fabric. Use the plywood form as a screed to get the surface even. Trowel the cement as it cures just like you would a slab to get a smooth surface.

    After it has cured 24 hours, use a spray adhesive to line the trough with aluminum foil.

    Run your water pipe the length of the trough at the focal point.



    When I read about this I didn't consider it for a project. Now that you bring it up and Cygnet told us about grampa, it seems like a great idea.
     
  8. Brad

    Brad Active Member

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    Is is this focal point location determined?
     
  9. gobug

    gobug Well-Known Member Supporter

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    Brad
    Each parabola has a focal point. While the cement trough would not be telescope quality, and the focal point may slightly vary along the length, I don't think it makes a lot of difference.

    If you imagine a cone, a parabola is the shape you get if you slice the cone. I will check to see if the slice is parallel to the axis or intersects the axis. I dont remember. I know that one is a parabola and the other a hyperbola.

    I also think there is a simple way to draw one with a string, but I don't remember the details here either. If I'm not mistaken it is like drawing an ellipse. You make a loop out of string, put two nails in the plywood and the string over the nails. (the loop has to be bigger than the string) A pencil in the loop pulled tight and drawn around will produce the ellipse. I think a parabola is a section of the ellipse, but your testing my memory.

    I think the nails are the focal points.
     
  10. Brad

    Brad Active Member

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    Sorry for my typo, I meant to ask HOW is the focal point determined in the reference you read on this project. Thanks for the geometry lesson ;)
     
  11. gobug

    gobug Well-Known Member Supporter

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  12. gobug

    gobug Well-Known Member Supporter

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    I'm still not certain that half an ellipse makes a parabola.
     
  13. BobBoyce

    BobBoyce Well-Known Member

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    Solar energy is so very underutilized here in the US, compared to the percentage of our population living "on the grid". Many villages in third world countries are making better use of solar energy than most of us "civilized" folk.

    Of course, many thanks need to go to those individuals and groups that are going out of their way to make it possible to sponsor and finance these installations/educational programs.

    Here is a link to a simple yet effective solar heating project.

    http://www.mobilehomerepair.com/article17solar.htm

    Bob
     
  14. indypartridge

    indypartridge Well-Known Member Supporter

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    Don't know much about it myself, but have a cousin who's into it in a big way.
    You might get a few ideas from his website: http://www.solarkitchense.com/
     
  15. DreamingBig

    DreamingBig Well-Known Member

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    I think you mean something like this? http://www.earthtoys.com/emagazine.php?issue_number=03.08.01&article=finch
     
  16. Grandmotherbear

    Grandmotherbear Well-Known Member Supporter

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    That's afascinating site. I love it when common sense solutions defy expert predictions. I don't think it's do-able for cooling purposes in most of FL. We have a very high water table- why houses don't have basements and there are no subways. Also, our high humidity would make mold a problem.

    I am interested in passive cooling not using earth berms. I don't remember the magazine, but I read an article about a passively cooled house that had one wall earth bermed, lots of shade trees, thick masonry walls and a 7 story high tower with top windows which had to be open by poles. Heated air rose up the tower to exit, and cooler air from the shaded outside was pulled into the living area. Our county extension agent for Palm Beach Co (zone 10/11) lives without a/c but he has a 5 acre stand of BIG trees around his house. He opens up for tours every month or so in hot weather.

    I just heard from the window people- we called shortly after Mean Jeanne took out most of the west facing windows. They will be here January 8 for an estimate.. Most FL houses leak air like crazy and few are well insulated. I intend to replace the broken awning type windows with energy efficient ones. My SIL electric bill wint down by 1/3 after she replaced the sunroom awning windows with energy efficient ones.
     
  17. waterguy

    waterguy New Member

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    I have some resources on the subject that I will send along as I find them.... we are in the process of building a home with a solar greenhouse as one of 2 primary components for heating the entire house... we live in Manitoba, Canada... its already below 0 up here....
     
  18. gobug

    gobug Well-Known Member Supporter

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    BobBoyce posted the web site which shows how to build a simple solar panel.

    Thanks Bob, I followed the basic plan and built one this weekend. The materials, not counting the thermal pane window I already had were $35 not counting a hole tool. The size is 2 x 5 1/2 feet.

    In the text of the site it says:
    There are some aspects to the design that got me to wondering. Maybe someone knows the answers.

    First of all, I can understand insulating the sides, but the back is against the house, right? So if you don't insulate the bottom, wouldn't the panel warm the wall behind it. And wouldn't the wall act as the absorption plate? The energy that isn't absorbed by the passing air would actually heat part of the house, right???

    Second, I'm not real clear on the absorption plate. It would seem that if you move air quickly through the space, that it could only absorb a certain amount of heat. If the plate actually improves the amount of heat the air absorbs on its path through the panel (which, if you have a fan attached is a constant rate), then the mass of the plate is important, right? Overnight, the panel drops in temperature to be close to the outside temperature. The morning sun must warm the plate to operating temperature before the panel reaches maximum output. So too much mass is not good due to the coasting effect.

    Third, I know there is a range of temperature where the air will absorb the most energy. It would seem simple to put a speed control on the 12v fan to acclomplish this. Does anyone know this temperature range?

    So, is the absorption plate important, and how massive should it be??

    I'm thinking the box temperature will rise quickly without a heat absorber, and moving the air through the box with a fan will harvest that energy quickly.

    I built one last weekend, and I used foil surfaced foam to line the inside, but did not use a separate absorption plate material. I used aluminum soffet vent strip that has little radiator style flaps in a thin strip. I cut the strips to length, bent them into tent shapes, staggered them to direct the air path, and painted everything inside the panel black.

    I just got the hole saw and conduit, so I haven't tried it out yet.
     
  19. Brad

    Brad Active Member

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    That's a good question gobug. I hope you let us know how yours works out. I was also wondering about an array of these downhill from the house and connecting to the house with insulated pipes of sufficient diameter. A small fan could help the air along. I see something like this working very well with a high thermal mass home, which would allow an overnight coast on the day's heat storage.
     
  20. BobBoyce

    BobBoyce Well-Known Member

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    gobug, the function of the absorbtion plate is not so much to hold heat, but to absorb most of the IR (infrared) and via thermal conduction, pass that into the passing air. Without the absorber, most of the IR reflects back out through the glass, and the substantial heat energy it would contribute is lost.

    If you've ever felt anything chrome plated in sunlight, you may have been suprised at the amount of heat it absorbed, regardless of it's mirror-like reflection qualities. This is because it absorbs IR well, while reflecting most visible light.

    Bare aluminum is a pretty good IR absorber. Aluminum foil, dull side facing out, would probably absorb IR just about as effective, and be much less expensive. It would not have as much thermal mass, so it would heat up quickly, and pass that heat on to the passing air.

    Chrome or black chrome plated thin metal or foil would work even better if you could find some reasonably priced. The best I've ever seen personally was black chrome plated copper sheet fastened to copper tubing in a solar water heater collector.

    Bob