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Solar air heating

Discussion in 'Home Power and Microgeneration' started by Frontier, Dec 11, 2010.

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  1. Frontier

    Frontier Guest

    I havent read alt.energy.homepower in years but have been doing some
    research regarding solar air heaters. We live 100% off grid solar PV and
    small wind generator but have a custom wood shop that is on the grid. It has
    a nice south facing wall that gets good sun in the winter months and has 3
    large overhead doors (12x10) on that wall which we are planning to frame in
    2 of the three as they are no longer needed and are huge heat loss openings.

    I got to thinking and remembered hearing here years and years ago (perhaps
    10) about building solar collectors out of things like aluminum cans and 2
    liter bottles and so on. I was wondering if any who read the group had toyed
    around with this or perhaps built one/some. I would like to try to keep it
    passive (no fans) but fans are not out of the question. My initial thoughts
    were to build a box to fit the opening with 2" foam on the back so it would
    have an R15 at night with the collector being a simple box with perhaps
    aluminum cans epoxy'd to the back wall and painted flat black. An inlet at
    the bottom and outlet at the top.

    The only thing I didn't like about the passive is the system wont really be
    automated and we would likely have to close dampers/gates at night and open
    them in the morning.

    Just kicking it around and wondering what others may have done especially
    with regards to glazing. This would be the hardest part I assume. Trying to
    find a cost effective material for 120sq' could get pricey. Lexan and
    similar products would be pretty costly for that size opening.

    I am thinking however that a collector this size may heat our 4000sq' shop
    any time the sun is out which would cut down on the gas bill.

    Any input is appreciated,
    Mark
     
  2. Guest

    Go to your local window/door contractor and offer to take all his
    take-out patio doors. Tempered glass panels for free if you strip off
    the aluminum frames for him and allow him to scrap the aluminum.
    Normally they need to pay their guys to strip them, and they shatter
    the units and trash them.
     
  3. vaughn

    vaughn Guest

    You need to talk to Morris, a semi-regular here. His passive solar system:
    http://www.iedu.com/DeSoto/solar.html

    Vaughn
     
  4. Frontier

    Frontier Guest

    Morris,
    I have seen your site before I think via Sawmill Creek perhaps? I think you
    may have sold a unit to a member there but not positive. I want to say he
    was a custom counter top manufacturer.

    Our shop is 4000 sq' metal sided structure which use to be the town fire
    station. Its fairly poorly constructed with regards to insulation though we
    are improving on that as much as possible. Concrete slab is no where near 6"
    thick in the few places I have had to cut it to install dust collection.
    Very poor ceiling insulation though we will be improving that once we get
    all the bad wiring fixed up and can blow in 12" of cellulose or fiberglass.

    The only reason I was talking 10x12 is that is the size of the overhead door
    opening that is going to be framed in. It doesn't need to be that big and
    being smaller would be much better with regards to the cost of glazing. I
    have looked into patio door panels and often have them ourselves as we are
    contractors however the double insulated panels often come apart over time
    especially once removed from the frames. I had just quickly looked into
    single panel polycarbonate from companies like US Plastics and the price on
    a 4x8 is reasonable at 200+freight. I may be able to find it locally as
    well. I know I can get polycarbonate greenhouse style panels as we use to
    have a nursery business and have ready access to that material.

    I guess I will have to re-think the metal can idea which was only because I
    had seen it before and then of course they are virtually free. What other
    material do you recommend inside the collector?

    I seem to remember at the time I saw your site last you were not in
    production or in limited production and were recommending people to build
    their own collectors or something to that effect.

    Anyway, thanks a lot for your time and reply. I use to be one
    alt.energy.homepower almost daily when we were getting this off-grid
    property underway and on line but havent been on in ages.

    Thanks,
     
  5. Frontier

    Frontier Guest

    Also forgot, we are in Central WV 38.34N approximately.
     
  6. Frontier

    Frontier Guest

    Morris,
    Thanks for all the information. I pretty much had gotten what you're saying
    with regards to innovation and so on from your posts I read previously and
    your reverse engineering page on your site now. I have to admit, my work in
    construction and the wood shop are so overwhelmingly busy right now that I
    was/am looking for a bit of a guide to doing something that would work
    rather than trying to re-invent the wheel. I really enjoy building
    prototypes and working out designs and so on when I have time but it is what
    I am doing all day and I simply don't have many more hours (or ounces of
    energy) to add something else to the mix.

    I am really not motivated by saving gas or money on this deal either its
    just that living off grid, seeing these two openings that are going to be
    closed up looks to be a prime opportunity to do "something" with them other
    than wall them in. Additionally our shop is right on the main street and
    seeing these panels would likely cause some buzz but I hate to think of it
    that way as someone will likely walk in wanting us to build them some and I
    have enough things to build. It would however be nice exposure for solar
    heating in general.

    I will do some reading on the site you posted. At a quick glance you may
    have also posted that information as it looks a little familiar.

    Agreed with regards to closing up/sealing up however its not going to be a
    quick process in this building as I don't have the time to re-wire the
    entire place in one shot and I am not willing to bury much of the work the
    old "firemen" did when they put up this building. It's a wonder the fire
    station didn't burn down.

    I will look to some sources for aluminum and see what I can come up with. At
    present I am thinking of a box unit made of 1/2" MDO ply and now will have
    to come up with something for the collector but it shouldn't be a major
    issue. I will get to reading.
     
  7. Gordon

    Gordon Guest

    OK,
    If you were to glaze the door openings with a store front type
    window system. The sun would shine in and directly heat the shop.
    Very passive, very cheap. To prevent heat loss at night, you
    could build a set of bi-fold insulated shutters or doors to
    fold over the windows at night. The advantave of this system
    is that it would also provide plenty of natural light for the
    shop.

    Other alternitives are to frame in the openings and leave a
    opening at the top and bottom for air flow. Sheath the frameing
    with plywood and paint it black. Then glaze with used sliding
    patio door glass as someone else mentioned.

    There is also a tromb (sp?) wall. Close the opening with a c
    concrete block wall. Paint the outside black then glaze, as
    above. The sun will heat up the wall, then the heat will
    transfer through the block to the inside. If you use hollow
    cinder block, you could force air through the interior of the
    wall.
     
  8. Frontier

    Frontier Guest

    I'm still amazed that someone would pour a less than 6" slab to support
    Well, this is a very country/rural area to say the least and what often
    shocks me in places like this is things are either grossly over engineered
    or horrendously under engineered. You see this all the time in old farm
    buildings or homes where something was slapped together out of parts or junk
    wood because the people either didn't have the money or were to cheap to buy
    what they needed but then they put 52 nails in a joint where two 2x4s come
    together so that its "nailed good". They go way over the top where it really
    doesn't matter and fall far short where it does.

    This floor is actually quite comical because we have had to cut it to form
    trough's for ducting. They threw anything and everything in the slab to act
    as rebar. Old telephone pole guy wires coiled around willie nilly, rod,
    pieces of pipe, and so on. Then it looks that they put large rebar on top of
    the pour and worked them down to the wet mix so now you have your mat in the
    upper third of the slab rather than in the lower third where it should be.
    This of course adds virtually no strength and then causes the thin layer of
    concrete over top of the mat to break/flake off. So in many places the wear
    layer of the slab has flaked away exposing a #6 bar an inch below the
    surface.

    How it held up as long as it did I don't know but we have heavy clay soils
    here so they have extremely high compressive strength and that is likely
    what saved them.

    The rest of the building is better but similar. It was put together with
    volunteer labor on donated land and I am sure on a shoe string budget so
    they did the best they could with what they had.

    Even with all that we have 4000sq' under roof for a very small fraction of
    what it would cost to build a new building so I have to count my blessings.

    Thanks again for the info and nice to talk,
    Mark
     
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