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solar floor heating

Discussion in 'Home Power and Microgeneration' started by Thomson Tim, May 15, 2005.

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  1. Thomson Tim

    Thomson Tim Guest

    I am probably dreaming here but here goes.
    Last fall I installed a air tight wood stove and I dropped my natural
    gas consumption down by 90%. I used the stove to heat the 1000 square
    foot main floor of a split bungalow. The basement was unusable because
    of the cold..........anyways here is what I am doing and almost done. I
    have installed ceramic tiles on the entire living section of concrete in
    the basement with electric in floor heating. The total will be about 8
    or 9 thousand watts of draw @ 110v.

    I have about 10,000.00 more CDN to blow and was just thinking what could
    I get for solar panels to put on my roof? Could I dump the energy
    directly into the floor heating system? How many watts of solar can I
    put on the sunny side of my roof 40x13 feet (520 square feet) and how
    much money? I am not worried about the pay back I just want bragging
    rights lol. My main goal is to be able to keep the pipes from freezing
    in the basement. I don't want to get into inverters or batts yet and
    wont discuss it. Just a few simple switches to go from line power to
    solar power in the floor.

    I know that electric is the most expensive back up heat but I just hate
    the gas co and plan on ripping out the gas meteor. I also plan on
    converting my hot water to electric and cooking stove to propane. To
    keep my house legal I also have to have a heat source that will maintain
    the house at 21 c all year so I will convert the furnace as well.
    Wood is free here where I live other than your time and a little gas for
    the chainsaw and truck. I also bought one of those electric wood
    splitters. Awesome machine......I don't have to be so picky when getting
    wood....It says it will split a maximum of 20" by 10" round. Ha all the
    garbage that people can't split with an ax I take. I easily split 20" by
    24" round
     
  2. Thomson Tim

    Thomson Tim Guest

    One more question I dont want to max out my 100 amp feed.
    Whats the formula for watts volts amps. How many amps does 8000 watts need
    at 110/120 vac
     
  3. John P Bengi

    John P Bengi Guest

    You better save your $10K to pay the electric bill. This would be a waste of
    time and energy and the gas company will have the last laugh on your dime.

    Solar to PV to electric to resistance heating is a very, very inefficient
    technique and a waste of everything. Find a way to store or move the solar
    heat directly where you want it. Much more efficient. Save the PV for
    electric appliances and lights etc. Use the solar to assist your gas hot
    water heater in a preheat mode. Put in a water heat exchanger for your
    showers etc.
     
  4. Thomson Tim wrote:
    ....
    ....

    Most PV panels run around 10 to 12 watts per square foot. This means
    you can install around 5,000 to 6,000 watts of PV panels at a cost
    of somewhere between $25,000 to $40,000 depending on various factors.

    You would do better to install solar air heating panels on the roof
    and duct the air down to the basement. Not only would it be more
    efficient (up to 80% instead of 12%) but it would also be a fraction
    of the price. These kinds of heating panels can even be home-made
    out of ordinary materials found in home improvement stores so the
    savings in cost over PV can be very significant.

    Anthony
     
  5. Thomson Tim

    Thomson Tim Guest

    No clue next!
    How in the hell can a direct usage of solar be less efficient than storing it?
    I will store some at a later date thanks any ways.
     
  6. Thomson Tim

    Thomson Tim Guest

    Wow I guess I better turn the floor off before I turn on the dryer.
     
  7. John P Bengi

    John P Bengi Guest

    Turning solar into electricity is at best about 13% efficient. Then the
    storage and recovery of the electricity is about 80% at best.

    Read the other reply to your post by Anthony.
     
  8. Thomson Tim

    Thomson Tim Guest

    Do you mean turning DC into AC?
    Thats not the plan. I would dump the DC directly with some regulation into the
    resistive wires. Its also coldest here when the east wind comes around the
    mountains
    So I am looking at a wind turbine as well.
     
  9. Worried or not, using PV to create electricity to heat a floor is a heck of
    a lot less efficient than using solar glycol-filled panels to circulate
    heat through the floor. Planning is kind-of important.
    How are you going to do that? Your floor is 110V resistive heating. You'd
    need to invert the power from the panels.
    That's just not smart. Get a solar hot water system from Thermo-Dyanmics
    (Dartmouth, NS).
    And you think dealing with the tanked-gas company will be any better than
    dealing with the piped-gas company? Don't bet on it. Superior Propane has
    a virtual monopoly on the propane market in much of Canada.
    You're kidding? I _never_ keep my house that warm!
     
  10. Well Bengi tends not to be too clued in, but you aren't talking about a
    "direct" use of solar. You're talking about converting the photons to
    electricty (much less efficient than converting them to heat), then
    converting them to heat. Using a solar hot-water system you avoid the loss
    of efficiency at the panel.
     
  11. Sure, this is probably easiest for a system that has to be retrofitted. For
    a Canadian manufacturer, look up "Cansolair".
     
  12. Thomson Tim

    Thomson Tim Guest

    All along I was talking electric solar panels

     
  13. Thomson Tim

    Thomson Tim Guest

    Maybe I meant solar electric panels....so how many watts od DC per square foot
    do panels put out?Any ideas of the best place to get them in Alberta?
     
  14. Thomson Tim

    Thomson Tim Guest

    Invert the power to what? AC? Resistive heating doesnt care if its ac or dc
    Just have to do the math on the volts and amps to get the rated output.
    I guess I should have said Electric on demand...more than tankless gas but
    still cheaper than tanked storage gas water.
    I talked to alot of locals here and all are happy with the differant propane
    suppliers.....my choice is the Coop
    They rent a four hundred litre tank for 12.00 month......cheaper than the gas
    co fixed fees of about minimum fifty a month.
    Its now about 650.00 a year just to have a gas metour on the wall now with no
    consumption. Once I get rid of the gas hot water I doubt that I would use four
    hundred liters of propane per year. The only time that my furnace would kick in
    is when I am not home to throw a log on the fire. I have allready proven that.
    All last winter I consumed 14 gigajouls of natural gas all for domestic hot
    water. More than anything just to stay insured and legal I still have to have a
    alternate heat source other than wood.
    Not kidding .....municipal bylaw I read it. Part of the spec to meet code when
    you install wood stoves here.
    I must mantain a heat source that can maintain 21 c even when no one is home.
    Doesn't mean I have to keep it that warm it just means be ready if needed.
     
  15. I suppose... Come to think of it, I'm not sure how well an inverter would
    work either without a battery backup. Still it gets pretty hairy trying to
    match panels to get to a reasonable DC voltage - and I'd expect the heating
    vendor to disavow any responsibility if you put anything but 110VAC into
    it.
    It doesn't matter. You're looking at the wrong ways to produce heat (btw, I
    don't think you can get a tankless electric water heater that will work on
    your 100Amp service). If you want heat from solar, collect it via liquid
    or air collectors. For direct heating, air is probably good, for hot water
    use a liquid collector. Then maybe use a tankless propane heater to keep
    it up to required temps.
    Yeah, I didn't _really_ think you were kidding. I just see red when I hear
    such stupid rules...
    Like, what's wrong with 3C, when no one is home? Bureaucrats!
     
  16. News

    News Guest

    But as you do not pay for the input, it is 100% efficient.
     
  17. News

    News Guest

    The elements in a floor don't care if ac or dc runs thought it. You just
    need to find out have dc voltage/current is applicable.
     
  18. daestrom

    daestrom Guest

    And that is silly, exactly what everyone is trying to tell you. Using a
    photovoltaic panel, it converts about 13% of the sunlight that shines on it
    into electricity. The rest of the radiant energy that shines on it just
    warms it up. So now you have 13% of the energy from the sunshine in the
    form of DC electricity. Run that through resistance heating (100%
    efficient) and you have 13% of the energy from the sunshine warming your
    floor.

    Instead, if you use a thermal solar collector (warm air, or warm water), you
    get a much higher percentage of the energy from the sunshine deposited into
    the warm water. Circulate the warm water under your floor, and even if it
    loses some heat in the piping as it runs down from the roof, you still are
    much further ahead when you count the number of BTU's delivered to the floor
    vs the square footage of collector area.

    A thermal collector can capture more than 50% of the total energy from the
    sunshine that shines on it (even as high as 80-90 %). Thermal collectors
    are much cheaper than photovoltaic on a per square foot basis. If all you
    want is low-grade heat, forget about the photovoltaic panels and look at
    thermal collectors.

    daestrom
     
  19. daestrom

    daestrom Guest

    'Efficient', maybe. But a very costly way to heat water for a radiant floor
    system. Thermal collectors with the same surface area are *much* cheaper.
    And since thermal collectors can deliver more energy to the floor for a
    given collector surface area, the savings are two-fold (cheaper collectors,
    and smaller total collector surface needed).

    daestrom
     
  20. daestrom

    daestrom Guest

    For a given square footage, 'solar electric' panels put out between 1/4 and
    1/5 the 'watts' for heating as simple thermal collector panels. So for a
    given *heating* need, you would need 4 to 5 times the collector surface area
    using 'solar electric panels' as you would using simple thermal collectors.

    daestrom
     
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