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Discussion in 'Home Power and Microgeneration' started by Adam Webster, Nov 16, 2003.

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  1. Adam Webster

    Adam Webster Guest

  2. Cor Stijgers

    Cor Stijgers Guest

    Hi Adam,

    I like your pictures very much!

    I understand that you may have some experience with heating the house on
    solar energy?

    I'm considering to heat my future home on solar power, but I can not
    find much information on the Internet on heating. Most of the
    information is about heating tapwater. We do not use much hot tapwater,
    so we don't expect serious savings there.

    I wonder how many square meters solar collectors are needed and
    how many liters storage for the hot water. Do you have any experience on
    this, or do you know where I can get some information?

    kind regards
    Cor Stijgers, Amsterdam
     
  3. Ecnerwal

    Ecnerwal Guest

    This question is a great deal like asking "How long is a piece of
    string?"

    With no information about where the house is, what size it is, what the
    incoming sun resouce is, the local climate, the specific values of
    insulation, it's quite impossible to say how many square meters of solar
    collector you need, or how much hot water storage you need.

    In a mild climate - less. In a harsh climate - more. Few cloudy days in
    a row - less. Many cloudy days in a row - more. Well insulated - less.
    Poorly insulated - more.
    alt.solar.thermal - read the archives for a lot of solar house heating
    background information, then post some specifics about your house design
    and house site. I'm guessing, since you asked about square meters of
    collector, that we'll need to try to recall what the European R-values
    for insulation actually refer to, since most regulars on that group are
    using US R-values based on imperial units and will need to convert to
    consider your design, and I'm not recalling what the underlying units
    for the metric version of the same number are.
     
  4. Nick Pine

    Nick Pine Guest

    Simple sunspaces are cheaper than "solar collectors."
    We can make things up... If 3 kWh/m^2 of sun falls on a south wall on an
    average 0 C day and the 20 C house has 50 W/C (284 Btu/h-F) of conductance,
    it needs 24h(20-0)50 = 24K kWh/day (82K Btu/day) of heat. If a square meter
    of U2.8 (US U0.5) sunspace glazing with 80% solar transmission collects
    2.4 kWh over 6 hours on an average day and loses 6h(20-0)1m^2xU2.8 = 336 Wh,
    for a net gain of about 2 kWh, the sunspace needs about 24K/2 = 12 m^2 (129
    ft^2) of glazing. If we needs 5x24 = 120 kWh for 5 cloudy days in a row and
    a liter of water releases 1.16Wh/kgC(70-20) = 58 Wh as it cools from 70 to
    20 C, the house needs 120K/58 = 2069 liters of cloudy day storage.
    R-values are measured in W/mC, conductance is measured in mC/W, and
    US R5.68 (Btu/h-F) becomes European U1 (W/C.)

    Nick
     
  5. News

    News Guest

    If you want to heat your house using solar energy, using a wet system, it is
    best to use a low temperature operation underfloor heating system. Using
    low temperature operation mean that even in winter you may be able to use
    low temperature hot water effectively. Have the roof panels, or better the
    whole of the south side of the roof, heat a large thermal store cylinder.
    The lower section of the thermals store should be used to heat the
    underfloor pipes, with the top section to heat the domestic hot water - if
    there is not enough high temperature heat for domestic hot water
    supplementary heating can heat just the top section. The thermal store
    should be sized to give 3-4 days of heat in cloudy conditions if possible,
    depending on climate of course.
     
  6. News

    News Guest

    Heat exchangers for forced air systems require high temperatures, otherwise
    draughts occur. That is why low temp underfloor heating is ideal for this
    application. How did it manage with the forced air?
    Was yours $25 per month?
     
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