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    Solar hybrid, the most efficient combi system? (2 Posts)

  • MarcHauger MarcHauger @ 11:13 AM
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    Solar hybrid, the most efficient combi system?

    An idea I have,  I am living in a 1890's home which was carved up into a four-plex in the 30's.  We are in the process of returning it to a single family home.
        The first floor is now gyp-crete with tubing 8" on center. Insulation below is four inches of foam in each bay with another 2 inches nailed to the joists below.  The ceiling height is 10'. I have added a second two by four exterior perimeter wall "double envelope", giving me 9" wall system.
     My idea for the solar hybrid system works like this, the floor would be heated with solar through a brazed plate heat exchanger off a solar primary loop, Bristol Stickney'ish.  Programmable thermostat for the floor calls for heat of 74 degrees at 8am til 4:30, 5:30, 6:30 based on time of year. Solar tank sensor is  in a thermal well in the primary solar loop.  Any heat energy put in the primary loop will be delivered to the gyp-crete floor first. Solar storage tank will be after the radiant floor off the solar primary loop.  I plan to install a btu meter on the floor supply/return leaders.
     Room comfort temperature will be met with a radiant ceiling and another thermostat set to my desired room temperature. Ceiling fluid will be heated with a ground source heat pump.   
     I have a 576 sq ft garage with 3 30 tube Apricus ET's panels It has been my test platform, low winter temperature with solar only heat has been 42, a warm 42 with heated slab.  It runs every day in the winter, every day!    
    Marc Hauger,
    New Era Plumbing & Heating
    Missoula, Montana 
  • jeffbuilds jeffbuilds @ 10:10 AM
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    Eliminate the HX to the floor loop, save money and work better.

    Nice design, and good project.  It's nice to read stories like yours.

    There are alternatives that may be less expensive, and operationally more efficient.  Consider a load-side solar thermal system like the Simple Drainback.  A load side heat exchanger has solar fluid in the tank, with potable water in the heat exchanger.  This allows solar fluid to move to the collectors, to the tank, and then directly to the floor.  No heat exchange, less equipment, less controls, better efficiency.

    The Solar Heat Exchange Simple Drainback system uses a controller with three temperature inputs, and two pump outputs.  The third sensor measures floor temperature, and activates a second pump based on the floor/tank delta T.  A thermostat on the floor loop cuts the pump when the floor gets too hot.

    Quite simple, inexpensive. 
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