Ground Source from Garage Inspection Pit

Discussion in 'Engineers' Talk' started by IanMKnight, Nov 19, 2020.

  1. IanMKnight

    IanMKnight Member

    Hello,
    I have a brick inspection pit in my garage that is mostly tiled and dry.
    I am wondering if the walls and floor of the pit could be used as a source of ground heat?

    I am thinking out loud now:

    But I wonder if I placed domestic hot water radiators in the pit and pump water thru them whether i could pull heat out to warm the garage/workshop. Mmmm maybe condensation would be an issue!

    Or maybe bore holes in the pit walls and put a double skinned tube (small bore 15mm copper inside 22mm copper) into the holes to pull ground heat out.

    Both solutions i guess would require a small heat pump.

    Any thoughts please? IK
     
  2. Bob Rathbone

    Bob Rathbone Screwfix Select

    Not deep enough, but you could use it as a start for the borehole that is needed.
     
  3. rogerk101

    rogerk101 Screwfix Select

    There are two types of ground source heat pumps ... either deep and narrow or shallow and wide.
    Your garage inspection pit is neither deep nor wide, so no, there is nothing useful that you can use it for with your heat pump.
     
  4. IanMKnight

    IanMKnight Member

    Hello again,
    Interesting experiment i did today in my workshop/garage today.
    This morning was cold with a garage/workshop air temperature of 3c to 4c, however the air temperature in the garage pit was 10c.
    So i lifted the corner of one of the boards that cover the pit and put and old CH boiler fan in it to blow garage air into the pit.
    Then i lifted a board at the other end of the pit to let the pit air out.
    I closed the garage/workshop up and went to have lunch, after an hour or so the garage air temperature was 9c, with an outside temperature of 6c.

    So for the price of running a small fan for an hour, it took the garage air temperature from just above freezing to not so uncomfortable.
    I think more experimenting is required, like if it is going to freeze overnight leave the pit air circulation fan running all night.

    I appreciate that this experiment may not work as a continuous process in freezing weather, but maybe a cheap way to warm up the workshop for the odd days i use it.

    I wonder if you could gut an old fridge to make a crude heat pump to pull heat of of the pit walls?
     
  5. kiaora

    kiaora Guest

    Hi
    I do like this type of idea, in my view, an improvement to your great observation, is to fill the pit with large rocks , say football sized, then when the is sola gain available, have fan draw any warm air into the stone/rock thermal store !
    It’s not my idea I must say, but I worked on a solar house project in the 70s,

    It was a simple design, south facing house with very big glass screen, as you can imagine, when the sun shone it would get very hot in the front entrance,

    but that was the plan, the house was built with a large basement filled with rocks,
    (you may have to research the type of rock)
    The hot air was drawn in from the glass ‘air boiler’ to be stored and released back in the colder weather.

    Regards
    Peter
     
  6. IanMKnight

    IanMKnight Member

    Hello Peter,
    I have heard of this heat stored in rocks ideas before and is defiantly worth considering.
    When i bought the house a year ago my plan was to use old car batteries and a small windmill on the garage roof to charge the batteries then convert the stored electric to heat.

    But am beginning to rethink the idea now and maybe modify the rock heat store into a water tank in the pit that is well insulated the put a hot water collector radiator on the roof which is gravity feed.
    Then pump the heat out of the garage pit water heat store into central heating radiator in the garage.
     
  7. kiaora

    kiaora Guest

    Hi
    Things to consider, when you convert energy the efficiency is less, wind to electric , then to hot water it’s more loss of efficiency each time, but keep up the experimental projects,

    Using air as the medium to transfer the heat to the rocks via a fan, (especially a solar powered fan,)

    is efficient, a coefficient of around 4:1, I.e. you using 1 unit of energy (the fan) to transfer 4 units of warm air

    the the heat can be transferred to the room by gravity I.e. warm air rises, !
    more efficient , especially when you don’t really have a lot to play with!


    good luck
    Peter
     

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