window heat pump to geothermal heat pump

[xboxman]

i have a window heat pump  and was wondering if i could take the out side radiator and but it in a hole about 6 feet deep and hook the lines from it back to the compressor and make it a geothermal heat pump ?

 or maybe better to pump water out of a well or from a river and have the radiator  in a tank and move river water around the radiator  to keep it warm in winter

lets hear what you all think

[veewee77]

Well, you could do that but then you'dm have to run pumps to move the river water to and fro unless you just live in a houseboat or right on the river close enough to put the exchanger in. . .

And the energy density wouldn't be very efficient.  In a typical geothermal system there are many feet of lines but they aren't in a dense fashion like in a regular exchanger (radiator).  Where geothermal gets the energy is from long lines spread out over a large area so the earth has the ability to absorb the heat (or cool).  Too much in one small space and it'd judt get hot in there and the earth couldn't 'sink' that much heat (or cold).

Doug

[maker of toys]

it can be done.  it just won't work very well.

 to just dump an air-style heat exchanger in the ground (low thermal conductivity), you wind up exhausting the available heat around the heat exchanger pretty fast.  you also wind up with corrosion problems, etc.

placing an air heat exchanger in river water doesn't solve the corrosion problem, but the heat exchange might work a little better, until the fins filled with ice.

 (no joke; I've seen fully iced-up fins in foggy 60'F weather)  flow velocity through the fins is critical.

if you wanna do the earth-source thing, you're better off getting a LONG line, and making a big loop out in the yard someplace.

for water use, you'd do better to get a purpose-built heat exchanger and pump water through it at a sufficiently high rate to prevent freezing.  you'd also have to keep the pump running at all times in a climate that has freezing air temps for more than an hour in any given day. . . so the pump would probably eat up a large portion of your potential energy savings.

I'd say that by the time you were done with the conversion, you might be money and agravation ahead to just go ahead and get a commercially engineered soil-source unit.

-Dan

[K3CZ]

The idea is on the edge of practicality, but the idea is sound.  Today, the geothermal heat pump system in my new 1500 sq ft house under construction in Maryland was fired up for the first time and is producing significant heat for the house as I write this.  This system uses a single 3-ton compressor and about 1500'(!) of polyvinyl(?) pipe buried 7' deep in the ground as a heat/cooling sink.  The temps entering and leaving the compressor heat exchanger seem to be about 50degF, with only a 3-5deg. temp diff between entering and leaving pipes. Now, whether these same thermal conditions are compatible with a recycled window unit, is unknown.  In any event, a different heat exchanger for submersion in the flowing wate r would probably be more practical (simple serpentine of copper tubing, perhaps?)  In any event you must be prepared to deal with refrigerant management (evacuation, recharge, etc.) to pull it all together. Its worth  trying!!                                VAN      K3CZ  

[Kwazai]

ran acros some 'rough' numbers on feet of pipe and payback times here-

http://www.popularmechanics.com/home_improvement/home_improvement/1275586.html?page=2&c=y

[Clifford]

You can purchase water based heat pumps.

My parent's got their first one in 1979....  been around for a while.  And, I think the new ones may be more durable now.

In their case, they pump well water up at 50-60 degrees to feed the heat pump, then just dump the water into the back pasture.

Thus...  in the summer, the water temp is cooler than the ambient temperature for cooling the house, and in the winter, it is warmer than the ambient temperature.

One could probably do a similar system by using a long, deep trench and a circular circulation of water in the loop.