Quote:
Originally Posted by Oval_Overload
Would it be possible to compromise, placing the coils in a root cellar or subterranean garage?
|
That would freeze the air in that garage pretty quick. Look at it this way: with ground source, there is a very large thermal mass in a relatively small volume, while air has very little thermal mass, so very large volumes of it are needed. Hence, the fan the blows air over the heat exchanger of an air source hp.
In the setup you proposed, there is a small volume of air enclosed in a cellar, so the heat pump would fairly quickly rob that air of most of its heat. Yes, the air would gradually warm up thanks to the heat seeping through the walls, but that takes a while, so it will be the bottleneck. If the walls of the cellar had the same surface area as the total area of the tubing that goes into the ground, then you might be close.
I believe that the most cost effective ground source (other than laying your tubing on the bottom of a lake) is a buried spiral just below the freezing level. This give less stable temperatures, but the ground work is cheaper than drilling.