site wouldn't let me edit, so had to repost;
site wouldn't let me edit, so had to repost;
I saw a lecture from an engineer who designs and installs these, primarily for chillers in large commercial buildings. He says the bored hole 'open loop' systems are proving to be the quickest payback (so far). He said the cost of drilling is the biggest cost. They use 1" HTPE plastic pipe with water and antifreeze inside (NW region).
For a private pond or lake site; Sink loops 10' deep in a pond or lake that's 30' deep.
You can dig a big pit or over-fill loops too, in a closed loop system. Quartz sand has better thermal conductivity, and moist/wet is better still.
Efficiency heating 50-70%
Efficiency cooling 20-40%
http://www.geoengineers.com/Sustainability.aspx
They partner with this firm;
http://www.geotility.ca/index.php
See also;
http://www.geo4va.vt.edu/
The advantage to GSHP (Ground Source Heat Pump) is that it's dispatchable - that is, the sun can go down and wind stop blowing - but the delta T is there 24 hrs a day everyday.