Last year, geothermal heat pump (GHP) manufacturers introduced new heat pumps with break-through efficiency based on variable-speed compressor technology. These manufacturers include Waterfurnace Renewable Energy (TSX:WFI, OTC:WFIFF) and ClimateMaster, a division of LSB Industries LXU -0.46% (NYSE:LXU).
Air Source and Ground Source
Variable speed compressor technology was not restricted to geothermal heat pumps (also known as ground source heat pumps or geoexchange): It had first found its way into what are often considered ground source’s poor cousins: air source heat pumps (ASHP).
Both types of heat pumps use a refrigeration cycle to draw heat from the outside in winter to heat a building, and pull heat from the inside to cool it in summer. GHPs use large loops of buried tubing to exchange heat with the ground, while ASHPs use an above-ground fan and heat exchanger assembly similar to the evaporator on a traditional whole house air conditioner (see photo.)
via Are Air Source Heat Pumps A Threat To Geothermal Heat Pump Suppliers? – Forbes.