ground and water source heat pumps

Ground and water source heat pumps (sometimes also called geothermal heat pumps) are based on a series of pipes buried in the underground to heat and to cool our homes or to heat domestic water. In winter these heat pumps use their pipes to profit from the relatively constant temperature of the ground to heat the home. In the summer the process is reversed: the heat pump moves heat from the indoor air into the underground pipes.

Even when we experience extreme temperatures in the peak of the summer or the winter, a few feet below the ground surface the temperatures remain relatively constant. Ground and water temperatures often range from 45°F (7°C) to 75°F (21°C). They are warmer than the air above it during winter time and cooler in the summer. And water and ground source heat pumps take advantage of these differentials, by exchanging heat with the ground/water using a series of pipes buried in the underground...

Ground and Water Heat Pump Schematic from Danfoss Ground and water source heat pumps interact with the ground or the ground water and their temperatures (instead of the outside air, as air-source heat pumps).

Temperatures below ground surface remain relatively constant year round, well above the freezing point, even in freezing climates and regions, allowing ground source heat pumps - contrary to air-source heat pumps - to be very energy-efficient in almost all weather conditions and climates.

Parts of Ground and Water Source Heat Pumps

Ground and water source heat pumps systems are different from air source heat pumps in what concerns their parts and locations. Unlike air-source heat pumps, ground and water heat pumps haven't an outdoor unit: the heat exchanger and the compressor (like the air handler...) are located inside; only the set of pipes are located outside...

The heated (or cooled) air is distributed around the house via ductwork.

Close and open-Loop Designs

Ground and water source heat pumps may have a closed-loop or a open-loop design. The closed-loop design uses a solution of water and antifreeze through the pipes of the system to get the air conditioning. The pipes are typically installed in the ground horizontally or vertically...

Open-loop systems use water drawn from a well, lake or other surface water source in their pipes. In these systems the water is subjected to a surface discharge or returned to a well after being used (it doesn't recirculate through the pipe system). Open-loop systems are rarely used or recommended for residential solutions. See, for more information: Ground Heat Pump Loop Installation.

Ground and rock loops

The loop’s length and configuration depend on the amount and layout of your site, landscaping, or on factors like the location of underground utilities.

Horizontal loops are typically the most economical, and are excellent for new homes with sufficient land. Ground and Water Heat Pump with a Certical Loop

Vertical loops are more compact and minimize the disturbance of the surrounding landscape. The existence of a convenient rock shell near the building (see picture at right) is also a factor that can make vertical loops a good choice.

Images credit: Danfoss

water Source heat pump loops

Water source heat pumps use underground water source (lake, river and mainly wells) as the heat source (see picture below). It's the water from the water source that circulates directly through the pipe system.

Well water designs are by far the most common and often the most cost effective. The well can both supply domestic water and the water needed for the heat pump (heat pumps require at least three gallons per minute of well water per ton of capacity).

The use of a water source heat pump system depends on factors such as the volume, depth and water quality; the disposal of the water (after once-through the heat pump) can be costly and demands compliance with legal requirements…