Ground Source Heat Pumps


Ground source heat pumps

Ground source heat pumps use the relatively constant temperature of soil, or surface water as a heat source and sink for a heat pump, which provides heating and cooling for buildings.

Ground source heat pumps are similar to ordinary heat pumps, but use the ground instead of outside air to provide heating and, in most cases, hot water. Because they use the earth’s natural heat, they are among the most efficient and comfortable heating and cooling technologies currently available.

Ground source heat pumps are durable and require little maintenance. They have fewer mechanical components than other systems, and most of those components are underground, sheltered from the weather. The underground piping used in the system is guaranteed to last 25 to 50 years and is virtually worry-free. The components inside the house are small and easily accessible for maintenance. Since ground source systems have no outside condensing units like air source heat pumps, they are quieter to operate. Ground Source heat pumps are an excellent partner for under floor heating.

Types of Loops

Ground source heat pump systems are usually not do-it-yourself projects. To ensure good results, the piping should be installed by professionals with the appropriate training. Designing the system also calls for professional expertise: the length of the loop depends upon a number of factors, including the type of loop configuration used; your home’s heating load; local soil conditions and landscaping; and the severity of your climate ( costal / non costal ect.). Larger homes requiring more heating generally need larger loops than smaller homes. Homes in climates where temperatures are extreme also generally require larger loops.

Here are the typical loop configurations:

Horizontal Ground Closed Loops

When there is plenty of land available this is normally the most cost effective method. Polyethylene pipe is laid in trenches approximately 1.2m deep and a mixture of water and food grade anti-freeze (‘brine’) is circulated to collect energy from the ground.

This type is usually the most cost effective when trenches are easy to excavate and the size of the yard/garden is adequate. We use track machines to dig the trenches 1. 2m below the ground in which we lay a series of parallel plastic pipes. We then backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. Fluid runs through the pipe in a closed system. A typical horizontal loop will be 200m to 400m long.

Vertical Ground Closed Loops

Where space is tight, vertical boreholes may be the answer. They can range from 25m – 150m deep but can be expensive depending on the location. A closed U-tube is placed in the borehole and a mixture of water and anti-freeze is circulated to collect energy.

This type of loop is used where there is little yard/garden space, when surface rocks make digging impractical, or when you want to disrupt the landscape as little as possible. Vertical holes 25m to 150m deep – much like wells – are bored in the ground, and a single loop of pipe with a U-bend at the bottom is inserted before the hole is backfilled. Each vertical pipe is then connected to a horizontal underground pipe that carries fluid in a closed system to and from the indoor exchange unit. Vertical loops are generally more expensive to install, but require less piping than horizontal loops.

Vertical Open Loops

This type of loop system may be cost-effective if ground water is plentiful. Ground water from an aquifer is pumped to a heat exchanger then transfers its heat to the heat pump. After it leaves the building, the water is pumped back into the same aquifer via a second well, called a discharge well, located at a suitable distance from the first.

Closed Pond Loops

This type of loop design may be the most economical if your building is near a body of water such as a large pond or lake. The brine circulates underwater through polyethylene piping in a closed system. The pipes may be coiled in a slinky shape to fit more of it into a given amount of space. Because it’s a closed system, there are no adverse impacts on the aquatic system.