A ground source heat pump uses the principle of extracting a large amount of so-called "low grade energy" from the ground which it then converts into a smaller amount of high grade heat for use in the building heating system. The Ground Energy Array (GEA) accesses that low grade energy.

The amount of heat that can be extracted from the ground via a GEA is affected by a number of factors.

1. Size of the array. The larger the area you extract heat from, the more heat you can extract. As heat is extracted from the GEA the temperature of the ground around it drops. Heat from the surrounding area will tend to move in to replace the heat that has been extracted. It’s important to correctly size the array or it may not be able to provide sufficient energy to meet the demands of the heating system.

2. Different types of ground affect the process. Heat does not flow as well in dry, sandy ground as it does in wet, loamy ground for example. Extraction rates vary from as little as 20 Watts per square metre for dry ground to over 35 Watts per square metre in heavy wet ground.

We use the ground as a rechargeable solar battery. During the heating season we extract energy from the ground. The ground is then recharged during the following summer as the sun shines on it and as warm rain permeates the ground. This recharging process can be enhanced by using the GSHP for cooling in the summer months.

Econic understand all these factors and have the expertise to make sure that your GEA is well designed. It is critical to get the ground energy array right; if the system has been incorrectly designed, the performance will degrade over the year and ultimately, could lead to the failure of the system.

Most ground source heat pumps use a closed-loop Ground Energy Array with vertical boreholes or horizontal trenches. Various types and methods of installation can be specified depending on site conditions and customer requirements.

The traditional method for vertical boreholes is to drill one or more boreholes, typically 80-100m and insert a “U” of pipe into this hole which is filled with a thermally conductive grout. Boreholes can be drilled with either a traditional rotary rig or a sonic rig.

On certain sites we recommend a concentric collector tube where a smaller diameter pipe is inserted inside a larger one. These types of collector can have significant benefit, such as speed, lack of noise and mess etc. Econic pioneered the design and installation of such systems. These can be installed with either a hydraulic pushing rig or a sonic drill rig.

Econic has significant in-house knowledge in the area of thermal or energy piles, where the piles themselves contain the thermal loops to allow collection or dissipation of heat. This is a growing area, but one that needs careful planning to ensure that using the piles in this way does not compromise the integrity or function of the piles. Econic are well versed in this developing area.

Ground source heating is often described as Geothermal. Although this is not incorrect, ‘true’ geothermal energy is actually derived from greater depths that those used for most ground source heating and cooling applications. True Geothermal systems access the heat from the earth’s core, compared to standard ground source heat pump installations which are accessing the suns energy that is stored in the ground at relatively shallow depths (0-200m).

In a horizontal array plastic pipes (usually 32-40mm diameter) are buried in trenches about 1.5m deep. In a so called “slinky” system the pipe is buried in a semi-coiled form in a slightly wider trench. Econic can advise on the most suitable form of horizontal collector for your site. As a general guide around 50 linear metres of heat extraction pipe are required to provide 1kW of energy so a horizontal array can take up quite a large area

In a closed loop system a heat transfer fluid is circulated around an array of pipes buried in the ground. In some situations an “open loop” system may be considered. Here water is pumped directly through the heat pump, usually from a well. The water is then returned to the ground via another well. This kind of system makes sense where a good source of groundwater is available or where a closed loop is not practical due to lack of space. In ideal circumstances an open loop water system can be the most cost effective and efficient solution.