Geowarmth Heat Pumps

Slinky trench system

Coils of 32mm diaameter polyethylene pipe, often referred to as slinkies, are laid in trenches 1,200mm wide and 1,200mm deep.  The length of the pipe and number of trenches varies according to the heating needs of the property.  Each trench is usually between 30 and 50 metres long.  A typical 3 bedroom house may require around 3 trenches.  Expressed another way a modern well insulated property of say 200m2 floor area would require trenches with a total length of around 100 metres which would be subdivided in to 3 trenches.  The trenches can be curved to fit the contours of the grounds of the property and can for example go around the sides of the property.

Horizontal loop system

Loops of 20mm pipe are laid in a wider excavation, also 1,200mm deep.  The layout resembles underfloor heating pipes.  The length of these excavations is 35 - 40 metres and the width and number of loops of pipe used varies according to the heating demands of the property.  Whilst this system may appear to require more earth to be moved, with a larger excavator it is often as quick as digging trenches which can collapse and require redigging in wet weather. 

Pond loops

Heat can be extracted from lakes or ponds: the bottom of a lake is the warmest part in the winter.  Coils of pipe are laid just off the bottom of the lake.  Sometimes lakes are built for the purpose as in the example on the left or the loops can be sunk in to existing ponds.  The pipes are installed in protective cages when the lake is used for fishing.  Only a small pond is required to heat a typical house: say 120 cubic metres as the minimum all year round volume for a modern 3 bedroom house.  If there is flow through the pond this further helps the system.  Loops can also be laid in rivers but this may require regulatory approval and methods of fixing to cope with rivers in flood.