vertical installation

This method of installation is used where space is too limited to dig trenches or where the ground is so rocky, it's impossible to dig trenches and it's necessary to drill through rock.  Plastic pipe forming a closed circuit system are used and it works much the same way as a horizontal trench system.

Similar to the trench method, in this closed loop system, heat is collected from the ground by means of a continuous loop of pipe buried underground.  An antifreeze solution chilled to several degrees colder than the outside soil by the heat pump's refrigeration system circulates through the piping, absorbing heat from the surrounding soil.

 

Boreholes are sunk by drilling rig boring into the bedrock.  A twin 40mm pipe with connector point is pushed down the borehole, pressure-tested, then grouted into the borehole.  Typically, a borehole is drilled to a depth of 70 to 100 metres.

The rock type determines the heat output that can be achieved from the borehole.  Hard rock such as granite and quartz yield 83 watts per metre of borehole.  Soft rock such as limestone yields less - 50 watts per metre.

Pipe from borehole to manifolds is connected by means of a "reverse return".  See diagram above.

Drilling costs vary but are expensive and cost implications need to be considered before chosing it as a method.  IHS recommends that at a minimum you ensure that your driller is accredited by the National Drillers Association which ensures a minimum standard of competence and adherence to health and safety.  However, outside that, drillers are not regulated by anyone within the renewables industry.