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Application of Directional Drilling in the heat pump industry...

Axis Drillings first project was near Oxford in 2006 and was designed to show how HDD can be used as an alternative to the trenching method.

Ground Source Heat Pump (GSHP) duct instillation using coiled and straight pipe

GSHP Trial Methodology
Two sets of ducts were installed for use with a GSHP in an oxford garden.

•One 600m loop using the traditional trenching method at a depth of 1m with coiled pipe.
•The other; a 550m loop using HDD in straight lines either side of the trenched coil between 1.1-1.3m depth and approx 1.5m apart.
•Both sets of ducts were connected to individual 14kw IVT GSHP’s.
•One heats an indoor swimming pool and the other for the house system.
•Internal plumbing was designed so either loop could be used on each system.

Data temperature points were taken for inflow and out over the course of 6 months between October 07 and March 08. These are plotted below.

Fig.1: GSHP started using the trenched pipe and changed over to the drilled pipe on point 28 after a month of negative outflow from the GSHP. Thereafter the drilled pipe manages to maintain a positive outflow until the last point.

heating

Fig.1: GSHP started using the trenched pipe and changed over to the drilled pipe on point 28 after a month of negative outflow from the GSHP. Thereafter the drilled pipe manages to maintain a positive outflow until the last point.
Fig.2: GSHP started using drilled loop to heat swimming pool. The change over to trenched pipe occurs at point 35, where the GSHP outflow is negative until the last measured point at the end of March.

Summary

The GSHP’s compressor should not have to work so hard at higher inflow temperatures therefore reducing power consumption. If indeed the drilled loop continues to provide higher or even equivalent performance ratios to the existing data then this coupled with its adaptive environmental and circumstantial properties would appear to be an effective solution for the installation of GSHP ducts in the future.

Coulston Basset, Nottingham:

laying ground loop for a new build energy efficient house fitted with a heat recover ventilation system,
super insulation and under floor heating. This loop consisted of 900m of pipe spaced evenly to create a balanced twin coil system (See Diagram Below). The purpose of this system is to provide cooling for the house in summer by pumping the recovered heat underground and then reverse the process in winter to meet heating requirements.


Coulston drilling plan.

The ground here is fine sticky clay so was perfect for drilling and should provide a high thermal conductivity and mass.

More information about Heat Pump Ground Loop installation