Mace completes first borehole for ground source heat pump system in City of London scheme

May 08, 2024

The first geothermal borehole has been completed for a ground source heat pump system in the the City of London's Salisbury Square scheme.

The Salisbutry Square scheme will deliver a new, purpose-built 18-courtroom legal facility called the City of London Law Courts and an industry leading City of London police headquarters.

The borehole is one of more than 60 240m deep planned boreholes to be installed by the scheme’s main contractor Mace and subcontractor heat pump system specialist G Core. A spokesperson for Mace told NCE that while other projects use geothermal borehole systems the Salisbury Square solution was the only standalone system in the City of London without the need for gas.

The boreholes each have a supply and return pipework grouted within the bore, which will be individually connected to eight manifolds with chambers and header pipework will be run back to the plantroom to form the Ground Energy Collector (GEC).

This will then feed through to the plantroom where Mace will install three simultaneous ground source heat pumps to provide the site heating and cooling requirements terminating at heating and cooling plate heat exchangers.

Excess heat will be rejected via the ground using a dry air cooler (DAC) system sized to 90% of the peak rejection from the ground source heat pump system.

The key phases of installation are as follows:-

Mace Construct project director Jeremy Eavis said: “This network of 60 deep geothermal boreholes is the starting point for the ground breaking installation of a closed loop system ground source heat pump in the City of London. This will mean the Salisbury Square Development will be off the gas grid, dramatically reducing its operational carbon.”

Salisbury Square is one of the first schemes in the Square Mile to use standalone closed loop cooling and heating. The geothermal borehole system uses consistent temperatures deep underground and is the most energy efficient method of heating and cooling using electric solutions, eliminating the need for gas.

Described as “a new civic hub” in the City, Salisbury Square is being funded and delivered by the City of London Corporation. It will house a flagship facility for His Majesty’s Courts and Tribunal Services and new headquarters for the City of London Police. It will also include office accommodation and expanded and enhanced public areas.

The borehole will help to reduce the development’s carbon emissions and play a part in the City of London Corporation’s commitment to net zero by 2040.

City of London Corporation policy chairman Chris Hayward said: “This is a significant milestone for the Salisbury Square Development. The completion of the first geothermal borehole is a major step forward in our plans to create a sustainable and low-carbon development.”

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