With the introduction of SAP10 in the UK large developments are now pushing the bounds of heat pump design. As buildings get bigger and taller the available footprint to place LZC’s is becoming tighter and a drive for ground source systems will increase. Although conceived as an expensive system to install the stability of thermal delivery over a development lifecycle should not be dismissed.
There are minimum distances associated with the boreholes, guidance generally is 1m to any underground service containing fluids, 2m to any building line and 5m to any other borehole. A GSHP system will not achieve high temperature outputs and as such a secondary system is required to lift the flow temperature for DHW generation (boilers or water to water heat pumps). Heat pumps need to be carefully factored into a design, particularly with network return temperatures.
The network should be optimized to return as low as possible to ensure maximum LZC contribution and carbon offset from the GSHP network. The pipework from a GSHP array on >1MW sites can be quite large (250mm+), ensure that the energy centre is adequately positioned in the building to receive this connection.
An GSHP system should never be connected in series with the network return pipework, these units are sensitive to fluctuations in temperature and should be separated via thermal storage to maximise runtime.
A GSHP network array can simultaneously deliver both chilled water and LTHW though the use of simultaneous heat pump modules.