Water Source Heat Pumps
The heat pump for a water source heat pump installation is the same as a heat pump for a ground source heat pump installation. The difference is in the source from which the heat pump extracts heat. A typical commercial GSHP installation will extract heat from the ground by circulating water through an array of closed loop vertical boreholes of up to 200 metres in depth: cold water from the heat pump picks up heat from the ground as it circulates through the pipes in the ground by heat exchange.
Groundwater Heat PumpsA groundwater heat pump extacts heat from water abstracted from an underground aquifer though an open loop borehole and returns the water to the aquifer through a second discharge borehole.
Surface Water Source Heat Pumps
A surface water heat pump installation is similar, but abstracts water directly from a river or a lake and discharges it back downstream to the river.
Reasons to use a Water Source Heat Pump
The reasons to use a water source heat pump are similar to the reasons for specifying a ground source heat pump installation. Both can provide efficient heating and cooling to buildings at a low running cost and with zero emissions of carbon dioxide - or any noxious gasses - on site. Both will outlive heating systems based on combustion. However, both systems will cost more to install than heating systems based on burning gas.
Which is the optimum solution?
There are a number of considerations for your designer to juggle with depending on the heating and cooling loads of your building, location, the local geology and environmental consents. A surface water source installation may be suitable for a large building if a river or open water is accessible close by. If there is no local water it may be possible to drill down to a local aquifer to install an open loop heat exchange system. If there is no suitable local aquifer then a closed loop borehole field array may be the optimum solution for heat exchange. In all cases professional advice will be required to design and install a system that meets the heating and cooling needs of your building for many years to come.
Code of Practice for Surface Water Source Heat Pumps
There are a number of key issues to be considered in planning to install a surface water source heat pump installation. These are highlighted in the Code of Practice for Surface Water Source Heat Pumps published jointly by CIBSE, GSHPA and the HPA. The lead authors of the Code are Nic Wincott and Jen Billings of the GSHPA and the Code can be bought from www.cibse.org/CP2.
Electronic copies are available to members of the GSHPA, without charge. Please request a copy via firstname.lastname@example.org.
Meanwhile, a short leaflet explaining how the Code can be used by building owners and developers can be downloaded by clicking the image on the right.
Installation of Water Source Heat Pumps
To get the full benefit of a water source heat pump installation or a surface water source heat pump you will need to employ someone with design and installation experience. A water source heat pump, like a ground source heat pump, may not perform well unless it is incorporated in a good design by someone who understands the needs of the building, the use to which the building is being put and the local geology.
To ensure a "soft landing" you should ensure that a ground source system is well understood and well maintained and this may include fine tuning the controls in the first years of operation.
For more information on installation of ground source heating from an experienced source please contact one of our members.