Water/water heat pumps use the heat contained in the ground water, certain areas of surface water or cooling water.
Water-source heat pumps achieve the highest energy efficiency ratios. Ground water has a more or less constant temperature of 8 to 12°C throughout the year. Compared with other heat sources, therefore, the temperature level only has to be raised a relatively small amount to make it usable for heating purposes. The water table should not be below approx. 15 m.
Well and water quality
Only ground water close to the surface should be used. A three-day long time pumping test is necessary in order to check the yield of the extraction well. The water temperature must be no lower than 8°C, otherwise alternative heating systems will have to be provided to bridge the temperature difference. That is also why surface water is often unsuitable, because the water temperature drops sharply during winter.
To prevent corrosion damage, certain limiting values for constituents of the water must be complied with. A water analysis is required. Bear in mind that water quality can fluctuate (for example if fertilisers are used on neighbouring fields).
The use of a submersible pump will prevent the introduction of air/oxygen. An appropriate filter should be used.
Design
Wells can be dug or drilled (min. diameter 220 mm for submersible pump), and the work must be carried out by a specialist company. If the rock is fine-grained, a larger hole diameter should be chosen in order to prevent sand from being extracted with the water. Blasting should not be used.
NB: If the well is too small, the excessively high flow rate will cause the filter to clog.
The deep well should be located in the direction of ground water flow quantity from the extraction well and at least 15 m away from it.
Consent
Consent for the use of ground water as a heat source for the heat pump must be obtained from the appropriate Water Rights Authority. The well sinking or drilling company or OCHSNER system partner will help you with your application.