Water Well Drilling
Geodrill can carry out water well drilling for water to water open loop geothermal systems as well as domestic and agricultural water supplies.
High water quality is important where water is being consumed or used in mechanical processes. Water with a high degree of impurities and suspended solids requires a lot of filtration which adds cost to the water being delivered at the surface. Correct drilling practices can eliminate many of these issues. Below is a brief outline of how a correct water well should be constructed and the benefits of constructing in this way.
Drilling a borehole for a Water well system involves creating a circular void in the ground in which a pump can be set to pump groundwater back to the surface. This involves drilling through the overburden (unconsolidated ground consisting of clays/gravels/sands etc.) until solid rock is reached. In order to keep this ground open a casing (steel tube) must be applied alongside the drill string.
Once rock is reached casing of the hole is discontinued as the rock is naturally stable and the inner drill string continues drilling into the rock until the required borehole depth is reached to provide the water quantities required. The inner drill string is then removed.
At this point a PVC liner narrower than the diameter of the well is lowered into the well. The bottom section of PVC liner that will sit in the section of the well that has water flowing into the void will contain small linear slots to allow water enter the PVC tube. The PVC tube above the water bearing section shall be solid and impermeable.
The space between the side of the PVC liner and the side of the well shall be then filled with a fine gravel or gravel pack which will act as a filter. The gravel pack should rise just above the slotted section of PVC.
A grout should then be poured to seal the well from the gravel pack up preventing water entering the bore from the upper sections and possibly contaminating the water. Failing to do this can leave you exposed to surface run off, leaching slurries etc. entering the water well.
The casing string should then be removed.
The Well pump can then be fitted and the well protected with a manhole at the surface to allow maintenance in future.
Water to water heat pumps
Water to water heat pumps work by pumping water from a well through a heat exchanger in the heat pump. The refrigeration system in the heat pump extracts heat from the water as it passes through the heat exchanger. The water continues flowing out of the heat pump and back to another water well constructed in the same fashion as the first..
A few factors must be considered when choosing to use a water to water system.
Water Quantity: Even small domestic water to water heat pumps will require two cubic meters of water per hour while commercial systems could require 10’s or even 100’s of cubic meters depending on the heat output required. Without sufficient supply a water to water system will not work
Water Quality: If the water contains impurities such as Iron this will attack the heat exchangers in the heat pump. Suspended solids will block heat exchangers. Filtering the high quantities of water required can be expensive so the correct construction of the bore is essential to minimise this issue.
Water flow direction: The water pump from the supply well must be set up in the up stream bore as when the water passes through the heat pump it is cooled by 3-4C. If this cooled water is returned upstream it can flow downstream and return to the heat pump once again. This short cycling would result in a huge drop in performance and perhaps even system failure.
Returning water: It must be considered that extracting sufficient quantities of water is only one part of the process. Returning this water to the ground is equally important. The dump well must be able to accept the quantity of water being returned otherwise the well will over flow. Water pumped from the ground cannot be discharged to surface water so two wells are required and both must be constructed to a high standard
While the above points must be considered when using water to water they are a fantastically efficient system because they extract energy directly from the heat source and don’t rely on intermediary circuits. GeoDrill can guide you through the planning and execution of a high quality water to water system. We will also inform you if it cannot be completed successfully and it is then possible to switch to a closed loop system if desired.