The scientific basis of the NotusPid single-hole system

The NotusPid system was modeled and simulated, and the results were compared to measurements at existing facilities built in Switzerland.   In the process, a good agreement was found between the calculations and the measurements made in practice . Our model considers both the movement of water and the transport of heat in the borehole as well as in the surrounding porous rock.  Both the movement of water and the transport of heat are based on a linear relationship between pressure and temperature and the corresponding flow (Darcy's law and Fick's law). The flow in the borehole is also modeled using this approach.

The NotusPid single hole system uses vertical groundwater flow which first, causes convective heat transfer and second and leads to a higher temperature gradient at the bottom of the borehole.  This also causes a significantly higher effectiveness of conductive heat transport.

The result of combining both processes (convection and conduction) leads to a significant increase in heat extraction compared to a closed one-hole system. (Probes etc.) The vertical groundwater flow is only possible if some permeability of water in the rock is available . However, it appears that a very low permeability of 1.00E-15[m²] (corresponding to a permeability coefficient of 1.00E-7 [m/s] ) is already more than sufficient.

The results of a modeled system at a depth of about 1.5 km indicate that at a permeability of 1.00E-15[m²] the operating yield of a closed system is approached in principle.  If the permeability increases to 1.00E-14 [m²] the yield already increases by a factor of 2.5. In short, relatively very low permeability is already sufficient.

Compared to two-hole systems (doublet), the single-hole system offers the advantage that water circulation is always possible.  The borehole filled with the patented granite pebble (in the single-hole system) and the surrounding porous medium should be seen as parallel resistors.  If the permeability of the surrounding medium were to drop to zero, the output of the well would still correspond to the heat output of a closed system.

The operational risk is eliminated with the NotusPid technology because the effectiveness of the technology is determined by the activation of geothermal currents and no quantities of water are required.

As a result of the above, geothermal energy extraction is possible at any location and also at the location where this energy and the amount thereof is required. The only remaining risk is the drilling risk. As drilling technology is very advanced and widely developed, the drilling risk concentrates mainly on the additional drilling risks such as the possible drilling of artesian wells, gas lenses, cavities.  For all these problems, there are drilling technology solutions available which, although resulting in additional costs, do not lead to the failure of the project.

Completion and operation of the well can not lead to problems since the construction and operation of the well are carefully engineered, planned and executed in a professional manner.

The flow volume of the circulating water in the borehole is accurately calculated, which results in a reliable production capacity.  The required pump capacity for the circulation can be determined beforehand by analogy.

When the well is put into operation, small quantities of gas can still be developed from gas flanges which can be extracted with the appropriate devices. When setting up an installation it may be necessary to treat the circulation water mineralogically. All these measures are only of a temporary nature since the circulation water always circulates in the same ring space and no additional water, gas and minerals are added from the formation.