Heat pumps on a vertical loop
The principle of heat recovery is similar to that for a horizontal loop: circulate a fluid through buried pipes which absorb heat contained in the ground and carry it to the heat pump.
For a vertical loop, this heat comes from either the heat contained in the ground or from the solar heat stored on the surface layer. Generally vertical loops are made up of two U-shaped pipes inserted in boreholes at depths down to 100 m and through which circulates a water-glycol solution (brine - 15°C)
The sensor is placed in a vertical borehole:
- Either in a U-shaped pipe
- Either in 2 U-shaped pipes
- The capacity extracted is between 20 and 50 Watt/linear metre of borehole which corresponds to an energy supply of up to 100 kWh/metre/year.
The vertical sensor generates excellent output because, as from a depth of 15 m the ground remains at a constant temperature, whatever the season.
This installation is recommended for small plots of land. For example, 2 sensors at a depth of 70m heat or cool a 150 m2 house.
The boreholes for vertical loops must be prepared by professionals who use specific equipment which conforms to legislation and to the restrictions imposed by such an operation.
The loops are made out of high or low density polyethylene with a diameter of 25, 32 and 40 millimetres for a nominal pressure of 12.5 bar
- They are
• impervious to corrosion
• impervious to heat and the cold.
• Planned for extended use (100 years)
• Do not lose their charge
• Pressure welded
• The lower part of the loop or sensor foot is fitted with a counter weight to facilitate its installation.
• The borehole should have a cross section of 110 mm to 165 mm
• Once the sensor is in place in the borehole, the latter will be filled with a mixture of cement and betonite (or a similar cellulose-based product) which stabilises the borehole into its original setting.