horizontal loop

Heat pumps on a horizontal loop

The ground stocks solar energy throughout the year. This constantly replenished source of energy is thus available and recoverable by a WATER-TO-WATER heat pump.

The theory is simple

circulate a fluid through buried pipes which absorb heat contained in the ground and carry it to the heat pump.

the fluid used is a glycol-water solution (brine -15°C).
the heat from the ground is essentially restored during the summer, but can also be renewed during sunny periods throughout the rest of the year.
rain also contributes to the loop's energy renewal.
95% of the recovered heat comes from the sun's heat; the calories that rise by convection from deep layers only represent a negligible 0.2 to 0.5 W/m2.

Dimensions of the loop

Firstly, the surface area of land available for the loop should be 1.5 to 2 times the surface area to be heated. For example: to heat a 130 m2 house, 200 to 260 m2 of loop is necessary.

Different types of horizontal loops

3 types of loop are generally used:

The traditional horizontal loop
Stripping off of top level of soil.
Depth 0.8 m, below the frost line
Minimum 0.4 m pitch, 25 mm diameter pipes
Laid on a bed of sand and delimited by boundary markers
The 2-pipe trench loop.
The 4-pipe trench loop
Dig to a depth of 0.6 to 1.20 m
Maximum length of trench 50 m
Distance between 2 trenches 0.5 m

Average recovered capacity according to loop type (watt/m)
Configuration	Per metre of trench (W/m)	Per metre of piping (W/m)	Per m2 of land (W/m)
Stripping*	/	15*	37*
2-pipe loop	30	15*	30*
4-pipe loop	44	11	37

(*) For regions in which the outdoor temperature can drop to -10°C, the values are 12W /m and 30W/m^{2
These values are indicative; they depend on the nature of the land.}

Table of minimum distances to be respected between the loop and other elements on the land

Obstacles	Minimum distance in metres
Trees	2
Non-hydraulic sunken networks	1.5
Foundations, wells, septic tanks, etc.	3

Geothermal energy

Heat pumps

Groundwater heat pumps

Horizontal loop