Piles - Energy pile - Franki Foundations UK

The energy pile, also called "heat exchanger pile", is a pile equipped with individual or several pipe circuits in order to enable exchange of heat with the surrounding soil. The function of energy piles is dual. The first function consists of transferring load from a construction into the bearing layer. The secondary function is the use as heat exchanger with the soil. Energy piles are installed either using soil displacement techniques (see 'Construction sequence'), or soil excavation systems.

Construction sequence

The functioning of the installation takes place over an annual cycle.

In winter, with the aid of a heat pump, when the water is colder than the soil, heat is removed from the circulating fluid (and indirectly extracted from the soil) and renders a higher temperature to the heating.

In summer, conversely, when the water is warmer than the soil, heat is dissipated into the soil for cooling

1., 2. & 3. During the screwing-in phase, a soil displacing screw head inserts the guide tube to the correct design depth

4. During the screwing-out phase - as the auger is simultaneously withdrawn while rotating - concrete is pumped into the borehole through the hollow central tube of the auger.

5. & 6. The reinforcement, fitted with integrated heat exchangers in HDPE (‘collector pipes’), is then placed into the concreted pile. A heat exchange fluid, usually simply clear water, circulates in an U-shaped pipe circuit (‘pipe loop’) located between the piles and a heat pump (HP) and is heated or cooled by the surrounding soil.

Construction chart

Fields of application

• "Nearly zero-energy building"

• Ideal solution for heating and cooling of buildings (housing, offices…)

• To be used in combination with a geothermal heat pump

Environmental impact

• Integration with existing components, low maintenance

• Ecological system, not subject to licensing procedures

• Sustainable concept; possible reduction of C02 emissions by approximately 40%

• Energy savings of about 45% possible.

Technical specifications

• The placement of reinforcing cage is required at the level where the exchange of temperature (heating/cooling) should take place.

• The energy pile is equipped with individual or several pipe circuits made out of plastic (polyethylene) so as to exchange heat with the surrounding soil.

• A heat exchange fluid, usually simply clear water, circulates in the pipe circuit (‘pipe loop’) and into a collector supplying one (or more) heat pump(s).