Installation of geothermal piles (CASE: Toriparkki Car Park, Turku)

A new car park is being constructed underneath the Turku Market Square. The parking lot will have 620 parking spaces and there will also be 20 charging points for electric vehicles.

The car park (called Toriparkki) is a so-called zero-energy car park. It will be heated using, amongst other things, the geothermal energy stored in the layer of clay underneath the car park. Paalupiste undertook the job of embedding the geothermal collectors into the clay layer underneath the car park.

Multiple screw piles were installed underground to be used as so-called energy piles. This way, the geothermal collectors were able to be embedded up to 36 meters deep – a depth in which heat production is excellent. The car park is also exceptional because the ground is heated using solar energy, which improves the heat generation capacity of the system even further.

Solar energy provides heat year-round

During the summer, the car park’s heating system collects heat generated by solar radiation from the surface of the market square. The pipework used for collecting the heat, which is situated underneath the paving of the market square, transfers a liquid heated by the radiation into the energy piles. The energy piles then give out heat into the surrounding land mass. The heat is eventually stored in the clay soil underneath the car park. The thermal input of a fully heated clay mass is approximately 6,6 MW.

In the winter, the warm clay mass releases heat into the liquid circulating in the energy piles, which in turn transfers it up to the surface of the market square keeping it free from snow and frost. At the same time it also heats the parking space in the car park. Whilst the car park is being constructed, Turku Market Square will also be renovated, which will be completed in stages throughout 2021.

Is it expensive to install long screw piles?

Usually, the more material is used in a piling project, the bigger the price tag. However, there is a positive side to this: if the piles can also be utilised as part of a heating system, then a lot of piles could be a good thing.

Roughly, even just 150 pile meters will be enough to heat and cool a regular detached house. The method can also be used in bigger buildings. 

In addition to Toriparkki in Turku, Paalupiste has installed energy screw piles into a 4 000 m2 sports hall (www.uusimaa in Porvoo. The hall has not had to be connected to the district heating system at all, since it’s more cost-effective to heat the building using the thermal energy generated by the energy piles.

Project details:

Location: Turku Market Square
Type of pile: Paalupiste machine installed PRO™ screw piles modified to be used as energy piles
Installation machinery: 8 tonne excavator with a 8 500 Nm screw pile drive head and a 5 tonne excavator with a 4 500 Nm screw pile drive head
Main contractor: SKANSKA


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