AGRULINE used to create a better hydrothermal system in Lake Geneva

Context

Since 2009, towns around Lake Geneva have used the lake to create thermal networks to supply heating and cooling for local buildings. The technology works by exploiting the static temperatures at the lower depths of the lake with a heat pump on land to supply heating more efficiently during winters and cooling during summers. The technology can reduce energy usage for heating and cooling by up to 50%, providing an environmentally friendly alternative to traditional techniques.

Project GeniLac was one of the first projects to use the lake’s unique properties, connecting the United Nations district buildings to the system. In 2016, a nearby municipality took a similar approach in La-Tour-de-Peilz to heat more than 400 homes. By 2018, leaders expanded the GeniLac system to support the Geneva city center and seven other municipalities, serving about 50 buildings.

In 2021, Centre Patronal sought to build a new employer center in Lausanne to cool and heat the building with the same hydrothermal technology.

Opportunities

The area of Lake Geneva near Lausanne presented a unique opportunity as it is the site of the lake’s deepest point. Hydrothermal power leverages temperature gradients, so creating the system’s intake point at a lower depth offered the potential for greater efficiencies. Other systems have drawn water between 45 and 70 m (147.64 and 229.66 ft) below the lake’s surface. Designers for Centre Patronal’s design targeted a depth of 80 m (262.467 ft). Here, the temperature hovers between 4°C (39.2°F) and 8°C (46.4°F) throughout the year.

The targeted depth, however, presented challenges. First, the total length of pipe for the project meant on-site fabrication. Second, the intake and outfall sections of the system would be at significant depths, requiring good pressure resistance. The depth would also cause more costly maintenance. Lastly, any fouling in the pipe over time would decrease flow capacity and increase pumping cost, negating the purpose of the system. The solution would need to address all these factors.

Solution

AGRU presented a solution with its AGRULINE system, which comprises solid-wall extruded plastic pipes made with OD 500 mm SDR 11 PE 100-RC. Pipes made with PE 100-RC offer superior durability, longevity, stress crack resistance and are near-impervious to most chemical reactions and biological fouling. The pipe’s characteristics meant that it would require far less maintenance than other piping materials and ensure a high internal smooth coefficient for high flow capacity throughout its service life. AGRU also custom manufactured pipe segments, such as 6 m high sweep bends, to further minimize flow resistance.

Hydrokarst Swiss handled the pipe installation starting at the delta of the Rhone. After assembly, the pipe was tugged on the lake over 20 km (12.4 miles) to the site. Divers then lowered the two pipelines to the target depth of 80 m (262.467 ft) before completing the installation.

Outcome

The intake and outfall pipelines for the Centre Patronal facility’s heat pump were completed in March 2021, using about 800 m of the AGRULINE piping system. The new facility can now use the water in Lake Geneva to cool and heat its building with improved efficiencies.

“The competition for this exciting project was great,” says Markus Ebster, head of XXL Piping Systems, “AGRU scored [well] with quality, engineering, and technical support during planning and realization.”

AGRU representatives conveyed the advantages of its solid-wall extruded plastic piping solution and proved its benefits over competing piping materials. The Lake Geneva project aligns with AGRU’s commitment to modernize infrastructure and conserve vital resources with innovative plastic solutions.