District heating for Wengen: waste heat from the wastewater treatment plant and wood chips

The signs of the times are clear: if the goals defined by the Federal Council to protect our climate are to be achieved, reducing CO2 emissions is a key pillar. Switching from fossil fuels to renewable energies helps to achieve this. Due to the great interest in a sustainable heat supply, BKW AEK Contracting AG (BAC) is therefore planning a district heating network in the municipality of Lauterbrunnen in the Wengen district. The first properties are expected to be supplied with renewable heat from 2030 at the latest. The project makes a significant contribution to protecting the local environment and also creates added value for tourism.

The district heating network – one heating centre for multiple properties

In a district heating network, various properties are supplied with heat from a central energy plant. The heat for heating and domestic hot water is transported via a district heating network with insulated hot water pipes laid underground to the individual buildings. BAC is responsible for the planning and construction of the heating centre and the district heating network in the street area, routing the pipes through the cellar walls, the building connection pipes, and the installation and commissioning of the heat transfer station. In many Swiss municipalities, the expansion of district heating networks is being promoted. This is linked on the one hand to national climate protection targets; on the other, district heating offers customers compelling advantages not only from an ecological and economic perspective, but also in terms of operation and maintenance.

A district heating concept for the entire village centre of Wengen

BAC wants to supply the entire village centre of Wengen with a forward-looking and sustainable heating system. The energy concept is based on the efficient use of waste heat from the Lauterbrunnen wastewater treatment plant (WWTP), a new woodchip heating plant and an oil heating system for very cold days at the same location. A transport pipeline connects the three heating plants with the village of Wengen. A local distribution network connects the individual properties – cleanly, efficiently and sustainably. For maintenance work or emergencies, an additional redundant heating plant based in Wengen will be used. The combination of all heating plants enables a resource-efficient energy supply. The aim is to leave the smallest possible CO2 footprint and make a significant contribution to the local energy transition.

The planned implementation of the district heating project

BAC has already examined the use of wastewater heat at the Lauterbrunnen WWTP as well as the construction of a woodchip heating system at the same location. Both projects are technically feasible and could be implemented following approval by the responsible authorities. From this location, the transport pipeline is planned to run along the existing wastewater pipeline to Wengen. As the municipal wastewater pipeline has reached the end of its service life, the municipality of Lauterbrunnen is currently examining the refurbishment of the pipeline. For both parties, there is shared synergy potential in this section in terms of costs and construction; where appropriate, both pipelines could be rebuilt at the same time. Construction logistics challenges are to be expected for the distribution network in the village. However, these can be solved.

The project is currently focusing on the heat supply for Wengen. Today, around 2.2 million litres of heating oil are transported to Wengen by rail every year and distributed locally by small lorries. For pellets, the transport effort for the same energy requirement is three times higher than for heating oil. This traffic burden is to be reduced to a minimum. The district heating network in Wengen will initially be developed as a basic network and later densified.

BKW AEK Contracting AG (BAC)

BKW AEK Contracting AG (BAC) is a company of the BKW Group. As a specialist in heat supply, it produces climate-friendly heat from renewable energy sources for residential buildings and industrial properties. Founded in 2018 through the merger of the contracting competence centres of AEK Energie AG, Solothurn, and BKW Energie AG, Bern, the company can look back on 30 years of experience. Its portfolio comprises 40 heat generation plants, including 22 district heating networks. Over 40 employees are committed to innovation and sustainability every day. Among other things, the Grindelwald wood-fired heating system and the heating network in Spiez are planned, built and operated by BAC.

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