Local, climate-friendly heating and cooling for 30,000 households
The Altstetten and Höngg energy network is the largest of its kind in Switzerland and an important milestone on the road to a fossil-free heating supply. In addition, it demonstrates how an enormous supply area can make the transition to renewable energy sources within a few years.
The energy planning of the city of Zurich envisages better use of renewable energy sources in the future. In February 2019, this was shown to also be in line with what the population wants. With 88 per cent support, the city of Zurich’s voters said yes to the property loan of CHF 128 million for the Altstetten and Höngg energy network. A good year and a half later, heat was already flowing into the first connected households.
The energy network as a success concept
The urban areas of Altstetten and Höngg offer ideal conditions for an energy network. They have a high density of heat consumption and are situated close to a source of heat, the Werdhölzli sewage treatment plant. Good experiences with our Schlieren heating and cooling network have already shown that using waste heat from purified waste water does work. The Schlieren energy network saves around 11,700 tonnes of CO₂ emissions per year compared to heating oil (average value 2021/2022). The commissioning of the Altstetten and Höngg energy network allows us to utilise the previously untapped heat potential of the Werdhölzli sewage treatment plant for the Schlieren network.
How does the energy network work?
The heart of the new energy network is the site of the Werdhölzli sewage treatment plant. The primary energy source, available all year round, is the waste heat from the treated waste water of the city of Zurich.
The temperature of the treated wastewater ranges from 11 degrees Celsius in winter to around 25 degrees Celsius in summer. Zurich’s disposal and recycling service treats up to 80 million cubic metres of wastewater each year (around half the volume of Lake Greifensee). Before the treated water flows into the Limmat river, it passes through a waste heat recovery facility (AWN building), where heat is taken from it. In the energy centre, heat pumps bring the temperature up to the level for useful heat.
Another heat provider is the sewage sludge incineration plant, which is also located on the site. The waste heat generated in the course of incinerating the sewage sludge is a valuable energy source. The network uses both the direct surplus heat from the sludge recycling plant (around 2 MW of power) and the condensation heat from the exhaust gases (2.5 MW of power). Because the sewage sludge incineration plant has temperatures of 70 to 80°C, this can be fed directly into the system without needing to go via a heat pump.
In addition, we direct the waste heat generated from ice production in the new Swiss Life Arena of the ZSC Lions into the Anergy grid. And from summer 2022 the energy centre of the Swiss Life Arena will produce cooling for connected properties that will be used to cool offices and commercial spaces. The cooling process is achieved (as with heat production) through highly efficient heat pumps.
Where and when can a connection be made?
The Altstetten and Höngg energy network consists of various subperimeters. The areas of Höngg and Altstetten North are mostly connected to the energy network. In the central Höngg areas, implementation will take place from 2023 to 2028, in Altstetten East from 2024 to 2030, and in Altstetten West from 2027 to 2033.
New connections to the energy network will be coordinated with other planned construction work on the respective road. This bundling minimises emissions and reduces costs for customers.
Here you can call up building-specific information for a connection to the energy network.
All property owners within the network area have the option of connecting their property to the network. Connection is voluntary, but there are benefits for homeowners: in future, they will heat their homes in an environmentally friendly manner and using local energy, and thus already meet the requirements of future energy laws.
Subsidies for collaborative projects
If you switch your heating to a district heating connection, you can apply for subsidies. The application can be submitted at least two years before the measures are implemented and must be submitted before the in-house heating system is upgraded. You can find further information and submit an application here .
- Planning, implementation, financing
- Heating and cooling solution with wastewater and waste heat as sustainable energy sources
- Operation of the energy systems
- 172 GWh of heat required per year (on completion)
- 35 GWh of cooling required per year (on completion)
- 30,000 tonnes of CO₂ saved per year
Join us in connecting around 30,000 households with renewable district heating.
With a connection to the energy network, we supply you with 75 or 100 per cent renewable energy for heating and hot water production. In sub-regions, you also have the option of using climate-friendly cooling to cool properties. The following options are available:
We lay a supply line into your property/properties for a one-off fee and with no further obligations. Our energy supply does not begin until the time of your choosing. That could be when you replace your heating system, for instance.
With a connection to an energy network, you benefit from environmentally friendly heating and cooling produced from renewable energy and no longer need to worry about supplying heating/cooling to your property.
If properties require a replacement heating system before being connected, we offer you an interim solution starting from a connected load of 100 kW.
We take care of the investments and bear financial and technical responsibility. You pay only for the volume of energy purchased and the output power.
Supply to your property is monitored around the clock. Any faults are taken care of at no further cost to you.
You use a locally available, renewable energy source and help to reduce CO₂ emissions in Altstetten and Höngg. In addition, you’re meeting current and future energy policy requirements.
