General Description of the Case Study

The project is currently under construction, waiting for the first stage to be implemented in 2024 and the second stage to be concluded in 2027. At its first stage, the project aims to supply 55 MWth and up to 56,000 households. The wastewater temperature is 12-23°C, which is raised to a higher level by heat pumps. In addition, an existing biomass plant raises the temperature level in the first stage. The full expansion with 110 megawatts of output will follow in 2027. The waste heat source will supply 110 MW (2nd stage) at 93°C to the district heating system. The district heating system serves about 440,000 households and businesses over a network of about 1300 km.

The project aligns with the energy target of the City of Vienna and the decarbonisation goal for heat generation by 2040. The heat production is 100% local and renewable using waste heat from wastewater, combined with 100% green electricity from a hydropower plant. It serves as a model for European cities. The concept can be replicated in cities with existing district heating systems and wastewater treatment plants, with similar projects planned for Berlin and Hamburg.

The first phase involves a total investment of €70 million in eligible costs. The project is financed by Wien Energie. The subsidies include the national subsidy (Umweltförderung Inland - € 5,742 million).

The plant is owned by Wien Energie on the site of the wastewater treatment plant. The waste heat is supplied by Ebswien, the operator of the WWTP. The right to use the wastewater after the treatment process is settled by a fixed fee per year. The price of the heat depends on the price of electricity. The project is currently under construction and the first stage of 55 MWth is scheduled for 2024.

Wastewater waste heat project - Vienna, Austria