Utilization of Waste Heat from Waste Water in Vienna
Austria’s goal of full decarbonization by 2040 necessitates a fundamental transformation of its heating sector, which currently consumes approximately 105 TWh of fossil-based energy annually. In Vienna, the shift from individual gas boilers to sustainable heating solutions is central to this strategy, with district heating expected to cover 56% of total heat demand by 2040. To achieve climate neutrality, Wien Energie is diversifying heat sources and integrating innovative technologies, notably large-scale heat pumps and geothermal energy. A flagship initiative is the deployment of one of Europe’s most powerful heat pump systems at Vienna’s central wastewater treatment plant, the Wien Energie Wastewater Heat Pump (WE WWHP). This facility treats around 200 billion liters of water annually, offering a stable and abundant lowtemperature heat source. The heat pump system, powered by renewable electricity from the nearby Freudenau hydroelectric plant, extracts thermal energy from treated wastewater and feeds it into the district heating network. The project’s first phase, completed in 2023, supplies climate-neutral heat to 56,000 households, with full capacity expected by 2030 to serve up to 112,000 households and save up to 300,000 tons of CO2 annually. The initial operational results show that the WE WWHP reliably delivers around 60 MWth of thermal output with a stable COP of 2.9, demonstrating efficient and robust wastewater-based heat production for district heating. This initiative not only advances Vienna’s climate goals but also serves as a scalable model for urban heat recovery, demonstrating the feasibility and replicability of wastewaterbased district heating systems in metropolitan areas worldwide.