Industry News: Energy

From Wastewater to District Heating – the Role of Large-scale Heat Pumps in the Energy Transition

At Wien Energie, Georg Danzinger is working on the future of district heating. A plant with up to seven large-scale heat pumps is being built in Vienna.

At Wien Energie, Project Manager Georg Danzinger is working on the future of district heating. He and his team are planning a plant with up to seven large-scale heat pumps in Vienna. The heat energy is supplied by wastewater. How does it all work?

The large-scale heat pump installation at the ebswien wastewater treatment plant is one of the Austrian energy supplier’s key projects. “This will be the largest plant of Wien Energie that uses heat pump technology,” says Georg Danzinger, Project Manager at the decarbonized heat generation assets department of Wien Energie. Currently in its first stage of expansion, the plant now boasts three large-scale heat pumps from the French manufacturer Johnson, which together yield a thermal output of about 55 MW. Together with his team, Georg develops projects to decarbonize district heating. “Our goal is to implement renewable heat generation in addition to renewable power generation,” he says.

Contacts mentioned in the article:

Markus Fuchs, Key Account Manager at KLINGER Gebetsroither

Energy from wastewater

Large-scale heat pumps represent an important step towards sourcing energy more sustainably. Using this technology, Wien Energie can draw heat energy from the wastewater of the adjacent main sewage treatment plant, helping decarbonize heat generation. “In the first phase, we are installing three of a total of six large-scale heat pumps, which together will produce a thermal output of 110 MW. We’d even have space for a seventh heat pump. The water for the district heating network has an outlet temperature of 93 °C (199 °F),” Georg continues. This heat is fed into a district heating network that distributes the heat to households and businesses in Vienna.

In winter, the wastewater coming from the treatment plant has an outlet temperature of 11-12 °C (52-54 °F); in summer, it reaches 24-25 °C (75-77 °F). If the source temperature is higher, a higher outlet temperature can be achieved. “This improves the heat pumps’ COP (coefficient of performance), i.e. their efficiency,” explains the experienced project manager, who has also managed environmental impact assessments (EIA) for major projects.

The large-scale heat pumps were manufactured in France, transported to Vienna in parts and assembled on site. The heat pumps are scheduled to go online in January 2024.

District heating with 100 percent renewables

That wastewater tends to be viewed negatively by the public is not an issue here, as it offers significant potential. Apart from being a source of energy that can be utilized for district heating, the heat pumps lower the temperature of the wastewater returning to the Danube, which reduces its heating effect on the river.

Extracting heat from the wastewater, and so our heat pumps have the added benefit of a positive impact on the Danube’s flora and fauna.

Georg Danzinger, Project Manager at the decarbonized heat generation assets department of Wien Energie

Not only that: the plant sources its energy for district heating from 100 percent renewables. Thanks to a direct line from the Freudenau power station, a third of the energy used comes from hydropower. The remaining two-thirds is sourced as heat from the wastewater from the treatment plant. “So if you put 1 kW of electrical energy in, you get out 3 kW of usable heat energy,” says Markus Fuchs, Key Account Manager at KLINGER Gebetsroither.

Wien Energie has assumed a pioneering role throughout Europe in decarbonizing district heating – not least thanks to projects such as the large-scale heat pump at ebswien.

Fact Box

Other (large-scale) heat pumps in Vienna

  • UNO City
  • Therme Wien
  • Simmering power station

True teamwork is called for

Georg plans to commission the plant in the fall of 2023, with the heat pumps going into regular operation in mid-2024. Throughout the planning phase, there were many details that needed to be clarified both with the manufacturer of the heat pump and with suppliers, such as KLINGER Gebetsroither. “We had to once again prove ourselves in the construction company’s bidding process,” says Markus. District heating is nothing new for Wien Energie, having been used to supply Vienna with heat for about 60 years.

KLINGER valves and gaskets have proven themselves over many decades.

Georg Danzinger, Project Manager at the decarbonized heat generation assets department of Wien Energie

That he can rely on these products’ high quality also makes his job easier. Unlike with other projects, there is no general contractor for this one. “We manage everything ourselves, although we also receive support from other departments of Wien Energie, such as Electrical Engineering and Control Station Technology. For that, we are grateful,” says Georg.

Regarding technical issues, Georg Danzinger (left) was always able to count on the solution-oriented approach of Markus Fuchs (right) and the KLINGER Gebetsroither team.

“Valves a safety feature”

Overall, the project cost around 70 million euros. The share of costs for KLINGER valves in this total was almost negligible. And yet they have a huge impact on the entire heat pump process.

Nobody wants to be standing next to a leaky valve, where hot water turns to steam in the atmosphere. When it comes to the danger of leaking valves, some think of media such as chemicals. But although water vapor doesn’t cause pollution, standing right next to a leak is not a good idea: The pressures and temperatures are very high; it’s not ‘just’ water.

Markus Fuchs, Key Account Manager at KLINGER Gebetsroither

KLINGER offers sealing elements specifically for district heating applications, and Georg even goes one step further, calling “valves a safety feature.”

The KLINGER KVN piston valve in its smallest size, DN15, provides venting and draining of pipework.

Fact Box

KLINGER Gebetsroither products in action

  • Ballostar KHSVI – these ball valves from KLINGER Fluid Control are installed at the site’s periphery to the district heating network and have weld ends. They shut off the return and flow and are used with nominal diameters up to DN800 (for the pump station). They must withstand pressures of up to 28.5 bar and temperatures of up to 180 °C (356 °F).
  • Ballostar KHA – This KLINGER ball valve has a pre-stressed, elastic sealing element. In the Wien Energie plant, it is sometimes used as a secondary shut-off downstream of a KVN piston valve.
  • Ballostar KHI – This ball valve is the ideal match for district heating due to its unique sealing element. It, too, comes from the KLINGER Fluid Control factory.
  • KVN – The design of this piston valve has been tried and tested for over 100 years. It is used for draining and venting the pipework and withstands the plant’s working pressure of 15-16 bars.
  • KLINGER TopChem2000 – The universal high-performance gasket from KLINGER Dichtungstechnik is used with flanged valves.
  • Combined shut-off and check valves – with its space-saving design, the Zwick product has a proven track record in pipework.

The future of district heating

Hydrogen and geothermal energy are hot topics, also at Wien Energie, “but we’ll save that for a future article,” says Georg. So, the future of district heating looks promising. With projects like its large-scale heat pump installation, Wien Energie demonstrates that sustainable, efficient heat generation is possible. And with partners like KLINGER Gebetsroither at their side, they are well equipped to master the challenges of the energy transition.

An architectural competition was held for the building’s facade.

The wastewater comes from Vienna’s adjacent main wastewater treatment plant.

With a length of almost 50 meters, the pipe network runs in the plant’s basement, supplying the process with wastewater and coolant.

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