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Heating at 170 metres – Hoval solution installed in Vienna’s Danube Tower

Heating at 170 metres – Hoval solution installed in Vienna’s Danube Tower

Vienna, Austria

Following a complete makeover, Vienna’s Danube Tower, the tallest structure in Austria, inspires a new sense of wonder in all those who behold it. The Viennese landmark has also been fitted with a heating solution from Hoval.

  • Other building
  • Renovation
  • Oil/Gas

420,000 visitors every year and six marriage proposals every week: extending 252 metres from the base to the spire and first opened in 1964, Vienna’s Danube Tower stands proud as the tallest structure in Austria and continues to be a real magnet for tourists. The rotating restaurant at 170 metres above the ground and the Turmcafé at 160 metres were fully modernised in 2018 alongside a number of other ground-floor areas. The opening of the spacious new Donaubräu pub in February 2019 marked the completion of the rebuilding and renovation works.

A new heating system high above the ground

The renovation of the technology behind the tower began in 2017 before the other work commenced. This included the installation of a new solution from Hoval to replace the outdated heating system. Given the high levels of efficiency of the Hoval system, this meant that the new standards for emissions limits could also be adhered to. Two Max-3 gas boilers were installed by Hoval installation partner Ledermüller while the tower was still up and running in the autumn.

They now supply the tower and also provide the new catering spaces with the greater capacity they need: while previously all buildings in the Danube Tower had a combined heating requirement of 450 to 500 kW, this has now risen to 650 to 700 kW.

However, the greatest challenge when it came to planning the system was the height of the areas to be heated at the very top of the tower. Hoval area manager Christian Böhm, who helped to develop the technical solution together with Hoval’s partner, explains:

The pressure reduces by 1 bar every 10 metres in height. That means that a pressure of 18 bar is needed in the boiler room so that the required pressure of 1.5 bar can be ensured in the central floor of the tower at 165 metres.

Since standard boilers are not designed for use at such high pressures, Hoval decided to split the systems. The two Max-3 gas boilers provide the power required, with each supplying 350 kW. The energy is transferred to a separate circuit via a heat exchanger. The two-boiler solution provides the Danube Tower with both the desired reliability as well as flexible operation.

Modern heating technology that rotates

Another key focus in the design of the new heating system was the two revolving platforms for the Turmrestaurant and the Turmcafé. Here, a heated plinth provides warm air to ensure that visitors can continue to enjoy the views of Vienna even in the cold winter months. From the centre of the tower, the air is guided to the rotating air channels in the floor by means of a new brush technology solution. A second heat exchanger is installed at the top of the tower in order to heat the air. Since this inevitably results in a small loss of temperature, the fact that the robust Max-3 boilers are able to keep the temperature consistently high is a particular bonus. Christian Böhm:

At the top of the tower, the warm air has to be heated to 80°C on cold days so that nobody freezes. In order to achieve this temperature, we heat the hot water in the boiler to around 100°C.

From design through to maintenance

Hoval oversaw the project for the unusual structure from calculating the cost of the installation right through to coordinating with installation partner Ledermüller during the execution phase. Claudia Pich, spokeswoman for the Danube Tower, was very happy with the collaboration with Hoval:

The heating system works perfectly. Hoval has met all of our expectations.

Since commissioning in October 2017, Hoval has taken care of both the management and maintenance of the boiler. So far, the TopTronic E control system has been deployed to great success to regulate use of the double boiler in line with demand. Using an online connection, service technicians are able to access the system remotely. And Hoval has even set up a small warehouse containing replacement parts especially for the Danube Tower to ensure that the Viennese landmark is always properly maintained.