Project Description

Europe’s most powerful large-scale heat pump

Making sensible use of waste heat is considered to be a cornerstone of efforts to ensure the success of the heating revolution. Wien Energie is spearheading efforts here with a Europe-wide showcase project. Simmering is where we run the most powerful large-scale heat pump in Central Europe, supplying around 25,000 households in Vienna with environmentally-friendly district heating, thereby saving 40,000 tonnes of CO2 every year. Total investment amounted to EUR 15 million.

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A picture says more than 1,000 words

See for yourself how our large-scale heat pump was built.

Project details

Our large-scale heat pump works like a beating heart, ensuring an efficient cycle that pumps heat into Vienna’s households. Utilising existing waste heat is an essential part of being able to supply heating in an even cleaner way. With its large-scale heat pump, Wien Energie is setting store by future-oriented technologies.

A heat pump works in the same way as a refrigerator – only in reverse. In a refrigerator, waste heat is generated by the cooling process whereas, in a heat pump, this waste heat is the end product that is wanted. The heat source used by the large-scale heat pump in Simmering is the cooling water from the power plant, in which heat that can no longer be used is transported away from the cogeneration plants. In addition, the ambient heat of the nearby Danube Canal can also be used as a heat source.

The large-scale heat pump consists of two identical heat pumps, each with a self-contained coolant circuit. This coolant absorbs the waste heat via a heat exchanger and is then compressed and heated by an electric compressor. Finally, the coolant is liquefied again and the resulting waste heat is released to the district heating water.

The technology installed in the highly complex system enables heat to be extracted even from very low temperatures. A heat pump can turn 6°C into 95°C for heating. Given that this temperature is still a little on the low side for the main district heating pipes in Vienna (with an average temperature of 100 to 150°C), an intelligent distribution system ensures that the water can be used optimally in the district heating network and is used where the required temperatures are lower.

Further reading

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Power-to-heat plant

The power-to-heat plant resembles an oversized kettle that converts excess electricity into environmentally-friendly heat. The plant has a total capacity of 20 MW and supplies 20,000 households with district heating, thereby playing a key role in maintaining stability in the power grid.


High-pressure heat storage tank

The world’s first high-pressure heat storage tank makes it possible for heating to be used when it is needed. Irrespective of when it is produced. It covers the annual heating requirements of around 20,000 households and saves around 11,000 tonnes of CO2 every year by optimising production and storage.