Vienna announced discovery of geothermal energy 3,000 metres under the city

The local energy company plans to test whether the source can be used to power the district heating and to reach sustainability goals

Yesterday, the Vienna municipal company Wien Energie announced the discovery and mapping out of a massive underground hot water deposit under the city. The announcement was the result of a long-running study by the company into sustainable geothermal energy alternatives to the city’s current heating system.

The water deposit is called the Aderklaa and the project has just entered its final phase – exploratory drilling. This process will make use of an old Wien Energie borehole, with the equipment checking rock and chemical composition, and pumping water in and out. After the test is complete, the borehole will be sealed.

Looking for water

The project for mapping the ground under Vienna started back in 2016 and it was done with special equipment by sending vibrations into the ground, similar to ultrasound. Researchers have mapped out the different soil layers and 3,000 metres beneath the surface, they found an abundant water basin.

Experts believe that the water in the Aderklaa deposit should be at a temperature close to 100 degrees Celsius, which would make it a perfect heat source for a sustainable district heating system. However, they also stress that the research needs to be detailed and an eventual exploitation project needs to be well thought out to minimise geological risk.

A visualisation of the layer underneath Vienna,
Source: Wien Energie

Huge amounts of heat are slumbering under the city

The research estimates the water deposit has the potential for 120 megawatts of thermal output, or, as Michael Strebl Chairman of Wien Energie put it – "huge amounts of heat". This is great news for the company, as they aim to provide 125,000 households with warmth from the terrestrial depths by 2030.

According to current climate goals, Vienna needs to cover 56% of the city through district heating by the year 2040 and this deposit offers a relatively easy solution on how to make that climate-neutral. The rest of the city’s heating should be provided through high-efficiency heat pumps.