Everybody has enjoyed it at some point: Outside, it is below zero degrees Celsius and you are swimming in a hot-water basin in an adventure pool.

Where does this hot water actually come from?

- from hot springs, which can be found all over the world. The water in these springs is between 30 and 80°C.

Humans have already used these natural springs for a long time. Today, spas are gaining increasing popularity. They are mainly used for recreational purposes, but are also said to have healing powers. However, that is not the only way to use these natural sources of energy.

- from the interior of the earth.

Huge quantities of heat are stored in the interior of the earth. The earth core has temperatures of above 6000°C and in the upper mantle of the earth there are still temperatures around 1300°C.

Bohrt man beispielsweise auf einer Wiese mehrer 100 Meter in die Tiefe, nimmt die Temperatur alle 100 Meter um etwa 3°C zu.If you drilled a hole of several hundred metres into the ground, for example, the temperature would rise approximately 3°C every 100 metres.

The hot springs are natural and environmental-friendly sources of energy. No air-pollutants are generated and the springs always supply the same amount of energy, regardless of the time of year or day. Because of these advantages, they compete with fossil fuels.

As of 1999, approx. 250 geothermal power plants exist in 21 countries from New Zealand to Iceland. More than 60 million people are supplied with electricity from these plants. For comparison: Austria has 8 million inhabitants.

Two to three 5000 m deep holes are drilled into the ground. If the pumped water is at least 150°C, the water vapour can be used to power turbines for generating electricity.

Used, that is cooled off water, is discharged into the deep again 1 to 2 kilometres away from the plant. This generates a closed cycle.