District Heating Graz Andritz

Entlarging the solar distrit heating supply of Graz

The combined use of solar thermal energy and heat pump technology, as used in this system, is unique at this point in time and on this scale in Austria.

In order to get one step closer to becoming the solar capital of Europe, the City of Graz and the urban energy utility company Energy Graz decided to work with SOLID to develop this flagship project on the grounds of the water works Andritz, the city´s central water supply station.

The aim was not only to relieve the environment, but also the budget situation of the city of Graz in times of rising energy prices.

The collector array with a total collector surface of 3,855 m² is installed as a non-attached elevated unit on the premises of the waterworks Andritz.

When the temperature necessary for feed-in is reached, the transfer station directly feeds the solar energy into the district heating network of Graz. If the feed-in temperature cannot be reached but the temperature level is still usable, the energy is loaded into the buffer. The latter provides a volume of 64,6 m³ and is placed in a lowered position inside a fountain house. The buffer is used to support the heating of the waterworks office buildings.

The described load management reduces occurring demand peaks in the district heating supply.

The integration of a heat pump for utilization of lower temperature levels during winter and transitional season was integrated in 2012. The solar plant is operated following a model for energy contracting.

The system contributes to a large extent to reduce fine dust emissions in the city of Graz. Beside that the economic aspect is highly valued in times of rising energy prices.

Technical Specifications


CO2 Savings
350 t/a

Collector area
3855 m²

60 m³

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