The world’s largest solar thermal district heating

20. June 2018


The largest solar thermal district heating in the world is being built in the Styrian provincial capital of Graz under the name “Big Solar”. This is being implemented, with a budget of around €100 million, by Energie Steiermark with one Danish and the two Styrian partners, Christof Industries and the Graz solar company S.O.L.I.D. In addition to the waste heat from the Sappi paper mill in Gratkorn and the Marienhütte steelworks in Graz, this showcase project will convert solar energy into district heating. A collector area of 220,000 m² together with the 900,000 m³ storage tank will cover 15% of the annual district heating consumption of the city of Graz.


Big Solar Graz – reaching next milestones


S.O.L.I.D. has been developing a concept for supplying up to 25% of district heating of Graz with solar thermal energy and a seasonal storage in late 2015. Today, the project has developed reaching significant milestones. The land for both, the storage and the solar collectors is secured. The consortium consisting of VKR/Arcon-Sunmark, Energie Steiermark, Christof Industry and initiator S.O.L.I.D. has recently announced the project progress to the media.

As per today, the project is designed to be resized to 220,000m² and will be built as originally intended in the south of Graz. Together with a storage of approximately 900,000m³ the system will cover 15% of the annual district heating demand of the city of Graz.

The plan is to move on with detailed engineering and permitting within the next months and start the construction in 2019.



Christian Holter
S.O.L.I.D. Gesellschaft für Solarinstallation und Design mbH
+43 316 292840

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