Solar thermal energy could be one central part of Graz´s future district heating energy supply


GrazThe city of Graz has supported and even stimulated the district heating network´s extension program for years. Although the systems are central to reduce fine dust emission, the city now faces enormous challenges.
A combination of 500.000m² solar thermal collector systems and long term storages could provide 20% of the district heating network´s energy demand.


Almost every 3rd household in Graz is connected to the district heating system and therefore is an active part of a massive Particulate Matter (PM) reduction initiative. Around 80 percent of the grid´s energy was provided by two fossil fuel plants, Mellach and Neudorf/Werndorf II. Within the city of Graz, both plants have contributed to massive PM reductions within the last years.


District heating systems provide convenient, easy accessible heat on demand. Households don´t need to provide storage facilities, organize fuels, or maintain chimneys. Energy from district heating systems is delivered by simple, easy to maintain pipes to every single household.

As of today, the city of Graz faces unpredicted challenges: The outdated coal-fired thermal power plant in Mellach is supposed to be de-commissioned by 2020. Therefore a brand-new, state-of-the-art highly efficient 832 Megawatt electric gas-fired CHP was implemented by 2011 as standby backup and for future security of supply. The CHP was designed to provide up to 300 MW heat to Graz.  Due to recent economic developments this new CHP plant can´t be operated from a profitable perspective. The oil fueled district heating plant in Neudorf/Werndorf II is already off the grid.


The city of Graz has to reorganize its entire energy sources to operate the district heating system. It seems to be a herculean task! How should 300 MW of energy be provided in the future?


SOLID developed a concept which has been presented to the City and the utilities.
A combination of 500.000m2 solar thermal collector systems and long term storages could provide 20% of the district heating network energy demand.
As opposed to natural gas plants today, solar thermal systems can be operated profitably. Currently the proposal is under discussion.