22 Sep 2021
by IEA DHC

Smart City Reininghaus in Graz, Austria

The „roadmap“ for heat supply strategy for the city of Graz from renewable sources envisages that, based on a share of around 25% in 2017, a share of 50% can realistically be achieved within the next 10 years. Before 2050 it should be possible to generate all the district heating with renewable resources - provided the appropriate framework conditions are in place.

Triggered by the shutdown of the heat supply from the coal-fired Mellach CHP plants by 2020, innovative solutions for a transition of the district heating system were developed and some cases already implemented. In pilot projects, several decentralised heat generators and low-temperature systems are used to support the integration of alternative energies (e.g. heat pumps, solar thermal, waste heat, and biomass).

The energy model Graz Reininghaus is a good example of a modern concept for heat supply in new ‘Smart-City’ construction areas. It is an urban development area in the west of Graz with an area of approx. 54 ha and up to 12,000 inhabitants in final development. The former area of the Reininghaus brewery is the largest development area in the city of Graz, offers the opportunity to develop an urban, dense and energy-optimized district (1.8 km from the historic old town). In the course of the development of the Reininghaus district, an innovative energy model is developed in cooperation between Energie Graz and Marienhütte. The energy utility Energie Graz initiated and developed the energy model Graz Reininghaus. Furthermore, they are the investor and operator of the plants. The cornerstones are:

  •  low-emission heat supply 
  • low-temperature heat network (appr. 69 °C) with the use of industrial waste heat sources from the steelworks Marienhütte 
  • two highly efficient large-scale heat pumps (each with up to 5.75 MW thermal) use the industrial waste heat and feed the district heating subnetwork Reininghaus at 69 °C and to the district heating network Graz at up to 95 °C
  •  annual amount of heat generation: approx. 40– 45 GWh/a (equals to 4% of the district heating demand of the whole city of Graz)
  • modular heat storages, volume up to 1,600 m³ as daily and weekly storage (so called “Power Tower”)
  • photovoltaic system with (85 kWp) built on the façade of the “Power Tower”