Green Solar Cities Site Salzburg

At Salzburg 57,000 m² of new buildings have been constructed. At the new building area “Stadtwerk Lehen” buildings with very low energy demand have been combined with a new local district heating network. The network integrates 2,000 m² of solar thermal collectors on the roofs of the buildings, a heat pump (for raising the efficiency) and a large buffer tank of 200,000 litres (Picture 1 and “More detailed”). At “Parklife” (Picture 2) a senior daycare center, a senior residence and an apartment building have been constructed according to very ambitious energy standard and integrate solar thermal collectors on the roofs for domestic hot water (DHW) preparation and support the heating system. At “Esshaver Straße” a new building with 12 dwellings according to the passive house standard has been finished in 2008. It features 3-pane glazing, 37 m² of solar thermal collectors (for DHW and support of the low-temperature heating) and a mechanical ventilation system with heat recovery. At “Neue Mitte Lehen” an apartment building with 48 dwellings (for rent) has been built. It integrates a solar thermal plant of 140 m² and a buffer tank of 30,000 litres.

All the new buildings are connected to the municipal district heating network for covering the remaining energy demand, which is not provided by the local energy supply system.

Also renovation of old building blocks in the area was part of the initiative. The first renovation project in Kuenburggasse (45 dwellings) was finished in March 2010. It was followed by a second large retrofit project, “Wohnpark Strubergasse”. Previously a study about a total renovation concept had been performed to show the possibilities of a total renovation up to plus energy standard.

An integrated overall planning concept for the whole city area has an additional focus on questions of traffic, mobility and green areas. Two new railway stations in the south will increase the infrastructure of the area.

Large scale storage, solar thermal collectors and heat pump in combination with a district heating network

In the CONCERTO area “Stadtwerk Lehen” it is being demonstrated how expanding the use of solar heating to a higher share (of the total need for heating and DHW) is possible, e.g. from today 15% to expected 45% in the future. The approach is the combination with a heat pump. At the same time a micronet will be established, connected to the

district heating, which is based on biomass and industrial waste heat (Figure 1). A big thermal solar plant with in total 2,000 m² collectors was installed on the roofs of the different buildings (Picture 4).

The working group “Solar and micro net” has worked out an optimized system for use of thermal solar energy, increase of efficiency by implementing the heat pump in the collector circle and distribute the heat by a low temperature micro net. The buffer tank was erected in May 2011 (Picture 4) and the solar plant was finished in winter 2011/2012. The solar energy now covers about 35% percent of the annual heat demand, the remaining energy is provided by the municipal district heating network.

A special visualization on the buffer tank gives information to all people about the performance of thermal solar collectors (Picture 5).

Monitoring and User Information

Monitoring started in Nov 2008 for project Esshaverstraße – and will continue until spring 2012. All energy use is counted and in three apartments all window contacts are monitored, so that relations between user behaviour and energy consumption can be examined.


For Stadtwerk Lehen a special monitoring concept is prepared. A working group has been founded to develop a monitoring system that takes special account on user information and user friendliness.

An „Energy traffic light“ in a social housing project is taken as an example, which shows the tenants the relation between energy need and energy use and the share of energy coming from the sun (Picture 6).