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Energy in Minds Site Weiz-Gleisdorf


Project status



The Weiz-Gleisdorf community is a co-operation between 17 villages and the two cities, Weiz and Gleisdorf in East Styria in the south of Austria. The community has the highest density of solar thermal and photovoltaic systems in Austria. It received two times the European Solar Energy award.

The objective of the co-operation is the promotion and implementation of renewable energy sources, which involves nearly 40,000 inhabitants. This region specifically demonstrates innovative solar thermal systems. These systems involve the installation of solar thermal collectors in 70 private houses for domestic hot water (DHW) and space heating. Most of these systems back up bio-mass boilers, which results in 100% reliance on renewable energy sources (RES). The installation of 60 kW photovoltaic (PV) systems on 20 private households supports the Weiz-Gleisdorf community’s use of RES.


Site facts and figures

  • Estimated population involved:  14.000
  • Approx. geographical area coverage: 30.000 m²
  • Approx. energy saving: 23,9 %
  • Approx. energy from RES: 30 %



In total more than 35,000 m² of residential, public, private and office buildings have been retrofitted during the time of CONCERTO. 13,000 m² new low energy residential houses were constructed (Picture 1).

During the five years 8 large solar systems and 111 smaller systems between 15 and 40 m² have been installed (2,860 m² in total). In the field of photovoltaics 25 systems were implemented with a total capacity of 106.7 kWpeak. One of them is a 5 kWpeak system, which has a 2-axis solar-tracking function to optimize the orientation towards the sun and thereby increase its annual yield. Furthermore 122 pellet boilers were installed for private households corresponding to a total installed power of 1,956 kW, often combined with the solar thermal collectors mentioned above.

Large bio-fuelled co-generation plants and district heating systems have been implemented to improve the efficient use of energy. In total a power of 4,085 kWtherm  in biomass district heating systems has been installed. This includes new small and larger systems as well as extensions to existing networks. One stirling machine and two linear generators (enabling combined heat and power from biomass) have been installed and monitored (Picture 2 and “More Detailed”). With three heat pumps for commercial buildings, using the thermal energy of wastewater, the first systems in Austria have been installed (see “More detailed”).

In the field of mobility cars have been converted for the use of biofuel and the first biofuel station of Weiz-Gleisdorf had been opened.


Retrofit of a Hostel for pensioniers

The retrofit (Picture 3 + 4) of the “hostel for pensioniers” (5,490 m² gross floor area) is one showcase in the “Energy Region Weiz-Gleisdorf”. Good insulation resulted in a higher thermal comfort due to higher surface temperatures at the inner side of the walls. The building is heated with district heat generated from biomass combined with a controlled ventilation system with 70% heat recovery and a 160 m² solar thermal system.

According to the passive house calculation method (PHPP) the energy demand was reduced from 157 kWh/m²a to 24 kWh/m²a thus reaching the passive house standard. The energy consumption for heating and domestic hot water has been measured at 138 kWh/m²a before and 55 kWh/m²a after the retrofit. Beside the energy demand the energy costs were strongly decreased from about 30,000 Euro per year to only 4,000 Euro per year.


Waste Water Heat Recovery

A new wastewater heat pump system was developed. This system is the first heat pump in Austria, which uses heat from a sewage treatment plant. The temperature of the wastewater ranges between a minimum of 10°C in wintertime and a maximum of 20°C in summertime. With the support of an electrical heat pump an office building is heated in winter and cooled in summer. The power of the heat pump is 90 kW.

Although cleaned wastewater is used, it is not possible to use a common heat exchanger. A special double tube heat exchanger built up with 32 elements each 4 m made of stainless steel is installed (Picture 5).The heat pump was installed at 3 places using the wastewater from the treatment sewage plant. Heat meters were installed for detailed monitoring of the plants.


Linear Generator

The Bison linear generator (Picture 6) is a free spool steam engine with a linear generator driven by pellets or wood chips. The electrical power of this engine is 0,3 to 2 kWel, the thermal power 3 – 16 kW. The heating system was realized in October 2009 as a research project at the company building of the AEE INTEC in Gleisdorf. Until March 2010 the Bison linear generator with 15 kW delivered about 11.500 kWh of heat and 880 kWh of electricity. The total working hours were about 1.800 hours.

It is one of the first linear generator engines in the”Energy Region”, which is running effectively. The energy region compiled a detailed documentation of the generator showing that it is possible to implement such a linear generator in every household with a thermal power between 2 and 15 kW.

Lessons learnt

The following information has been gathered as part of the CONCERTO Premium policy research.

Benefits of CONCERTO:

Owner and tenants were really pleased with the installed heating system. The solar thermal system produced more energy than calculated and the use of gas was much lower than expected.


Barriers encountered:

Administrative barriers:

Weiz Gleisdorf has been confronted with a lack of cooperation and acceptance between departments within the public administration Solutions:

The work was done by CONCERTO team instead of the communities themselves, so a cooperation of the communities was more likely.

Technical barriers:

Hot water solar thermal systems especially for new buildings are quite standard in Austria whereas combinede systems (also for heating) are not so common. Solutions:

Through a lot of information campaigns, press meetings, public relations and workshops the project team tried to convince house owners to implement these combined systems. For plumbers special documentation for planning and workshops was offered.

Economic barriers:

In Austria insulation materials are quite expensive as well as the costs for windows. The wages in Austria are also quite high


Combined funding (CONCERTO and other).

People were given support by the community for the installation of combined systems. However, they were only supported if they additionally reduced their energy consumption to less than 100 kWh/m²a by retrofitting their house.


Success factors identified:

Technical Success Factors:

In the communities an innovative energy efficiency advisory technique had been launched using infra-red technology. Qualified professionals performed a door to door energy efficiency test with thermo graphic – red cameras in order to identify eventual heat and energy dissipation. This procedure, supported by local dissemination campaigns, had been crucial for the success of the “retrofit single-family house programme”.

Social Success factors:

The good publicity of “Energy in minds!“ helped that a lot of inhabitants in the Energy Region Weiz-Gleisdorf had been willing to invest in a better energy standard. Also the financial support of Energy in minds! helped to push this trend.

Institutional success factors:

Well-timed adaptation of targets & good control of project development.

In Weiz Gleisdorf the Energy Regional Association called “ERWG” played a decisive role in the uptake of the CONCERTO initiative and its implementation. This instrument (ERWG) created in 1996, favoured the spread of sustainable culture at municipal level with a domino effect at the regional level. The ERWG Association supported this set up in Weiz and Gleisdorf using the legal and planning framework “the Energy Action Plan horizon 2015” .

Economic success factors:

  • The possibility of combining CONCERTO funding with local subsidies in these two municipalities had been a major driver in getting people interested in doing refurbishments, leading to comprehensive retrofits using solar thermal and/or pellet boilers
  • The interest for solar thermal systems was very high in Austria. The original goal of 1.000 m² was far exceeded. Budget was shifted to solar thermal systems. When installing a solar combi system, often people replaced their fossil central heating boiler with renewable energies (e.g. biomass, wood pellets or wood chips).
  • To reach the energy and environmental targets, every solar system for hot water should be a solar combi system. The inhabitants of the energy region Weiz Gleisdorf showed that they are willing to pay more for a solar combi systems.

The CONCERTO approach

A 400 kWel bio-gas based co-generation plant for the use of local energy resources in the community of Weiz-Gleisdorf involves the establishment of a bio-fuel infrastructure with pilot plants using plant oil. 30 vehicles are adapted to bio-fuel and put into operation throughout the community.


The retrofit of the “hostel for pensioners” is a showcase for a multi-family house in Weiz-Gleisdorf.

It includes:

  • New glass façade in front of the old façade turning the open balconies into additional living space
  • Good insulation
  • Modern control engineering
  • Controlled ventilation system with 70% heat recovery
  • District heat generated from biomass
  • 160 m² solar thermal system


Ewald Selvicka
AEE Institut für nachhaltige Technologien