Foto: Frontansicht des sozialen Wohnbaus Utendorfgasse Wien

IEA EBC Annex 64: Optimised Performance of Energy Supply Systems with Exergy Principles

To reduce CO2 emissions in cities, an overall understanding of energy conversion processes is necessary, which also takes temperature levels into account. This is particularly important when alternative heat sources such as waste heat, ambient heat, solar and geothermal energy are to be used, as these often have a low temperature level, i.e. a low exergy content. Accordingly, urban energy systems are analysed and optimised within the framework of the IEA EBC Annex 64 with the help of the exergy approach.

Short Description

This includes the analysis of possibilities for cascade heat utilisation, the identification of potentials for the integration of heat pumps, the comparison of national and international case studies and evaluation methods as well as the contribution of Austrian contributions. The main results of the Annex are "best practice examples" and guidelines for the exergy-optimised design of urban energy systems, which have been summarised in a comprehensive guidebook, taking into account exergy principles and Austrian expertise.

Cities are responsible for more than 2/3 of final energy consumption. To reduce CO2 emissions, it is essential to increase energy efficiency in consumption and the share of renewable energies. A holistic understanding of the consumer structures and conversion processes, which also takes temperature levels into account, is necessary to increase the potential in the heating and cooling sector. So far, however, energy planning in cities has essentially been based on a balance between energy demand and generation capacities.

The mission of the IEA program EBC: Energy in buildings and communities is to develop and support the integration of energy-efficient and sustainable technologies in buildings and communities through research and innovation. Within the framework of EBC Annex 64, urban energy systems are analysed and optimised with the help of the exergy approach. The aim is the development of cost-effective and low-emission supply concepts through the efficient use of renewable energy sources.

Within the EBC Annex 64 AIT was participating from an Austrian side and was leading the sub-task "Model Cities". This includes for Subtask A: The mathematical analysis of possibilities for cascading heat utilisation between characteristic building types, Subtask B: The elaboration of potentials for the integration of heat pumps in low-temperature district heating network , Subtask C: The creation of a database to summarise and compare all case studies of the Annex, Subtask D: the comparison of static and dynamic evaluation methods and optimisation algorithms and the integration of exergy indicators, Subtask E: The contribution of Austrian contributions to international expert meetings, the information of Austrian stakeholders, cooperation in the development of brochures, website and seminars/workshops as well as the integration of the Austrian Annex results into the design guidelines.


  • Documentation of best practice examples in Austria and international comparison
  • Preparation of 2 scientific publications in international journals and 5 conferences and short presentations
  • Newsletter and project website, implementation of a national workshop on exergy optimisation
  • Design guidelines for urban energy systems taking into account exergy principles and Austrian expertise


Austria, Denmark, Germany, Italy, the Netherlands, Sweden, USA and Turkey

Contact Address

Austrian Institute of Technology GmbH (AIT)
Charlotte Marguerite
Giefinggasse 2
A-1210 Wien
Tel.: +43 (0) 50550-6695

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