Cities grow worldwide. Considering the last ten years, Austrian regional capitals for example had a population growth rate of about 7.4 % compared to rural areas with a growth rate of 4.3 %. This means a shift of population from the rural areas to the cities and their banlieues. According to this development greenhouse gas emissions caused by urban population increases, too, counting already for 70 % of the worldwide induced greenhouse gases. Therefore activities of city governments in regard to energy efficiency, the deployment of renewable energy sources and sustainable mobility concepts are crucial, even though the achievements currently are not at all sufficient. However, a couple of years ago several city governments decided to develop binding strategies for “smart city” and “low carbon economy” concepts. Beside to successful demonstration projects realized, these city governments (in Austria especially the city governments of Vienna, Salzburg and Graz) developed new tools in respect of urban planning. Novel numerical methods for simulation of complex urban energy system have been developed in cooperation with research institutions.

In the current issue of “nachhaltige technologien” we would like to illustrate these developments.