Thanks to the expertise provided by the project partners, regional analyses on the city storage and sector coupling (CSSC) potential of 10 countries have been completed. More specifically, the reports focus on 19 target cities in Germany, Romania, Slovakia, the Czech Republic, Moldova, Montenegro, Bosnia and Herzegovina, Slovenia, Austria and Bulgaria.  These small to medium-sized cities were not only selected because of their CSSC potential but also their representative nature since it is important to draw general conclusions on the Danube region as a whole.

In the analyses, the existing use and potential application of a concrete number of technologies was highlighted. For example lithium-ion batteries, pumped hydropower and flywheels were considered for city storage while for sector coupling, the options included power to heating and cooling in 1) buildings, 2) district heating and 3) industry to name a few. For each technology, partners were asked to describe the existing situation in each city and to assess the potential future use.

The analyses not only show differences in the use of existing technologies, they also capture the diversity in city types in the Danube region: these range from the small city of Zlatna in Romania (less than 10,000 inhabitants spread over more than 100 km² with a post-industrial city profile) to mid-sized cities such as Freiburg im Breisgau in Germany (over 100,000 inhabitants over a space of more than 100 km², with a multi-faceted city profile). 

In general, the analyses revealed that big regional differences exist related to the current application of CSSC solutions as well as their actual potential.  This can be explained by the fact that the energy sectors of Danube countries are at different developmental stages. In Western Europe, decision-makers make steady investments in the energy sector because it is viewed as a key economic and political domain. These investments then trigger greater testing and uptake in innovative technologies.  The same cannot be said for Eastern Europe even though there is growing willingness to develop energy strategies in line with EU policies. 

Still, the analyses show an uneven level of ambition at the strategic level. For instance, Austria has set 2040 as a target year by which it should achieve carbon neutrality, Germany regularly amends the Renewable Energy Sources Act and Slovenia has a New Electricity Supply Act that includes sector coupling and energy storage. These countries could be described as very ambitious. Next there is Bulgaria, which is planning a new energy law for CSSC technologies and Romania, which has adopted the National Plan for Energy and Climate Change 2030 endorsing CSSC technologies. The other regions -the Czech Republic, Slovakia, Bosnia and Herzegovina, Montenegro and Moldova - are lagging behind in comparison, but steps are being taken towards adopting laws and regulation that increase RES production. 

It was also found that the energy storage and sector coupling projects in the target cities were of a pilot nature because of their limited economic competitiveness. However, investment costs nowadays are lower than ever, and they are expected to further fall, which will make such projects more economically viable and enhance their uptake on a wider scale. All countries reported that subsidies and financing programmes were the main factors that would influence the future development of the field.

In all regions, there are battery and thermal storage projects, which help balance the energy system and complement the production of renewable energy. The analyses reveal that Germany is applying mechanical and ice storage, which is rather innovative. Across the region, the sector coupling examples are mostly related to power to thermal and power to mobility. There are also several bigger scale projects in industry of the heat to power type. In Germany, there are sector coupling examples involving H2 production and in Austria the use of custom-made software based on an industrial grade automation system bundling medium scale flexibility assets. 

All in all, the analyses show that there is potential for storage technologies in each city targeted by the project partners and a clear need to couple different sectors when it comes to energy consumption. These analyses also pave the way for future project activities: they will form the backbone of the CSSC matrix and will support the definition of model solutions. Moreover, the information gathered will help to elaborate the transnational benchmark study of CSSC potential and development demand in the project regions. Finally, these analyses will directly feed into the regional energy strategies, which will promote CSSC in each country and ensure the necessary visibility at the political level.