This report aims to update the review of the main demonstration projects of synergies between different energy carriers in the context of Smart Energy Systems at a global level. The final objective is to provide a documented analysis for directing Research and Innovation activities in both the European and the national framework. In addition to ideas for future research, the activity is also aimed at providing perspectives for collaborations with other countries. The reason for focusing on synergies between energy carriers is the growing importance that these technologies are assuming as sources of flexibility in the future smart energy system for full decarbonization by 2050, as also indicated in the European SET Plan.

The work is the continuation of previous activities that, starting from the monitoring of Smart Grid projects, have extended to storage systems up to Power-to-Gas (including Power-to-Hydrogen) and Power-to-Heat synergies.

In this period, the analysis focused on cross-sectoral projects (Sector Coupling), including Power-to-Fuel/Liquid systems, or based on complex synergies, for example with hybrid fuels. The analysis benefited from the participation of RSE in the H2020 Intensys4EU project and the ERA-Net Smart Energy Systems initiative on transnational projects at the local scale. The updated international situation was also analysed, in particular based on reports from IEA.

From a technological point of view, PtX systems are characterised by high TRLs and are therefore ready for commercial exploitation. The challenge is to be able to reach an industrial scale and economically sustainable business cases to demonstrate the real feasibility of sector coupling, in combination with energy storage. However, minimising fixed and variable costs is a complex multi-variable problem, due to the wide range of possible couplings as well as the decarbonisation and related conditions. However, many applications are already close to economic parity, other applications are capable of achieving a sustainable carbon cycle in a circular economy perspective, and other ones broaden the spectrum of energy sources up to the concepts of District Energy and Waste Energy and their evolution into Community Energy, thus increasing synergies at the local level. All these approaches are promising for the development of Smart Energy Systems and we believe it will be interesting and useful to also continue analysing them in the next research period.