R²D² results are tested and validated in 4 large-scale complementary demonstrators in Greece, Serbia, Spain and Slovenia involving representative and complete value chains, a wide variety of energy sources, networks, systems and assets, and spanning heterogeneous climatic, geographic and socioeconomic conditions which will facilitate replicability, scale-up and eventual market launch. In this context and to effectively realize R²D² demonstration cases, the consortium involves a variety of demonstration partners that will ensure access to critical infrastructures for the project implementation. In the following paragraphs, such infrastructures are presented per demo site.