Most cited paper for each volume is the paper with highest score in number of citations during two calendar years following publication:
"Optimization of photovoltaic energy production through an efficient switching matrix"
coauthored by: Roberto Candela, Marzia Cardinale, Vincenzo Li Vigni, Domenico Musso, Eleonora Riva Sanseverino
"Optimal Renewable Energy Systems for Regions"
coauthored by: Nora Niemetz, Michael Eder, Michael Narodoslawsky