[1] Univ Sannio Benevento, Dept Engn, Piazza Roma 21, Via Traiano, 3, BN, I-82100 Benevento, Italy
[2] ENEA, Dept Energy Technol & Renewable Energy Sources, I-80055 Portici, NA, Italy
[3] Univ Naples Federico II, Dept Elect Engn & Informat Technol, Cso Umberto I, 40, I-80138 Naples, NA, Italy