[1] Tech Univ Crete, Elect & Comp Engn Dept, GR-73100 Iraklion, Greece
[2] Tech Univ Crete, Dept Environm Engn, Renewable & Sustainable Energy Lab, GR-73100 Iraklion, Greece
[3] Natl & Kapodistrian Univ Athens, Dept Phys, Sect Appl Phys, Athens 15784, Greece