Outdoor measurements for an effective PV module temperature characterization

PV system designers need an estimation of the temperature at which a system will be operating in the field, in order to evaluate the losses due to thermal effects. To that purpose the IEC Standards for qualification of modules point out at the NOCT, the Nominal Operating Cell Temperature, as an useful parameter. Anyway NOCT measurements require an accurate elaboration of data, since they are to be referred to quasi stationary conditions, and sometimes the correct interpretation of some clauses of the Standards are not so easy. Because NOCT measurements put severe restrictions on the specific mounting and measurement conditions some laboratories as the ESTER laboratory of the University of Rome Tor Vergata measure instead the NOST, the Nominal Operating Specific Temperature. So a better and a deeper understanding of what can be effectively used as the operating temperature is highly required. The paper intends to present and compare results of NOCT and NOST measurements, obtained respectively by two different laboratories located one, the ENEA laboratory, in the Southern Italy, near Naples, and the other in Rome, in the Central part of Italy.