THE EFFECT OF TEMPERATURE ON THE OPERATION OF MICRO INVERTERS

摘要

Typically, photovoltaic (PV) system inverters have been installed on buildings in a relatively-protected, preferably shaded location, such as on a North-facing wall. Micro inverters, on the other hand, are normally deployed directly underneath the PV modules, where temperatures may be markedly elevated. Only recently, in the 2008 National Electrical Code, were significant derate factors added for conductors in conduit located in full sun. Between 0.5" and 3.5" above the roof, the temperature "adder" is 22°C. Typically, micro inverters will be located a similar distance off the roof. Given that the high ambient temperature at a site might be 40°C or more, as indicated by ASHRAE "2% average" figures that are presented, applying the NEC adder puts the ambient temperature at the location of the micro inverter above 60°C. This affects the lifetime of vulnerable components because internal device temperatures may be a further 10 or 15 degrees higher.