Residential solar and electric vehicle bonding and grounding methods for galvanic compatibility

Residential Photovoltaic (PV) panels are typically roof-top mounted and their accompanying DC/AC inverters are either collocated or installed inside the building. The PV panels and associated DC/AC inverter metal enclosures must be interconnected and grounded to a grounding-electrode according to NEC690.41-64. A small potential difference exists between the enclosure and its interconnection to the ground. The potential differences between a PV system enclosure and its ground wire, as well as, the potential differences between the inverter enclosure and its ground wire are at opposite polarities. Likewise, an Electric Vehicle (EV) controller enclosure and its ground interconnection, and a battery and its ground interconnection are also at opposite polarities. This observation can be generalized to any collocated generator and load DC power system. Since the interconnection potential difference and galvanic voltage are either at opposite or same polarities, the traditional galvanic compatibility rules can´t be applied to the generator and load enclosures, where one side of the DC supply circuit is intentionally connected to earth ground at the source and load enclosures. This is because significantly less corrosive damage occurs under conditions of opposite polarity versus conditions of like (same) polarity. This article discusses galvanic compatibility issues of PV panels and EV groundings while providing a solution for this challenge using electrochemistry and electric circuit theory.