The basics: As mentioned previously, by far the most common configuration of a PV generation system is an array of PV modules feeding a grid-tied (GT) inverter that converts the DC power to AC power, then fed through the building’s service panel and on out to the electrical grid (see Figure 1). The grid acts like a battery and the renewable energy is placed on the grid for collective consumption, which, in turn, reduces generation other sources. The grid-as-a-battery is a great concept, until it’s no longer there – the grid-tied inverter requires the grid to stay powered per the UL1741 requirement for safety reasons. Without grid power to keep the GT inverter operating, the available PV power just sits on the roof unused. And during an outage, a home or business with PV electricity potentially available is in the dark just like everyone else.
A battery-based (BB) inverter system does not require the electrical grid to stay active, and is the mainstay of off-grid homes, businesses, and industrial installations such as cell phone broadcast towers. Using battery-based off-grid technology, a smarter type of “grid/hybrid” inverter technology is able to use PV, wind, hydro-electric and other renewable DC energy sources to keep the batteries charged and sell the excess to the grid, just like the grid-tied unit using the grid as its battery (see Figure 2).
For those that have not yet