Off-grid and Hybrid Battery Backup Power for Solar PV Arrays

home solar system battery backup

System / August 6, 2016

My neighbors took a newfound interest in my solar array after Hurricane Sandy. Most of our town in New Jersey lost power for two weeks, and everyone who knew about my panels was asking: Did they keep my lights on? Alas, no. When the grid goes down, our array goes down. The inverter mounted on my basement wall, which converts DC photovoltaic power to AC household current, trips during a blackout. The sun could be blazing and the array could develop a potential of hundreds of volts, but it’s potential in every sense of that word. Without the inverter to complete the circuit, not a single electron flows into my house.

Years ago, stewing over previous blackouts—they call this the Garden State, not the Reliable Infrastructure State—I investigated backup generators, but the expense put me off. I decided just to set up a transfer switch and battery backup for my steam boiler to ensure we don't freeze. But the extended post-Sandy outage and likelihood of a recurrence got me thinking about backups again. Last month, I chatted with Harvey Wilkinson and Phil Undercuffler of Outback Power, based just north of Seattle. Their bidirectional inverters can convert DC to AC (so the array can power the house or feed into the grid) or AC to DC (so the grid can charge a bank of batteries). “If there's a power outage, the system can drop the grid and continue powering the house, ” Undercuffler said.