This is a very common assumption made by grid-tie PV homeowners: PV systems will continue providing power during a power outage as long as the sun is shining.
However, commonly used grid-tie inverters safely disconnect from the utility grid if the grid goes down and won’t deliver power even though the sun is up and shining. This is, in part, a safety precaution required to protect utility workers repairing the wires and prevent fires.
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| SMA Inverters with Independent Operation Function |
Independent Operation Function: Power During Outages
In Japan, standard grid-tie inverters disconnect themselves from the grid, but can draw a small amount of power from the PV system even during daytime power outages. Production of emergency energy is enabled by a function of the inverter known as “independent-operation.”
According to a report published by the Japan Electrical Manufacturers' Association (JEMA), during the fiscal year 2013 (April 2013 through March 2014), over 630,000 inverters were sold for the residential PV market in Japan. This number is equivalent to about 3 GW in capacity. Out of 630,000, 99.9 percent of the residential PV inverters sold were equipped with an independent-operation function.
“We started selling PV inverters with the independent-operation function after the Kobe Earthquake,” said Ichiro Ikeda, marketing manager at Kyocera. The Kobe Earthquake knocked out power to over 2.5 million homes and businesses in the southern part of Hyogo Prefecture in January 1995 and it took about 150 hours before all the power lines were fully restored and recovered.
“[The earthquake] was a trigger to develop and market inverters with the independent-operation function,” continued Ikeda....Read More Here