Microgrids: Providing safe harbor in a storm/Part 1

We are back from being on the road and lead off this week with very interesting story, two parts, on microgrids:

Leia Guccione

Consultant

January 10, 2013

"As Hurricane-cum-Superstorm Sandy approached the Eastern Seaboard, millions of Americans living in New York and New Jersey spent the days before the storm stocking up on bread, water, batteries, and other critical supplies; many others sought safety by fleeing the area, seeking refuge with friends and relatives beyond the storm’s path.

The impacts of Sandy are now familiar to many: the electricity grid went down, leaving upwards of 8.5 million people without power. Yet, there were a handful of literal bright spots in the darkness. One man in New Jerseypowered his home with his Toyota Prius hybrid and inverter-based power balancing controls, which ensured that the power from his car was at the right voltage and frequency for his house. At the Brevoort Tower in New York City, the story was much the same: the building kept its lights on—and its heat and hot water—with a natural gas combined heat and power generation system, inverter controls, and most importantly, an automatic transfer switch (aka smart switch) that allowed the building to seamlessly disconnect from and reconnect to the grid. In other words, both the New Jersey homeowner and the Brevoort became microgrids.

But in New Jersey, which ranks second only to California in total installed solar capacity, scores of residential and business customers with rooftop solar PV sat in the dark, even after Sandy’s clouds parted and the sunshine returned. Why? Based on its lower cost and simpler setup, most customers had installed grid-tied solar, and in accordance with current regulatory codes nationwide, such systems are required to have a control feature that automatically disables the inverter—the device that converts power generated by the PV panels into usable electricity for home appliances—in the event that the grid goes down.

The control device is intended to prevent unintentional islanding, a scenario where a device—such as rooftop solar PV panels—continues to feed electricity into the local grid, even when that grid should be without power. Preventing unintentional islanding is important for a number of reasons, foremost among them the safety of utility electricians working to repair faults in the grid and restore power to customers..."