“As soon as microgrids are standardized and easy to integrate into the main grid,” Xu said, “we’ll start seeing them in areas with a high penetration of renewables and high energy prices.”
When Department of Energy and Oak Ridge National Laboratory researcher Yan Xu talks about “islanding,” or isolating, from the grid, she’s discussing a fundamental benefit of microgrids—small systems powered by renewables and energy storage devices. The benefit is that microgrids can disconnect from larger utility grids and continue to provide power locally.
“If the microgrid is always connected to the main grid, what’s the point?” Xu said. “If something goes wrong with the main grid, like a dramatic drop in voltage, for example, you may want to disconnect.”
Microgrids are designed to not only continue power to local units such as neighborhoods, hospitals or industrial parks but also improve energy efficiency and reduce cost when connected to the main grid. Researchers predict an energy future more like a marketplace in which utility customers with access to solar panels, battery packs, plug-in vehicles and other sources of distributed energy can compare energy prices, switch on the best deals and even sell back unused power to utility companies.
However, before interested consumers can plug into their own energy islands, researchers at facilities such as ORNL’s Distributed Energy Control and Communication (DECC) lab need to develop tools for controlling a reliable, safe and efficient microgrid.
To simulate real scenarios where energy would be used on a microgrid, DECC houses a functional microgrid with a total generation capacity of approximately 250 kilowatts (kW) that seamlessly switches on and off the main grid.
This grid includes an energy storage system that generates 25kW of power and uses 50kW•hours of energy built from second-use electric vehicle batteries, a 50kW- and a 13.5 kW-solar system and two smart inverters that serve as the grid interfaces for the distributed energy emulators. Programmable load banks that mimic equipment consuming energy on the grid can provide sudden large load changes and second-by-second energy profiles.