Providing resilient power

A partnership between Sandia, Emera Technologies, and Kirtland Air Force Base demonstrates DC microgrid technology for resilient power to homes and installations

This summer’s extreme weather events and wildfires are once again putting power grids under pressure. For decades, consumers have relied on electricity delivered across long distances from large, centralized power plants. That model has worked well — until it doesn’t because of wildfires, hurricanes, or record-high demand due to weather extremes.

But what if a neighborhood, military installation, or hospital complex could safely disconnect and run on locally produced power when power from the central grid was not available?

A microgrid demonstration project, launched by a CRADA between Emera Technologies and Sandia National Laboratories, is in its second year of successful operation and data collection. Since the ribbon cutting ceremony in 2019, researchers have been evaluating the microgrid’s stability and how to maximize its reliability while minimizing costs, among other measures.

As the name implies, microgrids are localized power grids. They have control capability, meaning they can connect or disconnect from the traditional grid and even operate autonomously. Microgrids can supply primary power or backup power in case of emergencies, along with other advantages thanks to their flexibility.

The KAFB demonstration project is novel in several ways. The main power bus is based on direct current (DC) rather than traditional alternating current (AC). Additionally, it is a hierarchical microgrid, meaning that control and integration occurs at multiple levels and enhances the ability to provide resilient power under a variety of circumstances. This hierarchical nature means parts of the installation can run independently, in combination with each other, or in connection with the traditional power grid. This project also ties into the central grid, which uses AC, making it a hybrid DC grid. Sandia is studying this hybrid DC structure to better understand the advantages, optimize the design, and seek out cost-savings. This makes the system more resilient than even a traditional microgrid, principal investigator Jack Flicker noted. The functionality is enabled by power electronic interfaces, an area of research for Sandia.

“We’re now looking at operations that typical microgrids cannot do, such as — in resilience events — being able to arbitrarily route power to critical nodes that are dynamic in both space and time as the situation evolves.”

Jack Flicker, principal investigator

“Since we started operations in December 2019, we’ve been concentrating on evaluating microgrid operations in three areas,” said Jack. “The first area concerned operations that all microgrids can do, such as provide power to all nodes and island when needed. We then moved on to operations that are more difficult for traditional microgrids to do, such as black start and maintaining full operations through fault events,” he said. Black start is the process of restoring power after an outage. Jack added, “we’re now looking at operations that typical microgrids cannot do, such as — in resilience events — being able to arbitrarily route power to critical nodes that are dynamic in both space and time as the situation evolves.” Coupled to the Distributed Energy Technologies Laboratory (DETL), the installation allows researchers to simulate varied scenarios and observe how well the microgrid performs.

While much of the power transported and delivered across the United States is AC power, recent advances and changes to the composition of the grid have revived interest in DC grid installations. According to a 2015 study that examined the potential benefits of DC microgrids relative to an AC microgrid, it was noted that DC microgrids might have cost, reliability, and efficiency advantages for certain applications. Seven national laboratories, including Sandia, participated in the study. The study identified potential areas of imminent and future study to verify and better understand any potential advantages. 

The connection between the DC microgrid and DETL provides researchers with information about the microgrid’s performance. Meanwhile, the demonstration project contributes renewable energy to the base facilities’ footprint. Increased use of renewable energy, which emits no greenhouse gas emissions, will be a key part of achieving the nation’s ambitious goals to tackle climate change, a Department of Energy priority.

“The project is, for me, the embodiment of all the things that microgrids have promised to deliver, especially the modularity and resilience.”

Gerro Prinsloo, project manager with Emera Technologies

“The project is, for me, the embodiment of all the things that microgrids have promised to deliver, especially the modularity and resilience,” said Gerro Prinsloo, project manager with Emera Technologies for the demonstration. “We have been able to integrate new technologies and test rapidly, doing so with little additional engineering effort post-commissioning. The rate at which it was done would have been difficult to achieve had it not been for the flexible nature of this microgrid architecture and the excellent resources Sandia brought to the table.”

The CRADA between Emera Technologies and Sandia was formed after Emera Technologies approached Sandia to work together on making clean, community-scale DC microgrids mainstream. Sandia researchers had already been studying control and stability of DC microgrids for military applications, striving to optimize design and performance at a lower cost.

Adding local control to energy distribution systems through microgrids can mean added resilience to the nation’s existing energy infrastructure.