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

As illustrated this summer, extreme-weather events and wildfires can put power grids under pressure and threaten their ability to produce reliable power.

For decades, consumers have relied on electricity delivered across long distances from large, centralized power plants. 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 Emera Technologies and Sandia, is in its second year of successful operation and data collection. Since the project 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.

Housed on Kirtland Air Force Base, the project integrates solar power, batteries and other local energy sources to power a community center and temporary housing located on the base. Each building has solar panels, and the energy storage is located at a separate node. Kirtland leadership envisions the project as a new model for resilient power.

“Our leadership at Kirtland Air Force Base has established a vision for an updated, resilient infrastructure that can provide mission-critical services for generations to come,” said Joseph Pellish, 377th Mission Support Group deputy commander. “Working with Sandia and Emera as partners has provided us the opportunity to showcase advanced technologies in real settings that meet current energy needs while also promising resilient solutions for our energy system of the future. This has the potential to serve as a model for other DoD installations,” Pellish added.

Sandia has led research for advanced microgrid controls, security and integration for over a decade. The Labs’ location on an Air Force base has offered a unique opportunity to demonstrate Kirtland leadership’s vision with this new technology: a research, development and demonstration partnership that addresses the need for greater resilience. “As threats continue to evolve — related to climate challenges as well as other threats — this demonstration and what we’re learning from it serve as a great example of a new paradigm for resilience through distributed and interconnected microgrids,” said Charles Hanley, Sandia’s grid modernization program manager.

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.

A novel demonstration

The Kirtland demonstration project is novel in several ways. The main power bus is based on direct current rather than traditional alternating current. Additionally, it is a hierarchical microgrid, meaning that control and integration occur at multiple levels and enhance 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 alternating current, making it a hybrid direct-current grid. Sandia is studying this hybrid direct-current 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, investigator Jack Flicker said. The functionality is enabled by power electronic interfaces, an area of research for Sandia.

“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.”

Black start is the process of restoring power after an outage. “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 said. Coupled with the Distributed Energy Technologies Laboratory, 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 U.S. is alternating-current power, recent advances and changes to the composition of the grid have revived interest in direct-current grid installations. According to a 2015 study that examined the potential benefits of direct-current microgrids relative to an alternating-current microgrid, it was noted that direct-current 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 direct-current microgrid and Distributed Energy Technologies Laboratory 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 DOE priority.

Strengthened grid stems from strong partnership

“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.”

Emera Technologies and Sandia formed a Cooperative Research and Development Agreement after Emera Technologies approached Sandia to work together on making clean, community-scale direct-current microgrids mainstream. Sandia researchers had already been studying the control and stability of direct-current microgrids for military applications, aiming 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.