Sandia National Laboratories and Emera Technologies will continue their work on the Kirtland AFB DC/AC hybrid microgrid project. By Samri/Shutterstock.com

Sandia National Laboratories and Emera Technologies are taking the next step to enable bidirectional flow between multiple interconnected microgrids — a grid of grids — under a project funded by the Department of Energy’s (DOE) Technology Commercialization Fund.

The effort stems from their partnership on a DC/AC hybrid microgrid demonstration project at Kirtland Air Force Base (KAFB) in New Mexico, which is designed to illustrate how direct current (DC) microgrids can be integrated into the current AC electrical system to provide resilient power to homes and military installations.

In the fall of 2019, Emera Technologies, Sandia National Laboratories and the DOE’s Office of Electricity brought the first phase of a single-bus, 10-node, 250-kW DC/AC hybrid microgrid online at the air force base.

The microgrid integrates solar panels, battery storage, natural gas and electric vehicle chargers. Since it was commissioned, it has successfully powered a demonstration site on the base that includes six housing units, a laundromat and a community center.

The microgrid’s hierarchical design sets it apart from traditional microgrids. Because control and integration happen at multiple levels, parts of the installation can run independently, in combination with other parts or in conjunction with the traditional power grid. The main power bus is based on DC power, but the microgrid can also supply alternating current (AC) power when connected to the central grid.

According to Joseph Pellish, 377th Mission Support Group deputy commander at KAFB, the microgrid demonstration project has the potential to serve as a model for other Department of Defense installations. In 2021, he said, “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.”

The DC microgrid technology offers “the promise to provide higher resiliency, facilitate integration of renewable resources and become a viable enhancement to AC systems for supplying electricity to new industrial or residential areas,” according to Sandia.

In this new phase of the demonstration project, Sandia and Emera will test the next generation of power distribution systems in an effort to show that linked microgrids, also called a grid of grids, are safe and highly efficient.

One of the components to be tested is Sandia’s HyGaiN DC power conversion circuit, which will be used to connect a 600-V solar array to a grid-to-grid tie line.

They will also test HyGaiN’s ability to facilitate bidirectional power flow as a grid-to-grid converter.

Separately, Emera Technologies is working on another innovative linked microgrid project that serves 37 homes in a neighborhood near Tampa, Florida. Using what Emera calls BlockEnergy, each home is set up as its own nanogrid with solar, batteries, a control system and an inverter. A central energy park powered by solar and natural gas is located near the neighborhood’s entrance to provide backup power to the homes, if necessary. The nanogrids and energy park are connected by a DC bus cable network system so that energy resources can be shared.

News of Sandia and Emera’s continued partnership on KAFB’s microgrid demonstration project comes on the heels of a slew of recent military microgrid announcements. In September, Joint Base McGuire-Dix-Lakehurst said it was amping up resilience efforts by incorporating a microgrid as part of a multifaceted, multiyear energy upgrade. In August, the White Sands Missile Range in New Mexico announced the installation of a microgrid to support its critical water infrastructure and the microgrid at Marine Corps Air Station Miramar helped California utility San Diego Gas & Electric avoid a power emergency.

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