Microgrids May Hold the Key to Grid Resilience

Since Moloka’i’s goal was zero emissions, researchers predicted what would happen if existing diesel generators were swapped with marine energy. When added to the mix of wind and solar, marine energy not only ramps up resiliency, but it also slashes reliance on fuel.

To meet the zero emissions goal, the research team found that using marine energy can cut the need to build solar and wind up to 50% compared to not including marine energy in the portfolio, plus less battery storage is needed. That’s good news for communities since batteries are expensive. Also, less emphasis on solar means a reduced land-use footprint. And space is a big deal on a small island.  

Resilient Microgrids to Rebound Faster, Longer
When Hurricane Sandy slammed into the Eastern Seaboard in 2012, the damage was so significant, parts of New York and New Jersey were without power for months after the storm. Yet a microgrid at Princeton University in New Jersey kept the lights on for emergency workers and at key facilities.

There is growing interest in designing microgrids to power things like hospitals, shelters, or police stations during emergencies. Yet microgrid design tends to focus on minimizing cost rather than enhancing resiliency, which means rebounding quickly when the power goes off. But the cheapest solution isn’t always the best.

“It’s hard to put a price tag on resiliency,” said Sarah Newman, a PNNL data scientist who led a study evaluating microgrid design for U.S. Army posts, which need to be self-sufficient for longer durations. For example, a hospital will place more value on reliable, resilient energy during disasters, as opposed to a homeowner who might be able to go a few hours without power.

Solar microgrids are typically powered by solar paired with batteries, with fuel-powered generators for reliable backup. Generators are critical in bridging gaps when batteries aren’t fully charged, such as cloudy days, or when energy demand is high and excess can’t be saved.

Newman and her team predicted everything from optimal generator sizes and how much fuel they’d need to store to energy use in different types of buildings, and even solar patterns and weather in different states.

They found that in some cases, the generators aren’t big enough for the microgrid to be resilient during a variety of outage situations. Plus, the generators need up to 30% more fuel than previously predicted if extreme weather isn’t accounted for during design. If that extra fuel isn’t planned for, then the microgrid won’t be able to meet the energy demand.

“Stopping after a week and a half may not be an option when a microgrid is the backup for critical facilities,” said Newman. “This underscores how important designing microgrids around resiliency actually is.”

Microgrid Modeling
The modeling work being done by PNNL can help decision makers weigh tradeoffs and ultimately design microgrids that are more likely to keep the lights on during an emergency or power areas without access to a main grid. With climate change-related extreme weather expected to climb, designing resilient microgrids will likely continue to be pertinent in the future. 

The modeling work was conducted using PNNL’s Microgrid Component Optimizations for Resilience platform and was funded by the Water Power Technologies Office, the U.S. Army Reserve, and the Army Office of Energy Initiatives.