SAN DIEGO — Col. Thomas Bedell had been commanding Marine Corps Air Station, Miramar in San Diego for just one day, in July 2021, when he got a message from the base energy management director. The city power system was straining under a heatwave, and it was time to start up the microgrid.

"So I said, yes! Start up the microgrid! And then I texted, what is the microgrid?" Bedell recalled with a laugh.

It fell to Mick Wasco, who has been energy management director at Miramar since 2010, to explain to Bedell that Miramar was set up to run the base without using power from the city of San Diego in the case of a local or national power grid failure.

"By 2012, we started producing landfill gas electricity specifically for MCS Miramar," Wasco said, "Keep in mind, this is the size of a small city."

Using energy sources including solar and methane gas from the rotting garbage in a massive San Diego city landfill located inside the base, Miramar can go 21 days in a self-contained state that's called "island mode." Or as Col. Bedell says, aircraft carrier mode.

"I half-jokingly refer to Miramar as the USS Miramar. If you think about the installation as an aircraft carrier, suddenly the need to have redundant power to have energy-resilience, water, food-resilience makes complete sense," he said.

It makes enough sense that it's official Department of Defense policy: The Pentagon's stated goal is that all bases be "power resilient." The best path to resilience in case of a disaster is often a local renewable source, and that pairs well with another Pentagon goal — for bases to be carbon neutral by 2050. That will keep key defense capabilities intact in the case of an attack on the U.S. power grid, or more likely an extreme weather event, as climate change worsens droughts, heatwaves, wildfires and storms.

Hurricane Michael devastated Tyndall Air Force Base in Florida in 2018. The rebuild is incorporating a microgrid built for the base by the local utility.

"Florida Power & Light provides us the ability to 'island' that critical headquarters building and its functions from the rest of the installation, should there be a power loss," says Mike Dwyer, deputy chief of the Air Force Natural Disaster Recovery Division.

Getting industry partners involved made funding and building the microgrid faster than the Pentagon's normally glacial procurement process. In the next big storm, Dwyer said, the base will be able to keep up critical defense operations.

"It's designed to operate the first Air Force or Air Force's North Headquarters building completely independently for up to four and a half hours," he said.

Dwyer said Tyndall is still at least 3 to 5 years away from having a grid that could run the whole base. A Pentagon spokesperson said 90% of key bases worldwide have at least a plan on becoming energy independent, and the Defense Department current gets 15.9% of its energy from renewable sources, and expects to be at 25% renewable by 2025.

The DoD is among the world's largest emitters of carbon dioxide, so it's exciting to see them take an interest in renewables, said Lisa Cohn with the site Microgrid Knowledge.

"The military's interest in microgrids is really, really important — because the military does tend to deploy new technologies before anyone else," she said.

The progress is mostly driven by the fact that it makes tactical sense. It can save soldiers' lives at war. Producing energy on base means trucks don't have to haul in fuel for generators to power bases in war zones, a vulnerability that proved deadly in Afghanistan and Iraq.

Brandon Newell was a Marine artilleryman in 2003. He remembers rushing north from Kuwait into Iraq, only to run out of fuel.

"It was about speed and agility and moving fast to attack Baghdad. We outran our logistics and it was ... a pause for four days sitting on side of the road so that our logistics could catch up," he said.

That experience marked him. Newell first spoke to NPR in 2011 at a remote combat outpost in Helmand, Afghanistan where he was setting up small-scale renewable power for the Marine Corps.

Newell says the troops don't really care if it's a carbon-neutral solution — as long as it helps them fight and survive. In Afghanistan, resupply convoys hit by roadside bombs were making up a huge share of U.S. military casualties.

"We have these distributed forces that are constantly requiring bullets, band aids, food and fuel," he said, "These huge convoys make you even more of a target."

Newell retired as colonel, and started a company promoting the mobile combat energy solutions he says will be even more important in the next war. He spent his last years in the Marine Corps helping stand-up the microgrid at Miramar Air Base.

Miramar is also demonstrating how microgrids in the military can make the civilian power-grid more resilient. It can provide a working headquarters during storms or heatwaves for the state or the Federal Emergency Management Agency (FEMA), according to Col. Bedell.

"Our ability to be able to continue to operate and provide that base from which we could help the local community or the state is really important," he said.

It makes sense for every state to have disaster-resilient grids on military bases, he said, and Miramar has already helped out. During a heatwave in 2022, the state energy grid was under the heaviest load in California's history. This time, Bedell got a surprise text from San Diego Gas & Electric asking if Miramar could go off city power to reduce the load and avoid outages.

"At the request of SDG&E, we turned on the micro grid to support our own utility requirements during peak hours for 10 days in a row. And that that prevented about 3,000 homes from having to go into potential blackout," said Bedell.

The Navy even "unplugged" its docked ships from the city's power grid to help.

While the military tends to focus on the use of microgrids against tactical threats, Bedell says climate change itself is also one of those threats.

"We need to be part of this solution. And if we are negatively impacting the climate change that is causing societal disruption, that's not working ourselves out of a job. That's creating the problem that we're wanting to solve," he said.