Refueling a destroyer or any other large piece of military hardware is incredibly dangerous because it leaves troops very vulnerable to attack, especially if it requires a huge convoy. U.S. troops have lost their lives trying refuel vessels that are ultra-dependent on oil. The Department of Defense knows this, and as more and more of its gear of all sizes becomes dependent on electricity, it is working with contractors to convert more of its fuel operations to renewables.

today has a briefing on the trends toward making U.S. military equipment green. Even though the DoD brass supports green energy initiatives, President Trump has pushback against any efforts he feel would undermine petroleum producers. Military leaders have long argued that their push for green power has nothing to do with climate change or anything dealing with the environment.

They also don’t seem to care about oil politics, either. The bottom line is keeping U.S. soldiers safe, as Col. Brian Magnuson, the director of the expeditionary energy office in the Marine Corps told .

“Our tag line is expeditionary energy. We don’t do green,” he said. “There’s a perception that the initiatives have to do with something other than extending our combat effectiveness.”

Another example is the Ground Renewable Expeditionary Energy System (), a portable 300W, photovoltaic/battery system that can be powered by the sun continuously. Introduced in 2009, GREENS was designed to be deployed in the most remote of locations to power communication, targeting and computing devices. It opens up from a wide metal case and take minutes to set up, making fueling times short and allowing troops to return fire against enemy combatants during an insurgency with enough response time.

Comparatively, you can’t hide an oil tanker or the convoys escorting them. Given that the U.S. military consumes more than 100 million barrels of oil per year—the in the world—troops are constantly under the risk of attack. A 2009 on refueling convoys found that one in every 24 resupply convoys in Afghanistan resulted in an American death. In 2000, The USS Cole from suicide bombers in a small boat full of explosives while in port in Aden, Yemen during a refueling mission. The attack left 17 U.S. sailors dead and 39 others injured.

Refueling in combat situations is very dangerous because it puts convoys in vulnerable positions. With solar-powered units, soldiers can operate in near secrecy. Consequently, the Navy began installing Hybrid Electric Drive (HED) systems in its destroyer fleets. As reported back in 2015, the Navy said that using the system 50 percent of the time will save thousands of barrels of fuel during a deployment and cut near three days of refueling.

As for who will be raking in the cash from these green projects, Reuters reports that the DoD has awarded hundreds of millions of dollars in contracts to solar power companies to reduce fuel consumption. Many of the projects are at U.S. bases so they can maintain independent power sources in the event of a natural disaster or a cyber attack that hits a power grid. L3 Technologies Inc. won a $119 million contract in 2013 to outfit Arleigh Burke destroyers with gas-electric hybrid engines. Under the Trump Administration SunPower scored a $96 million contract to power to Vandenberg Air Force base in California until 2043.

Reuters notes that 2011 and 2015, the military tripled its renewable energy projects. Military officials hope green power will cut into its annual oil bills of nearly $14 billion.

The U.S. military isn’t going to see a significant drop in its oil use anytime soon, but with the DoD investing more money in green projects, the armed forces do hope they’ll suffer fewer deaths trying to fuel its missions with oil.