Fewer batteries, more bullets. WSJ:

A company of U.S. Marines recently conducted a remarkable three-week patrol through southern Afghanistan, replacing hundreds of pounds of spare batteries in their packs with roll-up solar panels the size of placemats to power their battle gear.
By allowing the troops to recharge their radios, GPS devices and other equipment, the green technology freed the Marines of India Company from constant resupply by road and air. And by carrying fewer batteries, they carried more bullets.
The Marine Corps is addressing a paradox confronting military planners: Modern U.S. forces are more lethal than any in history, but they also gobble up more energy. That lengthens vulnerable supply lines and overloads soldiers and Marines in the field.
India Company, a component of 3rd Battalion, 5th Marine Regiment, is the first combat unit to be equipped with a new package of portable, front-line solar gear developed by Navy scientists. It’s a boots-on-the-ground example of the Marine Corps’ new blueprint for energy use. The Corps wants to cut per-Marine fuel use in half by 2025.
Navy Secretary Ray Mabus has pushed biofuels for fighter jets, hybrid-electric drives for Navy ships, and renewable-energy systems for Marines on the move. The Marines are part of the Department of the Navy. Mr. Mabus aims for half of the Navy’s energy to come from non-fossil fuel sources by 2020.
Batteries make up as much as 20% of the weight of the 100 pounds of gear a Marine infantryman typically carries. A Marine uses four times as much fuel as his counterpart did in the early 1990s—due to, among other things, laptops and other electronic gear that use electricity pumped out by portable generators.
Some 30% of all fuel trucked into Afghanistan—at great risk—goes to power those generators, at a time when roadside bombs remain the most dangerous weapon faced by allied troops.
While the U.S. military has been seriously studying renewable energy since at least 2001, the impetus for change was the high casualty rate on fuel convoys in Iraq and Afghanistan. Mr. Mabus told Congress last year that one U.S. servicemember is wounded or killed for every 24 fuel convoys.

The rest is here.