Tess Vigeland: Yesterday, we reported on how the U.S. military is looking to loosen its dependence on oil because so many casualties arise from the need to maintain fuel supplies in combat zones.

Today, in Part 2 of our series on the military and oil, we look at how that effort is playing out with Marines who are using solar power in Afghanistan.

From the Marketplace Sustainability Desk, Scott Tong reports.

Scott Tong: Ask a bunch of Marines if they're technology early adopters, and you get this: laughter. It does seem a bit off to be in Camp Pendleton, southern California, talking solar power with lance corporals -- like Jonathan Jacobson, 3rd battalion 5th regiment, or India Company.

Jonathan Jacobson: I got friends who are in the Army, Navy and everything. And they even look at me like... you're bad-ass.

Here, VC stands for Victor Charlie. But India Company was 'voluntold,' as they say here, to try out clean tech out in the valley. That would be Helmand Valley, Afghanistan.

Jason Morris: We were all fairly skeptical up front. Honestly, I wasn't all that interested in testing equipment.

Company Commander Jason Morris.

Morris: Because it's just another thing that somebody is throwing on us to test and here we are going into a combat zone.

Where your radio is your lifeline. This is actual tape from Afghanistan...

Afghanistan tape: If you can get directly overhead, it'd be much appreciated. We're taking fire.

Typically, radios are powered by bulky military batteries, single use, which means Lance Cpl. Joseph Hooper carries a lot.

Joseph Hooper: That's 15 pounds right there on your back. Along with all the extra gear -- ammo, water, food.

There are always tradeoffs -- not guns or butter, but guns or batteries. On this last deployment, India Company packed reusables charged on the battlefield by mini solar panels. Jacobson says they fold out and they're about...

Jacobson: The size of a clipboard. There's a few wires that go with it. You can put it in like a small backpack and it doesn't weigh at all.

Did the solar gizmos pass the battlefield test?

Jacobson: It's something none of us were used to, but I mean it actually started working really well.

Hooper: It was nice to have, we always used 'em and it never went down on us.

Taylor Wright: We just set the solar charger out, we just set the batteries in there every time we needed to and just rotated batteries out.

Hooper: Even at night. That thing works at night. It was unbelievable. We plugged it in, we're like maybe it'll work. So we started putting batteries on it, that moon came up and it charged it.

India Company guinea pigged three other devices -- including solar generators and tarp covers. In fact, it went three whole weeks without needing new batteries, creating more space to carry food, water, bullets. And it earned itself poster-child status in military PR machine. Afterall, energy efficiency saves on generators for electricity, which means fewer fuel convoys in harm's way. And it saves a lot of money -- fuel can cost $45 a gallon in Afghanistan, when you add in transportation and protection costs.

Now, here's the however.

Bob Charette: Are we gonna take a major dent out of the 200,000 gallons a day in Afghanistan the Marine Corps burns? Probably small.

Col. Bob Charette runs the Expeditionary Energy Office for the Marine Corps. Right now, he says he's in the start-up phase of innovation.

Charette: It has been really like an entrepreneur shop. An early Starbucks, if you will. How do you make it enduring? You know, you have this good initial momentum, now how do you continue on the initial success?

There are doubters. For his part, Charette keeps testing technologies. He's already sending portable solar chargers to every battalion in Helmand Province. And like all innovation, it comes with surprises. These things, they don't just charge batteries.

India company commander Morris.

Morris: It's amazing how quickly you saw iPods starting to be recharged on these things.

iPods, DVD players, laptops for movies.

Lance Cpl. Jacobson.

Jacobson: When you just get to listen to, like, some favorite song from back home that's already old by now, it feels good to be able to just be able to sit back and relax and just take your mind away, like, from that hellhole.

In fact, music played a role on the battlefield. Marines Taylor Wright and Terry Rittenhouse say their commanders often played linkin Park before each risky patrol.

Wright: Throw on some rock music, everybody'd start getting their gear ready, start getting all pumped up and hyped and focused on what we had to go do.

Terry Rittenhouse: Those were some of the last moments we got to spend with some of our guys. They become casualties on the patrol and didn't make it.

This battalion lost 25 men in seven months, more than any other in the 10-year Afghan War. So when it comes to clean energy, the whole point is making them better fighters and lightening the battery load.

As for the environment, Lance Cpl. Joseph Hooper.

Hooper: Come on, seriously it's not an environmental thing. It's all about trying to help us accomplish the mission. We're not the reason why the environment sucks. It's cities like L.A.

In Camp Pendleton, Southern California, I'm Scott Tong for Marketplace.

Vigeland: Tomorrow Scott looks at what the Pentagon's embrace of alternative energy means for businesses. We want to hear your thoughts on this series -- check out our new widget, The Big Question.