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Deployable renewable energy systems power critical equipment on the battlefield: harvested energy and advanced battery technologies combine to cut fuel consumption and improve operational energy in the military.

The United States Department of Defense (DoD) is the largest consumer of energy in the United States. Much of that energy is consumed in harsh environments by power tanks, armored vehicles, fighter jets, generators, small hospitals, command outposts, and operations centers out in the field. These applications are critical, but costly. In 2009, The Hill reported it cost as much as $400 to deliver a single gallon of fuel to a remote forward operating base (FOB) during operations in Afghanistan where, according to Operation Free--a coalition of veterans and energy experts--casualties struck one in 24 fuel convoys.

In recent years, the government has identified alternative energy as a way to mitigate the expenses and dangers of relying solely on fossil fuels. In 2012, the White House introduced "25 by 25", a policy objective that aims to reduce the amount of energy produced across the military by 25 percent by 2025. Microgrids--small-scale distributed electricity systems--are on the front lines of these efforts, using reciprocating engine generator sets, and harvested energy sources like solar, wind, and thermoelectricity to power critical equipment and systems in remote and harsh locations. The main benefit of the microgrid is its independence from main electrical grids found on large stationary bases and urban centers. Utilizing local sources for energy--particularly harvested energy--means fewer greenhouse gas emissions, and less money and resources spent on fossil fuels. As an added bonus, it reduces the burdens of transporting and protecting the supply.

The benefits of renewable energy in remote, harsh locations are clear, but powering critical equipment not tied to a main electric grid and managing that power are two substantial challenges. Deployable renewable energy systems are addressing those challenges by offering more efficient operation on the battlefield than standard diesel generators, evolving features to meet the military's increasingly demanding requirements, and creating rugged, modular designs for easy deployment.

An average generator on the battlefield runs at approximately 10 to 15 percent capacity, usually 24 hours a day, 365 days a year. This can mean increased maintenance on the equipment from wetstacking, which happens when a diesel/JP-8 generator is run at light load for long periods of time. Containerized deployable energy systems, which can combine solar, wind, and energy storage, can run both at maximum continuous output or at low capacity while maintaining high efficiency, so smart energy storage and integration are extremely valuable on the microgrid.

Deployable renewable energy systems have standard footprints, and come in sizes based on a 20-foot, ISO shipping container. For example, systems can be a Tricon, which is one-third the size of a container, or a Quadcon, one-quarter the size of a container. These sizes allow the containers to fit into the military's logistics train for transport over land, sea, or air. For extreme mobility, portable, stackable, remote battery systems can power microgrid devices in the field, measuring as small as 22" x 16" x 8" and weighing less than 50 pounds. The systems' construction includes shock resistance to prevent damage during transport and handling, and they adhere to mil spec 810 G's environmental requirements for new military equipment.

Supply and demand

Power outputs for deployable renewable energy systems can range from 2 kW or 3 kW up to 60 kW, and must meet the military's 3 phase standards for power generated equipment for their size. MILSPRAY's Scorpion Energy Hunter, for instance, provides up to 18 kW (120 V, 208 VAC, 60 Hz) 3 phase. Since each piece of equipment presents different power challenges, and because renewable energy is unregulated, deployable renewable energy systems are designed to ensure power quality along with availability. The Scorpion system can handle surges to almost 40 kW to maintain its 18 kW of continuous output power, and it reduces fuel consumption by up to 80 percent. Harvested energy, of course, is not always available at the right time, whether wind is not blowing or the sun is not shining, portable renewable energy systems have to ensure "balance of systems." Supply and demand in power systems must be matched.

"You can't just dump a bunch of solar at any given time at any ratio into a grid," says Doug Moorehead, President of Earl Energy, whose EARLCON and FlexGen renewable power systems have been used in Afghanistan. Reportedly, a 60 kW FlexGen system saved 50 to 70 percent in fuel in microgrid environments when used in generators. "If I have excess solar available above and beyond what the loads are requiring, I'll send that to charge the batteries. Putting regulation and control around that unregulated power source is one of the big things we do."

Cycling and density needs

Since deployable renewable energy systems are expected to perform in rugged, high reliability applications, the same is required of the batteries. "We look at maintenance-free batteries that can handle a lot of temperature extremes--typically high temperatures, not so much low, and the ability to handle deep cycling," says Joseph Gerschutz, Engineering Manager of MILSPRAY Military Technologies. Lead-acid chemistries are common among deployable renewable energy systems where lives depend on reliable power, and companies design them into deployable energy systems based on a proven track record.

Lithium-ion is also common in military applications, because it offers a very broad range of chemistries with different benefits. Lithium iron phosphate is suitable for vehicle (mounted) and smaller deployable renewable energy systems (dismounted). "You're looking to pack as much energy density into the battery as possible," says Jeff Helm, Defense Sales Manager at Saft. "That gets you the highest kilowatt-hour per volume rating." Saft's Lithium-ion based ultra-portable battery storage devices are finding uses in Raytheon's Improved Target Acquisition Systems (ITAS)--anti-tank weapons systems used by the light forces. The high kilowatt-hour per volume batteries offer long run times versus legacy battery solutions, and the lighter weight, smaller size, and enhanced capabilities means it can replace the vehicle mounted charger and the separate AC charging source.

Lithium titanate (LTO) is attractive for its cycling characteristics in high power discharge situations and equipment that can have as much as 7,000 to 8,000 full depth of discharge cycles in them. "We can get a lot of power out of it, and a lot of power into it on charging to load up that generator at its optimum point with effectively a smaller battery than we would be able to do with some of the other Lithium-ion technologies," says Moorehead. "You sacrifice some amount of energy density for a very high rate, high power dense battery system."

Gensets provide a reliable back-up plan

Deployable renewable energy systems are also designed to work alongside gensets--a combination of generator and an engine--that provides backup power to the end equipment when a renewable energy source is unavailable or the stored energy of the system cannot keep up with energy demands. "Our system will automatically start a connected genset, which will then pick up the load for the duration that it's on, recharge the batteries concurrently and then automatically shut it off," says Gerschutz. "This is done as needed."

Saft provides an ultra-portable battery storage device--called the advanced deployable renewable energy system (ADRES)--that can be used along with generators and solar power systems to power small microgrids. The company designed an AC/DC converter into it so it can take an AC charge source and also a DC charge source from 10 V to 36 V. That means it can also be charged from a genset or a military vehicle.

While the fuel savings and carbon footprint reductions deployable renewable energy systems enable are important, they are secondary to the military's objective of mission completion. Today's renewable energy use in the field would not be possible without deployable renewable energy systems with onboard energy management functionality working alongside gensets to make sure there is power to get the job done. Deployable renewable energy systems assist in mission completion with modular and flexible solutions for easy configuration in the field and offer intuitive user interfaces such as touchscreens showing only the information the soldier needs for the situation. They also offer easy troubleshooting and programmability, and multiple inputs and outputs.

With deployable renewable energy systems providing energy surety in the field, the military can see the benefits of energy savings and safer power delivery for personnel. "When you look at all the generators running in Afghanistan today, and you're able to reduce 25 percent of those generators, then the transportation and fuel cost savings could be huge," says Helm, "It has been well documented that reducing the number of transportation convoys will also greatly reduce the number of casualties."

As military operations shift from the harsh environment of Afghanistan and more special forces deploy to Africa, the logistics of supplying finite resources such as fuel and water will continue to be a challenge.

By Chris Warner, Executive Editor
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Title Annotation:Mil/Aero
Author:Warner, Chris
Publication:ECN-Electronic Component News
Geographic Code:9AFGH
Date:Jul 1, 2014
Words:1467
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