Maximizing the unit’s energy efficiency requires repeatedly deep cycling the batteries—discharging them to their full capacity before recharging them. Conventional lead-acid and nickel-cadmium batteries quickly lose storage capacity if repeatedly deep cycled. The advanced lithium-ion technology in Earl Energy’s batteries allows them to last close to 4,000 cycles, or 18 to 24 months, according to the company. Moorehead developed lithium-ion battery technology for battery maker A123 Systems before joining Earl Energy.
The hybrid power system also employs energy-management software that uses complex algorithms to maximize the generator’s efficiency. Steven Minnihan, an analyst at Lux Research says this energy management, together with the power electronics that allow the system to quickly switch between generator and battery power, is very important. “Companies will speak quite freely about the chemistry of the batteries they are using, but they are very tight-lipped about the energy-management systems and power electronics,” he says. “It is becoming an increasingly important piece of intellectual property.”
The technology is competitive in the battlefield because transporting diesel fuel to the front lines in heavily armed convoys is very expensive. Moorehead, a former Navy SEAL, says delivery costs for fuel transported to the front lines in Afghanistan typically range between $20 and $40 per gallon.
Reducing fuel use on the front lines saves more than money. Ray Mabus, Secretary of the Navy, spoke of the “fully burdened” cost of fuel at a recent DOE Advanced Research Projects Agency for Energy (ARPA-E) conference in Washington, D.C. “For every 24 [fuel] convoys, we lose a soldier or a Marine [who] is killed or wounded guarding that convoy,” Mabus said. “That’s a high price to pay for fuel.”
Earl Energy hopes to begin scaling up production of its high-efficiency generator systems. According to the company, the number of fuel convoys could be cut in half if its devices are widely deployed.