[Technology Report]
In Today's Military, More Than Just Fatigues Are Green
The world's mightiest fighting force also is a leading sponsor of environmentally friendly power systems.
S.A. Sherif, a University of Florida mechanical engineering professor and an expert in refrigeration, then tied the system to absorption units, which further cooled the gases. Users can either tap all the cooling power to obtain peak efficiency for the turbine or divert some energy for refrigeration or air conditioning.
Lear says his experiments and computer models suggest that with all the cooling directed to the turbine, it will be 5% to 8% more efficient than traditional turbines. With some cooling siphoned for other purposes, the system can still be 3% to 5% more efficient than conventional turbines. Additionally, compared with traditional gas turbines, the system maintains its efficiency whether operated at peak or partial power.
A few percentage points might not seem like very much. But it makes a spectacular difference when fuel is scarce or expensive, particularly if refrigeration and water are added bonuses. "Power companies would kill for a 1% gain," Lear says.
The system, which makes water by condensing the turbine's combustion gases, can produce about one gallon of water for every gallon of fuel burned. The water would need to be treated to be potable. Untreated, however, it could still be used for cleaning or other purposes. Because the system reuses gases so efficiently, it also has a very low pollution output.
Lear says further research is needed to make the plant more compact and to enhance its performance. He notes that larger, more powerful versions could be used in fixed locations as part of the standard power grid. Power utilities, for instance, could build the plant close to a grocery store warehouse that requires both electricity and cooling.
Electric Navy Like most of the world, the U.S. Navy is very interested in developing electric vehicles. Currently dependent on diesel fuel and nuclear energy to power its fleet, the Navy is looking forward to the day when it will be able to run at least some of its vessels off of batteries. To test the concept, the Navy has awarded Altairnano, a ceramic nanomaterial developer and manufacturer, a contract to develop a ship-mountable 1-MW power station.
"The ship would still be powered by diesel fuel and generators, but the Altairnano battery would act as the backup," says Alan Gotcher, Altairnano's president and CEO.
Altairnano's battery approach represents a new and safer take on lithium-ion technology. Since their development, lithium batteries have been considered too unstable and volatile for use in vehicles. The problem is that lithium batteries can explode: the bigger the battery, the bigger the potential explosion.
Gotcher says his company's NanoSafe battery eliminates lithium ion's explosive nature by forming the anode, the part that discharges electrons, out of lithium-titanate spinels (Fig. 2). These particles comprise two lithium atoms, three oxygen atoms, and a titanium atom. Conventional anodes are based on graphite. Graphite flakes can come loose and react with the electrolyte, the liquid carrying the lithium particles, and start a thermal runaway reaction. Altairnano's anode, however, is inert.
"It won't interact with the electrolyte," Gotcher says. "We haven't had a single failure of a cell in any safety tests, and that includes putting a nail through the cell and overcharging it."
Beyond Navy ships, Altairnano's technology promises to help pave the way for clean-running, better-performing electric cars, trucks, and buses. Gotcher says it's possible to power a full-sized five-passenger SUV with a NanoSafe battery (Fig. 3).
"It's very fast, meaning [the vehicle] can go from a standing start to 60 miles per hour in eight seconds," Gotcher says. "It has a range of 135 miles, and you can connect it to a rapid-charge station and completely recharge the battery pack in less than 10 minutes." The battery can also operate over a wide temperature range, Gotcher notes.
"To our knowledge, we're the only company anywhere in the world who has titanate spinels being used in batteries," Gotcher says (Fig. 4). "People are stunned at how quickly these batteries can be charged."
Gotcher believes it's inevitable that the military will increase its sponsorship of green research simply because so many eco-friendly technologies have definable tactical and operational benefits.
"The military has its energy needs, and businesses and consumers have theirs," Gotcher says. "It's great when these interests can meet in the area of green technology."
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