Aerospace OEMs and suppliers are investing billions of dollars to develop green technology, such as advanced jet engines and lightweight materials.
In the future, fuel cells, solar panels, electric motors and other green components will play an important role in aircraft. “Aerospace engineers tend to be very conservative, but there’s a paradox,” says AIAA’s Lewis. “At the same time, they’re constantly pushing the envelope and exploring state-of-the-art technology.”
Some of the latest green achievements have come in the form of solar-powered aircraft. For instance, QinetiQ engineers recently set a world record with their unmanned Zephyr, which features a 22.5-meter wingspan. The hand-launched aircraft stayed aloft for more than 14 days, despite constantly changing weather conditions, during a test in Arizona.
“The Zephyr airframe incorporates totally new approaches to aerodynamics, structures, propulsion, avionics, flight controls, power system management, thermal control, ground control station design, and payload, as well as overall operating processes,” claims Chris Kelleher, QinetiQ’s chief design engineer.
The aircraft flies by day on solar power delivered by amorphous silicon solar arrays that cover the wings, no thicker than sheets of paper. The arrays are also used to recharge the lithium-sulphur batteries that are used to power the aircraft by night. “Together, they provide an extremely high power-to-weight ratio on a continuous day-night cycle, thereby delivering persistent capabilities,” explains Kelleher.
A team of Swiss aviators plan to fly around the world in a solar-powered aircraft in 2012. The Solar Impulse features a 64-meter wingspan. It recently stayed aloft for more than 26 hours during a test flight in Switzerland. More than 10,700 solar cells cover the plane’s wings, which contain four electric engines.
Engineers at EADS Innovation Works have been studying a wide variety of electric propulsion systems. They recently unveiled a single-seat, all-electric plane dubbed Cri-Cri. Lithium-ion batteries power four brushless motors, which drive counter-rotating propellers.
The EADS team has also developed a hybrid helicopter that uses electric motors to drive the rotors, combined with diesel engines, to reduce fuel consumption and emissions by up to 50 percent. Take-offs and landings are possible on electrical power alone with the Eco2Avia, resulting in lower noise levels.
“The main components of this patented hybrid system are multiple diesel-electric motor-generator units, a pair of high-performance batteries, and a power electronics unit controlling the energy flows for best efficiency,” says Jean Botti, chief technical officer at EADS, the parent company of Airbus and Eurocopter. “The opposed piston, opposed cylinder (OPOC) diesel engines offer a fuel economy improvement of up to 30 percent compared to today’s helicopter turbine engines.
“The OPOC engine’s power output shafts are fitted with advanced, weight-optimized generators delivering electrical current to the power electronics unit,” Botti points out. “This unit manages the distribution of the electricity to the electrical motors driving the main rotor and the tail rotor to and from the batteries.”
Boeing engineers have been experimenting with a wide variety of fuel cell technologies. In fact, Boeing Research & Technology Europe flew the world’s first hydrogen-powered manned airplane two years ago. A hybrid system consisting of a proton-exchange-membrane fuel cell and lithium-ion batteries powered an electric motor coupled to a conventional propeller in the two-seat motor glider.
In addition, Boeing recently unveiled an unmanned, high-altitude surveillance aircraft called the Phantom Eye. It uses a hydrogen propulsion system to power two 2.3-liter, four-cylinder engines.
Despite those successful applications, many observers believe that fuel cells and solar panels will primarily be used as secondary power-generating systems on aircraft, such as auxiliary power units for large commercial airliners, rather than as primary power units.
“More electric architecture (MEA) will be widely used on future aircraft,” predicts Hans Weber, president of TECOP International Inc., an aerospace consulting firm. “MEA will help aerospace engineers reduce weight and improve fuel consumption, and require less maintenance, resulting in more efficient and cost-effective aircraft. The ultimate goal is to replace oil and fuel pumps with electric systems.”
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