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BRUSSELS—The intensive use of batteries in a hybrid-electric propulsion system may generate a replacement and obsolescence challenge, Todd Spierling, principal technical fellow for electrification at Collins Aerospace, said March 18.

The aging issue may add to the numerous problems that designers of hybrid-electric architectures face, from battery specific energy to high-voltage wiring. The promoters of hybrid-electric expect a reduction in fuel consumption, and ATR is considering such an evolution for its ATR 72-600 regional turboprop, with entry into service of a yet-to-be-launched variant in 2035. Batteries would be used as buffers in the electric system.

In the framework of the European Union's Clean Aviation research and technology program, Pratt & Whitney Canada is leading the Powerplant Hybrid Application for Regional Segment (Phares) project, hinging on a turboprop engine with improved thermal efficiency, an electric motor and a new propeller. ATR is leading the Hybrid-Electric Regional Aircraft Concept for Low Emissions (Heracles) project for integrated aircraft design, as well as the Demonstrator of an Electrified Modern Efficient Transport Regional Aircraft (Demetra) project for inflight demonstration.

Compared to electric cars, hybrid-electric aircraft would make much more substantial use of their batteries. “We would see thousands of charge-discharge cycles per year,” Spierling said, speaking on the sidelines of the Clean Aviation Annual Forum here in Brussels. “Depending on the chemistry, a battery can last 1,000-5,000 cycles. So we would need to replace batteries every year or every two years.”

While the aircraft could thus benefit from battery performance improvements, its certification basis may require a certain type of battery. Meanwhile, the battery supplier, for which aviation may be a niche market, may stop producing that type at some point, creating the obsolescence issue. “If we are using commercially based cells, what are the odds in five, 10 and 20 years that someone will continue to make those?” Spierling stressed during a panel discussion. “So we see almost a continual cycle of ... improvement, recertification, reintroduction, across the life of the airplane.”

Over the life of an aircraft, the operator may have to replace the batteries one or two dozen times, he added. The aircraft's design should factor in that necessity and make it easy to replace the batteries, added Daniel Cuchet, ATR's senior vice president for engineering.