High-Voltage Charger to Propel Hybrid-Electric Aircraft Demonstrator

A hybrid-electric flight demonstrator will feature an advanced mobile charging unit capable of supplying up to 1,500 V of power to the plane’s battery system. Pratt & Whitney Canada, a division of Virginia-based aerospace and defense giant RTX Corporation, plans to test a propulsion system linking to the high-power battery later this year. 

The mobile charging unit delivers up to 280 kW and 1,500 V, supporting the Megawatt Charging System standard in the works for high-voltage technologies. The Charging Interface Initiative is developing the standard for large battery electric vehicles (BEVs) like trucks and buses. However, it could be expanded to battery-powered planes and electric vertical take-off and landing applications. 

 

Pratt & Whitney Canada’s hybrid-electric experimental aircraft. Image used courtesy of Pratt & Whitney Canada

 

Pratt & Whitney developed the charger unit in partnership with National Research Council Canada, a government research and development center that assisted with hardware design, assembly, and testing. Quebec’s Innovative Vehicle Institute led distributed control and protection for the project. 

The mobile charger, made with off-the-shelf components, will serve batteries developed by H55, a Swiss electric aviation company. The battery pack will power the propulsion system for the regional RTX hybrid-electric demonstrator, which aims to improve fuel efficiency by 30% and reduce carbon dioxide emissions compared to current turbo propulsion engines. 

Pratt & Whitney Canada selected H55 in 2022 to build the energy storage system for a 49-seat De Havilland Dash 8 experimental aircraft. In mid-2023, the demonstrator completed a rated power test of its 1 MW electric motor by Collins Aerospace. 

 

Pratt & Whitney’s hybrid-electric demonstrator will feature a fuel-burning engine and a battery-charged electric motor. Image used courtesy of Pratt & Whitney 

 

The motor and controller will be combined with Pratt & Whitney’s efficient thermal engine to form a hybrid propulsion system with a lower carbon footprint. 

 

High-Voltage Mobile Charger for an Electric Aircraft Motor

Pratt & Whitney says the mobile charger has bidirectional capabilities, meaning it receives energy from a charger and can discharge it to an external load. This feature is increasingly popular in consumer BEVs, allowing owners to return their excess energy to the grid and receive compensation from their utility. 

Pratt & Whitney didn’t disclose how the bidirectional function would work. If deployed as planned, it would be an early application of vehicle-to-grid technologies for electric aviation. 

 

A close-up look at H55’s battery packs. Image used courtesy of H55

 

H55’s battery modules can charge up to 2,000 cycles. Each features a modular architecture of up to 1,250 V, a 200 Wh/kg energy density, and redundant analog and digital monitoring systems. The battery management system gathers data from individual modules and relays it to pilot control. 

The battery modules and cores were designed with a 21700 cell form factor. 

 

Other Components of the Hybrid-Electric Demo Aircraft

The battery pack and combined hybrid-electric propulsion system—including the thermal engine and 1 MW motor—will soon be fully integrated into a Dash 8 plane ahead of flight testing in 2024. 

Collins’ 1 MW motor boasts market-leading power density and efficiency. When tested last year, it was expected to deliver four times the power and twice the voltage of the company’s most advanced electric generators in the air today. It also has half the heat loss and half the weight. 

 

The preliminary design for Collins Aerospace’s 1 MW electric motor. Image used courtesy of Collins Aerospace

 

The Dash 8 will be re-engined on one side with a 2 MW-class propulsion system combining Pratt & Whitney’s fuel-burning engine and Collins’ electric motor in a parallel hybrid configuration. With a 50/50 power split, the design enables the motor to supply extra power during the take-off and climb phases, while the fuel-based engine supports cruise efficiency. 

Several aerospace giants are testing similar hybrid-electric technologies. Airbus, Daher, and Safran recently completed the first flight test for their EcoPulse demonstrator, with an electric distributed propulsion system powered by a battery and turbogenerator. Ampaire also tested its hybrid Electric EEL demonstrator in a 12-hour flight last December in California.