Zero-carbon Ammonia-Powered Turboelectric (ZAPTurbo) Propulsion System

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East Hartford,
Project Term:
04/29/2021 - 04/28/2023

Critical Need:

ARPA-E seeks to mitigate the growing environmental burden associated with commercial air travel at minimum economic cost. The REEACH objective is to develop a disruptive energy storage and power generation (ESPG) system to convert the chemical energy contained in energy-dense carbon neutral liquid fuels (CNLFs) into electric power for aircraft propulsion via electric powertrains and other key systems. Ultra-high conversion efficiency and high specific power and energy are critical for technical feasibility and commercial success of the ESPG systems due to CNLFs’ generally either lower specific energies or higher projected cost compared to incumbent fossil-based jet fuels.

Project Innovation + Advantages:

The Zero-carbon Ammonia-Powered Turboelectric (ZAPTurbo) Propulsion System is a very high efficiency and lightweight turboelectric system that uses green ammonia as a fuel and coolant via regenerative cooling. Coke-free heating of this carbon-free ammonia fuel enables a high level of waste-heat recovery that will be used for the endothermic cracking of ammonia prior to its combustion, significantly increasing the cycle efficiency. The proposed propulsion system includes an efficient AC electric powertrain for turboelectric cruise, with battery boost for takeoff and climb flight phases. The ability to optimize the gas turbine at the center of the turboelectric system for cruise power drives maximum efficiency. The proposed system is projected to operate in cruising phase of flight with a 66% energy conversion efficiency to offset the lower energy density of ammonia. The project comprises (1) risk-reduction experiments for critical components and conceptual evaluation and design of the ammonia-fueled propulsion system; and (2) sub-scale demonstration of the key components.

Potential Impact:

Electrified aviation propulsion systems have the potential to achieve ultra-high fuel-to-propulsive power conversion efficiencies compared with existing turbofan and turboprop systems.


This program could ensure U.S. technology leadership in ultra-high efficiency aircraft propulsion systems capable of exploiting CNLFs.


A high specific power electrified propulsion system framework could enable net-zero carbon aviation by facilitating the transition to carbon neutral liquid fuels (CNLFs) while meeting all mission requirements.


The developed ESPG sub-system could provide the foundational technology for a new industry in ultra-high efficiency propulsion systems while improving the competitiveness of the existing air transportation industry by reducing fuel costs.


ARPA-E Program Director:
Dr. David Tew
Project Contact:
Dr. Lance Smith
Press and General Inquiries Email:
Project Contact Email:


Pratt & Whitney
Gas Technology Institute

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