Following the successful completion of the design phase of the FLyCLEEN (fuel cell embedded engine) project (earlier post), ARPA-E’s REEACH program has awarded GE Aerospace Research $4.5 million in Phase 2 funding to take the next step of building and demonstrating a 25kW power generation subsystem integrating solid oxide fuel cells with a SAF-powered gas turbine for hybrid electric propulsion.

The use of fuel cells could vastly improve the efficiency of converting the chemical energy from SAF into electric power and move closer to net zero CO₂ emissions.

John Hong, a GE Aerospace senior combustion research engineer and FLyCLEEN project leader, says the team is bringing to bear nearly two decades of experience in solid oxide fuel cell technology to support the development and demonstration of a high efficiency power generation system with lower carbon emissions.

Hong explained that this hybrid approach uses SAF in both the fuel cells and gas turbines. A portion of SAF is reformed to Syngas to feed the fuel cells, while the rest of SAF is consumed in gas turbine engine. This is a novel concept to combine the two.

The system is configured to optimize the balance of plant and thermodynamic synergies for electrified commercial aviation. Any wasted heat from the reformer or fuel cell is re-captured as pre-heat to the genset system (equipment that converts heat capacity into mechanical energy and then into electrical energy).

This yields an overall energy storage and power generation system with superior performance parameters such as 58.0% cruise efficiency, 3.73 kWh/kg specific energy, and specific peak power of 1.4 kW/kg.

GE Aerospace Research’s ongoing programs in hybrid electric propulsion with ARPA-E are a complement to the CFM RISE (Revolutionary Innovation for Sustainable Engines) program, a major technology demonstrator GE Aerospace unveiled with its 50/50 joint venture partner, Safran, in 2021. This demonstrator program aims to deliver a 20% reduction in fuel consumption compared to engines today, which would represent a major step change in propulsion efficiency.

Along with advancing hybrid electric propulsion technologies, CFM RISE also is driving advancements in hydrogen-fueled and 100% SAF jet engines, as well as transformational new engine architectures such as an open fan design recently featured at the Paris Air Show this past June.