Regional turboprops retrofitted with hydrogen fuel-cell propulsion could service 15-20% of the market, reduce emissions by almost 90%, and help develop the hydrogen infrastructure at airports, concludes a study by the nonprofit International Council on Clean Transportation (ICCT). 

The study led by ICCT’s Jayant Mukhopadhaya looked at retrofits of turboprops with 42-70 passengers using the ATR 72 and De Havilland Canada Dash 8-300 as the reference aircraft. An ATR 72 retrofitted with hydrogen fuel-cell propulsion would pay a penalty in payload and range, but would be more energy efficient, the study says.

Both Universal Hydrogen and ZeroAvia are developing hydrogen-electric retrofits for the ATR 72. Universal Hydrogen is flying a Dash 8-300 as a propulsion testbed and is modifying an ATR 72, aiming for supplemental type certification in 2025. ZeroAvia plans to fly a Dash 8-400 propulsion testbed in 2024 but intends to certify an ATR 72 retrofit first, by 2027.

Using green hydrogen produced using renewable energy, greenhouse gas emissions would be reduced 88% relative to the fossil-fueled aircraft and by 30% when compared with an aircraft powered by e-kerosene produced from carbon dioxide and hydrogen.

Green hydrogen is expected to be more expensive than jet fuel in the near term, but the increased energy efficiency of a fuel-cell powertrain compared with a turboprop engine would bring the price premium down to 29-40% in the U.S. by 2030, ICCT projects. 

Green hydrogen could be cheaper than jet fuel in the U.S. by 2050, the study says, but is expected to be more expensive to produce in the EU, where the price premium over jet fuel is projected to be 100% in 2030, dropping to 50% by 2050. Liquid hydrogen is expected to be more expensive than gaseous hydrogen, because of the higher costs of liquefaction and handling, but would increase aircraft range.

Using 2019 data, ICCT calculated that a regional aircraft retrofitted with fuel-cell propulsion could have the payload and range to fly nearly one-fifth of all turboprop available seat miles. This represents 29-36% of all turboprop departures, the study says.

ICCT’s study concludes that fuel-cell retrofit aircraft such as the ATR 72 could “provide an initial testbed that could be scaled to prepare for the introduction of larger, clean-sheet hydrogen combustion aircraft that could decarbonize a larger section of the aviation market.”