Sustainable Energy: Decarbonizing Aviation
A Bombardier Q400 at Paine Field in Everett, Washington, given by Alaska Airlines to ZeroAvia for conversion to hydrogen-electric propulsion.
For the 2nd annual Alaska Sustainable Energy Conference, guest speakers and exhibitors traveled from across the country and around the world to convene at the Dena’ina Center in Anchorage. Each jet flight emitted approximately as much carbon dioxide per traveler as the entire annual footprint of a single person living in more than one-fourth of the world’s countries. Thus, improving the sustainability of air travel is one of the topics of discussion.
Plans for Hydrogen-electric Propulsion
In his welcome message to nearly 900 attendees, Governor Mike Dunleavy said the reason he began the conference last year, and the outcome he hopes for its sequel, is to understand the possibilities.
Face-to-face engagement helps to bring together those ideas, says Geoffrey R. Pyatt, Assistant Secretary for Energy Resources at the US Department of State. “You can get a lot done on Zoom,” he says, “but there’s also a limit to what you can accomplish. For somebody like me, it makes such a difference to travel to Alaska, to meet with Alaskans, to see your lived reality.”
Pyatt, a former US ambassador, told attendees that his travels around the world have shown him the energy transition that’s underway. “I’ve been to Japan, to Korea, to India, to Pakistan, to Europe a couple of times; a week and a half ago I was in the Caribbean—you see how fast this transformation is occurring,” he said.
International travel itself is transforming, year by year and month by month. Three weeks ago, Alaska Airlines formed a partnership with ZeroAvia, a company developing hydrogen-electric aircraft propulsion. ZeroAvia will retrofit a Bombardier Q400 (also known as the De Havilland Dash 8), a 76-seat turboprop that the airline’s sister carrier Horizon Air flew in Alaska until January of this year.
In January, ZeroAvia successfully tested a Dornier-228 equipped with electric motors powered by hydrogen fuel cells. ZeroAvia uses grid power to make hydrogen by electrolysis, and the hydrogen is stored in the plane (gaseous for now, but super-cold liquid in the future), and fuel cells convert the hydrogen into electricity to drive the Dornier-228’s propellers. The 19-passenger utility aircraft has a range of about 300 nautical miles with a 600 kW powertrain. The modified Dash 8 will have a 1.8 MW powertrain capable of flying 700 nautical miles.
Georgy Egorov, chief investment officer for ZeroAvia, says the company aims to fly the modified Dash 8 by the end of 2024. That type of plane would service routes from Anchorage to Western Alaska; the company already has an order from Ravn Alaska for thirty hydrogen-electric engines for its Dash 8 fleet, when they become available.
First, ZeroAvia must demonstrate point-to-point flights are safe. Egorov says the test flight with the Dornier-228 is scheduled in July.
Electricity from renewable sources is central to decarbonizing aviation, according to John Farrell, manager of the vehicle technologies program at the National Renewable Energy Laboratory. For ZeroAvia, hydrogen is a medium that carries energy from whatever source is locally available. Another approach, though, essentially converts electricity back into jet fuel.
Demonstration of electric-driven propellers on ZeroAvia’s ground test rig.
Sharing a panel at the conference with Egorov, Ashwin Jadhav explained the approach of his firm, Twelve, to catalyze carbon dioxide into hydrocarbons. The process demands an enormous input of electricity, which Twelve sources from renewables in Washington state. Construction is set to begin this year on a commercial-scale fuel plant at Moses Lake, Washington. Alaska Airlines last year placed a major order for E-Jet fuel. As a sustainable aviation fuel (SAF), E-Jet is functionally the same as Jet A, the grade of kerosene used in airliners. Jadhav notes that it is currently required to blend 50/50 with conventional fuel until E-Jet’s safety is assured.
The two approaches to decarbonizing aviation—ZeroAvia’s hydrogen-electric and Twelve’s SAF—might seem to be in competition. Neither Jadhav nor Egorov sees it that way.
“SAF, we like it because it can be implemented right now,” Egorov says. “I have such respect for the SAF.” He notes that ZeroAvia is on a pathway to fly 100-seat airliners, but jumbo jets are beyond the technological horizon.
“We need all of these technologies to work together,” Jadhav says. “We [the industry] are throwing darts, in some ways, but a lot of these darts are interchangeable; the optimization of the darts is unknown yet.” He adds that certain technologies work better for different categories of aircraft. ZeroAvia, for instance, can retrofit small Cessnas that service Northern Alaska and Southeast, where SAF for jets is no use.
“We’ll compete in 2050,” Jadhav says.
Another panelist, NorthLink Aviation CEO Sean Dolan, expressed the spirit of the conference: “Whether it’s geothermal or wind, there’s a huge opportunity here… To start to get these different silos—whether it’s the wind developers, SAF, hydrogen—let’s get everybody working together to focus on these different problems. I’m obviously super excited.”
The conference concludes May 25.