While most eVTOL aircraft developers have committed to either purely battery-electric or hybrid powertrains, Alaka’i Technologies believes that hydrogen fuel cells offer the best solution for sustainable, emissions-free air transportation. The company is developing a four-passenger, hydrogen-powered eVTOL aircraft called Skai that it says will boast an initial range of 200 miles. A subsequent larger version of the aircraft will be able to fly twice as far, Hugh Kelly, head of marketing at Alaka’i, told AIN.
Alaka’i, which unveiled the Skai concept in 2019, has already built three full-scale prototypes of the multicopter vehicle and has been conducting routine hover flight tests for the past few years at its hangar facilities at Minute Man Air Field, a small airport near Boston, where the company has set up a liquid hydrogen fueling station. While Alaka’i isn’t committing to a date for entry into service, the company has begun the FAA type certification process with the submission of its G-1 issue paper. “We expect to be done with G-2 later this year,” Kelly said, “and then we'll do G-3 and G-4 and hopefully be into the full inspections phase and all the testing next year, and that usually is a nine- to 18-month process.”
Kelly explained that Alaka’i chose the hydrogen route because the power-to-weight ratio of lithium-ion batteries greatly restricts the range and payload capacity of an electric aircraft. “The problem is the FAA requires us to have 20 minutes of reserved flight time, and that's very difficult to do with batteries and still maintain any reasonable distance,” he said.
Hydrogen, on the other hand, is one of the most energy-dense fuels available. “Because the energy density is so much greater and the power-to-weight ratio is so much better, we can get that longer range, so we don't need recharging infrastructure every time we stop,” Kelly said. While the first eVTOL air taxi routes expected to launch in 2025 entail approximately 10-minute flights between city centers and airports with downtime for charging, the Skai will have a flight duration of up to four hours and can complete multiple trips before needing to refuel.
Although hydrogen fuel cells are more expensive than the off-the-shelf EV battery cells most electric aircraft developers are using, Kelly said the company is “very confident that the benefits from the weight and the longer life cycle will more than pay for that.” Like lithium-ion batteries, hydrogen fuel cells must be replaced periodically, but not as frequently, Kelly explained, adding that 95 percent of the materials in hydrogen fuel cells are recyclable.
Alaka’i anticipates that new hydrogen tax credits proposed by the Biden administration will further reduce the Skai’s operating costs over time. The 45V Clean Hydrogen Production Tax Credit, established under the Inflation Reduction Act, provides hydrogen producers with a tax credit of up to $3 per kilogram of “green hydrogen”—meaning it’s made via electrolysis using renewable energy sources such as solar and wind. “Our models suggest that we could drop from an hourly operating cost of around $1,100 today down to less than $800 in five to six years,” Kelly said.
For its flight-testing activities in Massachusetts, Alaka’i obtains green hydrogen from a production plant near Niagara Falls in New York, which ships the fuel to Massachusetts in tanker trucks. Refueling the aircraft’s hydrogen fuel cells is “fairly simple,” Kelly said. “We have a fuel port on the vehicle, you plug a hose into it that locks in place, and it takes about 10 minutes to transfer the hydrogen.”
The Skai will initially serve customers in the business aviation and general aviation sectors that require transportation to and from small airports, said Kelly, who called the service “an extension of the private aviation market.” For example, “think of corporate aviation departments who need to transport people to their jets, or aircraft management companies who handle high-net-worth individuals, or fractional ownership,” he said. “This saves a lot in terms of having to relocate jet aircraft, which adds up on the hours that contribute towards maintenance costs.”
Eventually, Kelly said, Alaka’i will likely expand its operations with scheduled passenger services and potentially on-demand and ride-share air taxi services. He expects the flights will initially cost about three times as much per mile as a ground ride-sharing service such as Uber. Alaka’i is also considering an autonomous version of the aircraft that could transport five passengers with no pilot on board, but Kelly said he expects the FAA is at least a decade away from approving such operations.