ZeroAvia’s hydrogen-powered test plane is nearly ready for takeoff

Airports worldwide are swarming with travelers paying sky-high fares for jampacked flights this summer. Far away from those chaotic hubs, however, is a private airfield in the English village of Kemble. At a single asphalt runway surrounded by farms and grazing sheep, aviation experts are preparing to launch a different kind of trip, one that’s powered partly by hydrogen.

The startup ZeroAvia is planning to flight-test a 19-seat aircraft equipped with hydrogen fuel cells in mid-July at the Cotswold Airport in Kemble, the company says. A second test-bed plane will take flight in the coming months near ZeroAvia’s headquarters in Hollister, California. The two dual-engine aircraft will use fuel cells — which convert hydrogen into electricity to drive propellers — and batteries on one side, while the other side will use a conventional jet engine.

If all goes smoothly, the demonstrations could play a key early role in advancing hydrogen as an alternative to highly polluting, oil-based jet fuel. So far, hydrogen has only been tested a handful of times in tiny, single-digit-passenger prototype models. Yet major aviation companies are increasingly considering the carbonless fuel as a long-term solution for cleaning up the notoriously hard-to-decarbonize industry.

The test flights will follow a flurry of recent hydrogen-related developments. Delta Air Lines is partnering with Airbus, the world’s largest aircraft manufacturer, to develop a hydrogen-powered passenger plane and explore how to store and supply hydrogen at airports. Airbus itself is building a demonstration engine to test hydrogen propulsion in one of its A380 superjumbo jets. Universal Hydrogen, a Los Angeles–based startup, is building hydrogen planes as well as portable storage capsules designed to replace traditional pipes and hoses. The company plans to test its 1-megawatt fuel-cell powertrain in a 40-passenger plane in September near Moses Lake, Washington.

“Airlines are really interested in this because they’re under more and more pressure from governments but also from the flying public,” Val Miftakhov, CEO and founder of ZeroAvia, told Canary Media. ​“People started realizing that they have very significant carbon footprints from aviation.”

For its part, ZeroAvia has raised $115 million from United Airlines, Alaska Airlines, British Airways, Amazon, Shell and other investors. Miftakhov claims the startup is on track to launch a small hydrogen aircraft into commercial service by the end of 2024.

Hydrogen could meet a sizable share of aviation’s energy demand

Aviation accounts for about 2.5 percent of global greenhouse gas emissions every year, a percentage that’s projected to soar in the coming decades as passenger travel continues to grow. About half of aviation’s annual emissions can be attributed to just 1 percent of the world’s population — the fortunate few who fly frequently or travel abroad.

This year, the International Civil Aviation Organization, the United Nations agency that oversees the industry, is expected to set a ​“long-term aspirational goal” for reducing emissions in line with global climate targets. In 2015, nations committed to keeping global warming to well below 2 degrees Celsius, with an ideal limit of 1.5 degrees, compared with preindustrial levels.

Many aviation experts agree that hydrogen will play an important part in meeting the industry’s climate goals, albeit with two crucial caveats.

First, in order to actually reduce emissions from flying, hydrogen must be made from renewable energy, including through electrolysis — a process that involves using electricity to split water molecules into hydrogen and oxygen. Second, the renewable energy must come from additional wind or solar projects built specifically to produce hydrogen. Otherwise, the aviation fuel risks hogging electricity that could be used to power homes or charge electric cars, said Jayant Mukhopadhaya, an aerospace engineer and researcher at the International Council on Clean Transportation.

Mukhopadhaya co-authored a recent analysis that found that hydrogen could meet about one-fifth of aviation’s total energy demand by 2050. In the study’s most aggressive carbon-cutting scenario, most of the remaining energy demand is met by burning ​“sustainable aviation fuels,” or SAFs, in combustion engines. Today, most SAFs are made from used cooking oils and discarded animal fats, but eventually supplies may include synthetic fuels made using renewable electricity. A negligible amount of battery power rounds out the total for energy demand.

Using these fuels, along with improving how planes are made and operate, could shrink aviation emissions to near-zero levels by 2050, the researchers said. Such a feat would keep the industry in line with a 1.75-degree Celsius warming target. However, to meet the 1.5-degree goal, companies would need to take more drastic measures, including reducing traffic demand and possibly deploying ​“direct air capture,” a nascent technology that involves sucking carbon dioxide directly from the sky.

Looking ahead, ​“We’re not seeing this demise of the aviation industry,” said Brandon Graver, the study’s lead author and a senior aviation researcher at the International Council on Clean Transportation (ICCT). ​“I’m optimistic that we will have a sustainable aviation future,” he added. ​“But it’s going to take a lot of effort and a lot of money.”

Fuel-cell planes seem better suited for quick commutes

When it comes to using hydrogen, there’s a key distinction between what the ICCT experts envision and what startups like ZeroAvia are working toward.

Researchers say airlines are more likely to burn liquid hydrogen in combustion jet engines — a path that Airbus is pursuing — because engines are expected to produce more power, enough to cover most short- and medium-haul flights. A separate ICCT study found that hydrogen-combustion engines could technically handle one-third of total passenger traffic worldwide.

The alternative is to use a fuel cell. In these systems, gaseous hydrogen flows into the cell and spurs an electrochemical reaction that produces electricity; that in turn drives electric motors and propellers. Since fuel cells don’t burn the hydrogen the way engines do, they don’t generate harmful nitrogen oxides or fine particulate matter. But Mukhopadhaya said fuel-cell aircraft will likely be limited to short-haul regional routes, which are typically less than 400 miles.

ZeroAvia is targeting precisely those kinds of trips, at least to start, said CEO Miftakhov. An ideal route might include the 1.5-hour commute from San Francisco to Los Angeles, a short jaunt between islands in Hawaii, or an airborne cargo delivery to remote locations. Miftakhov said that around 10,000 small regional aircraft are currently in service worldwide.

This summer’s flight tests involve 19-seat planes, though all but the cockpit seats have been removed to make room for testing and monitoring equipment. The fuel-cell systems and hydrogen storage tanks are also kept inside the cabin during the experimental phase, but future configurations will have the hydrogen equipment mounted outside of the aircraft, according to ZeroAvia.

In previous experimental flights, the startup used a six-seat prototype propeller plane equipped with its hydrogen fuel-cell system and batteries. In September 2020, during an eight-minute flight, hydrogen fuel cells met about half of the aircraft’s peak power demand, while batteries supplied the other half, the company said. A later test flight had rockier results.

In April 2021, the prototype plane, called the Piper Malibu, was damaged during a forced landing near Cranfield Airport, about an hour’s drive north of London. After pilots turned the plane’s batteries off, leaving only the hydrogen fuel cell running, ​“power to the electrical motors was lost,” the U.K.’s Air Accidents Investigation Branch said in a statement. ZeroAvia said it has demonstrated and documented multiple times the plane’s ability to fly in hydrogen-only mode without batteries. But on that particular flight, ​“the electrical system did not perform as planned, which led to the incident,” ZeroAvia said in an email.

The newer, bigger test planes will use a different technology arrangement when they take off in Kemble and Hollister this year. Along with fuel cells and batteries, the two Dornier-228 aircraft will also use an oil-burning jet engine during the testing and development phase. ZeroAvia said it intends to demonstrate a ​“full hydrogen-electric flight over the course of the next year” and still plans to deliver a hydrogen-electric propulsion system that’s certified to fly in the U.K. and U.S.

As pilots prepare for the next tests, ZeroAvia is advancing its hydrogen-powered vision in other ways as well. Earlier this month, the U.K. firm Monte Aircraft Leasing agreed to purchase up to 100 of ZeroAvia’s 600-kilowatt powertrains, to be installed on existing small turboprop planes like the Cessna Caravan. In May, ZeroAvia partnered with the oil-and-gas giant Shell to design and build commercial-scale hydrogen refueling trucks, as well as to create a ​“landside-to-airside” pipeline that brings hydrogen from an on-site electrolyzer directly to the aircraft hangar.

Next year, Miftakhov said he expects ZeroAvia will fly a 50-seater on hydrogen. ​“We’re starting with these smaller aircraft and then going larger and larger,” he said.