Is Hydrogen The Jet Fuel Of The Future?

Hydrogen, the most abundant element in the universe, has been touted as a superior alternative to lithium-ion batteries in cars, but adoption has been painfully slow. For all the hype, one would think most cars would be running on hydrogen already, yet they are not.  So where are hydrogen proponents going wrong?

According to some, they may be focusing on the wrong sort of vehicles to power with hydrogen. True, there are billions of passenger cars on the roads around the world. But there are also millions of aircraft in the skies – or there used to be. The aviation sector may well be the game-changer for hydrogen.

One executive from this nascent hydrogen segment explains it in terms of energy intensity and utilization. Valery Miftakhov from ZeroAvia, developers of zero-emission powertrains for aircraft powered by hydrogen, says aircraft have much higher energy intensity and utilization than cars. As such, they should be the focus of attention for hydrogen backers.

In an article for Aeronautics Online, Miftakhov compared intensity and utilization rates for cars and aircraft, in other words the portion of the vehicle’s weight dedicated to fuel and the amount of time it spends in motion. Cars, he said, have an energy intensity average of some 2 percent and energy utilization rates of about 5 percent. A Boeing 737, on the other hand, has an energy intensity average of close to 40 percent and a capacity utilization average of 40 percent, spending about 10 hours daily in the air.

What does this all mean, and why does it matter? 

It means that planes are much greater energy guzzlers than cars, which is not news. It also means that it is a much better target for hydrogen fuel cell technology developers than passenger cars, for which, Miftakhov says, “even the current batteries are good enough.” There is simply not enough demand for a lot more energy-dense energy sources in passenger cars.

Yet in air transport, things look different, especially now, amid the coronavirus pandemic. The pandemic grounded millions of flights, which greatly reduced CO2 emissions. Now there are calls for a green recovery from the pandemic, and hydrogen-powered aircraft may find their place in this green recovery.

Hydrogen fuel cells generate no emissions. They are more energy dense than lithium-ion battery packs - a lot more energy dense - and they are more durable. The battery pack of the Tesla Model 3, for example, has an energy density of some 160 Wh per kg, and it is one of the best in the industry.

In comparison, a California company, HyPoint, makes hydrogen-fueled powertrains that sport energy density of 530 Wh per kg. It is now working on another version of the powertrain that would have energy density of up to 960 Wh per kg. According to ZeroAvia’s Miftakhov, hydrogen fuel cell systems could reach an energy density of up to 3,000 Wh per kg.

What’s so important about energy density? Things like length of journey, to mention the most basic. The more energy a battery - or fuel - cell can store, the longer it can remain in motion without needing to recharge. 

Higher energy density, in other words, extends the range of a vehicle.

But there’s more. There is also the matter of emissions. The air transport industry generates some 115 grams of carbon dioxide per passenger-kilometer, which adds up to 859 million tons of emissions annually, notes Berkant Göksel, an engineering entrepreneur and co-founder of Electrofluidsystems. Göksel and his colleagues at Electrofluidsystems just released a set of drones and air taxis, all hydrogen-powered, using plasma technology and capable of traveling at superhigh speeds. Because, according to them, this is the future: fast and emission-free.

“Governments of developed countries have new strategies for green gas and hydrogen which can be produced with zero CO2 emissions. This is most important in a sustainable energy supply,” Göksel told Oilprice.com. “We can imagine air taxis with amazing ranges up to 1000 km and beyond, which would also personalize regional air mobility.” 

And these will be fast. With plasma jet technology, the hydrogen-powered aircraft would, at some point, be able to achieve incredible speeds.

                                       

Of course, for all this promise in the air transport industry, hydrogen is not without faults, and challenges remain. Some experts note hydrogen fuel cells’ poor specific power output and the fact that range is not necessarily the top priority in air transport. 

“Hydrogen fuel cells can provide improved specific energy over batteries in vehicles that require sustained endurance or range over 100 miles,” the engineering director of aviation at Uber Elevate told Avionics in a recent article. “However, eVTOL [electric vertical takeoff and landing] aircraft serving metropolitan demand only require a 10-60 mile range. Fuel cells are not competitive weight-wise compared to lithium batteries at these shorter ranges.”

There is no universal solution for all priorities in the transport industry. Yet Zeroavia’s Miftakhov certainly has a good point: the success of a product depends on its target market. Hydrogen technology developers may well have been wrong in focusing mostly on passenger cars. Its characteristics appear to be much better suited for longer-haul, more energy-intensive journeys than the daily commute to work. There is definitely a lot going on in hydrogen powertrains for aircraft. Maybe it will lead to wider adoption of hydrogen fuel cells, given the right encouragement from governments and other decision-makers. Air transport could become a game-changer for hydrogen.