Boeing has committed that its commercial airplanes will be capable of burning 100 percent SAF by 2030. [Shutterstock]Boeing’s new sustainability report talks a lot about improved efficiency and the use of sustainable aviation fuels (SAF), but—while Airbus is aggressively researching hydrogen fuel technologies—the Boeing report doesn’t include many details about its vision for using hydrogen as an alternative fuel.
The report stands in stark contrast to Airbus’s announcement last February—in partnership with GE Aviation and CFM International—to “flight test a direct combustion engine fueled by hydrogen in preparation for entry into service of a zero-emission aircraft by 2035.”
Responding to pressure from airlines and government mandates, Boeing and other aircraft manufacturers have been devoting more attention to sustainability and alternative fuels.
In fact, the aviation industry generated 900 million tons of carbon emissions in 2019, Boeing says, which is about 2 percent of total global emissions and approximately 12 percent of emissions across all transportation sectors.
Boeing’s annual sustainability report, released June 29, touts several achievements surrounding Boeing’s plan to encourage use of sustainable fuel sources and reduce carbon emissions, including:
Sustainable aviation fuels (SAF)–including the most widely available type called HEFA-SPK–can be made from sustainable non-fossil feedstocks, such as grain, waste fats, oils, and greases.
“We’re investing heavily in sustainable aviation fuels, considered the safest and most measurable solution to reduce aviation carbon emissions over the next 20 to 30 years.” said Boeing president and CEO Dave Calhoun in the report.
Hydrogen is being considered as an alternative aviation fuel source because it contains more energy by weight than jet fuel. However, it has less energy by density. Airbus is looking at using hydrogen gas turbines to power engines with internal combustion, similar to traditional combustion engines that burn jet-A. Unlike traditional combustion engines, hydrogen burns cleanly.
The Boeing report says it is continuing “research, studies, and demonstrations of electric and hydrogen applications.”
But what kind of hydrogen research and demonstrations? The report singles out a recent test in partnership with Pentagon research arm, the Defense Advanced Research Projects Agency (DARPA), on a “new type of large, fully composite, linerless cryogenic fuel tank.”
Cryogenic fuel tanks are part of hydrogen fuel research because at room temperature it is a gas—making it difficult to store in large quantities unless it’s compressed and turned into a liquid. To do that, you have to cool hydrogen to extremely low temperatures.
As a result, hydrogen fuel tanks will be more complex and heavier than comparable jet-A tanks—adding more weight to an aircraft.
“While this particular cryotank was designed for space applications, the lessons learned from this testing campaign, along with our previous hydrogen demonstration flight-test programs, mark an important leap in materials technology for sustainable aviation,” Boeing said in the report.
The report also says, “Boeing is at the forefront of informing the future of aerospace and understanding how alternative power and energy solutions such as hydrogen and electrification systems will apply across market segments and missions.” It acknowledges that “the industry is considering using it as an energy carrier on board an aircraft,” but offered no details specific to Boeing, comparable to what Airbus is planning.
Boeing Commercial Airplanes vice president and general manager of product development Mike Sinnett spoke in Singapore last year about hydrogen and its potential. “We’re not pooh-poohing it, and we’re doing our hydrogen homework,” Sinnett said, according to FlightGlobal. “We’ve done a lot of work on hydrogen, but we don’t want to artificially create an expectation that this is the answer when we’re not convinced that it is.”
According to the sustainability report, Boeing has “innovated with hydrogen and fuel cell applications on board aircraft for over 15 years. We have developed insights through five flight demonstration programs with crewed and uncrewed aircraft using hydrogen fuel cells and combustion engines.”
Engineers across the aviation industry have been considering multiple ways to use hydrogen fuel cells, hydrogen gas turbines, and hybrid combinations. Hydrogen fuel cells produce electricity without combustion or emissions, similar to conventional batteries. However, unlike car batteries, they don’t run down or need to be recharged as long as they’re fed hydrogen and oxygen.
It goes without saying that Boeing has much on its plate already, including development of its more fuel efficient 777X twin-engine airliner and its recovery after the 737 Max groundings. But the strategic difference between how Boeing and Airbus are approaching hydrogen is hard to ignore.
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