Energy Blog: A Call for Dirigibles
Mitigating climate impact of flying may require lighter-than-air aviation.
Aviation is problematic in several ways. It’s a quickly growing source of greenhouse gas emissions as people take to the skies. Aviation energy use is growing, blowing past 8 percent of U.S. transportation petroleum consumption in 2018. The altitude at which the emissions take place are even more impactful than ground-level emissions from tailpipes or furnaces. What’s more, aviation is particularly hard to electrify for long-haul flights because the energy density and performance of batteries is nowhere close to what is possible with jet fuels.
In response, many activists have suggested we should reduce our air miles or eliminate flying altogether. But we shouldn't stop flying. In fact, back in 2019 I made the case in this column for flying more, not less, and I still believe that. But the improvements to aviation that are part of that argument are moving slowly.
For instance, alternative jet fuels with low lifecycle carbon emissions, such as those made from biofuels or synthesized from hydrogen, have their own impacts, whether it’s deforestation to make room for plantations of energy crops or the energy intensity and emissions of making hydrogen as a building block for synthetic jet fuel. Also, airlines and airplane manufacturers have invested in reducing their energy use per passenger-mile by flying fuller planes, using lightweight materials, and better engines. This approach creates a virtuous cycle whereby a lighter plane can use smaller engines which require less fuel, which makes the plane lighter, and so forth. Despite significant gains, that progress feels slow and steady at a time that we need faster improvements.
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Perhaps the way to fly is by ditching airplanes, which need the power density available from jet fuel to lift their heavier-than-air frames. Instead, it might be time to consider a whole new approach: lighter-than-air vehicles, or airships.
Airships (or dirigibles, which includes both blimps and zeppelins) don’t need as much power because they don’t have to move air through compressors, turbines, and nozzles at hundreds of miles per hour to get the required airspeed to achieve sufficient lift. Instead, they use the buoyancy of light gases to get airborne.
The net result is that airships are remarkably efficient at moving heavy cargo (or people), requiring about the same energy per ton-mile of cargo as rail or only a few percent of what conventional aviation require.
The efficiency is handy, but they have other conveniences. They take off vertically like a helicopter but can carry a lot more and stay aloft a lot longer. The infrastructure requirements are easy, which means they can work in crowded urban site or remote locations such as islands, jungles, or mountainous terrain where it’s hard to install a landing strip.
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Refueling can be easy, as hydrogen—which could provide both fuel and buoyancy—can be made on-site with electrolyzers. And before you make snarky comments about the Hindenburg, there are a lot of reasons to think that the fated airship’s disaster was because of its flammable skin rather than the hydrogen. But if that ill-fated example still makes you nervous, inert helium can be used as the bulk gas instead.
The minimal land footprint of airships—compare their needs of just a grassy field or parking lot to that of a sprawling airport with multiple runways for take-offs, landings, and taxiing—makes them suitable for disaster recovery efforts when wars, volcanoes, landslides, or earthquakes might have damaged the landing strip. Mines, oil and gas production zones, wind farms, and others remote worksites would benefit from their ability to lift bulky and heavy equipment to locations where wide highways or rail do not reach.
Bringing these performance, efficiency and climate benefits together, it might be time for us to push for airships as a cargo modality from the past whose time has come.
Michael E. Webber is the Josey Centennial Professor of Energy Resources at the University of Texas in Austin. His series, Power Trip: The Story of Energy, is available on Apple TV, Amazon Prime Video, and local PBS stations.