Are electric aircraft the future of aviation – or just wishful thinking?

Coming soon to a runway near you! Or not. Image: Pascal Rossignol/Reuters.

Since the dawn of aviation, planes have primarily been powered by carbon-based fuels such as gasoline or kerosene. These contain a lot of energy for their weight, providing the vast power required to lift large commercial airliners on journeys across the globe.

But with oil resources declining and penalties on greenhouse gas emissions increasing, the future of aviation is dependent on finding an alternative power source. Is electricity the answer?

A first step is to develop “more electric aircraft” – jet-powered planes that maximise the use of electricity for all the other aircraft systems. The idea is to significantly reduce fuel consumption by improving overall energy efficiency.

In practice, this means reducing the weight of the aircraft, reducing drag with improved aerodynamics and optimising the flight profile to use less fuel.

But though these improvements can save on fuel, that alone isn’t enough. The shift to more sustainable aircraft requires major, longer-term solutions.

Such significant innovations have often been driven by military requirements. The jet turbine engine was developed during World War II, and the US Air Force’s Chuck Yaeger first broke the sound barrier in the Bell X-1 as part of the Cold War race to achieve supersonic speeds. The drive for new technologies led to massive improvements in performance and reliability, which has since filtered through to commercial aviation and made mass intercontinental air travel a reality.

Left: the Bell X-1, the first supersonic aircraft. Right: a British Airways Concorde jet, the only commercial supersonic plane. Images: US Air Force; Aero Icarus via Wikimedia Commons.

Concorde was the ultimate expression of this transformation from military to high-performance commercial aircraft – but despite its phenomenal performance, it was plagued by complaints of excessive noise and pollution. Modern jet air travel still consistently raises such environmental concerns and, while the military has an obvious incentive to design the fastest aircraft, its motivation to go green is less obvious. We may need to look elsewhere for the next big innovation.

Cleaning up the skies?

Solar-powered endurance aircraft have received a lot of attention recently, with the Solar Impulse team attempting to make the first round-the-world flight. But solar power, while an interesting technical challenge, is not a particularly realistic option for mass transit of passengers. As can be seen from the Solar Impulse aircraft, the power output from the Solar Panels on a very wide wingspan is able to transport only the aircraft and the pilot for any significant distance.

Solar Impulse landing at Brussels Airport. Image: Brussels Airport, CC BY-SA

Battery storage is the key limiting factor for electric aircraft: if they are held back by either weight or fuel restrictions, it’s probably down to the battery.

Aircraft typically have a longer fuelling time than a car, so rapid recharging is possible and effective: current jet aircraft take about the same time to refuel (and also for passenger and cargo turnaround), so electric charging of about 1hr is reasonable. However, the critical problem is energy density – how much energy does the battery provide for its weight?

Typical lithium-ion batteries in use today have a maximum energy density of around 1,000,000 joules of energy per kilogram, and while newer research promises the possibility of higher densities, these are not available commercially.

A million joules sounds like a lot. However, compare this with 43m joules per kilogram for aviation fuel. Swapping the fuel tanks for a battery weighing 43 times as much isn’t a viable option: clearly there’s a significant storage problem to be solved before electricity can power large aircraft over long distances.


Wishful thinking?

So where does electric power fit in the long-term vision for consumer air travel? Despite the obvious technical challenges, The Airbus prototype E-Fan aircraft is due to be put into production by 2017. The E-fan is a very light two-seater plane powered by two electric motors, with a relative speed and carrying capacity far lower than those required by commercial carriers. 

Within the next decade, this technology may extend to short-range commuter and business aircraft – especially targeting routes that still use conventional propeller propulsion. Airbus has medium-term plans for such an aircraft, with a target capacity of perhaps 60 passengers – making it a suitable platform for short-haul commuter flights.

Safety and reliability must be addressed before electric aircraft are adopted by commercial airlines. Much as the electric car still has to achieve a critical level of public confidence, perceived reliability will have a significant impact on consumer trust in new aircraft.

If prototypes such as the E-Fan can build public confidence, this may mark a “tipping point” in overcoming the technical challenges inherent in any new form of transportation, especially in aviation which has a track record of rapid innovation. Advances – particularly in new materials, storage and power electronics technology – may offer the prospect of purely electric commercial aircraft within the next two decades.The Conversation

Peter Wilson is professor of electronics and systems engineering at University of Bath

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Coming soon: CityMetric will relaunch as City Monitor, a new publication dedicated to the future of cities

Coming soon!

Later this month, CityMetric will be relaunching with an entirely new look and identity, as well as an expanded editorial mission. We’ll become City Monitor, a name that reflects both a ramping up of our ambitions as well as our membership in a network of like-minded publications coming soon from New Statesman Media Group. We can’t wait to share the new website with you, but in the meantime, here’s what CityMetric readers should know about what to expect from this exciting transition.  

Regular CityMetric readers may have already noticed a few changes around here since the spring. CityMetric’s beloved founding editor, Jonn Elledge, has moved on to some new adventures, and a new team has formed to take the site into the future. It’s led by yours truly – I’m Sommer Mathis, the editor-in-chief of City Monitor. Hello!

My background includes having served as the founding editor of CityLab, editor-in-chief of Atlas Obscura, and editor-in-chief of DCist, a local news publication in the District of Columbia. I’ve been reporting on and writing about cities in one way or another for the past 15 years. To me, there is no more important story in the world right now than how cities are changing and adapting to an increasingly challenging global landscape. The majority of the world’s population lives in cities, and if we’re ever going to be able to tackle the most pressing issues currently facing our planet – the climate emergency, rising inequality, the Covid-19 pandemic ­­­– cities are going to have to lead the way.

That’s why City Monitor is going to be a global publication dedicated to the future of cities everywhere – not just in the UK (nor for that matter just in the US, where I live). Our mission will be to help our readers, many of whom are in leadership positions around the globe, navigate how cities are changing and discover what’s next in the world of urban policy. We’ll do that through original reporting, expert opinion and most crucially, a data-driven approach that emphasises evidence and rigorous analysis. We want to arm local decision-makers and those they work in concert with – whether that’s elected officials, bureaucratic leaders, policy advocates, neighbourhood activists, academics and researchers, entrepreneurs, or plain-old engaged citizens – with real insights and potential answers to tough problems. Subjects we’ll cover include transportation, infrastructure, housing, urban design, public safety, the environment, the economy, and much more.

The City Monitor team is made up of some of the most experienced urban policy journalists in the world. Our managing editor is Adam Sneed, also a CityLab alum where he served as a senior associate editor. Before that he was a technology reporter at Politico. Allison Arieff is City Monitor’s senior editor. She was previously editorial director of the urban planning and policy think tank SPUR, as well as a contributing columnist for The New York Times. Staff writer Jake Blumgart most recently covered development, housing, and politics for WHYY, the local public radio station in Philadelphia. And our data reporter is Alexandra Kanik, whose previous roles include data reporting for Louisville Public Media in Kentucky and PublicSource in Pittsburgh, Pennsylvania.

Our team will continue to grow in the coming weeks, and we’ll also be collaborating closely with our editorial colleagues across New Statesman Media Group. In fact, we’re launching a whole network of new publications this fall, covering topics such as the clean energy transition, foreign direct investment, technology, banks and more. Many of these sectors will frequently overlap with our cities coverage, and a key part of our plan is make the most of the expertise that all of these newsrooms combined will bring to bear on our journalism.

City Monitor will go live later this month. In the meantime, please visit citymonitor.ai to sign up for our forthcoming email newsletter.


As for CityMetric, some of its archives have already been moved over to the new website, and the rest will follow not long after. If you’re looking for a favourite piece from CityMetric’s past, for a time you’ll still be able to find it here, but before long the whole archive will move over to City Monitor.

On behalf of the City Monitor team, I’m thrilled to invite you to come along for the ride at our forthcoming digs. You can already follow City Monitor on LinkedIn, and on Twitter, sign up or keep following our existing account, which will switch over to our new name shortly. If you’re interested in learning more about the potential for a commercial partnership with City Monitor, please get in touch with our director of partnerships, Joe Maughan.

I want to thank and congratulate Jonn Elledge on a brilliant run. Everything we do from here on out will be building on the legacy of his work, and the community that he built here at CityMetric. Cheers, Jonn!

In the meantime, stay tuned, and thank you from all of us for being a loyal CityMetric reader. We couldn’t have done any of this without you.

Sommer Mathis is editor-in-chief of City Monitor.