The future of sustainable
and green transportation
Tomorrow's mobility is already here
It is New London; the year is 2050, and as I exit the hyperloop pod, walk from the center of the city towards the vertiport, I check the optical display for the next departure time. I select a two-seater electric vertical takeoff and landing (eVTOL) mode of transport which will give me an unobstructed view of the London Eye. It will also reduce my energy cost as a solo traveler for my monthly carbon allotment.
The images conjured in our minds of the future of transportation embody a utopian urban-scape surrounded in glass and encased in metal. The future of transportation was once science fiction but has evolved into science fact —a realm of technology enabling new capabilities. We are entering an era of technology with a purpose: the existential threat of climate change.
Our understanding of anthropogenic carbon emissions is well quantified. Approximately 16 % comes from the transport sector, 18 % from agriculture, and the remainder from industrial and residential uses. Therefore, when we consider the challenge of decarbonizing transportation, we must address our overall reliance on hydrocarbons as the energy source and carrier. The evolutionary path to green transport starts on land, transitions to the air, and allows us to protect our planet with an interplanetary perspective.
The Future of Land Travel
The concept of people travelling individually in tubes at tremendous speeds was first visualized in the 1960s in the arena of science fiction —for example the children's animated television program, The Jetsons, was about the family of the future.
Fast forward half a century and we have mag-lev trains, high-speed rail, and within the next decade, the Hyperloop. The Hyperloop can most easily be described as a spacecraft travelling on the ground. A pressurized passenger vehicle is magnetically levitated and electrically propelled in a vacuum tube over long distances at speeds of 1,000 kilometers per hour. The Hyperloop can replace regional air travel over land masses and, if connected to a renewable electrical supply, is carbon emission free. At capacities of over 10,000 passengers per hour between major hubs and speeds up to five times that of rail, it can create a ground-based network of passenger and cargo transport. The Hyperloop is more than a concept —there are numerous technology startups in North America and Europe. These companies are currently developing the system architectures and some of the new technologies needed to enable this means of transport.
As with all infrastructure-based transportation projects, the price tag for the Hyperloop is high —think high speed rail with the addition of a decade of research and development akin to spaceplane. Numerous governments, the public and investors are funding or investigating this innovation. We should see a project in implementation before 2035.
The Future of Air travel
Aviation accounted for just under three percent of global carbon emissions in 2020, which is less than 20 % of CO2 emissions for transportation as a sector. This is, however, expected to increase over the next twenty years due to decarbonization of ground-based transportation, an increase in air travel as the human population continues to grow, and more people having access to affordable air travel.
As an engineering professor, experienced pilot and CEO/founder of an electric aviation company, I can say definitively that technologies to decarbonize commercial large capacity jet or turboprop aircraft do not yet exist. Instead, the emphasis for the airline transport sector has been investment in hydrocarbon-based biomass aviation fuels. Biofuels have lower CO2 emissions compared to traditional aviation fuel, but this does not decarbonize the sector long term. Biofuels are also more expensive (per liter) than traditional aviation fuel, which means airline operators will be slow to adopt them without an incentive or penalty (for not doing so).
New technologies are under development to facilitate short range and low-capacity electric aviation platforms. Urban Air Mobility (UAM), a term coined recently, has seen the rapid development of electric-vertical-takeoff-landing vehicles —eVTOL— to facilitate short range air-taxi transport (up to 50 km) within urban-suburban centers. To date there are over 200 companies in the space, ranging from technology startups to prototype vehicles from Airbus. The business case and societal justification for UAM is to alleviate congestion in cities across the globe. UAM creates low altitude airways to get around within an urban-suburban environ.
UAM is likely the only viable use case for battery powered electric aviation, as batteries do not have the energy density needed for city to city or regional travel. Electric aircraft have benefits, in addition to being emission free —they have lower noise levels and energy cost per passenger/km. They also have the potential to be less expensive to maintain. It is debatable if the public will accept rapid growth of UAM in all cities —helicopters are typically met with strong opposition for comparison. We should expect to see the first offering with eVTOL this decade in a congested city near you.
The real future for commercial emission free aviation is the use of hydrogen as the energy source —specifically, hydrogen fuel cell electric power plants for air taxis up to and including medium capacity regional aircraft. Hydrogen fuel cell technologies are under development in the startup space and with larger aerospace companies. For long haul continental and trans-oceanic jet aircraft we will likely see a shift to direct hydrogen/oxygen internal combustion engines and supersonic flight. For smaller aircraft hydrogen powered flight can be a reality this decade. For larger capacity aircraft more investment is required and it will likely be well into the next decade.
With the popularity of electric cars there has been a technology quantum leap in the electric drive train and energy storage technologies. These have found synergies and new use cases with the Hyperloop, eVTOL, and aircraft electric propulsion. From an end-user perspective the future of transportation is shared, multimodal, and carbon emission free. It is a departure from individual vehicles to a networked on-demand system, enabled by artificial intelligence.
It is a synergy of new technologies that have energy efficiency, safety, and connectivity as a common thread. From the invention of the wheel 5,000 thousand years ago to powered flight at the start of the 20th century, transportation technology has always furthered the quest of humans into the unknown.
Anita Sengupta is a scientist, aerospace engineer, university professor and pilot who has spent over 20 years developing technologies that have made the exploration of outer space possible. At NASA, her research centred on the development of ion propulsion and the supersonic parachute system that was an integral part of the 'Curiosity' landing on Mars. Between 2012 and 2017 she directed the Cold Atom Laboratory, a laser-cooling installation which is now onboard the International Space Station. Her move to the private sector —in this case to Virgin— led her to head up the development of an in-vacuum, magnetically levitating, electrically propelled high-speed transportation system known as the Hyperloop. She currently combines her work as a Professor with frequent appearances as a specialised speaker on STEM and green mobility. She is also CEO and founder of Hydroplane Ltd., a company that focuses on the use of hydrogen fuel cells in aviation.