Friday, May 11, 2018

Shorter air routes may be served in the future by hybrid electric airplanes

Because of the time spent in travel to important air hubs then waiting in line to pass security, board and then waiting for takeoff, and finally traveling from the airport at the destination many people avoid using air transport for shorter trips.

In the United States only ten percent of round trips between 800 and 1,600 kliometers or 500 to 1,000 miles are taken by air travel. Under 800 kilometers (500 miles) only less than half a percent are taken by air.
Short haul air travel is expensive
Short hauls are actually more expensive and less efificent than surface transport by car, bus, or train as takeoffs and landings with small jet engines burn huge amounts of costly jet fuel. This contrasts with longer air flights in which larger engines use less fuel while cruising. Even regional operators are offering longer flights with larger planes. In the 1980's regional places averaged 20 seats but now they average 80 seats.
In the 1980's US airline operators made more use of the 13,500 airports throughout the country but now just one percent of all airports carry 96 percent of all air traffic. Regional door to door times are now worse than they were 50 years ago. As more and more communities lose their air services it has a negative effect on the local economies.
Rejuvenating the local air travel sector
Zunum Aero is planning to revive the local air travel business usng hybrid-electric aircraft propulsion. This type of propulsion is made possible by converging battery development, high-power motors and power electronics trends.
The company began working on a project in 2013 before anyone was actually thinking of doing so in commercial aviation. Electric propulsion was not considered feasible accept perhaps in a very light plane. However as trends in battery, motor, and power electronics have rapidly developed as well as regulations supporting the industry it became evident that by the 2020's the appropriate technology would come of age.
Bye Aerospace in Colorado has built a two-seat aircraft the Sun Flyer run by electricity alone as described in a recent article.
This shows that new technology makes it possible to develop all electric aircraft.
Zunum's 12-passenger hybrid-electric airplane.
The development of an aircraft typically will take five years or even longer, hence Zunum Aero started work on the aircraft immediately rather than waiting for the technology to mature first. This may appear somewhat risky for some potential investors as there may be delays in development due to the fact that the required technology is not yet available.
However, Zunum Aero feels that the decision is paying off as they have recently unveiled the design for a 12-passenger hybrid-electric airplane that they are now building. Plans for the first flight are as early as 2019. JetBlue and Boeing are backing the company's efforts. The company plans to sell the planes to airlines.
Costs will be competitive
Zunum Aero believes that operating costs for its plane will be 40 to 80 percent less than those of present regional aircraft, saving passengers money. The noise produced by the plane is also much less than conventional aircraft. The company envisions the planes as helping to invigorate thousands of underused regional airports, and cut down door-to door times for travelers.
This may be rather optimistic. Perhaps many of these airports will need upgrading in order to handle the increased traffic and the airlines using the facilities will be asked to help pay the costs and no doubt fees may be added on to tickets to help finance the improvements or repairs.
The company also touts the environmental advantages of the new propulsion which will lower carbon emissions by about 80 percent. The company sees that planes as going fully electric during the 2030's. Yet there are environmental costs associated with the manufacture of and disposal of batteries.
The company notes that the development of new battery and other technologies for EV's and even boats can to some extent be transferred to the propulsion of electric aircraft. Battery pack costs of lithium ion batteries have fallen from $1,000 per kwh to less than $250 per kwh today. The development of better supercapacitors and power converters have also been improved greatly.
How the Zunum Aero plane will be powered
Lithium-ion batteries will be stored in the wings for supplemental power. The power will be used particularly on takeoff. Cruising power is generated by a gas turbine that is linked to a generator in the back.
The aircraft is powered as follows "Our aircraft is powered by a pair of low-pressure ducted fans, each driven by an integrated 500-kilowatt permanentmagnet motor. The fans provide high static thrust for takeoff, high efficiency for cruising, and—in part because of the ducting—significant reductions in noise. Indeed, this design produces between a third and a fifth less noise than do traditional jet engines and turboprops, allowing our design to serve airports near towns without bothering the residents so much. We call these ducted fans “quiet electric propulsors” (QEPs)."
The QEPs a powered by electricity from the batteries but are supplemented by the 500 kw generator that is driven by a highly efficient gas turbine. The gas turbine does not produce any thrust just the electric power to drive the QEP's. In effect it is indirectly an all electric aircraft but with a hybrid power train.
The batteries are in the wing where normally there are fuel tanks. They are designed for quick swap out should there not be time for an adequate recharge. The battery cells have a minimum power density of 350 watt-hours per kilogram. The planes are designed so that they can accept the latest battery chemistries and form factors.
Zunum's testing plan
Sine the company is intending to deliver its first planes to airlines in 2022 it has developed precise testing milestones for the next year and a half. This includes producing a "copper bird" that models that electrical systems. This will be produced in a facility in Illinois. At the same time a subscale model of the QEP will be put in a test cell to evaluate how it performs and its aerodynamics. Finally, the power train will be take aloft on an existing airframe to gain flight experience. Finally it will be integrated with the Zunum aircraft. The company at present is using computer simulations to determine the size that each component should be an to optimize performance.
Costs of travely by Zunum Aero's 12-seater should be faster and cheaper than conventional flights
The range of the aircraft is said to be 1,125 kilometers which would be appropriate for changing a day to a day and a half road trip into just a few hours.
The trip from Boston Mass. to Washington DC is 640 km or 400 miles. The journey takes more than 8 hours by car. If one goes by air using the hubs Boston Logan International Airport and Ronald Reagan Washington National Airport estimated door-to-door travel time is around 4 hours and 50 minutes. However, it is estimated that using the Zunum plane out of secondary airports could cut the time to just two hours and a half.
Zunum's economic analyses showed that average fares from regional Mass. airports in Beverly, Hanscom, and Norwood, to regional airports in Marylan and Virginia would cost about $140 one way about a third less than average commercial rates.
Working out regulations for certification of electric aircraft
Regulations governing the certification of electric aircraft are still to come. Zunum Aero is working with the FAA to craft such regulations. It is expected that regulations will be forthcoming later this year. Zunum Aero sees in the not-too-distant future the present hybrids becoming all electric and that the technology will be used even for long-haul flights.
Not surprisingly, Zunum Aero has a very rosy view of the future for all-electric planes: " Following the rollout of hybrid and electric vehicles onto our roads and just now entering our waterways, conventional fossil-fueled aircraft will likewise become relics of the past. Air travel, which has been increasingly relegated to fewer and fewer connecting points, will become personal and local again. In a few years, traveling a thousand kilometers will be as simple as arriving at your nearest regional airport, strolling onto a hybrid plane, and taking a quick flight to the regional airport closest to your final destination.. "
Competitor Wright Electric
Wright Electric is a startup company located in Los Angeles California, aiming to create a commercial airliner that runs on batteries and can handle flights under 300 miles. The company with just ten employees was founded in 2016 but it has received venture capital from groups such as the Silicon Vallley accelerator Y Combinator. The company is named after the Wright brothers. Its plane will feature high aspect ratio wings for energy-efficient flgiht , distributed electric aircraft propulsion and swappable battery packs with advanced cell chemistry. The firm publishes a monthly newsletter on sustainable aviation the Weport.
Observations
The are still many hurdles to be overcome before the scenarios set out by Zunum Aero can become reality. So far the plane is still far from a reality let alone in the test phase. So far only quite small planes have been electrically powered. The duct system is also so far untested it would seem. While Zunum Aero seems to have the support of companies such as Boeing the company does not really go into its financing or show that it has the financial resources to carry on a long-lasting and no doubt expensive development program.
While Zunu's Aero vision of the future is enticing it remains to be seen what unforeseen roadblocks may stand in the way of its realization. However, the company is one to watch as it progresses towards its goal If it is successful it will be good for many local economies as well as the environment.


Previously published in Digital Journal

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