TECH TALK BY JOHN PAWLICKI | OPM RESEARCH ELECTRIC PROPULSION ENERGIZES AVIATION
THE REVOLUTION TOWARDS ELECTRICALLY POWERED VEHICLES CONTINUES IN ALL AREAS OF TRANSPORTATION, FROM THOSE THAT DRIVE ON LAND TO THOSE THAT FLOAT AND FLY. TESLA AND THE LEGACY AUTOMOTIVE COMPANIES (THAT ARE PLAYING CATCH-UP, FOR THE MOST PART, OUTSIDE OF TOYOTA AND A FEW OTHERS) SEEM TO GET MOST OF THE ATTENTION FOR THEIR ELECTRIC-POWERED CARS AND TRUCKS. IT SEEMS THAT NEARLY EVERY MODE OF TRANSPORTATION IS EXPLORING HOW TO MOVE AWAY FROM FOSSIL FUELS TO ELECTRIC OR ELECTRIC HYBRID PROPULSION SYSTEMS.
THE REVOLUTION HAS BEEN
UNEVEN, BUT IT IS HERE While electric vehicles have been around for quite some time, most had been vanquished by their petrol-powered competitors to exile or specifi c niches. Well, what comes around goes around. Electric propulsion is back in vogue, and in some cases provides for a much better economic argument that those old gas guzzlers due to advances in battery technology, lightweight materials, and new propulsion systems. As mentioned above, cars and trucks have gotten most of the press, but buses are quietly (pun intended) becoming battery-powered all over the world in large numbers due to economic and environmental reasons, as are other local fl eet vehicles. Maritime transport has been going electric. Ferries are a key example of this. Ferries are primed for electrifi cation due to their regular and often short routes, and now cargo ships are now also exploring various types of hybrid propulsion (and other technologies such as sails). Trains and urban transport (trams, trolleys) had also moved in this direction where it made sense in the past, and locomotives continue to move away from diesel globally. The worlds fi rst ultra-fast electrically- powered hyperloop will begin to be built in the third quarter of 2019 by a U.S. company (HyperLoopTT) in Abu Dhabi. Things are happening, and most of these things are being enabled by electrical power.
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DOMmagazine.com | dec 2018 | jan 2019 BATTERIES – THE GREATEST
CHALLENGE The number one challenge to design an electric aircraft is the current state of battery technology. In general, batteries cannot provide the power-to-weight ratio needed for electric aviation to be feasible for a signifi cantly-sized aircraft. According to reports, jet fuel yields approximately 43 times more energy than the equivalent mass of battery. Those working on electric aircraft are wholly dependent upon the never-ending march of technology to improve the energy storage technology quickly. Battery energy density has been increasing — rising by 5 to 8 percent per year (according to industry pundits), but some battery companies such as Panasonic have projected much faster increases. Battery technology still needs to be improved further to where it is economically feasible to work in smaller aircraft. Estimates are that they will need to achieve approximately fi ve times their current density. Some of this will be mitigated with aircraft re-designs to make use the smaller electric motors and related components. “Electric propulsion permits new
design architectures,” says Venkat Viswanathan, a battery scientist at Carnegie Mellon University, in a recent article in Wired magazine. “Future electric aircraft will look nothing like the aircraft of today, and they will be able to fl y with much less energy—as little as 400 watt-hours/
kg—thanks to distributed motors and reduced drag. We’ll redesign aircraft around electric motors.” This is an interesting comment, and this may allow new aircraft OEMs to enter the market due to this technological shift, since each time there is a major evolutionary change in an industry, new entrants seem to enter it. Some of the challenges for
engineers and support personnel at airports to develop mechanisms and processes to swap out batteries quickly so that aircraft can continue with quick turnaround times, and in adverse weather conditions. An entirely new support infrastructure will be needed by airports, operators and MROs to manage all of this.
ELECTRIC AIRCRAFT WILL COME
ALONG SLOWLY Smaller aircraft are driving the electric and electric-hybrid projects in aviation incrementally initially, which is partially due to limitations of the current state of battery technology, and in other cases, purely economic reasons. We are seeing a gradual movement towards how newer aircraft will be powered, with short-range vehicles looking at electrical or some type of hybrid technologies, and longer range aircraft mainly staying with legacy fuels (outside of the biofuels being used by some airlines). It is worth noting that electrically-
powered long-haul fl ight is feasible, but due to aircraft being rather well maximized for their use, this will
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