July/August 2019

n TRANSPORTATION years ago, has launched a company called H55 that is developing a two-seater electric aircraft aimed at flight schools. H55’s Bristell Energic craft, which had its first flight earlier this year, is driven directly by a 90kW, 350Nm electric motor with a 150kW liquid-cooled inverter and a 50kWh lithiumbattery. It can fly for up to 1½ hours at speeds of up to 200km/h. Borschberg sees it as a stepping stone to other craft such as electric taxis. Challenges There are immense challenges to be overcome if all-electric or hybrid aircraft are to make significant inroads into the commercial market – not least in terms of battery energy densities, which are even more critical in these applications than for land-based vehicle propulsion. Batteries have to compete with kerosene, the current fuel of choice for commercial passenger aircraft, which has an energy density that is 60 times higher than existing batteries. Another advantage for conventional aircraft is that as they burn fuel during a flight, they get lighter – unlike an electric aircraft that has to carry the same weight of batteries at all times. Around the world there are efforts to come up with battery technologies that will deliver more power from lighter weights. For example, a British company, Oxis Energy, is developing lithium-sulphur batteries with the aim of achieving energy densities of 500kWh/kg as soon as 2020, and to enter commercial production within 18 months. Its batteries are less than half the weight of current Lithium-ion batteries. The company already has 183 patents protecting its technology with another 101 pending. Oxis is collaborating with Bye Aerospace, a US firm which specialises in light aircraft. CEO George Bye says that Oxis has the potential to deliver a Li-S battery cell“that is truly a game- changer”. If large all-electric aircraft are ever to become a reality, we might have to move to more advanced technologies – fuel cells, for example. Nasa is investing $6m in a three-year project involving a group of US organisations – including Boeing, GE and the University of Illinois – that are examining the possibility of using liquid hydrogen as the feedstock for fuel cells that will drive ultra-efficient electric propulsion systems. The need to keep the hydrogen at extremely low temperatures could open up the possibility of using extremely efficient superconducting motors to power the aircraft. But it will be decades before such technologies become a commercial reality. At present, the prospects for all- and hybrid- electric aircraft look best when journeys are short and payloads are small. But 80% of the aviation industry’s emissions come from long- haul flights carrying scores or hundreds of passengers over distances of more than 1,500km. Electric aircraft are unlikely to make inroads into this market for many years – if ever. Developing part- or all-electric aircraft is a risky and costly business and there have already been casualties. Last month, for example, a US company called Zunum Aero which had been developing hybrid jet- electric aircraft ran out of cash and shut down with the loss of around 70 jobs, despite attracting funds from Boeing, the JetBlue airline, and the state of Washington. Zunum had hoped its first short-haul aircraft would enter service in in 2023. There are likely to be other failures before these emerging technologies are established as being commercially viable. But, in the long run, we could all benefit from cleaner skies. n In its E-Fan X demonstrator aircraft, Airbus is replacing one of the four jet engines in a conventional BAE 146 aircraft by a 2MW electric motor Faradair’s Beha hybrid craft could carry 18 passengers or five tonnes of freight from London to Manchester in 42 minutes AC, PMDC & BLDC Geared Electric Motors Semi-Custom & Fully Bespoke Options Available Made in the UK since 1947 +44(0)1202 512 575 www.parvalux.com sales@parvalux.com