Zero Emission Aviation – Are Electric Islanders the Solution?
The coronavirus crisis will transform civil aviation, giving airlines their best chance yet to address climate change, writes David Earl. But are electric Islanders the solution?
Recently, Airbus revealed three concept designs for zero-emission commercial passenger aircraft which they claim could enter service as soon as 2035. Each design represents a different approach to achieving zero-emission flight, exploring various technology pathways and aerodynamic configurations to support the Company’s ambition of leading the way in terms of decarbonising commercial aviation.
While traditional commercial aircraft manufacturers, such as Airbus and Boeing, see zero emission aircraft as the way forward, a growing number of start-ups are also investing a significant amount of money and resources into overcoming the technical challenges it poses. One of the early pioneers is a California based start-up, Ampaire, who have developed a hybrid electric aircraft, the Ampaire Electric EEL. On its website, the Company claims electric aircraft can result in a 90% reduction in fuel costs, a 50% reduction in maintenance costs, and 0% tailpipe emissions!
Based on a standard twin-engine 4-seat Cessna 337 Skymaster aircraft, Ampaire have replaced the aircraft’s rear engine with a battery-powered electric motor. It is what is known as a ‘parallel hybrid’ configuration in which both the electric motor and internal combustion engine are totally independent of each other. Back in 2019 it was the largest aircraft of its kind to have flown.
A year later, in May 2020, MagniX – a company claiming to be ‘powering the electric aviation revolution’ – and AeroTEC, an independent company focused on aerospace testing, engineering, and certification, announced the MagniX eCaravan had made a successful 30-minute maiden flight.
Image courtesy of MagniX
A MagniX press release described the first flight of the eCaravan – an all-electric version of the Cessna Grand Caravan 208B, – as a ‘significant milestone in disrupting the transportation industry and accelerating the electric aviation revolution’. However, the Seattle Times took a slightly more pragmatic view. ‘The flight does not herald the near-term introduction of all-electric, passenger-carrying Cessnas. The cabin of the plane was obstructed by two tons of lithium-ion batteries and cooling equipment. With little room for passengers, it certainly wasn’t a cabin setup that would make any sense commercially.’
The eCaravan is the second aircraft that MagniX has retrofitted with its Magni500 750SHP electric propulsion system. Working together with the Vancouver-based seaplane operator, Harbour Air, MagniX has been modifying a DHC-2 de Havilland Beaver, which made its first all-electric flight in December 2019.
However, in order to make the 15-minute test flight (with just a 25 minute reserve) it was necessary to fill the cabin of a DHC-2 Beaver with batteries. With just the pilot on board, this took the plane up to its gross weight leaving no room for its normal complement of six passengers. Despite this, the two companies have plans to electrify Harbour Air’s entire fleet of seaplanes.
MagniX, founded in Queensland, Australia in 2009, has poured hundreds of millions of Dollars into developing electric propulsion systems for aircraft. The company is funded by New Zealand-born billionaire Richard Chandler, who is also funding Israeli electric aviation start-up, Eviation.
A plane called ‘Alice’ is Eviation’s entry into the electric aircraft market. It is one of the first of a new generation of aircraft specifically designed for battery powered flight, with 95% of the airframe being constructed from composite materials. However, batteries will account for 60% of the take-off weight.
Designed to carry nine passengers and two crew, Alice is powered by three 260 kW (350 hp) MagniX electric motors – one on each wingtip and one in the tail. It is believed that Eviation has received a significant order from US regional carrier, Cape Air, for 92 aircraft. Delivery is scheduled for 2022 with a price tag of around $US4 million. However, a battery system fire which damaged the prototype early in 2020 may have delayed development of the aircraft.
Image courtesy of Rolls Royce
Meanwhile, in the UK, Rolls Royce are building a high-performance electric aeroplane they claim is unlike anything the world has ever seen. Originally scheduled to fly in 2020, it is hoped the aircraft will reach a speed of 300 mph, making it the fastest all-electric plane in the world. It’s part of a Rolls-Royce initiative called ACCEL – short for “Accelerating the Electrification of Flight” – that’s intended to pioneer a third wave of aviation in support of Rolls-Royce’s strategy to champion electrification.
Accel has the most energy-dense battery pack ever assembled for an aircraft. Each of the three battery packs consist of 6,000 individual Li-ion cells (similar in size to domestic ‘AA’ cells) and weigh 450 kg (excluding the liquid cooling system). The battery packs, which fill much of the fuselage, power three axial electric motors driving a 3-blade propellor. Together, they’ll continuously deliver more than 500 horsepower for the record run.
Energy density is usually defined in terms of the number of watt-hours per kilogram (Wh/kg). Currently, the energy density of lithium-ion batteries is only around 250 Wh/kg, while that of kerosene, is roughly 12,000 Wh/kg. Even taking into account the losses incurred when one converts the energy contained in jet fuel into useful thrust, the energy density advantage of jet fuel is still 6-8 times greater than Lithium-ion batteries.
Currently, Lithium-ion batteries are still the cells of choice for aircraft propulsion because they pack the most power into the lowest mass of any conventional battery. However, Lithium-ion batteries are not expected to reach the 500 Wh/kg – the minimum considered necessary for electric-powered aircraft – until at least 2025. All of which has resulted in a considerable amount of development funding being invested into alternatives, such as Lithium-air (Li/O2) and hydrogen fuel cells.
As mentioned in the introduction, Airbus are developing three concept aircraft – a short-haul turboprop aircraft, a long-range turbofan aircraft, and a radical ‘blended wing’ design. All of these concepts rely on hydrogen as a primary power source – an option which Airbus CEO, Guillaume Faury, believes holds exceptional promise as a clean aviation fuel and is likely to be a solution for aerospace and many other industries to meet their climate-neutral targets – a view an increasing number of people in the aviation industry would agree with.
“I strongly believe that the use of hydrogen – both in synthetic fuels and as a primary power source for commercial aircraft – has the potential to significantly reduce aviation’s climate impact.” Guillaume Faury – Airbus CEO
A Slovenian aircraft manufacturer, Pipistrel, was one of the early pioneers of zero-emission flight when, in September 2016, its twin-fuselage four-seat passenger prototype made its first flight powered by a hydrogen fuel cell propulsion system.
More recently, a start-up called ZeroAvia is focused on developing a hydrogen fuel cell powertrain following a £2.7 million grant from the UK’s Aerospace Technology Institute, as part of the HyFlyer project. In June 2020, having conducted initial flights in California, ZeroAvia conducted the first flight of their hydrogen fuel-cell powered 6-seat Piper M- aircraft from their UK base at Cranfield.
ZeroAvia’s test aircraft – Courtesy of ZeroAvia
The powertrain uses compressed, as opposed to liquid, hydrogen – which feeds a Proton Exchange Membrane (PEM) fuel cell. This converts chemical energy from the hydrogen and ambient oxygen to power an electric motor providing rotational energy for the propeller. As such, hydrogen fuel cells are truly zero emission – the only waste product being water.
ZeroAvia claims the system has a much more promising energy-to-weight ratio than battery powered electric aircraft. Initial flight testing is set to begin shortly, with 300-mile demonstration flights from Cranfield to the Orkney Islands, backed by substantial UK Government funding.
Initially, ZeroAvia plans to target the short-haul 10-20 seat air taxi/parcel delivery market, involving flights of less than 500 miles. To date, ZeroAvia has secured FAA experimental certificates for its air taxi prototypes, passed significant flight tests, and is on track for commercial deliveries by 2023.
Out of interest, ZeroAvia is in partnership with European Marine Energy Centre (EMEC), the organisation behind the innovative Surf ’N’ Turf project, currently on trial in the Orkneys. The system uses surplus renewable energy to power an electrolyser which produces the Hydrogen gas used to power ZeroAvia aircraft – something Alderney, with its strong tidal streams, should be taking a serious interest in if it wants to be one of the pioneers of zero emission aviation,
According to the founder and CEO of ZeroAvia, Val Miftakhov, he conducted market research on potential demand for zero-emission aircraft before building their prototype. ‘We went around and talked to a number of operators, regional airlines mostly, and asked them what would be the type of aircraft and type of mission profile that they would be willing to actually fly once we bring the product to the market’ – which is how ZeroAvia ended up focussing on 19-passenger twin-engine aircraft with 500-mile mission profiles.
With an eye on future developments in terms of sustainable aviation, it is believed that Aurigny have been following the progress of ZeroAvia with interest as one of the 19-seat twin-engine aircraft ZeroAvia is considering modifying for Hydrogen fuel cell power train operation is the Dornier 228.
Finally, there has been considerable local interest in Project Fresson – named after pioneering Scottish aviator Ted Fresson. The project is being led by Cranfield Aerospace Solutions with Rolls Royce participating in the initial effort to design, manufacture and integrate a hybrid-electric powertrain onto a nine-seat Britten-Norman BN-2 Islander. If successful, the next stage will be to look as modifying a larger existing 19-seat sub-regional aircraft type with a view to building a new 19-seat aircraft at some point in the future.
The big problem with an electric Islander is that current battery technology would only give the aircraft around 30 minutes endurance. While sufficient for a 20-minute flight from Alderney to Guernsey, safety regulations require all aircraft to have a minimum reserve of 40 minutes flying time plus the time it would take to reach a diversion airfield.
To overcome this, engineers plan to install a Rolls Royce M250 turboshaft engine (typically used in helicopters) in the tail of the Islander. This would drive a generator which would keep the aircraft’s batteries charged. It’s an interesting concept which could help avoid an aircraft spending time on the ground re-charging batteries. However, as the turboshaft engine will, almost certainly, be using conventional jet fuel (JET A1) it rather brings into question the aircraft’s green credentials.
‘Alice’ – Image courtesy of Eviation
While a hybrid-electric Islander could serve as a useful testbed, zero emission aircraft of the future, such as Eviation’s ‘Alice’, are going to be radically different to today’s 9-seat aircraft. Extensive use will be made of composites and ‘fly by wire’ technology to save weight. It is also likely that such aircraft will be powered by a hydrogen fuel cell power train. Certainly, the level of uncertainty surrounding zero emission aviation at the present time begs the question, ‘is now the time to be making any kind of decisions regarding electric Islanders’? -the answer is ‘probably not!’
© David Earl MMXX