Airbus partners with Siemens and Rolls-Royce to compete in the electric air race
Energy Digital takes a look at the race to deliver the first commercial electric aircraft. Mark Cousin, SVP Flight Demonstrators CTO at Airbus, talks about the company’s collaboration with Rolls-Royce and Siemens.
The great electric air race is underway. European aviation heavyweight Airbus is collaborating with Rolls-Royce and Siemens, while budget airline easyJet has teamed up with California’s Wright Electric, with both partnerships targeting the introduction of electric energy storage.
Analysts agree the probability of purely electric shorthaul airliners in the next decade is realistic, but these will be relatively small aircraft carrying 15-20 passengers. Energy storage capacity will be too low to fly a full journey on a 100% electric flight, so we won’t see 100-passenger aircraft flying from London to Amsterdam in 10 years’ time. The airlines involved in this endeavour are starting to ask whether their future fleet will still consist of large 100-plus seat aircraft, or if they’ll have a fleet of smaller aircraft flying shorter routes on full electric.
“We could see a proliferation of smaller aircraft flying out of the less congested airports on relatively short one-hour routes,” suggest Mark Cousin, SVP Flight Demonstrators CTO at Airbus. “This would change the dynamics of air transport and pave the way for autonomous aircraft with no pilot on board, resulting in aviation costs falling dramatically, while maintenance for an electric aircraft will be much cheaper than for one powered by gas turbines.”
Cousin is at the forefront of the Airbus Demonstrators initiative. The programme’s goal is to set an objective not achievable with today’s technologies to force the development of innovations – in this case, the future of hybrid electric propulsion. “In the next couple of years, we’ll see three major demonstrators,” reveals Cousin. “The first is being developed by our colleagues in Silicon Valley – Vahana is a tilt wing single person urban air mobility vehicle. By the end of 2018 we expect the first flight of the City Airbus, a proof of concept of a four-seater air taxi. And we’re also due to announce the successor to our E-Fan, the E-Fan X. The only way we can learn what the issues will be, and how we can overcome them to improve our product, is by flying and testing.”
Cousin identifies four key challenges Airbus has chosen to focus on…
Energy Storage Density
“Improvement in the power-to-weight ratio, or energy storage density, of batteries is required. Even when we take into account the favourable efficiency difference of electric motors versus gas turbines, the conversion of energy from kerosene to thrust is 50 times as high as the conversion we see with energy storage systems. That is going to limit how much energy you can carry and how far you can fly.”
“The weight of hardware with new electric propulsion systems will be greater than traditional aircraft with electric motors and power electronics in the system adding to the payload. A hybrid electric aircraft will be heavier so improvements will be needed to boost overall efficiency when compared with today’s traditional aircraft.”
“We’re running a 2MW motor directly powering a turbo fan which will generate thrust, so in order to achieve efficiency in the megawatt class, you need to transmit the power at a very high voltage. We’ll be transmitting power around the E-Fan X at 3,000 volts DC, yet the highest voltage on aircrafts flying today is 230 volts – it’s a big step. The challenge at 3,000 volts is what we call partial discharge. You get a corona effect. Unless you put massive amounts of insulation around the cables, there is currant leakage from the transmission line to any conducting elements. At sea level in trains and boats it’s not a big issue because air can be a good insulator, but at altitude the air is much thinner and that effect is less powerful. We need to establish the right levels of insulation on the wiring and the separations between cables and structure to control this difficult phenomenon.”
“Today, high-powered electric motors are around 96% efficient, which means the other 4% is coming out as heat. We need to get those losses down to less than 1% in the motor and transmission systems. All of these elements need to be addressed or the hybrid system will be less attractive compared to a traditional gas turbine because you can’t waste the energy you store and transmit.”
Tesla CEO Elon Musk states that once batteries are capable of producing 400 Watt-hours per kilogram, the potential for energy density to beat the weight problem and deliver pure electric transcontinental flight becomes ‘compelling’. Currently, it would be impossible to fly from London to Singapore with pure electric power because an aircraft would have to carry too much weight in battery to have any room for passengers. Until that goal is reached, Cousin believes larger, longer range aircraft will follow a hybrid model. “Initially we’ll see a large generator (2MW) installed between the thrust-producing fan and the gas turbine, and that motor/generator will be used throughout flight to either inject or extract power depending on the phase of flight you’re in,” he predicts.
When taxiing along the runaway, planes could operate purely electrically and during take-off would use the energy storage as back up. Then, if an engine failed during ascent, power could be injected into the other good engine to boost its thrust-producing capability. Gains could also be made at the top of a climb to deliver extra thrust to reach cruise altitude.
“We’re seeing efficiencies of over 50% which is as good as the best diesel engines,” adds Cousin. “However, they are horribly inefficient when they’re operating in off-design points. For example, in descent when you’re idling the engine so it’s ready to give power within eight seconds if the pilot pushes the throttles forward – it’s burning a lot of fuel to produce almost no thrust. We would hope to see the engine operated largely electrically in these types of descent phases, putting very little fuel into the engine, but still keeping it at a speed to deliver thrust via injection if needed. Big savings could come from that, especially on short range operations where a large portion of the flight is in descent (London to Paris would be 30%). In the first iteration aircraft will become hybridised.”
The hybrid model with electric energy storage could fill the gaps to allow a gas turbine to run at continual peak efficiency. It’s the sort of combination found in big ships, and even trains. The thermal engine will run at certain points in the journey, generating power at its peak efficiency. Once the power requirement drops, or the energy storage is full, the engine is shut down and the vehicle runs electrically, then when the battery’s down, the engine will start again. “It’s what you’re seeing with hybrid cars today,” notes Cousin. “Running the engine at peak efficiency then shutting it down to run electrically when the thermal efficiency of the engine would be low. For aircraft, it’s not a question of if, but when.”
Indeed, when Energy Digital spoke with Honeywell’s Mike Stewart, Aerospace VP for Advanced Tech, he confirmed Cousin’s vision: “Hybrid propulsion is already being supported by Honeywell with its 1MW generator. In fact, three 1MW generators are being used on Aurora’s LightningStrike demonstrator to exhibit the capabilities of hybrid-electric propulsion for vertical take-off and landing.
“The most recent solar power plant to go online in the UAE is generating electricity at three cents per kwh, which is half of what you can achieve today by burning natural gas and a quarter of what we see from suppliers of nuclear power,” says Cousin. “If that trend of lower costs continues, you can see this form of transport becoming even cheaper. The big advantage is that it’s very light on infrastructure. That might not make a difference in the UK, which has substantial rail networks, but there is a belief amongst many of the players that in markets where the rail and road infrastructure do not exist, this approach could be a more efficient way of putting in place mass transport.”
With electric aircraft, the only requirement would be the building of relatively small aerodromes at either end of the journey corridor. “Electric vehicles, by the nature of having very few moving parts, will be cheaper to maintain,” argues Cousins.
Energy Digital also heard from Cyient’s Anand Parameswaran, Senior VP Aerospace & Defence, who noted “increasing pressure from the European Union to cut aviation pollution” as a factor in the likely acceleration of the adoption of new tech. “An effective hybrid solution would cut noise pollution as well as CO2, while airlines could slash one of their biggest and most unpredictable running costs in jet fuel, thus areas of focus for 2018 hybrid development are reducing the weight of batteries and the cooling equipment they require.”
The Airbus collaboration boasts the involvement of Siemens, one of the market leaders in terms of the design and manufacture of large electric motors and power transmission systems. In 2016, it flew the largest lightweight electric motor to date – a 260kw motor on an aerobatic Extra 330LE plane. “We’re drawing on their expertise of lightweight high efficiency electric motors,” maintains Cousin. “We’re also leveraging the expertise of Rolls-Royce in the provision of highly efficient gas turbines for aviation, seafaring vessels and power plants where they operate in a mode of fixed power and peak efficiency. Airbus brings the knowledge on how to integrate these technologies into the airplane.
“Building is relatively easy. For example, in the air mobility, air taxi market we’re seeing more than 50 companies working on concepts, but I don’t believe any more than a handful of these will ever succeed in certifying vehicles as safe for flight in the urban environment.”
UK must stop blundering into high carbon choices warns CCC
The UK Government must end a year of climate contradictions and stop blundering on high carbon choices, according to the Climate Change Committee as it released 200 policy recommendations in a progress to Parliament update.
While the rigour of the Climate Change Act helped bring COP26 to the UK, it is not enough for Ministers to point to the Glasgow summit and hope that this will carry the day with the public, the Committee warns. Leadership is required, detail on the steps the UK will take in the coming years, clarity on tax changes and public spending commitments, as well as active engagement with people and businesses across the country.
"It it is hard to discern any comprehensive strategy in the climate plans we have seen in the last 12 months. There are gaps and ambiguities. Climate resilience remains a second-order issue, if it is considered at all. We continue to blunder into high-carbon choices. Our Planning system and other fundamental structures have not been recast to meet our legal and international climate commitments," the update states. "Our message to Government is simple: act quickly – be bold and decisive."
The UK’s record to date is strong in parts, but it has fallen behind on adapting to the changing climate and not yet provided a coherent plan to reduce emissions in the critical decade ahead, according to the Committee.
- Statutory framework for climate The UK has a strong climate framework under the Climate Change Act (2008), with legally-binding emissions targets, a process to integrate climate risks into policy, and a central role for independent evidence-based advice and monitoring. This model has inspired similarclimate legislation across the world.
- Emissions targets The UK has adopted ambitious territorial emissions targets aligned to the Paris Agreement: the Sixth Carbon Budget requires an emissions reduction of 63% from 2019 to 2035, on the way to Net Zero by 2050. These are comprehensive targets covering all greenhouse gases and all sectors, including international aviation and shipping.
- Emissions reduction The UK has a leading record in reducing its own emissions: down by 40% from 1990 to 2019, the largest reduction in the G20, while growing the economy (GDP increased by 78% from 1990 to 2019). The rate of reductions since 2012 (of around 20 MtCO2e annually) is comparable to that needed in the future.
- Climate Risk and Adaptation The UK has undertaken three comprehensive assessments of the climate risks it faces, and the Government has published plans for adapting to those risks. There have been some actions in response, notably in tackling flooding and water scarcity, but overall progress in planning and delivering adaptation is not keeping up with increasing risk. The UK is less prepared for the changing climate now than it was when the previous risk assessment was published five years ago.
- Climate finance The UK has been a strong contributor to international climate finance, having recently doubled its commitment to £11.6 billion in aggregate over 2021/22 to 2025/26. This spend is split between support for cutting emissions and support for adaptation, which is important given significant underfunding of adaptation globally. However, recent cuts to the UK’s overseas aid are undermining these commitments.
In a separate comment, it said the Prime Minister’s Ten-Point Plan was an important statement of ambition, but it has yet to be backed with firm policies.
Baroness Brown, Chair of the Adaptation Committee said: “The UK is leading in diagnosis but lagging in policy and action. This cannot be put off further. We cannot deliver Net Zero without serious action on adaptation. We need action now, followed by a National Adaptation Programme that must be more ambitious; more comprehensive; and better focussed on implementation than its predecessors, to improve national resilience to climate change.”
Priority recommendations for 2021 include setting out capacity and usage requirements for Energy from Waste consistent with plans to improve recycling and waste prevention, and issue guidance to align local authority waste contracts and planning policy to these targets; develop (with DIT) the option of applying either border carbon tariffs or minimum standards to imports of selected embedded-emission-intense industrial and agricultural products and fuels; and implement a public engagement programme about national adaptation objectives, acceptable levels of risk, desired resilience standards, how to address inequalities, and responsibilities across society.
Drax Group CEO Will Gardiner said the report is another reminder that if the UK is to meet its ambitious climate targets there is an urgent need to scale up bioenergy with carbon capture and storage (BECCS).
"As the world’s leading generator and supplier of sustainable bioenergy there is no better place to deliver BECCS at scale than at Drax in the UK. We are ready to invest in and deliver this world-leading green technology, which would support clean growth in the north of England, create tens of thousands of jobs and put the UK at the forefront of combatting climate change."
Drax Group is kickstarting the planning process to build a new underground pumped hydro storage power station – more than doubling the electricity generating capacity at its iconic Cruachan facility in Scotland. The 600MW power station will be located inside Ben Cruachan – Argyll’s highest mountain – and increase the site’s total capacity to 1.04GW (click here).
Lockdown measures led to a record decrease in UK emissions in 2020 of 13% from the previous year. The largest falls were in aviation (-60%), shipping (-24%) and surface transport (-18%). While some of this change could persist (e.g. business travellers accounted for 15-25% of UK air passengers before the pandemic), much is already rebounding with HGV and van travel back to pre-pandemic levels, while car use, which at one point was down by two-thirds, only 20% below pre-pandemic levels.