The Extinction Rebellion protests in London have finally died down, after several weeks of aggravation and disruption to City commuters making their way to work, protestors gluing themselves to overground trains and grinding traffic on Waterloo Bridge and at Oxford Circus to a halt. Their execution was annoying, but they had a point. Serious remedial action needs to be taken within the next 12 years, or humans will have taken our fragile environmental state one step too far away from recovery. The automotive, rail and shipping industries have already put electrification and environmentally conscious fuel-saving on the menu. Why then has the aviation industry, known to be a development trailblazer, not yet been able to make hybridisation more readily available in the commercial aviation space?
It may well be a question of scale. Batteries used for electric cars are fairly small and therefore easier to manufacture. Overall, battery packs are heavier than their combustion engine counterparts. Aircraft-grade batteries are weighing in between 2 and 3 metric tons (that’s Range Rover heavy). This means that aircraft manufacturers will need smarter materials to reduce some weight to compensate for those heavy batteries and their cooling systems.
Speaking of cooling, batteries get hot – really hot. Constantly operating a motor to spin a turbine produces excess heat, which would have to be cooled by water pumps. Also, there has been very little in the way of testing how batteries perform at the kind of high altitudes relevant to the commercial aviation space. When you are up at 35,000 feet, the air temperature drops to about -51⁰C.
What about power then? The power, thrust and turbine pressure required to lift a plane off the ground requires fast-paced fuel input. It is possible to achieve the same result with electric propulsion. Can the battery technology in existence at the moment keep up with the power output required? Possibly. But engineering experts say that electricity is not the holy grail. While electric power is good for take-off as it helps to produce high output thrust, it is not so good for cruising at 35,000 feet.
Fundamentally though, there needs to be supply and demand. The big manufacturers have prioritized burning kerosene more efficiently (presumably because the R&D is cheaper), rather than investing hundreds of millions of dollars into developing electric systems. (The average Airbus A320 manages only 77 miles per gallon per seat – not great MPG for a long-distance flight of several thousand miles).
On the other side of the coin, the airlines may have not yet demanded electric systems – perhaps out of caution, or perhaps out of comfort with the current system.
Tesla and Rimac, among others, have used their technological advances to make battery packs smaller, more efficient and more powerful, to generate high horsepower output for instant torque, but also to create more practical ranges to allow for long-distance driving on one charge. It is a question of being able to scale up this technology to power an aircraft. Although the aviation industry is often a technology leader, in the world of electrification, aircraft manufacturers and service providers have fallen behind the curve.
A team of engineers at Rolls-Royce’s Hybrid Electric Propulsion group, however, have aspirations for the future of aviation, which they are taking large strides toward achieving. The visions are grander than merely making aircraft with multiple electrically-driven propulsors. They envision wings that can lengthen and shorten electronically between take-off and high altitude cruising; noise controls when flying over busy cities; and enhanced propulsion to allow for take-off from short runways at local airports and smaller airfields.
It is not all just PR talk and fantasy. Rolls-Royce has teamed up with Airbus and Siemens to create a prototype hybridized aircraft (called E-Fan X), powered by three traditional kerosene-powered engines and a fourth fully electric engine producing 2MW of power. For some context, a Toyota Prius can output 68kW in electric mode, meaning the Rolls-Royce behemoth produces the equivalent of 29.4 Pri-ay (which I can only assume is the plural of ‘Prius’). The goal right now is to get commercial jets with “electricity plus fossil fuel” hybrid power to complete short-haul journeys (under 1,000 miles) in the next 7-10 years. EasyJet is also working with a start-up called Wright Electric to get a 120-passenger electric aircraft into the skies by 2027.
So in the infamous words of Jerry Maguire, “Show me the money.” The big players in the aviation industry have deep pockets, but their shareholders will not be best pleased if profits are all dissipated on R&D. A number of venture capitalists and hedge funds in Silicon Valley and across Europe can cut the cheques, as they know the manufacturers that master ecological innovation first will get the lion’s share of the newbuild market. The industry is quickly moving toward hybrid-electric supplementation.
The race for electrification of the aircraft has birthed a number of start-ups, into an industry which has traditionally crushed smaller companies that cannot keep up with the financial demands of operating in the aviation space. But with the accessibility of private equity funding, and the drive for Silicon Valley technology whizz-kids to break the mould of an industry with hundreds of years of history, maybe these start-ups are the “knights in shining armour” that we need.
In a world where jet fuel prices have risen exponentially, individuals are more conscious of their environmental impact, and there is a universal desire to get CO2 and NOx emissions down and meet our global climate change goals, we need to make some changes. Air travel emissions are increasing by 4.5-6% per year, and with over 1,800 new aircraft deliveries per year (between the big manufacturers alone), the industry needs to do something about it. We should embrace hybridization with open arms.