Laying the groundwork for decarbonising aviation

Decarbonising the aviation industry requires a range of disruptive solutions ranging from new fuel types to innovative technologies. And, hybrid-electric propulsion is considered to be one of the solutions to improve the energy efficiency of every aircraft class.

Experts believe hybrid-electric power can reduce aircraft CO2 emissions by up to five per cent and that figure could be as high as 10 per cent for helicopters, generally lighter than fixed-wing aircraft. 

According to the World Economic Forum report, Target True Zero: Unlocking Sustainable Battery and Hydrogen-Powered Flight, by 2035, lithium-ion battery-electric aircraft are expected to have a maximum operating range of approximately 400 kilometres, increasing to 600 kilometres by 2050.

If battery-electric aircraft continue to evolve, electrification could be significant within a global decarbonisation framework. Electric motors combined with other technologies, such as electric propulsion with sustainable aviation fuels (SAFs) or hydrogen can significantly extend the aircraft’s range, the report stated.

How can hybridisation be helpful?

In a hybrid configuration, an aircraft uses several energy sources in flight, either in tandem or alternately. The mix of energy sources, either jet fuel or SAFs combined with electricity, optimises the overall energy efficiency of an aircraft, thereby reducing fuel consumption.

Based on this idea, it is considered that hybrid-electric propulsion leads to better energy management, reducing fuel consumption by up to five per cent compared to a standard flight. The electricity can come from batteries or fuel cells that convert hydrogen into electricity. 

While battery-electric aircraft offer the advantage of zero direct emissions, their potential is currently constrained by the limited energy density of existing battery technology. These systems excel in rail and marine environments, where frequent shifts between low and peak loads are common. 

However, in aviation, their application is primarily limited to urban air mobility (UAM) and regional air mobility (RAM) markets, where shorter flight distances align with current energy storage capabilities.

“All of the necessary technology to bring electric air taxis to market exists today as electric propulsion and battery capacity are now at a point that can support the electrification of flight. We expect product development, manufacturing and usage costs to continue to decrease allowing us to achieve our goal of offering air taxi rides at prices competitive with ground-based ride share,” said Nikhil Goel, Chief Commercial Officer at Archer Aviation Inc. 

Hybridisation plays a key role in aviation’s future

A significant driver for safety, reduced noise and financial efficiency of an electric aircraft, the propulsion systems are literally crucial in helping the industry take-off.

“For these fast-developing markets, Rolls-Royce’s Advanced Air Mobility (AAM) team is developing innovative electrical propulsion systems that need to fulfil the highest demands with respect to performance and weight,” said Matheu Parr, Customer Director, Rolls-Royce Electrical.

Due to rapid urbanisation, the use of highly automated small aircraft to transport passengers and cargo at low altitudes in urban areas is becoming a significant area of interest for new entrants, Parr added. 

Predicting an installed base of around 90,000 eVTOL and 40,000 electric and hybrid-electric commuter aircraft in 2050, Rolls-Royce’s base-case forecast is a bit more conservative – yet it is still foreseeing an exciting future in which new ways of travel and transport will have become a commodity.

Moreover, electrical technology, being cost-efficient, clean and quiet could lead to the reinvigoration of thin-haul air cargo and travel with 9 to 19-seat aircraft over short distances, using wide-spread networks of already existing rural airports that are currently underserved. 

“We’re currently developing one of the first electric powertrains likely to be approved for use by the FAA in a certified aircraft in the US. While this technology will initially power short flights with zero direct emissions, it will serve as a stepping stone to develop more advanced electric and hybrid powertrains for larger aircraft in the future,” said Goel.

The way forward

Decarbonisation will require a combination of technologies and innovations, rather than a single silver bullet. Hybridisation is considered to be a big step in the aerospace sector’s decarbonisation journey and multiple companies are leading a cross-industry effort to make it happen. 

One of them being Archer Aviation who together with the Abu Dhabi Investment Office, aims to bring its Midnight electric vertical take-off and landing (eVOTL) aircraft to market in the UAE in 2026 and then implement a walk, crawl, run progression in terms of how its aircraft operations will scale from there. “We’re taking a careful but efficient approach to bringing our Midnight Aircraft to market,” Goel commented. 

A spokesperson from Joby Aviation also views battery-electric and hydrogen-electric aircraft as a key step towards achieving emissions-free aviation. 

“While we believe our battery-electric air taxi is optimal for shorter range flights up to 100 miles, we also believe that  hydrogen has the potential to enable regional air taxi flights of up to 500 miles. We’re confident that hydrogen-electric and battery-electric technologies will co-exist,” Joby Aviation spokesperson said.

Hybrid-electric aircraft are expected to combine evolutionary efficiency gains with the emissions benefit of electric propulsion. That said, research and development also needs to be complemented by government funding and policy. 

“The US, for example, has refocused minds worldwide with the Inflation Reduction Act, directing nearly $400 billion in federal funding towards clean energy. This will help to mobilise private capital, driving investment into technologies that will help to decarbonise the US economy and have an impact in other countries through exports,” Parr said.