Inside Green Innovation: Progress Report - Fourth Edition highlights:
- The number of patent applications in sustainable aerospace filed each year increased rapidly up to the time of the pandemic (2019/2020) and then fell.
- Highly-regulated regions such as the USA and Europe with established aircraft manufacturers dominate the sustainable aviation sector.
- Current trends suggest a shift from the filing of patent applications for gradual improvements to traditional technologies to more patent applications for disruptive solutions, e.g. based on hydrogen-fuelled technologies.
Aircraft efficiency has increased dramatically over the past two decades. The International Council on Clean Transportation (ICCT) reports that the carbon dioxide emissions per passenger and per kilometre have more than halved since 1990. This is largely due to improvements in aircraft design and layout. Simultaneously, demand for air travel continues to increase at a rate greater than the advances in sustainability, placing pressure on airlines to meet international sustainability goals. In 2022, the 41st International Civil Aviation Organisation (ICAO) Assembly adopted the goal of net-zero carbon emissions by 2050. According to the International Energy Agency (IEA) the aviation industry is not yet on track to meet this goal. Incremental options which have improved aircraft efficiency, such as engine, wing and airframe design, may now be producing diminishing returns. Therefore, there may be a need for further innovation and investment in more radical solutions in the coming years to achieve net zero.
Innovation in green aerospace
Conventionally, aircraft have been made more efficient by improvements in design, e.g. introducing lighter materials, improving aerodynamics and optimising airframes. The operation of aircraft has also been improved, e.g. by optimising routes. We can already observe the environmental benefits of such improvements in new generation aircraft which are gradually replacing existing fleets. Improvements such as introducing new fuel types and propulsion technologies are more radical and have therefore been developed more slowly – perhaps reflecting the necessary caution about safety which surrounds changes in aircraft design. Additionally, new fuel types require changes to the aircraft itself and also to refuelling infrastructure at airports. Another issue is that the most promising alternative fuels (e.g. sustainable aviation fuel and hydrogen) are still many times more costly than traditional jet fuel. Nevertheless, major aircraft manufacturers have unveiled bold plans to invest in new aircraft with alternative methods of propulsion. Airbus has recently announced its vision to manufacture a hydrogen fuel cell engine for its future hydrogen-powered aircraft. Rolls-Royce and Tata Consulting Services are researching hydrogen fuel systems technology and Universal Hydrogen has been testing a hybrid airplane comprising a jet fuel engine on one side and hydrogen fuel cells on the other. In our section on hydrogen power, we show that companies such as Airbus are rapidly protecting their hydrogen storage technology, bringing them closer to making their hydrogen-powered aircraft a reality. In this report, we will look at the overall trends in patent filings in sustainable aviation and will investigate whether the associated data reflects a shift from gradual optimisation to more disruptive technologies. The following graph shows the annual number of priority patent filings globally related to sustainable aviation. This covers all aspects of aircraft design and operation intended to reduce greenhouse gas emissions, including improvements in energy efficiency. Patent filings for relevant upstream processes, e.g. developing and manufacturing fuels, or fuel storage and distribution infrastructure outside of the aircraft itself, have not been included in the data.
Figure 1: Thirty-year trend (1993-2022) - global priority filings - green aviation
(Priority filing = the first time a patent application for a unique invention has been filed (the first filing))
Annual patent filings for green aviation have generally increased from the 1990s up to 2019, the year preceding the pandemic. This approximately follows the increase in demand for flights in this period, with filings dropping almost in tandem with drops in the amount of air traffic.
Figure 2: Thirty-year trend (1993-2022) - annual air passenger air traffic
Data sources: https://data.worldbank.org/indicator/IS.AIR.PSGR https://www.icao.int/sustainability/WorldofAirTransport/Documents/ARC_2022_Tables_final_12032024.pdf)
Comparing the above figures, while the increase in air traffic between 2010 and 2019 follows a very gentle upward curve, the increase in patent filings in the same period is steeper. This suggests that high air traffic may not be the only factor encouraging patent filing activity. The rise in the number of patent filings in the late 2010s were probably encouraged both by increased revenues from higher demand and also by the increased inclusion of aviation in regulatory programmes which had previously covered only other types of transport, e.g. the introduction of the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) in 2016.
In 2020, global patent filings began to drop rapidly to the level of the mid-2010s. This was related to the Covid-19 pandemic’s reduced demand for air travel. As demand for air travel climbs back to pre-pandemic levels and revenues along the aircraft supply chain rise, more budget could be allocated to developing technologies which can future-proof the industry, especially in view of increasing regulation. The dip in patent filings could prove temporary as further patents are filed to protect more sustainable technologies.
Filings by territory
The highest number of new patent filings related to innovation in green aviation come from the USA, followed by Europe. Russia, Japan and South Korea also produced a significant number of filings, albeit at much more modest volumes. Despite its significant contribution to global air traffic (see Figure 4 below), China is not one of the top filers.
Figure 3: Twenty-year trend (2003-2022) – priority applications by territory - green aviation
Figure 4: Passenger volume by country in 2019
Data source: Air passengers, 1970 to 2021 (ourworldindata.org)
The high number of filings coming from the USA and Europe may be explained by the fact that, of the top ten aerospace companies by revenue according to FlightGlobal, nine are headquartered in the USA or Europe. The other of the top ten aerospace companies is Russian. The aircraft manufacture industry is also strongly dominated by only a few major companies. According to a report by Simple Flying, the domination of the aircraft industry by only a small number of manufacturers is due to the high cost barriers which prevent new players entering this industry. Airlines from around the world therefore source their fleet from only a few companies, mainly based in the USA and Europe (e.g. Airbus and Boeing). The positions of these companies in the market are further strengthened by their patent portfolios. Nevertheless, China’s state-owned Commercial Aircraft Corporation of China (Comac) has recently pumped billions of dollars into developing its new passenger jet, the C919. Comac holds over 2,500 patents and patent applications (compared to 14,605 by Boeing and 12,337 by Airbus). Now, very few of these (four in total) are related to sustainable aviation. This could soon change if Comac establishes itself in the aircraft market and raises the necessary funds for sustainability-related R&D projects. The reason for the comparatively low number of patent filings from China in sustainable aviation may be regulatory. As of 2024, China was not yet a member of the CORSIA scheme while all EU countries, Japan and South Korea were. China is due to join the scheme, which aims to cap air travel at pre-pandemic levels, in 2027. China is also introducing its own more modest emissions trading scheme next year. The pressure to reduce carbon emissions in China is therefore still lower than in the USA, Europe, Japan and South Korea, but this could shift in the future. It is therefore possible that patent filings in China will begin to catch up with other major players in the coming years and decades, potentially excluding American and European firms from areas of development.
Filings by assignee
Figure 5: Fifteen-year trend (2008-2022) – top filers – green aviation
Today, the top filer in sustainable aviation is Rolls Royce, whose patent filings surged massively around 2019 before dipping during the pandemic years but are now rising. Rolls Royce manufactures the engines of various well-known aircraft, including the Airbus A330, A340, A350, A380 and Boeing 777 and 787. The company began checking the compatibility of its engines with 100 percent sustainable aviation fuel (SAF) earlier than others and could confirm in 2021 that all aircraft engines still in production by Rolls Royce were fully compatible with SAF. Rolls Royce now benefits from EUR 700m of EU funding for green aviation projects, suggesting that patent filings in this area will continue to rise. Filings by General Electric experienced a dip shortly before the pandemic but now are also climbing. These appear to address engine improvements and fuel supply systems, with a recent focus on hydrogen power. The number of filings by Boeing peaked around 2020 before dropping in 2021 and 2022. During the same period Boeing purchased significant amounts of sustainable aviation fuel (SAF) from renewable sources and committed to delivering commercial airplanes certified to fly on 100 percent SAF by 2030. An analysis of the most recent patent filings by Boeing Co. shows that some of these relate to the cryogenic storage of fuel, hybrid electric fuel cell engines and monitoring of emissions data, suggesting that investment in sustainability is part of the company’s long-term plan.
Filings by sector
Looking more closely at the IPC sub-classes (defining the technology sector) where we find the greatest number of patent filings over the past twenty years, the propulsion systems of aircraft are the focus of innovation.
Figure 6: Twenty-year view (2003-2022) – filings by technology sector
Figure 6 key:
- B64D: Equipment for fitting in or to aircraft; flight suits; parachutes; arrangement or mounting of power plants or propulsion transmissions in aircraft
- B64C: Aeroplanes; helicopters
- F02C: Gas-turbine plants; air intakes for jet-propulsion plants; controlling fuel supply in air-breathing jet-propulsion plants
- F01D: Non-positive displacement machines or engines, e.g. steam turbines
- F02K: Jet-propulsion plants
The most frequently occurring IPC subclass (technology sector) since 2017 has been B64D which covers the arrangement or mounting of power plants or propulsion transmissions in aircraft. Despite the drop in priority filings overall since the pandemic, the number of patent families within this subclass have only continued to increase. The rise in patent families in the IPC subclass B64D may indicate a trend towards integrating new propulsion systems into known aircraft bodies, rather than improvements in the operation and control of well-established technologies. Below we highlight four more specific subgroups (specific technologies) within IPC subclass B64D in which patent activity appears to be increasing.
Figure 7: Twenty year trend (2003-2022) - number of inventions - by specific technology
- B64D27/24 (Aircraft characterised by the type or position of power plants)
There was a significant increase in patent families in the subgroup B64D27/24 (aircraft characterised by the type or position of power plants) which appeared twice as frequently in 2022 (253) as in 2019 (126). These applications related most frequently to fuel cell systems. Beta Air LLC (which manufactures small electric aircraft for moving cargo), Joby Aero Inc. (which is developing electrical air taxis) and Alaka’i Technologies (developing hydrogen powered eVTOLs) were among the top filers. For now, at least, innovation in this subgroup comes from a diverse group of applicants.
2. B64D41/00 (Power installations for auxiliary purposes)
A review of recent patent filings within this subgroup revealed their connection to improved power systems for performing diverse functions such as starting engines, carrying out ground operations, air conditioning on an aircraft, providing emergency power and harnessing wind to provide additional energy to the aircraft.
Many of the patent applications related to hybrid aircraft optimised for improved fuel efficiency. For example, US2023/382552A1 by General Electric describes a method for reconfiguring a fuel cell assembly on an aircraft based on predicted electrical load data, e.g. by adding or removing fuel cell modules.
3. B64D27/10 (Aircraft characterised by the type or position of power plants of gas-turbine type)
This subgroup relates primarily to improvements in traditional jet engines, in particular by combining them with alternative power sources, most commonly an electrical power source. This subgroup is strongly dominated by filings from General Electric.
Some filings describe aircraft comprising a combustion engine and a fuel cell assembly, wherein a fuel cell parameter is used to prevent engine stalling (e.g. US2023/278714A1 General Electric). Other applications describe improved propulsion techniques to reduce contrails, which are also an important contributor to global warming. For example, US2023/279808A1 by Rolls Royce PLC describes an aircraft having two engines, each connected to an electrical machine – either to generate electrical power from an engine or to electrically drive an engine. A controller varies the proportion of the aircraft propulsion provided by the engines and the proportion provided by the relevant electrical machine to manage the formation of contrails.
4. B64D37/30 (Aircraft fuel systems for specific fuels)
Of the subgroups set out above, fuel systems for specific fuels showed the most exponential increase in priority filings in recent years. A keyword analysis of patent filings within this IPC subgroup show that these relate mainly to the use of cryogenic fuel, in particular liquid hydrogen, and fuel cells in aviation. Filings in this subgroup did not slow during the pandemic but continued to rise, dropping only slightly in 2022.
Figure 8: Ten year trend (2013-2022) - top filers - fuel systems for specific fuels
Taking a closer look at the top filers in this specific subclass over the past ten years, the filing trends are less dominated by traditional aerospace companies. Instead, various new entities such as Jetzero Inc. (est. 2021) and Zeroavia Inc. (est. 2017) also appear to have a foothold on IP in this area.
Figure 9: Twenty year overview (2003-2022) - patent filings - by technical field
Overall, about two-thirds of patent filings for sustainable aviation in the past 20 years have been in the field of mechanical engineering. Innovation relating to the mechanical design of aircraft, e.g. the propulsion system design, has therefore dominated over improvements to control systems and instrumentation. This small case study suggests there may be pockets of technological areas where innovation in sustainable aviation is still taking off and may continue to grow in the coming years. Possibly, large manufacturers are more focused on hybrid technologies, whereas start-ups are playing a greater role in more radical innovation. Given the recent growth in filings related to alternative fuels and alternative propulsion systems, as well as the increasing regulation and incentives to reduce greenhouse gas emissions, it is likely that patent filings in the coming years will increasingly seek to protect radical changes to aircraft design and operation.
Implications for innovation and future patent filings
While efficiencies related to incremental improvements in aircraft may be tailing off, there is vibrant innovation in disruptive sustainability solutions, e.g. aircraft adapted to use of sustainable aviation fuel, hydrogen fuel cells and hydrogen combustion, either alone or combined with traditional jet fuel. As regulatory forces have only recently begun to affect aviation in developed countries, it is likely that patent filings in many previously “quiet” areas may grow quickly in the coming years as businesses work to achieve their sustainability goals.
Adam Tindall
Partner
Alia Tayer
European Patent Attorney