Air transport
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Improving fuel efficiency on the ground and in the air is the easiest way to save energy and reduce greenhouse gas emissions in the aviation industry.
Aircraft weight
There are several ways to make aircraft lighter and improve their fuel efficiency, such as:
- ensuring the right amount of extra fuel is carried for each flight
- fitting carbon brakes
- redesigning for lighter engines, fittings and composite-fibre component.
New data analytics techniques make more accurate predictions of fuel requirements, helping to avoid the weight and waste of excess reserve fuel.
Combining multiple small weight reductions can add up to significant savings. There might also be other benefits. For example, using electronic flight bags (EFBs) on a tablet instead of paper flight manuals saves around 16kg per aircraft. Tablets are also searchable and can be instantly updated, which eliminates paper and printing costs. The Civil Aviation Safety Authority has rules around using EFBs in Australia.
Lightweight seating can also save hundreds of kilograms of weight meaning significant potential fuel savings.
Aircraft loads
The way an aircraft is loaded can significantly affect the fuel efficiency of a flight. If the load is not balanced, the pilot will need to trim the aircraft continually throughout the flight to compensate. Operating an aircraft in trim mode uses more fuel.
Flight logistics
Technology allows flight path optimisation in real time in response to changing weather patterns. In-flight re-routing can save a lot of fuel on international long-haul flights, where upper-level winds and jet streams can change quickly.
Flying at higher altitudes can also reduce drag and increase fuel efficiency.
Electrical energy efficiency
Although it may not show as a direct cost, electrical efficiency in aircraft can bring substantial savings across a fleet.
Electricity used in-flight, such as for data, lighting, audio and TV systems, can be made more energy-efficient and cost-effective.
Aircraft are usually powered by an auxiliary power unit, which tends to use a relatively inefficient gas turbine run on expensive jet fuel. More energy-efficient auxiliary power units are available, but they do have substantial up-front costs.
When aircraft are docked, it can be preferable to source electricity from the airport than from the plane’s own power unit.
Descent paths, scheduling and taxiing aircraft
Jet airliners have usually approached a runway by ‘stepping down’ rather than making a smooth, steady descent. So, at each step, the pilots adjust engine thrust, which uses more fuel. New technology means airlines can work with air traffic control for a much smoother descent, thereby improving fuel efficiency.
Airlines can also work with air traffic control to reduce fuel use while in holding patterns. Adjusting the flight times so aircraft have shorter holding periods can also save fuel.
You can also save fuel by using one engine to taxi the aircraft. Electrical taxi systems can save even more fuel by using the aircraft’s auxiliary electrical power so that the main engines can remain off until immediately before take-off.
Aerodynamics
The two main sources of drag for aircraft are skin-friction drag and lift-induced drag. For a typical long-range flight at cruise conditions, these make up approximately 50% and 33% of the total drag, respectively.
Reducing aircraft drag can result in significant fuel savings. The following are shown to have the largest effects:
- riblets
- large eddy break-up devices
- hybrid laminar flow technology
- innovative wing-tip devices
- trailing-edge optimisation
- control of the shock boundary layer interaction and of the boundary layer separation. For example, special aerodynamic coatings can be applied to the nose cone and other key regions of the craft.
New engines and aircraft
Investing in lighter, more efficient engines will improve fuel efficiency. You can purchase aircraft engines that are up to 15% more fuel efficient than what was available 15 years ago. Similarly, upgrading airline fleets to more efficiently designed aircraft can bring significant fuel savings.
Technologies required for significant engine weight reductions include:
- improved materials, especially composites
- improved aerodynamics, to reduce the number of turbine and compressor stages
- increased turbine entry temperatures, to reduce airflow and core engine size needed to produce power.
Combining these measures can result in huge energy efficiency gains in the short and long terms.
Jet streams
Using jet streams is vital in aviation, as they can save flight time and fuel. In Australia, flights from west to east can take advantage of tailwind jet streams, while flights in the opposite direction need to avoid the jet stream as much as possible.
Airlines can improve fuel efficiency for international flights by forecasting jet streams better. New technology is also available to help pilots avoid clear air turbulence, which improves fuel efficiency and passenger safety.
Sustainable aviation fuels
Sustainable aviation fuels (SAF) can have substantially lower lifecycle emissions than standard jet fuel.
SAF is produced from sustainable feedstocks. It is chemically very similar to traditional fossil jet fuel and can be used in traditional jet engines without modifying them.
Depending on the feedstocks, production methods and supply chains used, SAF offers an approximately 20% to 90% reduction in lifecycle emissions compared to traditional jet fuel.
SAF blends are certified to meet safety, technical and quality standards for the aviation industry.
Ground operations
Ground operations could take advantage of electric options for equipment such as aircraft tugs and baggage and cargo transportation. Upgrading this equipment will increase efficiency, reduce pollution and reduce the overall cost of company operations.
Innovations
Hybrid electric planes
Until fully electric planes become capable of longer flights, hybrid planes are an interim solution. High-energy liquid fuels can be used for take-off, when most of the energy is required, and batteries used for cruising.
To read more, see the Advanced Science News website.
Biofuel trial flights
In 2018, Qantas operated the world's first dedicated biofuel flight between the US and Australia. The 15-hour Melbourne to Los Angeles flight used 24,000 litres of blended biofuel (50%) derived from mustard seed oil, abating 18 tonnes of carbon emissions.
Qantas has purchased blended biofuel derived mainly from used cooking oil, helping to reduce its carbon emissions by around 10% for its flights from London. This marks the first time an Australian airline will purchase biofuel for regular scheduled services.
Hydrogen-powered planes
Hydrogen propulsion shows some promise for use in:
- medium-haul commercial flights for which battery powered aircraft are not suitable
- longer domestic routes with small passenger loads that may not be viable with large aircraft
- general aviation such as private and recreational flying, instruction, and aerial work (agriculture, surveying, photography).
Small hydrogen powered aircraft may also be well suited to regional aviation. After 2050, liquid hydrogen combustion may help decarbonise long haul domestic flights, though further testing is required to demonstrate the feasibility of this technology.
Hydrogen could also play an increasing role as a feedstock for production of synthetic SAF, but this technology is at an early stage.
Read more
Maximising aviation’s contribution to net zero
Clean energy and infrastructure: Pathway to airport sustainability (PDF 5.4MB) Clean Energy Finance Corporation (CEFC)
Aviation biofuels Qantas
Fuel efficiency Qantas
Technology Roadmap International Air Transport Association
Aviation – tracking clean energy progress International Energy Agency
