Air transport required to clean its acts

Air transport gets more energy efficient as it comes under scrutiny for its environmental impact

By Morand Fachot

Transportation is a major source of emissions of greenhouse gases (GHG); air transport is a contributor and efforts have been under way to cut emissions from the sector for many years. These are not limited to cutting down emissions from aircraft alone, but include also limiting the environmental impact from airports, and all associated support services and installations. IEC standardization work contributes significantly to this development.

Mototok electric tow truck Mototok remote-controlled electric tow truck in operation (Photo: Mototok)

Leaner aircraft are good but not enough

Air transport is the world’s second largest consumer of fuel for personal mobility (11% of the total modes of transport) after light-duty road vehicles (44%). However, it uses less fuel than modes of transport for freight, such as trucks (23%) or marine vessels (12%), according to estimates from the US Information Energy Administration (EIA). 

Fuel consumption per seat and per km of passenger aircraft has improved constantly and significantly, with the latest generation of passenger aircraft using about a quarter of the fuel per seat and per kilometre compared to the first generation, thanks to better overall design and more fuel-efficient engines.

However, according to the International Civil Aviation Organization (ICAO), aviation still contribute to approximately 2% of the global GHG emissions, and the amount of CO2 emissions from aviation is expected to grow around 3-4 percent per year. This overall increase results from the robust growth of the sector in general, even as aircraft become more fuel efficient.

Getting down to earth

One area that can contribute significantly to mitigate the negative environmental impact of air transport is to be found on the ground.

It concerns the operation of airports and all associated services ranging from aircraft ground operations and services, to airport installations, to the management of the flow of passengers and freight to and from the airport. 

ICAO and other industry organizations, such as the Airports Council International (ACI), agreed on a series of measures to address environmental issues related to the operation of airports.

Getting aircraft in the air and on the ground

Flights start and end on the ground. A significant volume of noxious emissions may come from systems needed to power aircraft during ground times.

Stationary aircraft require electrical energy (115 volts at 400 Hz) for flight systems and other on-board electrical systems. They may also need preconditioned air (PCA) for heating or cooling of the cabin depending on the ambient conditions.

All jet aircraft have so-called auxiliary power units (APUs) that are small turbines burning aviation fuel to run an electric generator, which provides electric power, air pressure, when the main engines are off, and to start the main engines before departure. APUs can also be used in flight in case of problems with the aircraft’s main generators.

Power can be provided to stationary aircraft by ground power units (GPUs) that burn diesel fuel, but emit 20 times less CO2 than APUs.

Solutions that provide power and PCA from ground installations make it possible to avoid using APUs to power systems, prevent noxious emissions and burn expensive jet fuel. Furthermore, some airports restrict APU use to, for instance, “to start engine, but no earlier than five minutes before off-block time” (Zürich airport).

Power can be provided by ground energy systems (GES) that include transformers, converters and cables. Cables are usually mounted underneath the passenger loading bridge or on the ground in special ducts.

International Standards for transformers, converters and cables are developed by IEC technical committees (TCs), such as TC 14: Power transformers, TC 22: Power electronic systems and equipment, and TC 20: Electric cables.

Systems that provide pre-conditioned air use chillers and even in some cases produce ice when power is in low demand and cheaper (i.e. at night) to cool PCA during daytime. International Standards for cooling units for household and commercial use are developed by IEC Subcommittee (SC) 59M: Performance of electrical household and similar cooling and freezing appliances.

Once aircraft are about to leave, they have to be pushed back from their gates by low-profile tractors, some using towbars, putting them into a position from which they can taxi using power from their own engines. Until now pushback tractors have been powered predominantly by internal combustion engines; however a new generation of tractors uses hybrid or electric propulsion, a growing trend in the sector.

A recent example of electric-powered tractor is provided by Mototok, a German company which has introduced a series of compact towbarless electric wireless remote-controlled aircraft tugs, the largest of which can manoeuvre aircraft of up to 195 tonnes.

Airports started introducing fleets of electric vehicles, including buses, for various servicing tasks.

International Standards for electric vehicles, secondary [rechargeable] batteries and for plugs, socket-outlets and couplers for industrial and similar applications, and for electric vehicles are developed by TC 69, TC 21 and SC 23H, respectively.

Getting aircraft on the ground to their gates and from these in the air safely requires the right and reliable lighting systems that can operate in different, often adverse conditions such as heavy cloud cover or darkness. International Standards for electrical installations for lighting and beaconing of aerodromes are developed by TC 97.

Airports are like small towns… just with more systems

The entire infrastructure and operations of airport depend on electrical systems, from the handling of luggage to and from aircraft, the processing of departing and arriving passengers and crews, including security screening and checks.

Handling luggage requires complex and often energy-hungry systems that are hidden from passengers. Many airports have started looking at ways of cutting down on the energy demand of these systems. This includes the introduction of more energy-efficient drives, such as variable speed drives. International Standards for these are developed by TC 2: Rotating machinery, which has published Standards related to efficiency classes for variable speed drives.

Airports are like small towns, with shopping and food outlets, and systems to move large numbers people around, like escalators and lifts.

As such, airports rely on the same IEC International Standards needed to ensure the smooth operation of large commercial buildings, shopping centres, etc. These include energy-efficient heating, ventilation and air conditioning (HVAC) systems and lighting, alarm systems, sensors, building management systems, etc.

International Standards for all these systems are developed by a multitude of IEC TCs and SCs. The introduction of smart and connected systems is set to make airport installations more energy efficient and will require more International Standards, like those needed in smart homes and smart cities.

One aspect that is important too is the movement of people to and from airports and between terminals. In a growing number of airports this movement depends to a significant extent on automated or "self-driving" electric-powered personal transport systems, such as driverless shuttles or innovative pod-type vehicles.

Mototok electric tow truck Mototok remote-controlled electric tow truck in operation (Photo: Mototok)
preconditioned air supplied to parked aircraft Power and preconditioned air being supplied directly to parked aircraft (Photo: Zürich Airport)
Driverless pod at Heathrow airport Driverless pod in service at Heathrow Airport (Photo: Ultra Global)
Hong Kong airport approach Hong Kong airport approach (Photo: Safegate Group)
Hella LED-based runway Hella LED-based light runway inset (Photo: Hella KGaA)
Dubai airport duty free area Duty free area at Dubai international airport