Hydrogen Fuel Vs SAF(Sustainable Aviation Fuel)

What is hydrogen aircraft?

hydrogen aircraft is an airplane that uses hydrogen as a power source. Hydrogen can either be burned in a jet engine, or any other kind of internal combustion engine. It can also be used to power a fuel cell to generate electricity to power a propellor.

Unlike most aircrafts that use wings for storing fuel, hydrogen aircraft are usually designed with the hydrogen fuel tanks carried inside the fuselage.

PHOTO : horizon-magazine.eu

Can hydrogen be used to power an aircraft?

Hydrogen combustion has already been used to fuel aircraft. In fact, in 1988, the world’s first experimental commercial aircraft operating on liquid hydrogen (and later, liquefied natural gas) took to the skies- the Tupolev Tu-155 (15 APR 1988).

PHOTO : en.wikipedia.org

Design Considerations

Liquid hydrogen has about four times the volume for the same amount of energy of kerosene based jet-fuel. In addition, its highly volatile nature precludes storing the fuel in the wings, as with conventional transport aircraft.

  • Wide flammability range: Hydrogen can be combusted via a wide range of fuel-air mixtures. In fact, hydrogen can run on a “lean” mixture, which means the amount of fuel is less than the amount needed for combustion with a given amount of air. This results in greater fuel economy and a final combustion temperature that is generally lower, which reduces the amount of pollutants, such as NOx, emitted via the exhaust.  
  • High auto-ignition temperature: Hydrogen’s high auto-ignition temperature enables higher compression ratios in a hydrogen engine compared to a hydrocarbon engine. A higher compression ratio results in greater thermal efficiency or less energy loss during combustion.
PHOTO : http://www.bloomberg,com

New hydrogen-powered aircraft from Airbus

After teasing hydrogen innovation in a July(2020) panel, Airbus has released prototypes of a line of hydrogen aircrafts, including a passenger airliner, a prop-boosted plane, and a wild stealth-looking little blended wing,which the Airbus says, represents the future of passenger aircraft.

PHOTO : http://www.airbus.com

Airbus’s new program to be supposedly launched in 2025.

Sustainable Aviation Fuel (SAF)

SAF stands for sustainable aviation fuel. It is produced from sustainable feedstocks and is very similar in its chemistry to traditional fossil jet fuel. Using SAF results in a reduction in carbon emissions compared to the traditional jet fuel , it replaces over the lifecycle of the fuel. 

Why is it important?

  • SAF gives an impressive reduction of up to 80% in carbon emissions over the lifecycle of the fuel compared to traditional jet fuel it replaces, depending on the sustainable feedstock used, production method and the supply chain to the airport. 
PHOTO : adsgroup.org.uk

Is it safe to use?

  • SAF can be blended at up to 50% with traditional jet fuel and all quality tests are completed as per a traditional jet fuel. The blend is then re-certified as Jet A or Jet A-1. It can be handled in the same way as a traditional jet fuel, so no changes are required in the fuelling infrastructure or for an aircraft wanting to use SAF.
  • Any aircraft certified for using the current specification of jet fuel can use SAF.
PHOTO : intelligent-aerospace.com

Drawback(s) :

  • The main challenge is that the price of SAF today is higher than petroleum-based Jet A fuel. Fuel price is a hurdle because fuel is 20%–30% of the operating cost of an airline (IATA 2018).
PHOTO : http://avstop.com/ac/apgeneral/turbineenginefuels.html

And so it follows…

To reduce transport emissions by 90% within 30 years, all low-carbon pathways will be needed and hopefully one or more methods shall be used in combination or otherwise to achieve minimum or zero carbon footprint.

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