Air travel is a major contributor to greenhouse gas emissions and is seen by many as a luxury we cannot continue to afford if we are halt or reverse climate change.
Main picture Airbus Blended-Wing Body concept hydrogen aircraft credit Airbus
Electricity is, at least right now, not a solution to the majority of air travel as the batteries and engines required to fly over longer distances are far too bulky and heavy to be viable.
Hydrogen fuel cells produce electricity by combining hydrogen and oxygen atoms. The hydrogen reacts with oxygen across an electrochemical cell similar to that of a battery to produce electricity, water, and small amounts of heat. Hydrogen can produce energy with zero smoke, pollution or climate warming emissions – the only product is water.
Aircraft manufacturer Airbus have plans to develop the world’s first zero-emission commercial aircraft by 2035. The planes would be powered by hydrogen.
The company has already produced three prototype aircraft:
- Turbofan – two hybrid-hydrogen turbofan engines provide thrust. The liquid hydrogen storage and distribution system is located behind the rear pressure bulkhead.
- Turboprop – two hybrid-hydrogen turboprop engines, which drive eight-bladed propellers, provide thrust. The liquid hydrogen storage and distribution system is located behind the rear pressure bulkhead.
- Blended-Wing Body (BWB) – this futuristic looking aircraft has an exceptionally wide interior, which opens up multiple options for hydrogen storage and distribution. Here, the liquid hydrogen storage tanks are stored underneath the wings. Two hybrid-hydrogen turbofan engines provide thrust.
All three ZEROe concepts are hybrid-hydrogen aircraft. They are powered by hydrogen combustion through modified gas turbine engines. Liquid hydrogen is used as fuel for combustion with oxygen.
In addition, hydrogen fuel cells create electrical power that complements the gas turbine, resulting in a highly efficient hybrid-electric propulsion system.
The turbofan and BWB lanes would have a range of around 2,000 nautical miles carrying up to 200 passengers. The turboprop would have a range of around 1,000 nautical miles, carrying up to 100 passengers.
The Problem With Hydrogen
One of the biggest challenges to hydrogen power is creating the hydrogen in a useable form.
Producing hydrogen requires energy, but the majority of hydrogen produced today is through burning fossil fuels which would not be suitable for clean transport solutions. It can be produced using electrolysis, driven by sustainable power, but it is currently very expensive and requires large amounts of energy.
Liquid hydrogen is not as energy efficient as jet fuel. Aircraft would need to either have much larger fuel storage tanks or carry fewer passengers if powered by hydrogen.
Hydrogen has higher energy by mass than jet fuel, but it has lower energy by volume as it is a gas at normal atmospheric pressure and temperature. To be usable it needs to be compressed or turned into a liquid by cooling it to extremely low temperatures. Storage facilities would need to be large and would be expensive.
Producing Sustainable Aircraft Fuel (SAF) Using Hydrogen
Biotechnology company LanzaTech UK, and cleantech company Carbon Engineering (CE), have partnered on a first-of-a-kind project to create sustainable aviation fuel (SAF).
Carbon dioxide (CO2) captured from the atmosphere using Carbon Engineering’s direct air capture (DAC) technology, and hydrogen from water electrolysis, will be converted into SAF using gas fermentation and alcohol-to-jet technology. Project members British Airways and Virgin Atlantic will study offtake potential and go-to-market routes for the fuel.
The proposed facility is targeted to be operational by the end of the decade and will demonstrate how this clean infrastructure can be rolled out across the UK and elsewhere to deliver significant aviation emission reductions, while creating thousands of jobs and cascading economic benefits.
The project is one of eight projects shortlisted for the UK Department for Transport’s Green Fuels Green Skies Competition that will share £15 million in government funding to support plant development.
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