Aviation and fossil fuels
produce 43MJ/kg whilst a top of the range lithium-ion battery only produces 1MJ/kg (Real Engineering, 2018). Car manufacturers deal with this problem by having a very heavy battery and reducing the weight of the rest of the car (Kamal and Chang, 2021). This difference in energy between a fuel tank and battery of the same mass grows with the weight. So, the difference in weight needed for a petrol and electric car to travel 360 miles is 870lb (Kamal and Chang, 2021). The petrol car being the lighter of the two. But, for a commercial airliner to travel 5 hours, the difference increases incredibly to around 5.7 million lb (Kamal and Chang, 2021). The electric plane in this example needed 48 times the mass of fuel of the regular plane to achieve the same energy. The mass of the batteries is also around 5 times the mass of the aircraft itself. On top of this already fatal figure, the increased mass of the plane would require more energy to be burnt to stay in the air as the power needed is proportional to the mass of the plane squared. Meaning that the electric airliner would not be capable of the same distance as the regular plane. Smaller recreational aircraft are significantly less hampered as they weigh so much less. Projects like the Alpha Electro demonstrate some feasibility in short and often recreational flights. But even at the incredibly light weight of 368kg, its 20kg battery offers only 1 hour of flight time. It’s clear that our battery technology would have to be somewhere around 20 times better than it is today before we can even begin to consider putting them in an airliner. Therefore, we cannot expect to see a battery powered airliner fly within the next decade or two. If Tesla-style lithium- ion batteries don’t work, then what will? Many engineers are already focused on this problem and ongoing research bears a list of alternatives. This essay will focus on the three most popular options being considered by the industry. Those are: Sustainable Aviation Fuels (SAF), Hybrid Power, and Hydrogen Power.
Sustainable aviation fuels
Sustainable aviation fuel (SAF) is the most viable solution at the moment. If battery and hydrogen technology really are decades away, new fuels may be the crucial stop gap needed to hasten the move away from kerosene. The International Air Transport Association (IATA) went as far as to say that ‘In the medium term, SAF will be the only energy solution to mitigate the emissions growth of the industry’ (Net zero 2050: sustainable aviation fuels - IATA, 2022). Despite needing to meet strict requirements, these sustainable fuels can achieve a reduction in lifecycle CO2 emissions of 80% (Net zero 2050: sustainable aviation fuels - IATA, 2022). Additionally, 215,000 flights with 60 different airlines used an SAF mixture for fuel before December 2019 (Net zero 2050: sustainable aviation fuels - IATA, 2022). Whilst it appears that the gears are already turning for SAF, it still has drawbacks. Firstly, it costs up to eight times more than conventional fuels (Pavlenko, Searle and Christensen, 2019). Secondly, there are some concerns that this new demand for biofuel would encourage deforestation (Furness, 2021). There is also not enough of it being produced. Only 100m litres were produced in 2021, while the IATA has stated that 449bn litres are needed to achieve their goal of net zero by 2050 (Furness, 2021). The IATA itself appears cautiously optimistic that this enormous increase is feasible, but a lot of work is clearly needed before SAF can make a serious difference. Support from airlines themselves appears strong but they have only agreed to use 10% SAF by 2030 (Furness, 2021). Despite being the best candidate to
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