Lithium-Sulfur Battery-Powered Commercial Aircraft & Net Zero Airports

https://www.youtube.com/watch?v=ctsnpgFpNTc

Navigating the airports and boarding the flights was quite fun. I felt powerful and in control, everything was clear to me. I felt independent and trotted through at quite a pace, taking everything in. What was especially cool to imagine as a Physicist was the jet engines going to full power and pushing air particles backwards, and these air particles must in turn push forwards on the blades of the jet engine, by Newton’s third law. The atmospheric density is most certainly sufficient for the interaction between the blades of the jet engine and the air to provide a thrust force to get the plane moving. As we reached full speed on the runway, I imagined the blade-atmosphere interaction providing the thrust, and also the air split at the front of the main wing. This air must leave the wing at the same time, independent of whether it is travelling along the curved upper wing, or the comparatively flat lower wing (the curved upper wing is a longer distance). This means that the air travels faster along the upper wing than the lower, which means the air particles are more dispersed above the wing than below. This creates a pressure difference above versus below the wing – low pressure above the wing, and high pressure below the wing. This means that the force exerted on the upper wing by the air is less than the lower wing, and so there is a net upwards force, which goes by the name of “Lift”. I was having quite a fun time imagining the operation of this contraption as it was transporting me. Really a marvellous thing. What was bothering me was that jet fuel is carbon-based and so while it was a fantastic feeling to be piercing through the atmosphere in the machine first devised by a certain Orville and Wilbur Wright, I was also involved with carbon emissions. Yes, carbon compounds released into the atmosphere, which would reflect back towards the Earth radiation that would normally be lost to space. This would cause more extreme winters and summers, more frequent storms/flooding, contribute to rising sea levels, and potentially ocean acidification as well.

In terms of attempting a “reciprocal relationship” with the natural world it is important to understand that the machine that is the universe conserves energy. All energy that the planet receives comes from the fusion reactor that is our Sun, and all lifeforms on the planet – past, present, and future – rely on it. When the Sun’s heat energy hits the leaves of trees it causes evaporation, which in turn causes a negative pressure such that the trees can suck up water. In other words, the Sun’s energy enables the trees to increase the gravitational potential energy of water to nourish themselves. The Sun’s energy in light form is a vital ingredient in the photosynthesis process, which produces sugar. If the tree is fruit-producing, the excess sugar will be distributed to the growing fruits and these fruits can be thought of as possessing chemical potential energy. When an individual consumes a fruit, their body converts this chemical potential energy into energy that the body uses to move around and think.

In the case of fossil fuels, these are the remains of past lifeforms, which contain energy in their chemical bonds. When the fuel is ignited, the bonds are broken, and the energy stored in them is released. In the case of a jet engine, this energy is converted into rotational energy of the blades, and since the blades push air particles backwards which in turn push the plane forwards, is ultimately converted into the kinetic energy of the plane. In this way everything is connected.

Of course, since the machine that is our universe conserves energy, there are other ways of powering heavier-than-air flight such that our “reciprocal relationship” with the natural world is more balanced. Currently, the use of carbon-based jet fuel is taking from nature and upsetting the natural carbon cycle of the planet. With innovations in battery technology (energy storage) such that enough energy to power a commercial sized craft for three quarters to a whole revolution around the Earth (as it is not necessary to travel more than halfway around the world) is available with a single charge, and clean energy sources such as solar and wind farms, it is physically possible to store the energy collected at these farms and use it to charge an electric commercial-sized plane. What I am imagining is an airport which is next-door to a solar/wind farm, or potentially has solar on the roof, such that commercial aircraft can be charged. Many may think that this charging process will be slower than refuelling, however innovations in charging technology (superchargers) can overcome this as well. If this were the case, we could fly around with a perfectly clear conscience in that we have zero carbon footprint and are not contributing to offsetting the balance of the natural planetary systems. The “reciprocal relationship” with the natural world goes from breaking the bonds of fossil fuels and upsetting the carbon cycle to using clean electricity. If we use lithium-sulfur instead of lithium-ion batteries, we can also eliminate the environmental harm related to mining required for lithium-ion, while tripling the energy density and doubling the amount of charge cycles.

The question here is whether electric commercial flight is really feasible. Companies such as Lilium have a working electric jet, which has a rotating engine set up such that vertical take-off is possible, however it seems to only seat around six passengers. To compensate for its small size, the company uses a fleet of them, and recently formed an agreement with SAUDIA airlines related to this. Another promising company is Airbus, which states that, “Electric and hybrid-electric propulsion is rapidly revolutionising mobility technologies across industries, from automotive to marine. And the aviation industry is no exception. At Airbus, our work in electric flight aims to lay the groundwork for future industry-wide adoption and regulatory acceptance of alternative-propulsion commercial aircraft and urban air vehicles.” In 2013, the E-Fan 1.0 became the first electric aircraft demonstrator developed in the Airbus portfolio. In 2017, they demonstrated the hybrid-electric E-Fan X and so it seems like things are moving towards a future in which all modes of transport are electric, possibly with the exception of rockets. Rockets are necessary as the Sun that is providing the planet with energy has a life cycle and in ~ 500 million to 1 billion years will become a red giant which evaporates the oceans, leading to an uninhabitable planet.

With some government spending (as airports are government owned and redirection of government resources is possible), talented engineers, researchers, businesspeople, and some luck, we can realise Net Zero Airports and improve the relationship between humans and nature – from taking, to living in harmony. For land-locked airports, possibly a large solar array with excellent batteries to compensate for fluctuation would enable the facility to function. For coastal facilities, the fluid flows could be taken advantage of with a wind farm nearby. Hydroelectric power, where it is possible, is also an alternative.