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EasyJet May Trial Hydrogen Fuel Cells For Taxiing (thestack.com)
An anonymous reader writes: Low-cost airline easyJet is discussing plans to install hydrogen batteries as part of a proposed zero emission fuel system, which would power its aircraft during taxiing. The budget service revealed designs for a hybrid plane this week, and said that it would begin trialling the technology later this year. The system will involve embedding a hydrogen fuel cell on board the aeroplanes, with the energy captured from the brakes on landing able to power the jet on the ground. As the only waste product from a hydrogen cell would be fresh, clean water, Ian Davies, head of engineering at easyJet, also suggested that this could be used to refill the planes' water systems during the flight, providing a water source for passengers to drink and for flushing toilets.
The system will involve embedding a hydrogen fuel cell on board the aeroplanes, with the energy captured from the brakes on landing able to power the jet on the ground. This technique is similar to the high-end kinetic energy recovery systems (KERS) used in Formula One cars, which store recovered energy to later use for acceleration.
TFA mentions harvesting the braking energy as being similar to KERS used in Formula 1. But no mention is made of the additional mass or equipment (unsprung at that) that would be needed to be added to the landing gear in order to harvest that energy. Such equipment needing to be robust and large enough to capture a worthwhile amount of energy in the 10 seconds of braking that a plane experiences when landing. For the rest of the 99.9999% of the flight this is dead weight that the plane has to burn fuel in order to carry it around.
So color me surprised if anyone really thinks that is practical. (let alone the bizarre notion that the recovered energy could somehow be funneled into a hydrogen based fuel cell - super cap yes! fuel cell ? are you kidding me?)
It would probably make more sense to assign a tractor to drag each aircraft from the gate to the start of the runway rather than use the planes fuel to taxi around.
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You'd also need special humans for it. Pure H20 cannot be consumed by humans [...]
Life Hack: Pure H2O becomes safe to drink by adding a sticker that says; "Gluten Free".
I tried it and it totally works!
Less sexy would be to develop a tug that could not only push the plane back, but also perform taxi duties.
This is already done. The pushback tugs are also used for repositioning aircraft between gates and/or hangars. There are many reasons why aircraft start their engines at the gate. This serves primarily as a checkout of the aircraft systems. If an engine behaves oddly, or has trouble starting, pulling back into a gate is simple. Doing it at the runway would be a lot more complicated, as it would require a full back-taxi, which on congested airports is already a major PITA. In addition, many of the internal systems such as flight control hydraulics are powered by the engines, so for example you won't have all flight controls fully functional (meaning, you can't perform a F/CTL check) and you can't fully extend flaps for takeoff unless you have at least one of the engine-driven pumps running. Secondly, the air conditioning packs inside the cabin are engine-powered and they take a lot of juice as well as compressed air (or you'd have to carry a sizable battery just to keep them running for the 20-30 minutes on the ground). On very long taxis to takeoff or after landing, many aircraft already do reduced-engine taxi. 747s routinely shut down 1 or 2 engines right after landing. Twins routinely do single-engine taxi. When there is a long queue for takeoff, similarly, engines get shut down. But doing the whole taxi completely shut down and only starting once close to lining up would probably result in tons of operational complications and possibly safety issues.