Comment on New fuel cell could enable electric aviation | MIT News
perestroika@slrpnk.net 4 weeks ago
Thanks for the tip, both the popular and scientific article are interesting.
Short summary of the pros an cons:
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energy density: 3 x better than lithium ion
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power density: really poor (if they raise their power density by 10 times, it will suffice for cruising, takeoff will require supplementary high-current batteries)
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exhaust: sodium oxide, converted by moisture in air to sodium hydroxide (caustic), converted by CO2 into sodium bicarbonate (harmless) --> this is a tech for cruising up high, not for takeoff or flight above settlements
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operating temperature: reasonable (about 100 C)
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mass production of sodium: doable, but somewhat messy (electrolysis of seawater?)
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fire safety: sodium burns just as bright as lithium, nothing cheerful here
My personal conclusion: currently, this is a potential military technology (“electric cruise missiles with 500 km range”), but likely won’t reach passenger or cargo aviation soon.
hydroxyl@freeradical.zone 4 weeks ago
@perestroika @Wahots thanks for the breakdown! a short question: so military aviation applications need less km range or is it something else that leads to the conclusion of military tech direction. it's very frustrating seeing the hard work we make for the benefit of our energy community as researchers ending up in military applications :tiredcat2: :firepoop: how can we avoid this?
perestroika@slrpnk.net 4 weeks ago
With this technology, it’s just the combination of fuel and exhaust that makes it unlikely to reach peaceful applications sooner. A user of this technology must be willing to tolerate (and cause) considerable inconvenience just to increase the range of their electric aircraft.
Fuel distribution would be an annoying but surmountable problem. Not the easiest, but doable. Sodium needs to be stored either in mineral oil or inert gas. Otherwise it will spontaneously oxidize quite fast. Airports would need sodium warehouses with specialized equipment (either oil baths to submerge it or an unbreathable atmosphere). Trucks with the same kind of equipment would be needed to deliver the stuff.
Fuel production efficiency would be a problem. I don’t know the efficiency of sodium production, but intuitively this is likely to be around 80% (plus road transport). Charging a battery from the grid is more efficient, so the user of this technology must either have cheap electrical energy (this might be true in future with lots of renewables) or be willing to ignore the cost of energy (military users will do that already now).
Finally, the debate over a caustic exhaust stream is likely to be non-trivial. I predict that people will be quite worried about the direct effects of NaO and NaOH air pollution - it’s one of those things which is clearly health negative, even if climate positive. Unsurprisingly, military users are pretty unconcerned about being health negative.