Which portion of the transport sector do you think is the most difficult to electrify aviation or maritime?

Aviation, simply because the regulations are so intense. The technology is there for both already, but it will be far easier to cram a freighter with batteries than a plane because of the engineering and safety requirements. Ships need a minimum of fault tolerance compared to planes, for example.

I disagree with the "the technology is already there" statement. Source: I was part of an aviation electrification research project.
Small regional planes are technologically possible, yes, but transatlantic or transpacific flights? We're nowhere close to that.
- The battery density needed to make electric flight possible is ~400wh/KG, which we are well past. There's no technological limitations blocking transatlantic flight.
  Also, the question wasn't if we were close, it was if it's easier in ships or planes.

Airplanes for sure. If solar gets crazy efficient, that will help. But with other fuels the plane gets lighter and more fuel-efficient as it flies. With batteries, the plane is just as heavy when it landed as when it took off.

There are some really interesting companies working on hydrogen for planes though, which might be the one sector that could really make that work and has good incentives to do so.

Great podcast episode about that here

https://www.everybodyinthepool.com/items/episode-8-transcript%3A-what-if-planes-only-emitted-water

For ships, they used to be wind powered (sails) and some are going back there again, at least for wind-assisted hybrid kind of models. Throw turbines on there and you can even "sail" into the wind while recharging a bit. It's also less weight sensitive than airplanes for obvious reasons, so batteries aren't immediate nonstarters.

I would assume that maritime would be much easier, since battery weight would be more easily dealt with, and propellers and screws can be turned by motors more or less as effectively as by engines.

I hadn't really thought about it, but aviation is potentially going to be a challenge. Traditional jets won't work - they'll need to use propellers or rotors or something like a turboprop, which means lower altitudes and slower speeds.

Hmm...

Aviation. Aside from the regulatory aspects, the mass and relative lack of power density in batteries is a MAJOR hurdle to broader effectiveness and acceptance.

Planes, like the ones that do commercial passenger and cargo flights, are much harder to go fully electric compared to ships. Ships, unlike planes, don't need to maintain a minimum speed and are less constrained by battery weight. Recharging their batteries would take a long time, depending on their size.

Also, you can make nuclear powered ships, though the operating costs are very high and thus unsuitable for most civilian needs.

There are some interesting proposals for electric ships using containerized batteries which can be loaded/unloaded with the same cranes they use for shipping containers and charged in port. https://cleantechnica.com/2025/05/24/beyond-the-harbor-electrifying-short-sea-routes-and-hybridizing-blue-water-shipping/
It may not be suitable for transoceanic trips but a lot of shipping follows the coasts or even travels by river where this may be more practical.

for aviation, we already have airships (which use something like 8% of the power of an airplane)

the biggest “gotcha” is time – taking a week to get to a destination when you only get two weeks vacation is a no go – which means, just like trucks, electrifying aviation and maritime is going to be limited to cargo and commercial for the time being

It's definitely easier to electrify maritime transport.

Long-range aviation might not be electrified at all because it's so hard to get enough energy from batteries without making the plane unable to lift off due to weight, or enough power from fuel cells without taking too much space. Instead we might see hydrogen turbines or synthetic fuel engines.

Either way, maybe we should ask ourselves if a future society should have flight at all? Of course it's cool that humans were able to achieve flight but right now it mostly serves an overheated capitalism and the short-lived pleasure-seeking of (globally speaking) a few fortunate people.

Maritime. You've got open seawater, no way to recharge that you don't carry with you, and a lot of balancing issues that can't be messed with.

Mind you, navies have done some of the work to get it there. Just not sure what aspects would be available for commercial/civilian use.

Aviation is difficult because of weight and balance constraints, but I think you'd still have less trouble on average.

But, this is way outside my wheelhouse, so I'm playing guesswork here.

Maritime. The problem for both of them is range and energy density of batteries compared to oil based fuel. That is a problem, when you want to cross oceans or similar distances with planes.

There are a lot of cases in the maritime enviroment, where you do not need to cross an ocean and it is economically sensible. Currently a big one are ferries. Those are relativly short routes, with known port infrastructure. So it is easy to charge the ferries in the ports and then make the journey. The next ones in line would probably be feeder ships. Those are smaller vessels transporting cargo from smaller ports to larger ones. In the large ports they then are loaded on ocean liners. Cruise ships are also a market to watch. For Europeans style crusises it is very common to only be on sea for a night or maybe a day, to then go to a port and dump the tourist on some city. Should be possible to go electric.

For aviation it is also not nothing. There are short flights as well. Again islands are a common one. There are also things like agricultural planes, which can be electrified or say medical helicopters or maybe even fire fighting planes. However there is a lot more competition from land based transport, such as high speed rail.

I believe aerospace would be the final frontier of electrification since space is so difficult to reach.

Aviation is already getting electrified, look at the drones that are already replacing helicopters in several cities

Electrification can encompass hybrid, like diesel-electric trains. It’s not where I’d like to end up, but it’s a start. I believe many ships are already configured this way, but I may be mistaken.

Reconfiguring long haul ships as Plugin Hybrid Electric Vessels could allow them to operate in electric mode when in populated areas which would reduce the score health risks of their particulate emissions.

In the long term, I think that maritime transportation can be electrified fully, using a combination of modern sailing technology and battery-electric propulsion. However, there’s some areas where this will be quite difficult until battery technology improves.

Planes just don’t have the capacity for the necessary weight at this time.

Latest big thing in ships are the Azipods, fully electric motor pods on swivels. Of course powered by massive diesel generators due to battery technology. Ships could be made full electric, but it would eat into cargo space more than fuel tanks and engines do now. And since the point of a cargo ship is cargo space that's going to be a stumbling block for a while.