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Comment by bryanlarsen | Hacker News Reader

Trains are a silly use case for hydrogen. Electric trains have been used and viable for approximately 100 years. The only problem is how expensive it is to electrify thousands of miles of tracks.

That problem is now gone, batteries can be used to bridge gaps in the catenary wires.

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Think mountain passes or similarly difficult terrain. Or lower volume cargo trains, like into and out of industrial areas in the north. Catenary networks not only take a lot of money to set up, the maintenance is huge - especially in rough terrain or over long distances!

ed: Not saying that all trains should be hydrogen, there just are use cases for some when we're talking zero-emission.

For tracks that cannot justify the cost of electrification, you will want hydrogen trains. Battery trains make the least sense, since it is easier to electrify those short gaps than to buy an entire new class of locomotives.

Power cables are an attractive theft target, many places.

An extra insulated car filled with lightweight LH2 would not appreciably increase the cost of operating a train.

Liquified ammonia under low pressure might be more practical, if safety worries don't dominate. We already move tanks of ammonia on trains. And much worse.

Liquid green hydrogen costs an order of magnitude more than electricity, and always will since it's created from electricity and uses electricity for liquification. It definitely will appreciably increase the cost of operating a train.

The weight of one extra car will increase the operating cost of a 100-car train by 1%, give or take a bit. Using cheap hydrogen instead of expensive kerosene may save much more than that. Moving light hydrogen instead of heavy kerosene may save more than that.

If the electricity could be delivered directly to the train, the energy used would be cheaper, but installing (and replacing "shrinkage" of) many thousands of miles of "third rail" would cost a lot.

The hydrogen is not yet cheaper than the kerosene, but costs on that side are falling fast.

You don't need thousands of miles of third rails or catenary wires. Just a ~mile every ~hundred, and a battery on the locomotive.

That is an interesting alternative.

You need a battery that tolerates many many cycles, and being charged at 100x its usual discharge rate. Maybe a molten CaSb battery, from Ambri.

I guess if all the cars can be wired to take in power, you just need a short stretch of 3rd rail at each charge point, say 60 m, not 1600. If each car has its own battery and drive motors, they don't need to be wired together. Relative charge rate goes to 10,000x, but the grid load stays the same.

It's cheaper to just electrify the gaps. His views are fundamentally nonsensical and shows that he hadn't really thought about the problem. Hydrogen trains are for remote tracks, sometimes thousands of miles of unelectrified rail. If you can't justify ever electrifying those tracks, then hydrogen trains are the obvious answer.

Ammonia trains might be a better answer.

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