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Comment by greglindahl | Hacker News Reader

So, for example, a power line from Algeria to Europe is cheaper than a ship-based ammonia scheme? Or northern Australia to China or Japan?

Power lines are a winner for short distances. Pipelines some longer distances. And ships for the longest distances.

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You're right that there's a reason we constantly transport so much liquid fuel around the world.

But the Europe and North Africa connection is already a relatively serious proposal precisely because of the efficiency gains. It's definitely an ambitious project, but more from the politics than from the technology. Electrons are just easier than atoms, even underwater. HVDC has made long distances realistic for cables.

China's Anhui to Xinjiang HVDC link will be around 2000 miles. There's a planned HVDC submarine cable from Lincolnshire to Denmark that will be 472 miles.

So for Australia to China, we might be able to pull off Darwin to Jakarta, then Jakarta to Hong Kong within 10-20 years, if you really wanted to. Would break some records, but it's not crazy impractical.

Though with the most efficient transfers you're taking some percentage hit per mile. Closer generation is generally going to be smarter, especially if you're running cables through what would be really viable offshore wind fields.

https://en.wikipedia.org/wiki/European_super_grid

https://www.power-technology.com/features/chinas-mega-transm...

I totally agree that power lines have improved recently. That fiddles with the details, and doesn't change the fact that even if these advances pan out, there will be (very long) distances that you'll want to ship energy that will be more efficient with ships than power lines.

You're right to point out that tankers are phenomenally efficient, but that's _for oil_. Just as LNG is much more expensive to ship than oil, because of the increased handling complexity, any shipping of hydrogen is going to lose that advantage completely to electrification.[0]

> there will be (very long) distances that you'll want to ship energy

This is probably the real crux driving the difference in how we see this.

The main reason we have to ship hydrocarbons long distances is because those resources are so concentrated. Wind and solar aren't perfectly distributed, but they are so much more distributed that local generation would be much more efficient than transporting anything much beyond what current HVDC projects can easily handle.

So, sure, we're not going to stretch a cable for 12,000 miles. But we're also not going to build a solar farm in Saudi Arabia to generate hydrogen to ship to Canberra. We're just going to put a solar farm in the outback instead.

[0] "Relative costs of transporting electrical and chemical energy" by Saadi, Lewis, and MacFarland, studies this very question.

Even in that report, you could quibble with a lot of their assumptions that I think bias it against HVDC, project lifespans, ignoring loading and unloading costs for tankers, etc. But it's not a crazy starting place, and HVDC still beats hydrogen on $ per mile per Joule. My takeaway from it was that if we're stuck with a carbon economy, sure, we'll keep using tankers. If we're talking about going carbon neutral, the difficulties of working with hydrogen relative to oil and LNG will probably tip us back towards electrification and local generation, except in the most highly specialized of situations (fueling Antarctica or something).

The report was a good reminder why we have an oil-based economy though. It is so obnoxiously practical and well suited to everything we want to use it for. Ditching carbon will be hard.

The article you mention has no discussion of ammonia, just hydrogen and LOHC. That plus your mention of shipping energy into Canberra makes me wonder if we're actually communicating with each other at all.

Since ammonia and LOHCs face some overlapping constraints I don't expect an order of magnitude difference in cost. But you're right, it would have been more useful with an explicit comparison.

If you are seeing stuff that suggests ammonia will get very close to parity with oil, that's really fascinating, I hope it pans out that way. The IAE is more optimistic than I am about ammonia transport, while still listing some significant hurdles:

https://www.sciencedirect.com/science/article/pii/S036031991...

I think it's a good report, and you could read it to be more convinced of either of our positions.

Sorry we're talking past each other. You did actually change my mind a bit, if it's any consolation. Agree it's too hasty to say electrons are always better than atoms, though I'm still optimistic about more supergrids. My main remaining concern is just that, as you change your power mix away from oil to generate more ammonia, or electrolytic hydrogen, or whatever, the case for shipping fuel erodes significantly, because you can just move generation closer instead.

Sorry we couldn't get to ground on this one. Thanks for your points all the same.

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