"Heaving oscillators" use wave power to extend shipping range | Hacker News Reader

"Heaving oscillators" use wave power to extend shipping range

newatlas.com

49 pointsxbmcuser43 comments

> One thing this study didn't investigate is how much power it could be expected to contribute on an average trip – and that, along with space considerations, will be key to whether systems like this reach widespread deployment.

Someone on this team almost certainly did some estimations of how much energy could be generated on real ships. Since these calculations are not mentioned, it must be assumed that the energy output is not enough to be useful, but saying that would reduce media coverage and grant funding.

People generally underestimate how much work gets taken out of papers because it doesn't fit with the argument of the paper. Someone absolutely estimated this, and its absence is conspicuous.

As older researchers will often tell you: the job of a reviewer is to refuse your paper. It doesn't have to be completely black and white though. Maybe they did the maths and the results were middling/unclear, their calculations were filled with assumptions that they didn't want to/didn't have time to defend.

In ML it's not uncommon to drop datasets that you evaluated on but that don't achieve SOTA because the reviewer will focus on that and ignore your other results. An article must have a clear concise point.

It’s a bit like those old Poplar Mechanics stories about giant zeppelins, or aircraft with eight wings. They make for great articles with graphics to inspire the imagination, but are really just speculative fiction in retrospect.

That said, this does seem to have some merit from a feasibility perspective.

This is the worst type of comment.

Speculation about the author’s motives, without putting in any work of your own to confirm any of it, then just assuming the worst possible case.

This is a forum for technologists to discuss interesting new ideas. “Hacker News”. Even if it’s not fully scalable in this iteration (all new ideas have issues), maybe someone can read it and be inspired and improve the ideas.

What’s the point of coming here and choosing to leave miserable speculation?

> This is a forum for technologists to discuss interesting new ideas.

It's not a sci-fi board though. One of the distinguishing characteristics of science and technology is that it's usually based on objective data and evidence. If you want to make a claim that something is more efficient than an alternative, you are generally expected to provide measurements and show that hypothesis to be true. If you can't prove a claim at-scale then you can show a model or a small-scale example. Or show an equation that uses known data applied to your model, that explains why you think your claim is true.

But there's simply no room for feel-good, trendy, pie-in-the-sky experiments that don't contain any data. That's reminiscent of the viral knee-jerk behavior against plastic straws a few years ago. Somehow people who lived hundreds of miles away from the ocean thought that forgoing straws would have some positive impact on the environment, but it was all for nothing (most of the ocean's trash comes from a handful of third-world countries).

I'm not sure if you're aware, but there is a bunch of academic fraud going on and lack of reproducibility in journal publications recently. Adding skepticism is completely warranted given the various levels of academic dishonesty.

The point is that it’s intellectually dishonest to present a power generation technology and not even once mention how much power it generates.

Eh, depends on the context. But I would agree that in this context is dishonest.

The abstract goes as far to say "Furthermore, the effects of ... wave energy capture performance ... are investigated.". [1] So It really seems like they do know and don't want to say.

That said, doing ideas that might not be economical now isn't a bad idea. Basic research is useful; but do be honest.

[1]: https://www.sciencedirect.com/science/article/abs/pii/S09601...

Going by your definition, since the article refuses to show actual meaningful numbers, it is too a miserable speculation

I think there are variables with a huge amount of variability for a ship: how heavy it is(heavier - less jumping around), how long, what seas it floats in, how much space they can spare. I agree that this article is too premature: before even tank testing has been done, but I can see how this is hard to calculate on a computer model.

> Under these conditions, the system could reach "up to 90.71% of theoretical maximum absorbed power by an axisymmetric point absorber under a certain wave period."

It's telling that they don't mention any wattage figures.

Let me elaborate. Let's say we have largest ship in the world, a Triple E-class container ship[1]. 366m long, 49m wide, 15m draft.

Let's also assume this ship has decided they will position themselves in the most violent position possible on "rough" seas[2]. These crew member & cargo are getting thrown up and down 3 meters every 10s[3] -- think of the bridge of the Star Trek USS Enterprise.

Let's assume the weight is 30m wide, 10m tall, 30m long, and full of water. That's 900000kg. Running the math... and that gives us 2.6MW of power generated. That's assuming perfect efficiency, assuming everything is in the best case scenario (aka worst case for safety).

At the same time, the engines on the same ship are rated at 60MW total. 4% fuel savings.

Assuming the crew is not suicidal, they will try and face the ship into the waves as much as they can. I can't be bothered to calculate 366m ship and 80m wavelength, but let's say half a meter of up and down motion? Comes out to 440kW, or 0.7% of rated power.

Will this complex system ever be able to pay itself off with that kind of savings?

[1]: https://en.wikipedia.org/wiki/Triple_E-class_container_ship [2]: https://en.wikipedia.org/wiki/Sea_state [3]: https://en.wikipedia.org/wiki/Wind_wave

> Let's assume the weight is 30m wide, 10m tall, 30m long, and full of water. That's 900000kg.

I think that's missing one order of magnitude: 30m * 30m * 10m = 9,000 m^3; at a density of 1t/m^3 that's 9,000,000 kg.

you're right--thank you for catching that.

I think the idea is still sound though. there is so much loss (4m waves ≠ 3m height change; rocking motion is not up-down motion) that these wattage numbers would in practice reduced by orders of magnitude.

This is the energy machine bottleneck, what kinds of machines are net-energy positive? Probably only hydrocarbon extraction/burning, nuclear, hydroelectric dams and maybe, maybe solar PV (barely, not convinced we can continue building solar panels without hydrocarbon or another source).

solar PVs are definitely producing more than put in. It takes years, as opposed to months or days for fossil fuels and nuclear, but it does pay back. look up EROI https://en.wikipedia.org/wiki/Energy_return_on_investment

And the EROI on solar is constantly improving. Every year we are using less material per cell to make more efficient cells.

Exactly the point, EROI of PV is questionable. It relies on a lot of industry (mining for example) that is/was only possible from oil/"fossil"

Some food processing plants are net energy positive - they burn waste products and produce more then they need. But in general yes, only machines designed to produce energy, produce energy.

And the fact this system is damping the natural motion of the boat means the boat is going harder into the waves - thereby most certainly nullifying any energy savings.

> At the same time, the engines on the same ship are rated at 60MW total. 4% fuel savings.

Would a ship keep its engines constantly running at max output?

That's an interesting hack. I was on a cruise ship once, and noticed that it's easier to climb the staircase when the ship is falling, and pause when it's rising.

There are a few things you can do with acceleration like that. I do the same thing with metro/trams/trains/buses when getting off. Slowing down gets you to the door almost for free.

On ships another interesting feeling is being on an elevator and then feeling the forces get smaller and larger while you're going in either direction.

Tangentially related. I was on a train today and walking in a straight line (relative to the train) while it’s going around a long corner is an odd experience. You’re leaning into the curve, but walking straight. Confusing the first time it happens

The first time I experienced that was on the Shinkansen.

It was pretty wild.

Ships that use wave motion as auxiliary propulsion have already been built.

A company called Wavefoil Technologies[1] designed a retractable foil that could be mounted on the bow of a ship. In moderate sea conditions, the vertical motion from waves was converted into forward thrust, which they claim resulted in 5-15% energy savings.

A 71 metre fishing boat using the technology was commissioned in 2023 [2]

[1] https://wavefoil.com/

[2] https://www.cemreshipyard.com/en/references/nb0078-liafjord

Free the science. Full PDF https://www.wosonhj.com/forum.php?mod=viewthread&tid=594810

Interesting concept but am curious about the efficiencies and if the ends justify the means.

Reminds me of some articles about microfluidics in shoes that would generate an electric potential during steps.

Smaller boats/yachts can much more easily leverage wave power for speed - surfing basically revolutionized sailboat racing.

Here's the paper (paywall maybe?): https://www.sciencedirect.com/science/article/pii/S096014812...

"The results show that the concept of heaving oscillator inside ship has no significantly adverse effects on the ship seakeeping performance."

Looks like a pretty preliminary study where they are just trying to build a good model.

That is such an excellent idea!

Too much of a good thing could be considered harmful:

Destroying the Earth by Using Tidal Energy

Jerry Z. Liu

https://cs.stanford.edu/people/zjl/pdf/tide0.pdf

This is just a special case of this general phenomenon:

https://dothemath.ucsd.edu/2012/04/economist-meets-physicist...

We can't have unlimited economic growth for ever without boiling the oceans, or without figuring out a way to have economic growth without increasing energy usage. It's not about global warming, it's about just waste heat and entropy, even assuming maximally efficient engines and 100% renewable energy.

And really, all of that blog post is a special case of the observation that life is a way to more rapidly increase entropy on earth by finding and exploiting energy sources. Eventually earth will reach a life-induced thermal equilibrium which will be incompatible with the continued existence of life on earth.

Reversible computation doesn’t need to result in waste heat so that’s one path towards unlimited economic growth.

This paper is either naive or a joke, as it assumes energy consumption will increase by 2% per year for 1000+ years.

The sun imparts a certain amount of energy into the earth through tidal forces. We can either capture that energy for our use, or let it heat the Earth (https://en.wikipedia.org/wiki/Tidal_heating). The slowdown of the Earth's rotation is the same either way. The paper demonstrates that if you could capture an absurd amount of energy from tides, the earth's rotation would have to slow. But this is vacuously true: you simply can't capture that much energy from tides.

This article needs to die. People see stanford and think it's legit. This is an early grad school student's work and it probably shouldn't be visible outside the dept.

tldr: If global energy usage grows at 2% every year, and we generate 1% of the total demand annually with tidal energy, the Earth's rotation will cease in ~1000 years.

While i won't dispute that tidal energy is not truly sustainable, at least not in the way solar appears to be, i think we can agree that in the short team (a few centuries) cargo ships saving fuel would be a net positive with no measurable impact on the rotation of the planet.

Edit: after some more napkin math, i have a hard time taking this paper seriously at all. It appears to suggest that the available tidal energy would remain constant throughout this process? Also, 1.02^1000 equates to a roughly 400 million factor increase in the current energy demands of the planet. That's not something i'd expect such an advanced civilization to be trying to generate out of some waves.

I think the general lesson is that 2% annual growth - of anything - is not sustainable for long.

Or even 1%. Neither is shrinking continuously.

None of this is to say that we're at a maximum.

The rule of 72 is useful. It would give roughly doubling every 35 years for a 1000years means 28 doublings or a bit over 256million x increase in power usage. Only off by ~50%.

I'm guessing that would put the population over a quadrillion, as well, with efficiency increases.

Can also think in terms of half-life.

For example at an inflation rate of 2%, that rule of thumb means the value of money has a half-life of 72 years.

A day needs more than 24h anyway.

I think I've seen arguments from the same person before.

The key assumption here is a 2% annual increase in world energy demand. No shit sherlock, after 1000 years numbers are huge. Funny thing is he only criticises renewables this way, but if we make the same calculation for any any energy source we pretty much come to the same conclusion. Maybe the person has an agenda?

Reply on news.ycombinator.com