6 ms·

"Heaving oscillators" use wave power to extend shipping range

49 points by xbmcuser 3y ago

alright2565 3y ago
> 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.
- alright2565 3y ago
  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 https://en.wikipedia.org/wiki/Triple_E-class_container_ship [2]: https://en.wikipedia.org/wiki/Sea_state https://en.wikipedia.org/wiki/Sea_state [3]: https://en.wikipedia.org/wiki/Wind_wave https://en.wikipedia.org/wiki/Wind_wave
  - nicup12345689 3y ago
    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).
    - 10u152 3y ago
      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.
    - flavius29663 3y ago
      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 https://en.wikipedia.org/wiki/Energy_return_on_investment
      - rgmerk 3y ago
        And the EROI on solar is constantly improving. Every year we are using less material per cell to make more efficient cells.
      - nicup12345689 3y ago
        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"
  - almostnormal 3y ago
    > 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.
    - alright2565 3y ago
      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.
  - aredox 3y ago
    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.
  - froggit 3y ago
    > 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?
craig_s_bell 3y ago
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 https://cs.stanford.edu/people/zjl/pdf/tide0.pdf
- liquidise 3y ago
  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.
  - HPsquared 3y ago
    I think the general lesson is that 2% annual growth - of anything - is not sustainable for long.
    - kurthr 3y ago
      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.
      - HPsquared 3y ago
        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.
p1mrx 3y ago
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.
- korhojoa 3y ago
  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.
  - xcskier56 3y ago
    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
    - don_neufeld 3y ago
      The first time I experienced that was on the Shinkansen. It was pretty wild.
dieselgate 3y ago
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.
callalex 3y ago
> 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.
- gretch 3y ago
  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?
  - callalex 3y ago
    The point is that it’s intellectually dishonest to present a power generation technology and not even once mention how much power it generates.
    - lesuorac 3y ago
      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/S0960148123014416 https://www.sciencedirect.com/science/article/abs/pii/S09601...
  - Almondsetat 3y ago
    Going by your definition, since the article refuses to show actual meaningful numbers, it is too a miserable speculation
lnwlebjel 3y ago
Here's the paper (paywall maybe?): https://www.sciencedirect.com/science/article/pii/S0960148123014416 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.
xaellison 3y ago
Free the science. Full PDF https://www.wosonhj.com/forum.php?mod=viewthread&tid=594810 https://www.wosonhj.com/forum.php?mod=viewthread&tid=594810
ricksunny 3y ago
That is such an excellent idea!
rgmerk 3y ago
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/ https://wavefoil.com/ [2] https://www.cemreshipyard.com/en/references/nb0078-liafjord https://www.cemreshipyard.com/en/references/nb0078-liafjord

49 points by xbmcuser 3y ago

> 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.

alright2565 3y ago
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 https://en.wikipedia.org/wiki/Triple_E-class_container_ship [2]: https://en.wikipedia.org/wiki/Sea_state https://en.wikipedia.org/wiki/Sea_state [3]: https://en.wikipedia.org/wiki/Wind_wave https://en.wikipedia.org/wiki/Wind_wave
- nicup12345689 3y ago
  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).
  - 10u152 3y ago
    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.
  - flavius29663 3y ago
    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 https://en.wikipedia.org/wiki/Energy_return_on_investment
    - rgmerk 3y ago
      And the EROI on solar is constantly improving. Every year we are using less material per cell to make more efficient cells.
    - nicup12345689 3y ago
      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"
- almostnormal 3y ago
  > 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.
  - alright2565 3y ago
    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.
- aredox 3y ago
  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.
- froggit 3y ago
  > 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?

craig_s_bell 3y ago

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

liquidise 3y ago
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.
- HPsquared 3y ago
  I think the general lesson is that 2% annual growth - of anything - is not sustainable for long.
  - kurthr 3y ago
    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.
    - HPsquared 3y ago
      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.

p1mrx 3y ago

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.

korhojoa 3y ago
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.
- xcskier56 3y ago
  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
  - don_neufeld 3y ago
    The first time I experienced that was on the Shinkansen. It was pretty wild.

dieselgate 3y ago

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.

callalex 3y ago

> 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.

gretch 3y ago
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?
- callalex 3y ago
  The point is that it’s intellectually dishonest to present a power generation technology and not even once mention how much power it generates.
  - lesuorac 3y ago
    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/S0960148123014416 https://www.sciencedirect.com/science/article/abs/pii/S09601...
- Almondsetat 3y ago
  Going by your definition, since the article refuses to show actual meaningful numbers, it is too a miserable speculation

lnwlebjel 3y ago

Here's the paper (paywall maybe?): https://www.sciencedirect.com/science/article/pii/S0960148123014416 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.

xaellison 3y ago

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

ricksunny 3y ago

That is such an excellent idea!

rgmerk 3y ago

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