[HN Gopher] Floating wind turbines could rise to great heights
___________________________________________________________________
Floating wind turbines could rise to great heights
Author : prostoalex
Score : 100 points
Date : 2021-07-23 12:33 UTC (10 hours ago)
(HTM) web link (www.economist.com)
(TXT) w3m dump (www.economist.com)
| kumarvvr wrote:
| Those wind turbines are upwards of 10 MW each. That is massive.
| People dont get the scale of it.
|
| If the dynamics, control amd reliability are proven, then the
| only hurdle would be drawing high power carrying cables through
| corrosive sea waters. And, build cables that withstand constant
| movement and bending.
|
| Edit - Wind turbine capacity.
| gameswithgo wrote:
| I believe most of the huge ones you see on the interstate are
| ~2MW, so imagine ~5x the scale
|
| woooo
| jhayward wrote:
| > imagine ~5x the scale
|
| For wind turbines power is proportional to the swept area,
| and to the square of the diameter. Doubling the diameter
| quadruples the available power.
|
| So for the same wind speed the difference between a 3MW
| (commonly installed today) land-based turbine and a 15MW
| turbine (largest offshore class today) would be a little over
| twice the diameter. Of course, the offshore monsters are also
| taller to allow greater swept area, and to take advantage of
| better resource at height.
| danans wrote:
| > Those wind turbines are upwards of 10 MW each
|
| Assuming a 35% capacity factor (taken from land-based wind
| turbines, offshore should be higher), that's 84MWh/day.
|
| The average California single family home uses 20 kWh per day,
| which means that that capacity factor this turbine could power
| about 4200 homes per day.
|
| For comparison, a 10 megawatt solar project, assuming a
| standard 20% solar panel efficiency and one kilowatt per square
| meter insolation, would require a five square kilometer solar
| array. The capacity factor of PV solar is inherently limited by
| sunlight hours, but it is around 28% in California.
|
| If offshore wind is available 24 hours at such a huge scale, it
| could change the renewable energy mix considerably.
|
| In that world the biggest advantage of solar would be lower
| maintenance costs and greater visibility at smaller scale (for
| example, coupled with batteries to form micro grids).
| philipkglass wrote:
| I think that you made a mistake with the solar farm area
| comparison. 10 megawatts per square kilometer (annualized,
| already accounts for night time and clouds) is a decent rule
| of thumb for solar farms. So 84 MWh/day (3.5 MW) would take
| 0.35 km^2 of solar farm. If solar farms were completely tiled
| over with 20% efficient panels achieving 28% capacity factor,
| 3.5 MW would occupy only 0.0625 km^2.
|
| But offshore wind still has advantages in that it doesn't
| occupy on-shore real estate and can supply power at night
| without batteries.
| danans wrote:
| > 10 megawatts per square kilometer (annualized, already
| accounts for night time and clouds) is a decent rule of
| thumb for solar farms.
|
| Oops, you're absolutely right, I didn't square the power,
| and it messed up the answer by a factor of 1000!
| danans wrote:
| Thanks for the corrections on solar output! I was off by a
| factor of 1000 because I didn't square from square meters to
| square km.
| kumarvvr wrote:
| In India, a 10 MW installed capacity solar plant occupies 52
| acres, about .25 sq.km
|
| You 5 sq.km figure, even for Cali is suspiciously high.
|
| Maybe you missed a decimal?
|
| Edit
|
| https://en.m.wikipedia.org/wiki/Topaz_Solar_Farm
|
| Topaz farm is 550 MW on 19 square Km.
| guerby wrote:
| Offshore capacity factor can be very high:
|
| https://www.equinor.com/en/news/20210323-hywind-scotland-
| uk-...
|
| "With an average capacity factor of 57.1% in the twelve month
| period to March 2020, the floating offshore wind farm set a
| new record in the UK."
|
| In France 2019 nuclear capacity factor was 68.7% (379.5 TWh
| produced out of 63.1 GW installed capacity).
|
| Edit: nice sortable table here https://energynumbers.info/uk-
| offshore-wind-capacity-factors
| dtgriscom wrote:
| Unit problem: such a turbine could power about 4200 homes; no
| "per day" involved.
| danans wrote:
| I should have clarified: the energy produced by one such
| turbine in a day could provide for the 1 day electrical
| energy needs of 4200 CA homes.
| kolinko wrote:
| 5 sq km is 5 million square meters, so 5 sq km would give 1GW
| according to your assumptions :)
| subpixel wrote:
| > then the only hurdle would be
|
| (In New England) the lobsterman, the fishermen, and their
| political allies, who see offshore wind as a threat and an
| opportunity, respectively.
| eloff wrote:
| I wonder if they're wrong to see it that way. Given these
| would "defend the area" from birds, that might actually
| increase fish stocks without really getting in the way of
| fishing in nearby waters. Also just marking some areas as off
| limits to fishing tends to improve fish stocks over time and
| benefit everyone.
|
| I'd be very curious to see if fish are capable of learning
| that they can use the turbines to shelter from both humans
| and birds. They're not that smart, but life tends to find a
| way.
| krisoft wrote:
| Fish are already being attracted to floating stuff, so who
| knows? Maybe these will also attract them.
|
| Source:
| https://en.wikipedia.org/wiki/Fish_aggregating_device
| mrguyorama wrote:
| Maine recently passed a law preventing offshore wind in our
| state waters :( . Our lobstering industry is very politically
| strong because they are very well united and put other
| political issues aside to improve the lobster industry.
|
| However, state waters only legally go out a few miles, and
| our (democratic) governor, while signing the law,
| specifically called out wanting offshore wind power in the
| federal waters off the coast, but we also have a shitload of
| mountaintops that could have wind power, and a few
| installations already, as well as our biggest state
| university having a hugely and important wind energy lab and
| facility
| swman wrote:
| BIT OFF TOPIC sorry, but - What about the crazy rain fall that's
| happening right now?
|
| Could some sort of devices be placed into subway tunnels and
| storm drains that pushes a turbine to generate power?
|
| Sorry if that sounds dumb, I'm just curious.
| teruakohatu wrote:
| Not really. Micro-hydro is a thing (YouTube is your friend
| here) but there is surprisingly little energy to be harvested
| from small rivers with only moderate drops. Great for a someone
| living off the grid who wants to generate power overnight, but
| not worth it otherwise.
| amelius wrote:
| I guess turbines will slow down the water, leading to more
| floods.
| xyzzy21 wrote:
| Yeah but... if the barge base the tower is attached to isn't of
| the order as large on each side as the tower is tall, the first
| gale will capsize it.
| dasv wrote:
| Don't forget that although the base floats it is also tethered
| to the seafloor with chains and anchors! The mooring provides
| most of the stability, and if it were not tethered then it
| would not stay in place at all.
| jnwatson wrote:
| It could also use an adjustable centerboard like some
| sailboats.
| nradov wrote:
| Centerboards are really only effective when the boat is
| moving. For static stability you need a _keel_ with enough
| ballast to provide a sufficient righting moment.
| _joel wrote:
| Would this reduce the environmental impact? Particularly noise
| pollution during the pile driving for traditional turbines, that
| affects whales and such.
| Symmetry wrote:
| I wonder if balloon wind turbines might not be a better approach
| in those circumstances. You have to accept smaller blades but I'd
| think the other advantages would be worth it.
| LinAGKar wrote:
| Yes, floating ones won't rise higher than to the surface.
| flavius29663 wrote:
| Wind turbines output grows with the size of the blade (it's
| squared). http://large.stanford.edu/courses/2011/ph240/parise1/
| edit: When you take into account that the blade size increase
| means a higher tower (and thus higher wind speeds), the
| increase is more staggering, because wind speed is cubed in the
| final output:
|
| > Combining the effects of height and blade length, doubling
| the height and doubling the blade length will result in an
| increase of power over 22 fold.
|
| This is why companies try so hard to build bigger blades,
| higher.
|
| Current blades are just massive https://cdn.vox-
| cdn.com/uploads/chorus_asset/file/10382023/W...
|
| The wingspan of a 747 is 68 meters. The newest GE turbine has a
| diameter of 220 meters, each blade is 107 meters. One blade is
| 50% longer than the whole wingspan of 747. You can fit 3x747
| planes inside the area swept by a current turbine.
|
| This is why Google's Makani project never took off...I really
| hoped for that project to succeed, it was very cool, but there
| is no way to compete with the bladed giants.
|
| edited to address cjbest and baq valid comments
| cjbest wrote:
| I think you meant it grows as the square of the blade length
| (and the cube of the wind speed)
|
| From your link: > Thus, the power passing through the blades
| of the turbine, and thus in turn the power of the electricity
| the turbine generates, is proportional to the square of the
| length of the blades: a doubling of blade length leads to a
| quadrupling of wind power passing over the blades.
|
| Doesn't change your conclusion of course. Thanks for the
| interesting link!
| flavius29663 wrote:
| you're right, and I roughly knew that, I just didn't knew
| how to express it well enough in a short manner. When you
| increase the blade you also have access to higher winds, so
| the total output is much much bigger. I was focusing on the
| quote below and I didn't knew how to express it better.
|
| > Combining the effects of height and blade length,
| doubling the height and doubling the blade length will
| result in an increase of power over 22 fold.
| baq wrote:
| > grows exponentially with the size of the blade (it's
| cubed).
|
| sorry, couldn't resist nitpicking. you're contradicting
| yourself here :)
| kitd wrote:
| _The newest GE turbine has a radius of 220 meters, each blade
| is 107 meters._
|
| My last maths class was decades ago, but ... 'diameter'?
| flavius29663 wrote:
| ha, I think I need more coffee this morning. Or maybe i was
| just too excited to type that out, finally something I know
| a little bit about on HN
| mLuby wrote:
| I did a research project on this.
|
| Aerial wind turbines have two key advantages over terrestrial
| ones: access to steady high-speed winds at altitude, and
| limited ground footprint. But floating or flying imposes limits
| on their size and efficiency.
|
| So they only fit niche uses in nomadic settings, like a
| temporary research camp. But then it's probably cheaper and
| more reliable to just use a fuel-powered generator.
|
| Also they're a bit of a hazard to aircraft (and each other if
| not steerable), are more at risk to storms, and the floating
| ones require expensive or explosive lifting gas.
|
| Too bad, because I think they're beautiful!
| perihelions wrote:
| >" _Principle's uses a buoyant steel triangle that has water-
| filled cans at two of the vertices. These ballast tanks balance
| the weight of a turbine at the third vertex, with water pumped
| around inside the triangle to trim its stability._ "
|
| Do they mean trimmed in real time, like active control?
| epistasis wrote:
| It's been a while since I watched this NREL talk, but my fuzzy
| recollection is that there is some amount of active control:
|
| https://youtu.be/SavaSnOOrvw
| WJW wrote:
| Yes, since the turbine creates different force vectors for
| different wind directions/speeds and the power generated is
| greatest when the mast is fully vertical, they actively re-trim
| when the wind direction and speed changes.
| mrfusion wrote:
| > taller they get, the harder they will be to repair
|
| If they're floating couldn't we have a mechanism to sink them to
| a reasonable height during repairs?
|
| Or it wouldn't seem to be that hard to have ships with large
| ladders or a crane for repairs.
|
| (I couldn't read the article because it's completely paywalled.)
| flavius29663 wrote:
| Interesting idea. I think the problem is with getting salty
| water everywhere. Salt is the main killer out on the ocean.
| Also, it you lower it enough you will end up with the blades in
| the water, I really don't think you want that during wavey
| weather.
|
| Anyway, this extra height would solve a non-problem. It makes
| little difference if a human has to climb 100 or 300 meters.
| It's still work at heights - same kind of protocols and gear.
| If it's something that the humans can't fix (replace the
| gearbox or something massive) - then you need a crane anyway.
| Maybe the only issue would be with the waves moving the
| turbines enough to make the humans seasick at that height. Not
| sure, I can't see the whole article.
| throwaway0a5e wrote:
| It's basically a fiberglass tube. Corrosion from a quick dunk
| is a trivially solve-able issue since everything that could
| corrode will already need to be protected enough fora decades
| long service life in salt spray. I can't see sinking it for
| routine maintenance being cost effective. Even at a hundreds
| of dollars per man hour it's still probably not gonna be
| cheaper than making the maintenance people climb a ladder.
|
| That said, being able to lay over the main tube at like 60deg
| would make it way easier to construct them since you could
| use a much smaller and cheaper crane to assemble and it would
| minimize the side to side movement caused by rolling. You
| basically just need a cleverly engineered chamber to pull
| that off since the ship can have all the pumping hardware.
| flavius29663 wrote:
| > lay over the main tube
|
| In my opinion, the main tubes are nowhere near strong
| enough to support the weight that way! They are weaker than
| they appear. The companies can built them so high because
| they gave up the idea that the tower can withstand any wind
| thrown at it and still oppose the wind enough to produce
| energy. Instead, smart computer programs turn the propeller
| angles independently, so that when the blade reaches the
| top (where it exerts maximum torque trying to topple the
| tower), it is angled such that it won't catch too much
| wind. Then when the blade is near the bottom, it's turned
| again in order to capture most wind.
| void_mint wrote:
| Some offshore turbine companies have developed a lift that
| attaches external to the base and carries people up. There's a
| lot of interesting technology in the space - the maintenance
| cost is the most difficult (at least, in my experience) so
| there's lots of research and innovation happening to lower that
| cost. When I stopped working with them, the company I worked
| for was using drones to take high res images of turbine blades
| to better plan for what to work on, rather than just climbing
| up and looking.
| xondono wrote:
| It's technically possible, but this things are barely cost
| effective already. A system for sinking them and raise them for
| repairs would be too expensive.
|
| As for ships, they already use custom barges, but if they're
| deployed somewhere it's because there's heavy winds, so most
| repairs need to be workable even in (somewhat) adverse
| conditions. This also makes matters worse, because you don't
| want your ship to be tied to a massive windmill if the wind
| picks up.
| WJW wrote:
| > but this things are barely cost effective already.
|
| This really needs some citations. Wind turbines at sea
| typically have well in excess of 15% return on investment
| over their expected lifespan and are being financed without
| any government subsidies these days. 15+% is not "barely cost
| effective" territory for this kind of capital intensive
| infrastructure, that is "how can I reinvest this torrent of
| income quick enough".
| xondono wrote:
| "Wind turbines" and "floating wind turbines" are not the
| same. Floating wind turbines are not as cost effective as
| their stationary counterparts.
| jcampbell1 wrote:
| The article talks about how oil service crane ships are
| designed for heavy, not high. There are prototype crane ships
| for the task, but they cost $250 million minimum which hampers
| growth of offshore wind installation. The issue is the blade
| length and positional stability, so sinking isn't much of a
| solution. My takeaway is that this is promising but a few
| engineering feats from being economically sensible.
| Bhilai wrote:
| Off topic: I see a lot of interesting Economist articles posted
| on HN. Is it worth subscribing to?
|
| Current offers show $94.50 for first year and then $189 from
| second year for digital access.
| jmackinn wrote:
| Turn of javascript when loading the economist website and you
| can read all the article with no subscription. You miss out on
| the audio version though, which is excellent.
| aurora72 wrote:
| $94.50 for first year and then $189 recurring? I would suggest
| staying away from this ridiculously unashamed rip-off at all
| costs.
| hwc wrote:
| I considered an _Economist_ subscription twenty years ago, but
| I was put off by their endorsement of George W Bush in 2000. I
| now notice that they have not endorsed a single Republican for
| US president since then, so maybe I should give them a chance
| now.
| crazygringo wrote:
| If you're interested in international news, politics, and
| economics with extensive analysis, then there's no better
| source.
|
| If you're interested mainly in domestic news, mainly
| tech/science/culture, or "just the facts" without analysis,
| then probably not.
| CyanBird wrote:
| Heavily disagree Le Monde Diplomatique or Voltaire Network
| are just infinitely better for acquiring a better macro
| perspective of the world, if anything Economist is just
| renowned for bounding the scope of debate
| crazygringo wrote:
| Wow, "infinitely" better? That's quite a strong opinion.
|
| But I'm curious how you think they give a "better macro
| perspective"?
|
| Is it in the range of stories covered, and so what kind of
| stuff do they cover that the Economist doesn't?
|
| Or is it the "debate", and I'm curious what positions you
| don't find in the Economist? Especially since their
| articles are very often in dialectical format, presenting
| competing interpretations of events as seen from the
| different sides involved in an issue.
|
| I mean it's true they're not going to apply a European
| democratic socialism lens to American political issues...
| but then they're looking at European issues through a
| European lens.
| gpresot wrote:
| It is one of the few subscriptions to media / news sites that I
| really value. Apart from their Editorials section, all articles
| have a balanced point of view, presenting all sides of an
| argument. They are all well written, and manage to explain
| complex topics (science, economics) in a fairly accessible way.
| And is also a good way to keep up to date on what happens
| around the world as each world region is covered and articles
| are often a well argumented summary of any relevant topic in
| that area in the past week(s). Their Christmas double issue is
| joy to read. But you can buy the print version at your
| newsagent for a few weeks as a trial.
| CyanBird wrote:
| When it comes to it, I would generally discourage from doing
| it, Le Monde Diplomatique is just heads and shoulders above the
| Economist on both breath of reporting as well as scope and
| coverage
|
| They also have Spanish and English editions besides French
|
| https://mondediplo.com/
| robocat wrote:
| Perhaps submit some articles you think HN would appreciate.
| So far not many have been submitted, and only one in 2013 got
| some conversation going:
| https://news.ycombinator.com/from?site=mondediplo.com
| pomian wrote:
| Their audio versions are very well done. The reading is clear
| and non monotonous. You can play back faster obviously. They
| are a very good magazine. They have their stance, but it is
| consistent. For knowledge of what's going on in the whole
| world, it's very good. I recommend it. Those prices sound high
| though.
| Confiks wrote:
| Reminds me of the incredible engineering done by Makani, as told
| in this 2 hours long autodocumentary [1]. They shut down in 2020
| because they didn't see a path towards commercializing their
| airborne wind turbine. They made a non-assertion pledge on their
| patents, and open sourced much of their code (simulations,
| firmware) [2].
|
| [1] https://www.youtube.com/watch?v=qd_hEja6bzE
|
| [2] https://github.com/google/makani
| elliottkember wrote:
| A whole bunch of their equipment started showing up on auction
| sites recently - including a few fire engines. I was extremely
| tempted to pick up a $3,000 fire engine.
| [deleted]
| eloff wrote:
| Those sell for a quarter million used, I think that's worth
| it barring major mechanical issues.
| krisoft wrote:
| Spoilers follow!
|
| I usually don't cry at movies. I cried when Mufasa died in the
| Lion King, and I nearly cried when the last prototype of Makani
| crashed into the sea in the linked documentary.
|
| So much good engineering, and effort, and hopes and dreams and
| sweat went into the whole project. I really felt for the team
| there.
| bserge wrote:
| What a great project and so incredibly nice of them to open
| source at least something.
|
| There was another airborne wind turbine project that was based
| on a blimp filled with hydrogen/helium, the name escapes me
| right now.
| latchkey wrote:
| You just beat me to this! I deleted my comment. I can't agree
| more. If you are at all curious about this topic, the
| documentary is well worth the viewing!
| [deleted]
| philipkglass wrote:
| California's renewables mix is currently solar-heavy. Water depth
| increases steeply off its coast so traditional fixed bottom
| offshore turbines don't have many viable locations. Floating wind
| would be a great complement to solar there if the technology
| matures.
| eloff wrote:
| Much of the West Coast is in the same boat.
| scrooched_moose wrote:
| See Duck curve https://en.wikipedia.org/wiki/Duck_curve
|
| Essentially, solar is great from 8am to 4pm, and California has
| replaced about half of their load during those hours with
| solar. However, they have negligible renewable capacity during
| other times of the day, including peak demand from 6-10pm.
|
| There's a more up-to-date version of California's Duck Curve
| here: https://www.energy.gov/eere/articles/confronting-duck-
| curve-...
| okareaman wrote:
| I live on the Central Coast and it never struck me as very
| windy around here, at least compared to other places I've been.
| I looked it up and as I thought, the winds are further North:
|
| 2020 Offshore Wind Resource Assessment for the California
| Pacific Outer Continental Shelf
| https://www.nrel.gov/docs/fy21osti/77642.pdf
| nradov wrote:
| It gets plenty windy just a few miles out into the Pacific
| Ocean. Pay attention to the marine forecast for a few months
| and notice how often they include small craft advisories.
| _rpd wrote:
| It's interesting tech, but a big part of offshore wind power is
| bringing the power back to shore. Onshore wind and solar are
| going to have the advantage there for the foreseeable future.
| spenrose wrote:
| https://twitter.com/ramez/status/1418261837255118849
|
| "1. No need for ocean bed fixation hardware. 2. Ultimately lower
| tons of steel & cement per MW (not true now, but coming). 3. Much
| lower EPC costs. Build in port, tow to destination. (No jack-up
| ships.) 3. Lower O&M (tow back to port) 4. Better wind resource,
| meaning higher AEP per year (amortizing capex over more MWH). 5.
| Better wind resource also means higher capacity factor ->
| increased value, slower value deflation.
| [deleted]
| yreg wrote:
| This is about wind turbines floating in the ocean[0]
|
| There are also ideas for wind turbines floating in the air[1]
|
| [0] no paywall :
| https://www.bloomberg.com/news/articles/2021-07-15/shell-joi...
|
| [1] : https://en.wikipedia.org/wiki/Airborne_wind_turbine
| teh_klev wrote:
| Sans paywall:
|
| https://archive.is/T5tic
| xwdv wrote:
| What toll are all these wind farms going to take on global
| weather patterns if they continue to multiply?
| eloff wrote:
| Basically rounded down to none. While we continually
| underestimate our unintended impacts, I don't believe that's
| the case here. Even if we sourced 100% of the world's energy
| needs from wind it would be slowing a miniscule fraction of the
| total atmospheric movements. Think of the three dimensional
| space occupied by turbines versus the vast volume of air with
| no turbines.
| jandrese wrote:
| I'm thinking they may have a double impact on combating global
| warming. Not only do they displace fossil fuel emissions, but
| they pull excess energy out of the atmosphere.
|
| However, the scale they operate at is a rounding error on a
| global scale.
| [deleted]
| WaitWaitWha wrote:
| Can someone explain if they are not anchored to something, are
| they self positioning? i.e. have some propulsion to put
| themselves back where they were placed initially? Otherwise,
| these will be floating nightmares for shipping and sailing.
| londons_explore wrote:
| They appear to still be anchored, but just with a rope rather
| than solid steel.
| Gravityloss wrote:
| You need the power cable anyway. So it must be anchored.
| de_Selby wrote:
| I would imagine they are anchored to the seabed the same way
| floating oil rigs are.
| EMM_386 wrote:
| The article explains all of this, and a lot more. It's
| absolutely worth the read if you are interested in this stuff.
|
| This diagram shows some of the proposed anchoring systems.
|
| https://www.economist.com/img/b/1000/679/90/sites/default/fi...
| ncmncm wrote:
| This is actually an easy problem. (Anyway, easy given the size of
| the things.) Make a ship that can nest the top of the tower close
| to horizontally, axis up. Winch the top of the tower down into
| its nest. Fix the turbine using cranes attached to the ship. When
| finished, unwind the winch, and let the tower right itself.
|
| There will be complications. You might need to release (one or
| more of) the tower's mooring lines after it has tilted some ways,
| and re-attach them on its way back up. You will need a cable
| attached to the top of the tower to winch it down with, either
| left there from construction or attached at need. The ship
| probably needs a boom sticking out aft to the base of the tower,
| with a grabber that can swivel up as the tower comes down.
|
| The nest and boom need to be customized for the tower design
| operated on, but the ship can get those mounted before it goes
| out. The nacelle probably has to be re-designed from scratch to
| be worked on from that angle.
| ChuckMcM wrote:
| For some definition of easy :-).
|
| Consider the following, in order to work, the turbine (which
| has a fairly high mass) has to avoid being blown out of
| position by the very winds it is trying to harness. Because it
| is quite high, the distance between the turbine and the base
| form a moment arm of great length. So the entire system
| understands the torque moment on the turbine and has in place
| the ability to avoid tilting.
|
| Compare that with the displacement mass of pretty much any ship
| you might send out there to work on it. I'm guessing that
| you're more than likely to winch the maintenance ship out of
| the water than your are going to get that turbine to tilt over.
| (disclaimer here, a spent a lot of my youth sailing and got a
| pretty good appreciation both for how "hard" ocean winds could
| try to tip you and how much a boat with a serious keel could
| resist that attempt to turn them over.)
| ncmncm wrote:
| You might also need to attach a float at the bottom of the
| tower, and inflate it while winching down. As I said, there
| will be complications. But that's what engineers are for.
|
| Anyway, ships are often astonishingly massive.
| ChuckMcM wrote:
| Not disagreeing, I just tend to flinch at the word "easy"
| for complex engineering tasks :-).
|
| Certainly a ballast transfer system would be useful, and
| there are examples of that with deep sea drilling rigs that
| transition from horizontal to vertical.
| ncmncm wrote:
| "Easy" is provocative. But the Economist publishing an
| article on an engineering problem by someone who
| evidently didn't bother to talk to an engineer is more
| provocative.
|
| To an engineer, there little space between "easy" and
| "too expensive for you".
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