[HN Gopher] 28-ton, 1.2-megawatt tidal kite is now exporting pow...
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28-ton, 1.2-megawatt tidal kite is now exporting power to the grid
Author : bornelsewhere
Score : 265 points
Date : 2024-02-12 07:50 UTC (15 hours ago)
(HTM) web link (newatlas.com)
(TXT) w3m dump (newatlas.com)
| bruce511 wrote:
| The sea is a harsh environment, but the energy it contains, in
| the form of waves (basically concentrated wind) and tides is
| enormous (partly thanks to the density of water.)
|
| Of course, like with all renewable, location matters. But there
| are lots of places with strong tides, and lots of places with
| reliable waves.
|
| Harvesting this abundant energy at scale, with reasonable
| maintenence costs will be the next breakthrough in green energy.
| mywacaday wrote:
| I've often thought why not dam a whole estuary or bay and use
| hydro to collect the energy on the the fall and rise of the
| tide. I know the environmental impact wouldake it unpalatable
| but are there any reasons it wouldn't work?
| flipbrad wrote:
| https://www.gov.uk/government/publications/1-severn-tidal-
| po...
| hardlianotion wrote:
| That Severn project has on-again, off-again cycles that are
| typical of so many UK infrastructure projects. It's a
| little depressing.
| lelag wrote:
| It's been done. Biggest one is Sihwa Lake Tidal Power
| Station[1] and France had a 240MW tidal plant since the 60s
| [2].
|
| This type of project has been few and far between and I would
| guess they might be very costly to build and maintain
| compared to the harvested energy.
|
| [1]
| https://en.wikipedia.org/wiki/Sihwa_Lake_Tidal_Power_Station
| [2] https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station
| macNchz wrote:
| This is interesting-it made me wonder if this had ever been
| considered on NYC's East River, which is a tidal estuary
| with strong currents. Turns out there's been a company
| working on it for a while, with free-moving turbines rather
| than something that spans the whole thing:
| https://www.energy.gov/eere/water/articles/tidal-testing-
| und...
| KeplerBoy wrote:
| Meet project Atlantropa, a proposed plan to dam the
| Mediterranean (or more accurately the atlantic ocean) at the
| strait of Gibraltar. A project so absurd and gigantic it
| would deserve its own thread really.
|
| https://wikipedia.org/wiki/Atlantropa
| bagels wrote:
| Meanwhile, Egypt wants to expand the mediterranian:
| https://en.wikipedia.org/wiki/Qattara_Depression_Project
| KeplerBoy wrote:
| That's interesting,I have never heard of it before.
|
| It seems outright feasible and sensible in comparison.
| himinlomax wrote:
| https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station
|
| 240 MW, built in 1966.
| theropost wrote:
| Where I'm from they have some of the highest tides in the
| entire world and there's an area not far from here that has
| always been sort of a local talking candidate for such a huge
| project.
|
| https://earthsciencesociety.com/2014/05/01/a-tidal-power-
| lag...
| IshKebab wrote:
| Definitely seems more feasible than a lot of crazy energy ideas!
| E.g. I think this makes more sense than the air versions because
| you don't have problems launching/landing or when the wind stops.
|
| Probably the biggest issues I could imagine are maintenance and
| wildlife. They might be minor issues though. Also in most of the
| world (maybe not the Faroe Islands) this has to compete with
| solar & batteries which are getting cheaper and cheaper. If this
| is more than PS5-10m then I think solar and batteries would be a
| much better option in most of the world.
| Someone wrote:
| > Probably the biggest issues I could imagine are maintenance
| and wildlife. They might be minor issues though.
|
| Might, yes, but I think it's unlikely all problems will be
| minor. Salt water isn't kind to metal, no matter how well
| painted. Also, I expect barnacles will start growing on it. If
| you're a filter feeder, this may be even better than sitting on
| the sea bed or on a whale.
|
| Question will be how much that effects their $/MWh calculation.
| The only real way to find out is to try, I guess.
| usrusr wrote:
| The good news is that we do have a bit of experience with
| metal machines that operate in sea water for decades. We (as
| in humanity, I don't) know exactly what to expect. You'd want
| to have a permanent service operation scaled exactly to how
| much overhauling capacity you need to put the tide kites in a
| round robin maintenance loop.
| hoseja wrote:
| And yet, every other tidal powerplant has been rendered
| hopelessly useless by barnacles.
| usrusr wrote:
| Have they? And how many of them can be ordered to surface
| under tide power, for easy maintenance access and towing
| into a maintenance dock without involving expensive
| divers?
|
| I presume the tether on this would be built long enough
| for controlled surfacing, a longer tether means larger
| deadzone between inbound and outbound tide, but there
| won't be much energy in the flow close to the turning
| point anyways.
| Sammi wrote:
| We are perfectly capable of removing barnacles from ship
| hulls. What makes these kite hulls different?
|
| These are just fancy boats you know.
| Brian_K_White wrote:
| Maybe we don't even care if barnacles grow on it since it's
| kind of a water catcher anyway.
|
| Or if not this design, maybe one could be designed to either
| not care or even benefit from barnacles.
|
| Remove the whole problem of fighting it.
| Tarq0n wrote:
| I wonder to what extent its output correlates with that of wind
| energy in the same region. Having a reasonably independent set
| of generating technologies might help with the intermittent
| generation of sun-based renewables.
| Super_Jambo wrote:
| I guess power output will basically be the derivative of this
| tidal height chart: https://www.tide-
| forecast.com/locations/Gamlagatt-Faroe-Isla...
|
| The steeper the slope the higher the power output.
|
| I think the real question on tidal generation is how costly
| is maintenance. The sea is just a very unforgiving
| environment. Salt water and marine life fouling everything
| are difficult engineering problems that just add more expense
| than I can imagine wind turbines having.
|
| If they can make tidal work I guess we'll end up in a world
| where most of their profit comes from keeping the grid alive
| when it's a calm and there's no sun.
|
| I guess this may mean these technologies aren't going to
| really take off until we stop using hydrocarbons to make up
| the shortfalls...
| justsomehnguy wrote:
| > maybe not the Faroe Islands
|
| Capital and largest city:
|
| Torshavn, _62deg00'N 06deg47'W_
| leoedin wrote:
| The huge difference between solar and tidal energy is the
| predictability. Tides can be predicted in advance - you always
| know exactly when and how much electricity you'll get. That's
| really valuable in a world of increasingly volatile electricity
| supply.
|
| Solar will probably be far cheaper per installed MW (although
| capacity factor will be much lower), but batteries are still a
| long way from being cost effective. The cheapest batteries
| right now cost $100/kWh or $100k/MWh. Battery costs are still
| falling, but the curve is levelling off.
|
| That price means that time-shifting 1 MWh of energy a day for
| 10 years would add $27 per MWh to the cost of electricity
| (ignoring ongoing maintenance costs, and assuming a 1MWh
| battery can do 4k cycles). The company behind this is
| forecasting $50/MWh of generation. Solar on its own right now
| sits at $30/MWh, although presumably that's for places with
| relatively high capacity factors.
|
| The limitations are obvious - this is very geographically
| constrained. I suspect there will be a small place for this
| type of technology in the renewable mix - especially in remote
| and northern places. Then again, offshore wind is already
| sitting at below $50/MWh and doesn't have the same geographic
| constraints - so maybe it's a better bet.
| throwbadubadu wrote:
| More renewable is good.. but there is always one fear in my crazy
| mind about these: This isn't actually renewable but taking energy
| out of a huge reservoir (Same for solar if pea counting, but
| solar is really endless until the end of the solar system).. and
| if we'd scale it massively the result could be another
| catastrophe. (Same btw. with geothermal?).
|
| (Btw.. I maybe got tidal wrong, so if it is just taking energy
| from waves via wind this counts as endless solar. Still, consider
| systems which would really break the tides and take energy out of
| the earth<=>moon system).
|
| The answer to this fear is that this reservoirs are so massive
| they are quasi endless in regard to what we ever could take out?
| It is hard to find numbers for these crazy thoughts :)
| lm28469 wrote:
| > (Same btw. with geothermal?).
|
| Not a chance, we're barely scratching the surface
|
| > More renewable is good.. but there is always one fear in my
| crazy mind about these
|
| It depends a lot on the rate of maintenance, materials used,
| &c. For example small windmills are next to useless:
| https://solar.lowtechmagazine.com/2009/04/small-windmills-pu...
| zakary wrote:
| You're right that nothing is unlimited. Luckily in this case,
| the energy of waves and tides is given to the oceans mostly by
| the gravity of the moon pulling the water as it passes
| overhead. Also a little bit by the wind which is fed by solar
| heat energy. The moon is slowly moving away from earth and
| eventually, in hundred of millions of years, it will impart
| significantly less energy into the tides.
|
| The energy that the moon gives the tides is essentially the
| same as how the sun gives energy to the ground with light. That
| is to say: If we don't collect it, it just gets turned into
| another kind of energy that is absorbed by the environment. For
| tides and waves that would be mostly heat, and a little sound.
| And most of that heat would eventually be radiated back out
| into space. So suffice it to say, while there is a finite pool
| of energy stored in the tides, it is so massive we could never
| make a difference, and it gets recharged everyday by the moon.
| HPsquared wrote:
| There's also ocean thermal energy conversion, which exploits
| the temperature gradient in the ocean.
|
| https://en.m.wikipedia.org/wiki/Ocean_thermal_energy_convers...
| opeon wrote:
| the tidal systems are insanely vast and powerful. the
| gravitational pull of the moon and the sun is so large that
| even if you deploy a massive amount of kits on a small surface,
| you're unlikely to have an impact on the tides. theoretically
| it's possible, but it'd require an implausible scale of
| deployment
| ben_w wrote:
| Tidal energy comes from the moon (and the sun) pulling the
| oceans as the Earth spins. Extracting energy from this
| effectively increases the drag between the ocean and the land,
| which slows down the rotation of the Earth. This effect even
| occurs without extracting tidal energy, and some of the
| dinosaurs (IIRC) had 19 hour days.
|
| The amount of energy in the rotation of the Earth is so huge
| that this basically doesn't matter, 10 TW for 660 million
| years, which is into the realm of "will too much carbon be
| subducted for photosynthesis to continue?" timescales.
| Y-bar wrote:
| I propose two possible solutions:
|
| A. Build some huge-ass rockets on the moon to accelerate it
| to offset any slowdown from changes in tidal energy.
|
| B. Divert a few billion tonnes of asteroids to crash into the
| moon's aft, adding both to the moon's velocity and mass.
|
| I believe that if we begin working on any of these solutions
| within a hundred thousand years or so from now we should be
| able to offset most of the projected long-term lengthening of
| the day.
| ben_w wrote:
| You'd have to put the rockets/target the asteroid impacts
| on the Earth, the effect on the Moon from this interaction
| is to push it into a higher orbit to conserve angular
| momentum of the combined Earth-Moon system.
| Mistletoe wrote:
| > "will too much carbon be subducted for photosynthesis to
| continue?"
|
| Great, you gave me a new fear. :)
| jacquesm wrote:
| You're edging on the laws of thermodynamics there: on a long
| enough time scale all energy is non-renewable, every little bit
| of consumption gets you that much closer to the heat death of
| the universe. But given the vast reserve in that system for
| once humans won't be able to meaningfully affect it unless we
| start consuming far more than we do today. Interesting aside:
| that momentum is a giant energy reserve and conceivably you
| could rob some of it to create a means of escaping the gravity
| well even if there had not been any other.
| card_zero wrote:
| Some numbers here:
| https://en.wikipedia.org/wiki/Tidal_power#Principle (last
| paragraph). Tidal energy is wasted by natural coastlines all
| the time, being converted into heat and erosion. If this effect
| is constant, it looks like the day gets longer by 7 minutes 12
| seconds every 36.5 million years. (I calculated that because
| it's a 1% reduction in rotational energy.) Human extraction of
| tidal energy is much smaller than the energy wasted by tides
| acting on all the world's coastlines, I assume. To some extent
| it takes energy away from coastal erosion, which also seems
| fairly benign.
| whatisyour wrote:
| Erosion is not always wastage.
| mft_ wrote:
| Could you expand? I'm interested in what you're getting at.
| Eddy_Viscosity2 wrote:
| I think he's referring to nature making less florida.
| actionfromafar wrote:
| OTOH there's a case to be made for keeping florida
| diluted.
| idontknowifican wrote:
| erosion actually creates nests for various sea birds
| wongarsu wrote:
| Erosion makes gravel and sand, which are quite useful. It
| also makes minerals and nutrients accessible to life.
|
| But we spend a lot of time and money managing erosion,
| and at the same time (often accidentally) create lots of
| erosion in other places. I doubt extracting tidal energy
| will have effects on a global scale, though it might
| cause some local changes
| bbor wrote:
| For a detailed discussion of "what _is_ the environment,
| and what does preserving it look like?", see the Red Mars
| trilogy. Very interesting questions about nature as
| aesthetic vs nature-in-its-own-right
| piaste wrote:
| It's good that you are aware it's a crazy thought :) Nothing
| wrong with looking into it though. Wikipedia offers:
|
| > Movement of tides causes a loss of mechanical energy in the
| Earth-Moon system: this results from pumping of water through
| natural restrictions around coastlines and consequent viscous
| dissipation at the seabed and in turbulence. This loss of
| energy has caused the rotation of the Earth to slow in the 4.5
| billion years since its formation. During the last 620 million
| years the period of rotation of the Earth (length of a day) has
| increased from 21.9 hours to 24 hours;[10] in this period the
| Earth-Moon system has lost 17% of its rotational energy. While
| tidal power will take additional energy from the system, the
| effect is negligible and would not be noticeable in the
| foreseeable future.
|
| and there is some simple math in the [Tidal acceleration] page
| [0] that you may want to read. Basically, the tides slow the
| rotation of the Earth, with some of the energy being
| transferred to the Moon but most of it going into friction. The
| natural friction is estimated at a (surprisingly low, IMO) 3.64
| TW, and at this rate the Earth will stop rotating in 50 billion
| years, long after the Sun has blown up.
|
| So if we want to keep the Earth spinning (albeit slowly) until
| the Sun goes red giant, we can afford to cut that time down to
| a tenth, meaning we can produce 36 TW (before conversion to
| electricity, i.e. ignoring efficiency).
|
| If we are being reckless and just want to use power until we
| figure out nuclear fusion or something better, let's say a
| million years or so, we can make some 180 PW from tides. But
| since it would almost all turn to heat, and since that is more
| energy than the Earth gets from the Sun, that would probably be
| unwise unless we find a way to get it off-planet with very high
| efficiency.
|
| (Global electrical energy production is currectly about 28 PWh
| per year, equivalent to a constant 3TW or so.)
|
| [0] https://en.m.wikipedia.org/wiki/Tidal_acceleration
| lloeki wrote:
| > If we are being reckless and just want to use power until
| we figure out nuclear fusion or something better, let's say a
| million years or so, we can make some 180 PW from tides. But
| since it would almost all turn to heat, and since that is
| more energy than the Earth gets from the Sun, that would
| probably be unwise unless we find a way to get it off-planet
| with very high efficiency.
|
| I think you're touching on the problem very nicely here: the
| problem is not "how much raw energy is there" (because
| there's an absolute fuckton of it) but "when does the impact
| of capturing this energy - thus removing it from a complex
| ecosystem whose stability may depend on it - and turning it
| into something else - thus adding to a complex ecosystem in
| other ways - becomes a problem", which may or may not come
| well before the theoretical raw energy cap.
| piaste wrote:
| I'm not sure those considerations are applicable. There is
| no "ecosystem" that depends on the rate of slowdown of
| Earth's rotation - we do need to leave _some_ rotation to
| keep flora and fauna alive, but that 's a "reservoir"
| problem, to use the OP's formulation, not an intensity one.
|
| As for the addition of energy (heat) to the planet, sure,
| but there's nothing specific about tidal energy here. All
| energy sources except solar (and wind/hydro which are
| direct solar derivatives) add heat to the planet that would
| otherwise have stayed sequestered. But it's many orders of
| magnitude less than the heating from solar energy, which is
| why increasing Earth's absorption factor by a few points is
| an infinitely bigger problem than all the energy we are
| directly producing or can hope to directly produce in the
| next few centuries.
| zaroth wrote:
| Also worth noting that trying to extrapolate the effects
| of current technology at this timescale is pointless.
|
| There will be tide changes in human's technological
| capabilities long before there could be any reckoning for
| over-extraction of the Earth's rotational energy.
|
| For example, in our ability to bring mass into orbit. Add
| a couple orders of magnitude in that capability, and
| humans can start directly tuning the Earth's total solar
| irradiance by shooting lunar dust into a Lagrange point,
| reducing the amount of sunlight hitting the Earth by
| fractions of a percentage.
|
| The Lagrange point is not perfectly stable, so the dust
| naturally dissipates over a 10-20 year timescale. If you
| don't keep sending more dust, the "planetary sun-shade"
| naturally dissipates, so there's zero risk of overdoing
| it.
|
| Basically, within the next ~50 years, I predict we will
| gain the ability to turn down the planet's thermostat in
| a very safe and predictable fashion, without having to
| pollute our own stratosphere. Overheating the planet
| becomes a total non-issue.
| ComputerGuru wrote:
| How much dust would you need to shoot up to affect a
| statistically significant change in the amount of
| sunlight getting through?
| zaroth wrote:
| A fuckton.
|
| Roughly 100 million tons annually of lunar regolith
| launched into L1 by railgun.
|
| https://journals.plos.org/climate/article?id=10.1371/jour
| nal...
| SoftTalker wrote:
| > within the next ~50 years
|
| Very optimistic. We haven't even been to the moon again
| in 50 years.
|
| 500 years, maybe.
| bbor wrote:
| With all seriousness, I'll throw in "the unexpected
| breakthroughs in intuitive AI will aid this effort." I
| sincerely think that LLMs will at least make R&D cheaper.
|
| Beyond that, "we haven't been to the moon" isn't a fair
| summary of our tech imo - a HUGE portion of that is
| political in origin, and private companies have invented
| _reusable_ rockets which is pretty damn important
| tremon wrote:
| _I sincerely think that LLMs will at least make R &D
| cheaper._
|
| How, exactly? Because to me it's just as likely that LLMs
| will hallucinate alternative solutions based on their
| flawed world model which will send numerous unfortunate
| researchers on wild goose chases that turn out to be
| exactly that. And I expect the volume of impossible-yet-
| probable-sounding solutions will dwarf the actual costs
| saved by using an Automated Induction system.
| lloeki wrote:
| > There is no "ecosystem" that depends on the rate of
| slowdown of Earth's rotation
|
| I mean, raise acidic/temperature levels only so slightly
| and it kills off coral reef, which in turn destroys fauna
| that depends on it, leaving huge areas barren.
|
| What I'm getting at is that small changes can have
| dramatic domino effects. Mass-scale tide dampening could
| have unforeseen effects.
|
| Not saying any of the solutions are going to be a
| problem, merely that it's better to ask crazy questions
| about what happens when they ramp up at scale than
| handwave things away with uniform spherical cows.
| Karellen wrote:
| > at this rate the Earth will stop rotating in 50 billion
| years,
|
| That's not what the link you posted says. It states that
| that's when the Earth-Moon system will be tidally locked, so
| that the Moon orbits the Earth at the same rate that the
| Earth rotates around its axis.
|
| Kind of if the earth slowed so that one "day" took the
| equivalent of 28 days now. The earth would be locked with one
| side always facing the moon, so there would be no tides, but
| it would still be rotating. Except it will end up be a longer
| "day" than that, because as energy is transferred to the Moon
| its orbit is raised, which slows it down.
| dylan604 wrote:
| This is nice and all, but in 50 billion years, the moon's
| distance from the Earth will much greater which means it's
| gravitational effect on Earth will be much smaller.
| Karellen wrote:
| OK. Do you have any reason to suspect that the people
| making their calculation didn't take that into account?
| Of all the things that will vary over time, including the
| distance between the Earth and Moon, do you really think
| they'd have missed the fact that the Earth's gravity
| varies with distance?
|
| If you've got what you think is a more accurate number,
| and can show your working, I'm sure the wikipedia editors
| would be willing to take a look at it.
| LM358 wrote:
| "Tidal Energy Is Not Renewable":
| https://cs.stanford.edu/people/zjl/pdf/tide.pdf
|
| Previous discussion on HN:
| https://news.ycombinator.com/item?id=37383283
| dogtimeimmortal wrote:
| Thanks for this! Something has always bugged me when I hear
| about big plans for tidal energy.
|
| TLDR, the 1000 year estimate is is derived from the geometric
| series proof(i needed a refresher). Wolfram explains it
| pretty well:
| https://mathworld.wolfram.com/GeometricSeries.html
|
| ...then i needed a refresher on exponents and logarithms:
| https://wou.edu/mathcenter/files/2015/09/Exponents-and-
| Logar...
|
| It's good to do the math and think about the big picture
| sometimes. ;)
|
| p.s. i tend to feel somewhat skeptical about a lot of
| renewable projects i read about in the news. And even if the
| math all works out and it really IS The Best Solution i cant
| help feeling we are ignoring the elephant in the
| room(population growth). Maybe human beings should start
| preparing themselves to live with less(and be happy with
| that).
| ComputerGuru wrote:
| Population growth is effectively over.
| dogtimeimmortal wrote:
| Little addition, couldn't resist sry:
|
| After reading a bit of the comments thread above, i
| couldn't resist adding a bit more.
|
| > The single most important assumption in this paper is
| that energy consumption will increase by 2% per year.
|
| Quick reality check: 1.02^1000years = 398,264,652x
| increase! This could potentially be an unrealistic
| projection. Let's consider what we know from the
| article(and google).
|
| Here's a few numbers pulled from the article for reference:
| ~1.73 x 10^20 J tidal energy lost per year naturally
| 5.67x10^20 J was the total global energy consumption in
| 2013(10^18 is 1%)
|
| So 398,264,652 x 5.67x10^18 J = 2.258 x 10^27 J! That does
| seem like a lot. In comparison total sunlight absorbed on
| earth's surface each year is roughly 3.85 x 10^24 J.[1]
|
| > It might also be that tidal energy extracted by humans,
| comes out of some fixed 'budget'
|
| So lets compare that to what is already being consumed and
| think about what amount of energy generated might be
| realistic. Top google result tells me global energy
| consumption is about 5.80 x 10^20 J2 these days.[2]
|
| I guess the next question is what would be a realistic
| upper limit for the amount of energy we could harvest
| globally from the tides? Referencing the Stanford article
| again, we have an estimated annual energy loss of 1.73 x
| 10^20 J total from natural friction of the tides globally.
| Is it realistic to think we can harvest an equivalent
| amount of energy for the grid? I wonder what sort of impact
| a turbine project that size would have on the earth? Is it
| even possible? For sake of being rational, let's say we
| think a network of turbines 1% of that size(10^18J) is
| potentially possible. How many turbines might you need to
| make for something that size?
|
| So lets take the kite-turbines from the article at the top.
| Each one of the produces 1.2MW. Does that mean it produces
| 3.78x10^13 J annually? Or is it closer to half
| that(1.89x10^13J)? In a 10^13 J ballpark we would need to
| produce about 10^17 to approach our max limit 10^20 J
| harvested. Correspondingly a project 1% the size still
| needs 10^15(a quadrillion) of these turbines globally. That
| seems like a lot and it just sort of seems in my mind(maybe
| i'm wrong) that there would be some sort of environmental
| impact. Also, now that you have shrunk your project the
| total energy produced is now a fraction of 1% of the
| current total global annual energy consumption, and grows
| more insignificant every year consumption rises.
|
| Not sure I agree that population growth is over, but isn't
| it true that energy consumption per capita is also
| increasing? Either way I think we still have the realistic
| expectation of continued 2% growth in global energy
| consumption for the next few decades at least, doubling
| every 35 years. Unless we can find ways to harvest larger
| quantities of tidal energy without breaking the ocean it
| just doesn't seem like a silver bullet to me as far as
| climate goes. Assuming we could harvest 25% the quantity of
| what occurs naturally, that only gives us 0.4325x10^20J
| annually, which is only 7% current global consumption - in
| 35 years that number will only equal 3.5% of the total
| consumption. I guess it's a question of how much you want
| to screw up the environment in order to save it.
|
| TLDR, saving the planet with tidal energy seems kind of
| misrepresented imho. Build wooden megaliths instead. ;)
|
| [1] https://www.ucdavis.edu/climate/definitions/how-is-
| solar-pow...
|
| [2] https://www.theworldcounts.com/challenges/climate-
| change/ene...
| lloeki wrote:
| > Same for solar if pea counting, but solar is really endless
| until the end of the solar system
|
| Imagine you wrap the Earth inside a sphere of perfectly
| efficient solar panels, that would be energetically
| troublesome! Every bit of solar panel we lay removes a bit of
| that overall energy flux; the question is then how much can we
| afford without detrimental impact.
|
| Essentially we dampen tides with these devices. Windmills are
| slowing the wind. How much can we afford before it has an
| actual detrimental effect?
|
| Also, pedantically, "renewable" is a fun word.
|
| The question of "renewable" is whether the energy/matter
| somehow gets back in some way... Of course there's entropy and
| such.
|
| Say you cut wood (CHO) and burn it. If you grow enough wood
| it'd recapture H2O+CO2 and you have a nice endless loop (plus
| entropy). That would presumably be renewable.
|
| In that sense (again, pedantically):
|
| - nuclear (and so the sun) is not renewable: reversing
| U/Pu/whatever fission is a teeny bit out of our league so
| someday the supply will dry out. Fusion as we do it (and the
| sun too, being main sequence) is H->He and we don't exactly
| know how we could reverse that so someday the supply will dry
| out.
|
| - fossil fuel is renewable... on a geological timescale, which
| is not really practical; we can't exactly grow big enough
| forests and bury them for millions of years to get fuel back.
| So someday the supply of humans surviving will dry out.
|
| - tides/wind is not renewable: we get mechanical energy but
| don't return it to the original place (or maybe _extremely_
| indirectly in the form of heat)
|
| So it's all named backwards!
|
| Or really there's no renewable... Essentially it all pans out
| because the Earth is not a closed system, there's loss in every
| transformation but it's balanced by the energy influx from our
| nearby star.
|
| So I guess the "renewable" thing is not really, it's more like
| "capturing energy from an astoundingly immense and complex
| system in a way that doesn't throw it in a runaway catastrophe
| one way or another before the sun exits its main sequence".
| IanCal wrote:
| I think you're assuming renewable means infinite.
|
| > - nuclear
|
| Nuclear isn't renewable, but there's a huge amount of it and
| it doens't have the same problems.
|
| > (and so the sun) is not renewable:
|
| The energy we get from it is. It's not a fixed resource that
| we're depleting. When we burn all the coal, it's _gone_.
| Tomorrow there will be more sunlight. We 're not cutting
| chunks off of the sun to get energy for solar.
|
| > - fossil fuel is renewable... on a geological timescale,
|
| Only some of them, and only if we change the definition of
| renewable. Coal is there because there weren't fungi that
| could break down lignin at the time.
|
| > Imagine you wrap the Earth inside a sphere of perfectly
| efficient solar panels, that would be energetically
| troublesome! Every bit of solar panel we lay removes a bit of
| that overall energy flux; the question is then how much can
| we afford without detrimental impact.
|
| We could probably benefit significantly with reducing the
| energy flux right now.
| lloeki wrote:
| > I think you're assuming renewable means infinite.
|
| No, for the purpose of this dumb exercise of mine, I mean
| the resource we use for energy production is replenishable.
|
| > It's not a fixed resource that we're depleting.
|
| What I mean is that the Sun is going to exhaust its H
| supply. We just happen to harvest part of its output, but
| it's depleting itself whether we harvest it or not, so we
| might as well do it :shrug:.
|
| So at our scale it looks like infinite but in the strictest
| sense it's a consumable that does not replenish.
|
| Fundamentally that makes it not different from nuclear fuel
| (whether heavy fissile ones or hydrogen if we manage fusion
| someday) which as you mention are in ample supply, yet we
| consider them to not be renewable while the sun would be?
| The only difference is a) the Sun is (much) bigger thus
| will last (much) longer and b) we delegate fuel logistics
| and fusion reaction to the sun.
|
| But then again, trees are not really renewable, they got to
| get energy from somewhere to grow... IOW they're
| essentially CHO-based solar batteries.
|
| As I said, I was not trying to make any point, just being
| extremely pedantic about semantics for fun ;)
|
| > the definition of renewable
|
| > A renewable resource (also known as a flow resource) is a
| natural resource which will replenish to replace the
| portion depleted by usage and consumption, either through
| natural reproduction or other recurring processes in a
| finite amount of time in a human time scale. When the
| recovery rate of resources is unlikely to ever exceed a
| human time scale, these are called perpetual resources
|
| https://en.wikipedia.org/wiki/Renewable_resource
|
| Essentially the definition is focused on resource when it's
| really about time (esp. our extremely small time scale vs
| stellar scale). The resource in reality doesn't replenish,
| rather it's so huge that we can consider our usage of it
| well below rounding error. IOW from our very small
| "rounding error" human point of view it might as well be
| considered infinite.
| IanCal wrote:
| We could push it further and say there's no renewable
| source possible - at least until the multivac finally
| gets the answer.
|
| > The resource in reality doesn't replenish
|
| Sunlight does. Wind does. A water wheel in a river is
| renewable power. Solar panels producing power today don't
| make tomorrow darker.
| amelius wrote:
| And most electricity eventually turns into heat. So there's a
| limit there too.
| dsign wrote:
| Alien archeologists from the future: "Earthlings caused a
| catastrophe by trying to suck every bit of tidal energy. Via
| tidal acceleration[^1], they made their natural satellite fall
| into their planet. The curious thing is that the kind of
| planetary technology level they deployed to extract energy from
| the tides was more than enough to build huge rotating habitats,
| which they even knew of and called O'Neill cylinders[^2]. But
| Earthlings called names anybody proposing the idea, and it
| never really took off before their moon fell on their heads.
| This is a textbook case of how a civilization's culture affects
| their development."
|
| [^1]: https://en.wikipedia.org/wiki/Tidal_acceleration
|
| [^2]: https://en.wikipedia.org/wiki/O%27Neill_cylinder
| jvanderbot wrote:
| Yeah I sometimes wonder about our use of energy.
|
| Like two whole percent goes to cracking puzzles, and if you
| prove you crack those puzzles we let you buy things. Those
| puzzles? Guessing hashes for Blockchain. Not cancer or
| science or engineering, just automated planet wide gambling.
|
| Then how much is used for ads? Like top to bottom, serving
| ads. Must be a ton. As a planetary anthropologist, seeing how
| much infra we built to watch people do silly dances or say
| things on TikTok... Like we're so addicted to ourselves that
| we built all this to watch ourselves do things.
| MRtecno98 wrote:
| I get your point with blockchain(altough i'd like a source
| for 2% of the entire human energy production going into it)
| but ads are useful actually, they make people know about
| what other people do which drives economy, and economy is
| basically a fancy word for the system that distributes each
| human's limited time into the various tasks society
| needs(which do include large scale planetary development
| but also for example, your local supermarket which makes
| you eat).
|
| As for tiktok and silly dances, humans don't need only food
| and water to work reliably, they also need mental health.
| So leisure, amenities, relationships etc.(yeah tiktok
| included) are an addiction in the same sense food water and
| oxygen are an addiction, we just need them to
| work.(obviously while "addiction" to leisures is in general
| not a real problem, addiction to a specific thing in this
| list is, just like addiction to a specific food is a
| problem. I'm not saying tiktok addiction is a good thing)
|
| If you think humanity's purpose is to develop their
| knowledge of the universe and techonological grasp, then i
| reassure you that(almost) everything we do on this spinning
| ball is a cog in the machine that ultimately sustains that
| development
| smolder wrote:
| > economy is basically a fancy word for the system that
| distributes each human's limited time into the various
| tasks society needs
|
| That's a bit too idealist a view for me. The economy
| isn't strictly or even mostly about fulfilling _needs_ of
| society, but the aggregated demands of those with
| economic power, both wants and needs. A lot of what we
| spend effort on is not useful to society and a lot of
| needs go unmet. Certainly not every wasteful activity can
| be waved away as investing in our mental health. Some
| leisure is a net negative there, too. Some spending is
| destructive, with no upside. We humans are only somewhat-
| rational actors.
| usrusr wrote:
| How would solar be the same? That "reservoir" is emptying
| wether we hold silicon into the photon flow or not. Tides and
| wind aren't quite as far from just taking what is already
| disappearing, but even there: the natural drag of land and sea
| floor shapes is not only so many more orders of magnitude
| larger than anything we could ever build, there's also the
| nonlinearity of drag, if we slow down the natural flow a tiny
| little but the effect of natural drag will decrease accordingly
| and the total difference to natural flow will be much smaller
| than it would be if drag was linear to speed.
| doubloon wrote:
| in the past twenty years the plains states like kansas and
| oklahoma began having earthquakes due to injection of petroleum
| wastewater into the ground. The government had to stop them
| because private industry literally does not care what gets
| destroyed
| friend_and_foe wrote:
| Yes, you're right. What you're doing when harvesting tidal
| energy is introducing a friction like resistance on the moon as
| it revolves around the earth and on the rotation of the earth,
| and taking energy from it's energy of motion, that is, slowing
| it down. But I'd expect with the masses and velocities involved
| that this amount is miniscule and not even close to being
| measurable. That said, we didn't think we could impact the
| earth by burning fuel, and if something like this were adopted
| large scale the impact could surprise us and be a real problem.
|
| Solar isn't as limitless as you'd think. It is limited to the
| surface of the earth, more precisely, the surface area of the 2
| dimensional disk from the perspective of the sun. And on earth,
| that's what drives life, so harvesting solar energy on the
| surface is something that, if deployed beyond what we think we
| need right now, can have a negative impact on the earth.
| Harvesting it in space and beaming it down would heat the earyy
| up too, as the energy is used it produces waste heat which
| means on a large scale even using the energy on earth would
| have a negative impact.
| tetha wrote:
| Since the number 1.2MW didn't mean much to me, modern on-shore
| wind turbines seem to supply 3-4MW and offshore ones 8 - 12MW.
|
| But this seems a lot easier to transport and install compared to
| cranes and the nightmare of navigating turbine blades on trucks
| through places. And if these hold up to water and don't cause too
| many problems for wildlife, there would be a lot less discussions
| about these "messing up my skyline", while tapping a new source
| of energy.
|
| Quite interesting and cool.
| out_of_protocol wrote:
| > too many problems for wildlife
|
| There were a meta-analysis regarding population of birds in
| areas with/without wind turbines, found no statistically
| significant difference (unlike coal, where difference was huge)
| tetha wrote:
| Yep. I mostly meant for or rather caused by this kite. I
| wouldn't expect it intuitively, as it's just a big object in
| the water, not moving erratically or obstructing anything.
| thfuran wrote:
| I guess erratic is in the eye of the beholder, but it's
| certainly moving.
| imzadi wrote:
| It has a 39-foot wingspan and moves in a figure 8 pattern
| on a seabed tether. There's going to be at least some
| implication for local wildlife, but is it worse than the
| impacts of fossil fuels? I have no idea. It's definitely an
| interesting concept. I'm sure it will get more efficient
| and require a smaller footprint over time, assuming we
| invest in it.
| duskwuff wrote:
| > There's going to be at least some implication for local
| wildlife, but is it worse than the impacts of fossil
| fuels?
|
| For that matter, how does it compare to the local impact
| of other watercraft?
| m0llusk wrote:
| Like much statistical analysis there are some details that
| might not be well captured. Much of the opposition to wind
| power based on bird deaths is caused by the Altamont Pass
| facility which is placed in a golden eagle breeding area and
| has significantly disrupted that species. There could be
| similar risks here if generating equipment like this were to
| be used in sensitive marine habitats such as the Monterey
| Bay. It will probably be worth ongoing study to avoid
| potentially serious problems that broad statistical analysis
| may not catch.
| jtriangle wrote:
| Yeah, if you're looking to save the birds, the first order of
| business is to ban cats, because turns out those cute little
| guys are rather adept at bird murder.
| morkalork wrote:
| Apparently that isn't true and just shifting the blame away
| from the pesticide and agricultural industry which have
| decimated insect populations. Which are the food source for
| many birds. Much like blaming consumer's personal choices
| for CO2 emissions.
| bjourne wrote:
| "We estimate that free-ranging domestic cats kill 1.3-4.0
| billion birds and 6.3-22.3 billion mammals annually. Un-
| owned cats, as opposed to owned pets, cause the majority
| of this mortality. Our findings suggest that free-ranging
| cats cause substantially greater wildlife mortality than
| previously thought and are likely the single greatest
| source of anthropogenic mortality for US birds and
| mammals." https://www.nature.com/articles/ncomms2380
| amenhotep wrote:
| This is the first time I've seen the statistic quoted
| with the distinction that it's about _feral_ cats, and it
| makes a heck of a lot more sense now than it did when I
| had the impression they were saying the cats I 've had,
| which were on the whole utterly useless at catching
| things, were secretly massacring birds by the dozen.
| Thanks for the drive by enlightenment :)
| bronson wrote:
| What isn't true?
| https://www.sciencenews.org/article/cats-kill-more-one-
| billi...
|
| Yes, pesticides are also an issue.
| justsomehnguy wrote:
| > In April 2022, Minesto announced a detailed plan for large-
| scale buildout of tidal energy arrays in the Faroe Islands. The
| large-scale buildout plan sets out a stepwise installation of
| _tidal kite arrays, each with 20-40 MW_ installed capacity, at
| four verified locations.
| aqme28 wrote:
| A common blocker for offshore wind is people* complaining about
| seeing wind turbines on their formerly immaculate horizon.
| These don't have that problem.
|
| *: e.g. Ted Kennedy. Rich and politically connected people like
| to live on the coast
| rootusrootus wrote:
| What's interesting is that we can stop off-shore wind
| projects for that reason, but can't seem to stop the
| advertising barges that run up and down the coastlines.
| debok wrote:
| A kettle uses ~1.5KW, a geyser ~2KW, an oven ~5KW, a stove
| about ~3KW. These are fairly high estimates I got from some
| quick googling. If you add these all up, and account for some
| more appliances (HVAC, fridge/freezer etc.), I think it is safe
| to estimate that a household less than 20KW at peak, even
| though it is a fairly high estimate.
|
| So going backwards from there, 1.2MW = 1200KW and 1200KW / 20KW
| = 60 households at peak usage. Which is a very conservative
| estimate.
|
| For future reference I will use 1MW = 50 households as a
| conservative rule of thumb. Maybe 100 households per MW is
| closer to reality, but that feels fairly lenient to me.
| TotempaaltJ wrote:
| > The current national average (through Q2 2022) of homes
| powered by a MW of solar is 173.
|
| https://www.seia.org/initiatives/whats-megawatt
| jtc331 wrote:
| If the average home was using 10kW constant it be using 240
| kWh a day, which is enormously high.
|
| In terms of average usage an average sized home in the US is
| much closer to 50kWh a day, so roughly 2kW average demand.
| That would mean 1 MW is enough for 500 homes on average. The
| one thing that doesn't is peak demand load, say when everyone
| gets home from work and turns everything on at the same time
| or a particularly cold or hot day.
|
| Edit: the average US home uses just shy of 1000 kWh a month,
| or just over 30 kWh a day.
| methyl wrote:
| I'm really surprised by this data. In Poland, it's around
| 2000 kWh/year, which is 6kWh/day - 5 times less!
| Symbiote wrote:
| The USA includes many places where air conditioning uses
| electricity, and some places where heating uses
| electricity.
|
| They also have huge and inefficient appliances, but
| that's probably a smaller impact on the figures.
| gambiting wrote:
| Ok, but what do you actually use? I have a very small
| 3-bed house in the UK, and over the last few months we've
| been averaging 1100-1200kWh of electricity per month(and
| we heat using gas, although we do have an electric car).
| methyl wrote:
| It's not me, I'm talking about average for Polish
| houselhold
| wongarsu wrote:
| Air conditioning makes up a big part of that, made worse
| by worse insulation and larger houses.
|
| Of course Poland needs heating, but that doesn't show up
| in Electricity usage as most people heat with natural gas
| or oil.
| Detrytus wrote:
| Actually, most people would heat with coal. Natural gas
| and oil are far less popular.
| tzs wrote:
| According to to stat.gov.pl [1] the average Polish
| household uses ~24.6 GJ of energy annually per 1
| inhabitant. That's 6800 kWh annually per 1 inhabitant.
|
| According to eia.gov [2][3] the average US household uses
| annually 56.6 million BTUs of natural gas and 10500 kWh
| of electricity. 56.6 million BTUs is 16600 kWh. That
| would bring the total to 27100 kWh.
|
| But wait...the Polish data is per inhabitant. The average
| number of people per household in the US is 2.6. Dividing
| 27100 by 2.6 gives 10400 kWh. Alternatively, the average
| Polish household is 2.47 people, which would give Polish
| per household usage of 16800 kWh.
|
| The US does appear to use more energy per household
| (total or per inhabitant) than Poland, but by a factor of
| about 1.6, not 5.
|
| [1] https://stat.gov.pl/en/topics/environment-
| energy/energy/ener...
|
| [2] https://www.eia.gov/todayinenergy/detail.php?id=57321
|
| [3] https://www.eia.gov/energyexplained/use-of-
| energy/electricit...
| Taek wrote:
| Thanks for breaking this down cleanly and providing
| sources! Greatly appreciated!
| nawitus wrote:
| Finland is probably like 15000 kWh/year/house (for a new
| house more like 10000 kWh/year). All the heating of the
| house & water is done by electricity, though.
| mndgs wrote:
| 8.2 kwh/day for a household in Lithuania, neighbours
| Poland. Sounds about right.
|
| 2022 stats: 3.289 TWh during 2022 consumed, 1.1M
| households, do the math...
|
| Source: https://www.lrt.lt/naujienos/verslas/4/1887046/li
| tgrid-60-pr...
| BizarroLand wrote:
| Last month I used 1402 kwh in Washington State, which is
| high for me.
|
| 2600 sq ft home kept at 71f, electric heat pump, & heat
| pump water heater, but I had a few holes in the walls for
| several days due to repairs during the coldest month of the
| winter so far which messed up my average using electric
| heaters to backfill the gap.
|
| Obviously, the holes were covered over when not being
| worked on but it wasn't as air tight as compared to
| buttoned up and fully insulated as usual.
|
| My power consumption is usually 30 to ~75% of that
| depending on weather and activity.
| kevinbowman wrote:
| Also relevant, houses aren't boiling a kettle and running
| their oven 24x7, so this is more like worst-case peak load
| and will be spread across different houses. Having some kind
| of battery storage closer to the houses will help a lot - the
| tidal generator can run fairly constantly and fill the
| battery, and the houses can draw in short bursts from the
| battery.
| bbsz wrote:
| Yeah. I always feel that the solution for clean and
| abundant energy globally is to start with better energy
| grid management (and storage). There's already so many fit-
| to-all-geography solutions available. It's just that
| current grid is used to supporting lines centralized around
| big energy plants and not small producers.
|
| I also always feel that there's a lot more to take down
| from energy consumption per household by simply making more
| efficient devices (especially for heating and cooling).
| It's possible that modern AC/heaters are already close to
| the peak electrical efficiency, but I guess even better
| producer standards for things like insulation, thermal
| conductors or precision sensors could still squeeze
| something out of the nation-wide usage.
| bagels wrote:
| There is synchronized kettle use and toilet use around
| televised sports games.
| tremon wrote:
| So advertising is one of the biggest factors in
| determining the required grid capacity? Perhaps we should
| charge them for it.
| Sammi wrote:
| Minesto CEO is quoted in local Faroese news saying 800
| households:
|
| https://kvf.fo/greinar/2024/02/09/drekin-framleidir-nu-
| strey...
|
| https://kvf.fo/greinar/2024/02/09/minesto-og-drekin
| ComputerGuru wrote:
| (What's a geyser?)
| coderedart wrote:
| Water heater for bath/showers
| ragebol wrote:
| From top of my head: my grandma used to have one. There was
| always a little flame running for safety in case of leaks,
| but when she used hoy water, I think the geyser just heated
| it on the go, instead of preheating a reservoir.
|
| Could be wrong though.
| tremon wrote:
| A device for heating water on-demand, usually a gas burner
| with a spiraling water pipe surrounding/above it. As
| opposed to a boiler, which pre-heats water and stores it
| for later use (and also needs to keep reheating the water
| as it cools if not used).
|
| Spanish wikipedia is the only with a picture of the
| internals: https://es.wikipedia.org/wiki/Calentador_de_agua
| _circulante?...
| pappn wrote:
| I think 100 households per MW in milder climates is very
| conservative.
|
| Anectdata: I have a ~150 square meter, 50 year old house
| heated by electricity and heat pump. I live I Norway, and
| where I live winter temperatures usually don't get lower than
| -12C. I have 2 EVs that are driven around 50k km a year
| combined, charged at home every night, simultaneously.
|
| I peak out below 15kW (1h average). That number is deliberate
| since I get a higher tariff if I go above 15kW. I have some
| minor smart house installations that most significantly cuts
| power to my hot water heater if I get close to 15kW, but even
| without that I would rarely get above 15kW, and never above
| 20kW.
|
| Average power this January was 4.75kW, December was 4.96kW,
| August was 2.25kW.
|
| (Edited for typo)
| tomtomtom777 wrote:
| It is also a completely different scale. A 11M wind turbine has
| a 200m (!) rotor diameter. This thing is 12m.
| thfuran wrote:
| But it's moving around through some larger area.
| rootusrootus wrote:
| > modern on-shore wind turbines seem to supply 3-4MW
|
| That sounds like the very largest of the most recent wind
| turbines. I think most of the in-production wind turbines
| people are used to seeing these days are closer to the 2
| megawatt range.
| jabits wrote:
| Actually, these seabed moorings can create rich, local eco-
| systems. I know local fishermen here in Maui are drawn to areas
| around the off-shore buoys...
|
| "The FADs are located 2.4 to 25 miles offshore and in depths of
| 80 to 1,510 fathoms." --
| https://www.lahainanews.com/sports/local-sports/2016/05/19/s...
| philomath_mn wrote:
| Another reference point: the coal plant in my area outputs
| 2.3GW. It would take almost 2,000 of these tidal kites to match
| that output.
|
| I just don't understand why we spend so much time and money on
| renewables like this when Japan has an 8GW nuclear plant. If
| the US focused on building these en masse then we'd be in a
| great place.
| someuser2345 wrote:
| Because a lot of people hate nuclear energy, and don't
| support building new plants. So it's not really a choice
| between nuclear and renewables, it's a choice between
| renewables and fossil fuel power plants. Besides, I think
| there's definitely a benefit to decentralizing the power
| grid, and to learning how to tap different energy sources. I
| imagine that there are places in the world where nuclear is
| not appropriate, but tidal energy is abundant.
| philomath_mn wrote:
| > a lot of people hate nuclear energy, and don't support
| building new plants. So it's not really a choice between
| nuclear and renewables
|
| I guess that is my point: the hate is counter-productive.
| Neglecting nuclear was one of the biggest blunders of the
| 20th century.
| mukundmr wrote:
| While 28 tonnes appears to be a lot of material for generating
| 1.2MW of energy, it compares favourably when you look at wind
| turbines. How often does this need maintenance though?
| pbmonster wrote:
| > How often does this need maintenance though?
|
| Moving parts in salt water? Frequently.
|
| The positive thing about this design is that maintenance is
| potentially much easier than on an seafloor mounted turbine: if
| the tether is long enough, you can just make the craft surface
| next to a maintenance vessel with a small crane. No divers
| necessary, and no giant crane platforms like for offshore wind
| turbines, either.
| Sammi wrote:
| > No divers necessary, and no giant crane platforms like for
| offshore wind turbines, either.
|
| This is critical to the economic viability of the project.
| pbmonster wrote:
| It's certainly one advantage.
|
| I still worry about some of the technical aspects. The
| craft is going to pull it's own tether through the water
| behind/"under" it while it "flies" loops in the current at
| a speed faster than the current itself. That must induce
| quite a bit of drag, right? Especially because that tether
| is delivering several megawatts of electric power do the
| anchor, while holding all the mechanical load of that power
| being generated. That has to be a beefy cable. And the
| joints where that cable meets the craft and the anchor are
| moving parts, for all intents and purposes.
|
| I also wonder how much the craft actually resembles a full
| submarine. Are there ballast tanks and ballast pumps for
| altitude control? Full set of diving and directional
| rudders? What happens when any of those fail?
|
| Potential complexity is certainly higher than for an
| offshore wind turbine.
| Mistletoe wrote:
| Yes I'm envisioning this thing covered in barnacles. Surely
| they've thought of that?
| rsynnott wrote:
| > While 28 tonnes appears to be a lot of material for
| generating 1.2MW of energy
|
| Really? I was thinking the _opposite_; look at the size of
| hydro and conventional tidal plants.
|
| A 1.5MW on-shore wind turbine (which generates less energy in
| practice as the wind isn't constant) weighs about 150 tonnes.
|
| Even a 1MW diesel generator weighs about 10 tonnes (obviously
| not including fuel infrastructure).
| LysPJ wrote:
| For those wondering how they transfer the generated energy from
| the tidal kite to the shore:
|
| > The turbine shaft turns the [onboard] generator which outputs
| electricity to the grid via a power cable in the tether and a
| seabed umbilical to the shore.
| bjourne wrote:
| How on earth can such a small device generate so much energy?
| Wouldn't 1.2 MW of power make it very brittle just like a real
| kite? Or else why not scale it up and make one 100 times larger
| that generates 120 MW of power? Since tidal currents are much
| more reliable (I think) than offshore wind it almost seem to good
| to be true. There has to be a catch.
| KaiserPro wrote:
| The speed of the tide between those islands is something like
| 5-6mph, and in some places much much higher (think tens of
| miles an hour).
|
| Water is 800 times more dense, so moving water contains much
| much much more kinetic energy when its moving.
|
| But that also means it has a lot more drag. That drag can be
| quadratic, meaning that you'd need to a monster fucking cable
| to stop it being dragged away by the tide.
| arethuza wrote:
| The Grey Dogs channel between the Scottish islands of Lunga
| and Scarba has a peak flow of about 15km/h with large
| standing waves - quite incredible to watch this up close and
| watch the sea shooting past!
| Super_Jambo wrote:
| And of course some lunatics will go and find a way to have
| fun in them! Here's a sea kayaker at Penrhyn Mawr off
| Anglesey in Wales.
|
| https://www.youtube.com/watch?v=l5o7qV1Gy04
| btbuildem wrote:
| Looks like fun! FPV [1] and drone footage [2]
|
| 1: https://www.youtube.com/watch?v=Qo28x0CYBaA 2:
| https://www.youtube.com/watch?v=ehN9c7WfLMI
| arethuza wrote:
| Here is a video from a boat in the Grey Dogs:
|
| https://www.youtube.com/watch?v=zLFG7x6rrKw
|
| Definitely not somewhere I would want to fall in!
| rsynnott wrote:
| > There has to be a catch.
|
| I'd wonder how long it'll last; it's a very harsh environment.
|
| That said, there's a lot of energy available.
|
| It may be that lots of small units like this will be more
| practical than one big one.
| tamimio wrote:
| It's just a matter of time before the orcas start playing
| spikeball with it, hopefully the team considered that.
| Sammi wrote:
| Fortunately they are smart. They will learn fast. This isn't a
| new problem. Ships do get whales caught in the propellers from
| time to time. I was in a ship that had exactly this experience
| in 2001. Whole ship stopped and wouldn't start again until the
| third attempt to start it. A crew member reported he saw blood
| and guts at the stern.
| ksec wrote:
| Too good to be true?
|
| I assume this does no harm to fish. And electricity can be easily
| transported back to land ( there was no mention of how this was
| done in the video ). Since it is portable, small, fits into a
| 40ft Container. And you could mass manufacture these, ship it
| with container. There isn't another manufacturing problem and
| transportation problem like wind turbine.
|
| If Yes. You could have tens of thousands of these in north of
| Scotland of or seas around England.
|
| Surely there has to be a catch somewhere. Right?
| PaulRobinson wrote:
| I will 100% guarantee that the unique brand by Brit NIMBY-ism
| will rise, and some of my fellow citizens will complain about
| them affecting the nesting habits of the migrating lesser-
| spotted blue crested greeb warbler or something, and that'll be
| that. It's happened to many wind projects, this won't be any
| different (despite there being no evidence).
|
| Never mind that if CO2 in the atmosphere continues to climb,
| all those birds will die anyway, the global food ecosystem will
| go crazy, hundreds of millions of people will die and so on:
| that picturesque estuary has to remain unencumbered with man-
| made engineering, or else!
| Sammi wrote:
| Production of the kites is partly in the UK and there are
| projects in the works to put them to use there:
| https://minesto.com/holyhead-deep/
| jokoon wrote:
| > Surely there has to be a catch somewhere. Right?
|
| Underwater things are expensive to maintain, nothing is 100%
| waterproof, so rust rust rust.
|
| Underwater cables are no joke either, especially if you're
| building a network of sea cables. Making watertight is not
| cheap.
|
| And there is the question of doing high power electricity under
| seawater. I'm not an engineer in that field, that I think it is
| going to being a whole lot of new headaches.
| ksec wrote:
| Underwater cables has been done as in all the Network
| connection across continents. The same with high power
| electricity under seawater.
|
| None of these are new. However they are all 1 to 1 build up.
| These new tidal kite requires many to one. And I am not quite
| sure how this could be done. At least cheaply.
| vitiral wrote:
| > Underwater cables has been done as in all the Network
| connection across continents.
|
| Those are stationary cables. I don't know anything about
| this field, but I guarantee you that there are going to be
| differences.
| Eddy_Viscosity2 wrote:
| I was hoping for some sort of diagram or animation about what
| this thing is set up and does underwater and how this movement
| gets converted to electricity. Does anybody know?
| ljf wrote:
| Check out the embedded video in the story (link:
| https://www.youtube.com/watch?v=dkXinDn67Kw )
|
| The turbine (propeller) at the back of the kite rotates and
| generates electricity.
|
| Since this can 'fly' at an angle to the current, the speed of
| the 'kite' moving through the water, will be faster than the
| movement of the water - therefore the turbine can be spun
| faster than if it were just anchored in one spot.
| Eddy_Viscosity2 wrote:
| thank you!
| DrNosferatu wrote:
| The long-term projected levelized cost of the generated
| electricity really has to hit that $54/MWh target, otherwise the
| economics won't work - unless you absolutely must use some form
| of offshore energy production, then I guess it's an interesting
| niche application.
|
| It will be interesting to see.
| Sammi wrote:
| The tides are always moving so this energy is much more useful
| as baseload energy. They will lessen the need for energy
| storage for wind and solar, making wind and solar even cheaper.
|
| So tidal doesn't actually have to be as cheap as wind and solar
| by itself, as it will lower the total cost of wind and solar
| and be economically viable as a part of the mix.
|
| If you're a company operating wind or solar, then you will be
| able to have a much smaller battery installation, by using
| tidal kites for most of the baseload instead. And the kites
| actually generate energy instead of just storing it.
| DrNosferatu wrote:
| This system, as presented, will be really prone to
| *mechanical wear*. Maybe it can be done, but I need to see
| long-term (price & reliability) performance to believe it.
| Sammi wrote:
| What type of mechanical wear are you thinking of?
|
| I can think of a propeller and generator, but those are
| solved problems. This is just a boat with a propeller. Only
| instead of using the generator as an engine to spin the
| propeller, the tides spin the propeller which generates
| power in the generator.
|
| Steering is also a solved boat problem.
|
| Then there's the tether and anchor. This is the reason it
| swims in a figure 8, instead of it just being a propellar
| anchored straight to the seabed. So the "pulling" force is
| actually mostly to the sides instead of directly on the
| tether and anchor.
| DrNosferatu wrote:
| That swinging tether immersed in saltwater(!) will have
| to work miracles.
| Sammi wrote:
| I'm trying to see what prior art we can find on the
| internet on tethers and anchors used in fish farming and
| offshore oil industry, but I'm not finding many sources.
| ederamen wrote:
| We should probably just do nuclear.
| mikro2nd wrote:
| Per Wikipedia, nuclear LCOE runs to $81-82/MWh, so is not cost
| competitive.
| h1fra wrote:
| Neat, I just didn't get why they designed it this way vs a
| regular turbine at the floor of the ocean? if anybody knows
| Sammi wrote:
| That has been attempted in the same location in Vestmanna in
| the Faroe Islands. From what I've been told it pulled itself
| loose immediately, and the anchoring was pretty significant.
| This kite swims in a figure 8, so I guess that doesn't pull as
| much on the anchor.
| titzer wrote:
| Interesting! Given the small amount of power relative to the
| total amount in the tides (I've seen an estimate of 3.7TW), this
| doesn't make a big difference to the Earth/Moon gravitational
| system, but I'm curious how this will affect the Moon's orbit
| (yes, I know it's millimeters or meters). For example, the Moon's
| orbit is increasing by stealing rotational energy from the Earth
| --i.e. Earth rotation slows down, Moon speeds up and orbital
| distance increases. Does this friction in the tidal system
| _reduce_ the energy transfer to the Moon and therefore preserve
| Earth 's rotational energy, or just redirect that rotational
| energy into our power grid? I would guess it would have to be the
| latter...
| vikingerik wrote:
| I believe it would reduce the transfer to the Moon. The Moon's
| orbit increases by stealing rotational energy from the Earth --
| this happens because Earth's rotation carries its tidal bulge
| ahead of the Moon angularly, so the bulge pulls the Moon
| forward. The tidal harness uses some of the motion of the water
| to do work, so it gets carried less farther ahead by Earth's
| rotation, so it pulls the Moon forward less.
| dylan604 wrote:
| When the wind isn't blowing, no wind generation. When the sun
| isn't shining, no solar. So these guys come in with a "gap"
| filling idea of using tidal, yet their own marketing says this
| "kite" parks itself when there is no tidal flow. So how is this
| continuous power generation?
| 7952 wrote:
| It's not continuous, but would presumably be very predictable.
| And times of less movement would be different across the world
| which makes it possible to have some geographic resilience.
| beefman wrote:
| For comparison, electricity was sold to the U.S. grid at about
| $48/MWh in 2023. This is less than any of the cost projections
| mentioned in the article.
|
| Howabout materials? It says this weighs 28 tons and makes 1.2 MW.
| That's 21g/W assuming a 100% capacity factor, no balance of
| plant, and assuming those are short tons. Compare to an iPhone
| 15, which consumes about 1W per 150g in use. That's a materials
| intensity multiple (EROI estimate) of ~ 7. An average automobile
| on an average commute dissipates about 67kW, or 27g/W for a
| multiple of ~ 1.
| rsynnott wrote:
| That would benefit from various subsidies; from the article it
| _looks_ like the $54/MWh projected figure is before subsidy.
| beefman wrote:
| Subsidies would be useful in getting it from $108/MWh to
| $54/MWh faster, but they don't change the underlying physics
| of the technology.
| rsynnott wrote:
| Sorry, what I mean is that the $48/MWh figure benefits from
| significant subsidy; it's not a realistic cost of
| provision.
| beefman wrote:
| Perhaps surprisingly, it is a realistic cost and could be
| much lower if the electricity market were efficient (as
| opposed to being an amalgam of regional monopolies with
| essentially no price incentives).
| bagels wrote:
| Does it present a navigation hazard?
| vitiral wrote:
| maybe for submarines. Pretty sure the video said the depth is
| 50m
| User23 wrote:
| The Earth's angular momentum is the exact opposite of renewable.
| It's even less renewable than so-called fossil fuels.
| ars wrote:
| True, but it's being wasted anyway. The amount of power
| dissipated in the daily tides is around 3.75 terawatt, around 3
| million times as much.
|
| And don't assume this 1.2 MW adds to that total, a good portion
| of it is simply substituted.
| vitiral wrote:
| ??? by that metric literally nothing in the universe is
| renewable.
|
| RENEWABLE ENERGY IS IN VIOLATION OF THERMODYNAMICS. WE ARE ALL
| HEADING TOWARDS THE HEAT DEATH OF THE UNIVERSE.
| hnthrowaway0328 wrote:
| I'm thinking loudly about three questions:
|
| 1. How does the maintenance fee and replacement fee look like,
| per year?
|
| 2. Is it possible to develop a home use version?
|
| 3. I assume the tide is going to be consistent, but need to dig
| deeper into this.
| jszymborski wrote:
| > Is it possible to develop a home use version?
|
| I suspect that these things are heckin' dangerous unless they
| are far from humans, so that would be a challenge I think.
| hnthrowaway0328 wrote:
| Good point.
| moffkalast wrote:
| > a home use version
|
| > 28-ton, 1.2-megawatt tidal kite
|
| Yes, one for your shower drain.
| hnthrowaway0328 wrote:
| I was thinking a much smaller version TBH, or a big one for
| multiple homes.
| _whiteCaps_ wrote:
| This would be great in the
| https://en.wikipedia.org/wiki/Skookumchuck_Narrows
| taldo wrote:
| Kinda reminescent of Makani, Google/X flying kite-turbine-
| generator-thingies. https://x.company/projects/makani/
| tlbsofware wrote:
| Reminds me of the the wind based KitePower that was shared here a
| month or 2 ago
|
| https://spectrum.ieee.org/micro-wind-power-kitepower
| vitiral wrote:
| What happens when a 28 ton kite slams into a whale or shark?
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