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.
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)
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...
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.
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
> 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.
> 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.
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.
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 :)
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.
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.)
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.
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.
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.
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.
> 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".
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.
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."
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
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
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.
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?
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?
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.
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.
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.
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!
> 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.
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.
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.
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 £5-10m then I think solar and batteries would be a much better option in most of the world.
> 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.
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.
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.
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?
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.
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.
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.
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...
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.
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.
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?
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.
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.
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.
tetha|2 years ago
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|2 years ago
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)
tomtomtom777|2 years ago
jabits|2 years ago
"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...
debok|2 years ago
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.
aqme28|2 years ago
*: e.g. Ted Kennedy. Rich and politically connected people like to live on the coast
justsomehnguy|2 years ago
rootusrootus|2 years ago
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.
philomath_mn|2 years ago
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.
throwbadubadu|2 years ago
(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 :)
card_zero|2 years ago
piaste|2 years ago
> 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
zakary|2 years ago
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.
LM358|2 years ago
Previous discussion on HN: https://news.ycombinator.com/item?id=37383283
usrusr|2 years ago
ben_w|2 years ago
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.
jacquesm|2 years ago
lm28469|2 years ago
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...
lloeki|2 years ago
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".
friend_and_foe|2 years ago
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.
HPsquared|2 years ago
https://en.m.wikipedia.org/wiki/Ocean_thermal_energy_convers...
dsign|2 years ago
[^1]: https://en.wikipedia.org/wiki/Tidal_acceleration
[^2]: https://en.wikipedia.org/wiki/O%27Neill_cylinder
opeon|2 years ago
doubloon|2 years ago
amelius|2 years ago
bruce511|2 years ago
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|2 years ago
mukundmr|2 years ago
pbmonster|2 years ago
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.
rsynnott|2 years ago
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).
Mistletoe|2 years ago
LysPJ|2 years ago
> 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.
ksec|2 years ago
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|2 years ago
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!
jokoon|2 years ago
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.
bjourne|2 years ago
KaiserPro|2 years ago
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.
rsynnott|2 years ago
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.
unknown|2 years ago
[deleted]
IshKebab|2 years ago
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 £5-10m then I think solar and batteries would be a much better option in most of the world.
Someone|2 years ago
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.
leoedin|2 years ago
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.
Tarq0n|2 years ago
justsomehnguy|2 years ago
Capital and largest city:
Tórshavn, 62°00′N 06°47′W
Eddy_Viscosity2|2 years ago
ljf|2 years ago
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.
DrNosferatu|2 years ago
It will be interesting to see.
Sammi|2 years ago
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.
titzer|2 years ago
vikingerik|2 years ago
beefman|2 years ago
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|2 years ago
dylan604|2 years ago
7952|2 years ago
tamimio|2 years ago
Sammi|2 years ago
taldo|2 years ago
tlbsofware|2 years ago
https://spectrum.ieee.org/micro-wind-power-kitepower
_whiteCaps_|2 years ago
hnthrowaway0328|2 years ago
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|2 years ago
I suspect that these things are heckin' dangerous unless they are far from humans, so that would be a challenge I think.
moffkalast|2 years ago
> 28-ton, 1.2-megawatt tidal kite
Yes, one for your shower drain.
vitiral|2 years ago
h1fra|2 years ago
Sammi|2 years ago
User23|2 years ago
ars|2 years ago
And don't assume this 1.2 MW adds to that total, a good portion of it is simply substituted.
vitiral|2 years ago
RENEWABLE ENERGY IS IN VIOLATION OF THERMODYNAMICS. WE ARE ALL HEADING TOWARDS THE HEAT DEATH OF THE UNIVERSE.
ederamen|2 years ago
mikro2nd|2 years ago
bagels|2 years ago
vitiral|2 years ago
Benbobby|2 years ago
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Donaldbendo|2 years ago
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