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Underwater Ocean Kites To Harvest Tidal Energy

timothy posted more than 4 years ago | from the best-use-for-string dept.

Earth 203

eldavojohn writes "A Swedish startup has acquired funding for beginning scale model trials of underwater kites, which would be secured to a turbine to harness tidal energy for power. The company reports that the kite device allows the attached turbine to harvest energy at 10 times the speed of the actual tidal current. With a 12-meter wingspan on the kite, the company says they could harvest 500 kilowatts while it's operational. This novel new design is one of many in which a startup or university hope to turn the ocean into a renewable energy source."

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Haha (2, Funny)

SlothDead (1251206) | more than 4 years ago | (#32115062)

At first I read "Ocean Kitties" and wanted to see pictures of those...

Re:Haha (1, Funny)

Anonymous Coward | more than 4 years ago | (#32115104)

Haha omg that's hilarious. It doesn't say that. Get glasses.

Re:Haha (1)

davester666 (731373) | more than 4 years ago | (#32116232)

But it could.

Put kittens in burlap sack.
Attach sack to kite.

Sit back and watch those kittens generate power for you!

Re:Haha (4, Funny)

ColdWetDog (752185) | more than 4 years ago | (#32115188)

Careful what you ask for [peta.org] . You might get it.

Re:Haha (0)

Anonymous Coward | more than 4 years ago | (#32115908)

I had a delicious sea kitten sandwich today.

Re:Haha (2, Funny)

A. B3ttik (1344591) | more than 4 years ago | (#32115938)

That just makes me hungry for actual kittens.

Land Fish (0)

Anonymous Coward | more than 4 years ago | (#32116248)

I'm feeling hungry for some land fish [wordpress.com] .

Hello Slashdot (-1, Offtopic)

Anonymous Coward | more than 4 years ago | (#32115414)

Hello slashdot! Today six of my accounts have mod points. The most offensive reply to this post will be modded "+5 Flamebait".

Be creative and have a good time!

Re:Hello Slashdot (-1, Offtopic)

Anonymous Coward | more than 4 years ago | (#32115762)

Go fuck yourself.

Re:Hello Slashdot (-1, Flamebait)

Anonymous Coward | more than 4 years ago | (#32116066)

"Underwater Ocean Kikes to Harvest Tidal Energy"? Drowning Jews generates electricity? Why didn't the Fuhrer figure this out?

Re:Hello Slashdot (1)

biryokumaru (822262) | more than 4 years ago | (#32116436)

Belgium.

Unintended consequences... (4, Funny)

synaptik (125) | more than 4 years ago | (#32115074)

Because of the tides, the Earth's rotational energy is being stolen by the moon, which is using that energy to slowly escape from orbit. (This is a diminishing effect over time, that will eventually reach equilibrium.) But when we leach this energy for our own purposes, we are changing the delicate balance of that equation. ...Siphon off too much energy from the tides, and we could either increase the rate at which the Earth is slowing, bring the moon crashing down upon us, or both!

Won't somebody think of the children? We owe future generations a planet fit to live on and capable of sustaining the future.

Re:Unintended consequences... (1)

t33jster (1239616) | more than 4 years ago | (#32115360)

This is an interesting answer to a question I always wanted to ask - how does the first law of Thermodynamics play into harnessing tidal/wave energy? Very interesting, and I'd love to see a citation if available.

I suppose the next question would be, What's the overall supply, and can/should we focus on not depleting it like we have done with hydrocarbons?

Re:Unintended consequences... (1)

clone53421 (1310749) | more than 4 years ago | (#32115604)

This is an interesting answer to a question I always wanted to ask - how does the first law of Thermodynamics play into harnessing tidal/wave energy?

Exactly as GP described. Well, sort of.

I suppose the next question would be, What's the overall supply

Millions of years.

Re:Unintended consequences... (1)

sanosuke001 (640243) | more than 4 years ago | (#32116396)

I always thought about this in regards to geothermal. What if we cool down the planet enough to stop the core from spinning or solidify it? I've heard numerous "guesses" at the amount of energy available in geothermal, one of which was 9000 years. That is a lot, but in 9000 years we could be out of a magnetic field? Doesn't seem worthwhile to me...

We got into all this mess with oil because we didn't think ahead at all; It seems we're doing it all over again, just not as an immediate issue as oil is.

Re:Unintended consequences... (5, Funny)

Yakasha (42321) | more than 4 years ago | (#32115376)

Won't somebody think of the children? We owe future generations a planet fit to live on and capable of sustaining the future.

Don't worry, it is being developed by a private company. Private industries regulate themselves.

Re:Unintended consequences... (1)

elashish14 (1302231) | more than 4 years ago | (#32115382)

Jeez. I was just gonna suggest that this could disrupt marine life... but you... bravo! -gasps-

You are overlooking the obvious... (4, Funny)

postermmxvicom (1130737) | more than 4 years ago | (#32115462)

The solution is obvious. I am selling gravity credits to absolve you of your moon-doom guilt. Each credit you purchase represents energy gathered from sources not directly linked to the moon's potential energy plus some of the profits will be used to fund missions that will increase the moon's potential energy. This gravity offset program will save the earth for our posterity. As the administrator of this program, I will, of course, take a percentage of the sales as compensation. My motives are, however, purely in the interest of the future.

Re:You are overlooking the obvious... (0)

MBGMorden (803437) | more than 4 years ago | (#32115836)

Anyone else find it scary that this was modded Interesting instead of Funny?

Re:You are overlooking the obvious... (2, Insightful)

h4rr4r (612664) | more than 4 years ago | (#32116010)

No, because the rest of us know that Funny gives no karma, so people choose other options.

Re:Unintended consequences... (2, Informative)

T Murphy (1054674) | more than 4 years ago | (#32115486)

I know you aren't serious, but in case anyone is curious: Last I heard, this process is so slow the sun going red giant on us is a more pressing issue. Somehow changing this moon escapism process shouldn't have any real effect on people even billions of years from now.

Re:Unintended consequences... (1)

fahrbot-bot (874524) | more than 4 years ago | (#32115868)

Siphon off too much energy from the tides, and we could either increase the rate at which the Earth is slowing, bring the moon crashing down upon us, or both!

Joking aside, and I'm sure you already know this, but the Moon's orbit increases as the Earth's rotation slows.
See: Is the Moon moving away from the Earth? When was this discovered? [cornell.edu]

Re:Unintended consequences... (1)

RabbitWho (1805112) | more than 4 years ago | (#32115882)

LoL you just made all that up. Trolling! How are the tides any more likely to "siphon off energy" than say a cliff? Or a sea turtle swimming against the current?

I once sat on the bus behind an old lady talking to a young boy about how she was against wind power in case we would run out of wind. I wanted to scream CONVECTION at her.. and I've a similar feeling here.

Re:Unintended consequences... (1)

HeckRuler (1369601) | more than 4 years ago | (#32116160)

oooo! I haven't gotten to do this yet! Ahem:

WHOOOSH!

sweet (4, Insightful)

gandhi_2 (1108023) | more than 4 years ago | (#32115094)

now whales can enjoy the "renewable revolution" like migratory birds and bats do with windmills.

Alternative? (0)

Anonymous Coward | more than 4 years ago | (#32115292)

I suppose the whales might prefer it to the alternative:
http://news.bbc.co.uk/2/hi/americas/8664137.stm

Re:sweet (1)

DeadCatX2 (950953) | more than 4 years ago | (#32115934)

I think that the bird:windmill size ratio is much, much smaller than the whale:kite ratio.

I also think that birds move much faster through air than whales move through water.

Re:sweet (1)

scorp1us (235526) | more than 4 years ago | (#32116158)

Indeed [youtube.com]

Re:sweet (1)

Anne_Nonymous (313852) | more than 4 years ago | (#32116408)

Back off you smelly hippie. I demand my right to fly a sea kite out of the screen door on my adobe submarine.

Hopefully Naboo has enough... (1)

will.perdikakis (1074743) | more than 4 years ago | (#32115116)

...supply of their starfighters to provide us with more of these kites.

Re:Hopefully Naboo has enough... (1)

will.perdikakis (1074743) | more than 4 years ago | (#32115144)

Actually, looking again, it looks more like the SS Enterprise.

Stupid question, but one that's always bugged me.. (2, Insightful)

Anonymous Coward | more than 4 years ago | (#32115134)

Is it possible to exhaust the wind or sea's natural momentum, if there is such a thing? Where does the energy ultimately come from? In other words, is it theoretically possible to have so many wind farms (or, in this case, tide farms) that the atmosphere becomes still?

(captcha: "universe". heh.)

Re:Stupid question, but one that's always bugged m (5, Informative)

Nadaka (224565) | more than 4 years ago | (#32115212)

short answers: No, there is. The sun. No.

Re:Stupid question, but one that's always bugged m (0)

Anonymous Coward | more than 4 years ago | (#32115364)

We're talking tidal energy, so for the sea it's the moon (not the sun).

Re:Stupid question, but one that's always bugged m (0)

Anonymous Coward | more than 4 years ago | (#32115460)

GGP here - sorry, that sounds pretty stupid. The moon is orbiting the earth, i.e. doing nothing but falling. For that to be a source of energy, shouldn't the moon be coming closer and closer to the earth? Otherwise you're just creating energy out of nothing, by the mere fact of having celestial bodies close together.

Re:Stupid question, but one that's always bugged m (1)

everett (154868) | more than 4 years ago | (#32115614)

Rotation of the earth + gravity = tides.

Re:Stupid question, but one that's always bugged m (1)

Chris Burke (6130) | more than 4 years ago | (#32115640)

The moon is orbiting the earth, i.e. doing nothing but falling. For that to be a source of energy, shouldn't the moon be coming closer and closer to the earth?

Actually what's happening is that the moon is getting farther away from the earth, gaining orbital velocity at the cost of earth's rotational velocity.

The source of energy is actually the earth's rotational energy [wikipedia.org] , of which there is quite a bit.

Free energy until... (0)

Anonymous Coward | more than 4 years ago | (#32115710)

So we have free energy until the moon crashes into the earth. I highly doubt that anything we are doing to suck that energy up is actually accelerating the process.

Re:Stupid question, but one that's always bugged m (1, Informative)

Anonymous Coward | more than 4 years ago | (#32115896)

If moon is doing the tide then how come there's high tide 2 times a month.

So actually sun contributes at least as much as the moon or a bit more. And the interference max of those is the high tide.

But earths rotation and continents actually make it meaningful.

Re:Stupid question, but one that's always bugged m (1)

Chris Burke (6130) | more than 4 years ago | (#32116012)

If moon is doing the tide then how come there's high tide 2 times a month.

So actually sun contributes at least as much as the moon or a bit more.

No, the sun's effect is about half that of the moon. Though that's still significant.

But earths rotation and continents actually make it meaningful.

Earth's rotation is where the energy is actually coming from. It's why the earth is slowly losing rotational velocity to the tune of about ~15 microsecond longer day per year

Re:Stupid question, but one that's always bugged m (1)

HeckRuler (1369601) | more than 4 years ago | (#32116240)

Yur gul-durned tidal power is throwin off me coal-fi'ed atomic clock! Ain't chou hippies ever tink 'bout keepin proper TIME!

Re:Stupid question, but one that's always bugged m (1)

Chris Burke (6130) | more than 4 years ago | (#32116394)

Not my fault. If you'd power your atomic clock with a renewable energy source, like hamsters or grad students, then you wouldn't have this problem!

Re:Stupid question, but one that's always bugged m (1)

pclminion (145572) | more than 4 years ago | (#32116320)

If moon is doing the tide then how come there's high tide 2 times a month.

I assume you meant two times per day? That's because the moon raises tidal bulges on both the near and far sides of the earth. Thus, as the earth turns, you pass under these bulges roughly twice per day. That's essentially the exact definition of a "tidal effect."

It's not like the moon pulls water away on the near side and does nothing on the far side. The tidal effect is caused by the differential of the moon's gravity across the earth's volume. This has a "squashing" effect.

Re:Stupid question, but one that's always bugged m (1)

tompaulco (629533) | more than 4 years ago | (#32116264)

He also mentioned the wind, which is ultimately an effect of the sun heating different sections of the Earth to different degrees.

Re:Stupid question, but one that's always bugged m (2, Insightful)

NeutronCowboy (896098) | more than 4 years ago | (#32115798)

Wind farms are unlikely to stop the wind. Wind is a byproduct of temperature differentials, and as such, as long as the earth isn't exactly the same temperature everywhere all the time, there will be wind.
Tidal farms, on the other hand, I don't know. Tides are due to the difference in gravitational fields at different points on the earth. As such, the tidal energy comes from the Sun's and the moon's gravitational field. Since neither the sun nor the moon are losing mass through the use of tide turbines, what has to change is the distance between the sun, moon and earth. Somehow, I think the time scales on which this becomes a problem are large enough that we'll have entirely different problems then.

The only real problem I can see with tidal turbines is that if they are large enough, they will restrict the flow of the tides, and tides will become less pronounced - which will have an immediate impact on any tidal areas. And since tidal areas and shallow bays are pretty much where the food chains for a lot of marine animals reside, this could be a real problem. But again, it would have to be something on the scale of putting turbines across the entire straight of Gibraltar, and reducing the flow to near zero. Unlikely to happen, but not impossible.

Re:Stupid question, but one that's always bugged m (2, Informative)

Bearhouse (1034238) | more than 4 years ago | (#32115814)

Is it possible to exhaust the wind or sea's natural momentum, if there is such a thing? Where does the energy ultimately come from? In other words, is it theoretically possible to have so many wind farms (or, in this case, tide farms) that the atmosphere becomes still?

(captcha: "universe". heh.)

I think we're OK for a while. There's many 'renewable' energy sources that can, and are, being tapped, and we're nowhere near extracting any significant fraction of them so far:
1. Tides, as in this article, come from the sun & moon interacting with the earth; http://en.wikipedia.org/wiki/Tides [wikipedia.org]
2. Sunlight; there's plenty to spare: http://en.wikipedia.org/wiki/Solar_energy [wikipedia.org] "Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used."
3. Let's not forget geothermal: http://en.wikipedia.org/wiki/Geothermal_power [wikipedia.org]

Of course, that last one, being strictly a gift of today's Earth, could be compared to 'traditional' energy sources such as hydrocarbons (oil, gas, coal) and nuclear. We're nowhere near running out of those yet either.

Forget Tidal Energy (-1, Offtopic)

Anonymous Coward | more than 4 years ago | (#32115168)

Make oil-capturing devices!

Maintenance (3, Interesting)

Saishuuheiki (1657565) | more than 4 years ago | (#32115178)

Seems this would be relatively high maintenance. Anyone who owns a boat knows that stuff can and will grow on it, which will have to be cleaned off eventually, no? Setting aside the initial cost, which isn't mentioned, wouldn't the maintenance be costly?

Re:Maintenance (2, Informative)

Bearhouse (1034238) | more than 4 years ago | (#32115876)

Keep 'em deep enough, and nothing will grow. (No sunlight)
Corrosion will of course be a problem, as will be keeping the electrical generating and transmission bits nice and watertight.

Re:Maintenance (1)

brainboyz (114458) | more than 4 years ago | (#32116288)

As we're finding out, lack of sunlight does not mean lack of life/growth. Animals living on sinking waste, and lifeforms which use chemical-based metabolism (thermal vents), both would remain a problem.

Global consequences of tidal energy harvesting (1, Interesting)

RichMan (8097) | more than 4 years ago | (#32115186)

So has anyone considered what will happen when we massively start harvesting global tidal energy?

Will it affect global oceanic heat redistribution? (( If the ocean currents slow down then northern Europe reverts to looking like northern siberia. ))

What about the earth/moon relationship that drives the tides? Do we end up sucking more energy out of the moons orbital velocity leading to a decay in the moons orbit?

Environmentally, what happens to the organisms that live in the tidal zone?

Someone should have done the calculations before we started the petrochemical revolution. Where are we headed with the tidal energy thing?

Re:Global consequences of tidal energy harvesting (1, Informative)

Anonymous Coward | more than 4 years ago | (#32115340)

no, the scale is too large even if you deploy hundreds of them you're talking hundredths of points of degree change.

The real strawman er I mean issue could potentially be the net effect on the moon's orbit. (It will slow marginally with the increased drag.) So will we get into a static orbit with the moon sooner than 1 billion years for now or not if we deploy these all over the ocean floor.

Re:Global consequences of tidal energy harvesting (1)

fahrbot-bot (874524) | more than 4 years ago | (#32116098)

What about the earth/moon relationship that drives the tides? Do we end up sucking more energy out of the moons orbital velocity leading to a decay in the moons orbit?

No. Slowing of the Earth's rotation, which is due to drag by Moon, increases the Moon's orbit. The Moon orbits slower than the Earth rotates causing a "gravitational/tidal bulge", or warping of the Earth's shape (the ocean tides are caused by this too). This creates drag on the Earth, slows its rotation and the Moon's orbit increases - due to, I believe, conservation of angular momentum. Think about what happens as a spinning ice-skater moves her arms/legs in to speed up and out to slow down the spin. See:
Is the Moon moving away from the Earth? When was this discovered? [cornell.edu]
How The Moon Affects Ocean Tides [hiwaay.net]

Keeping them Up (3, Funny)

Mikkeles (698461) | more than 4 years ago | (#32115208)

If they're anything like my kites, they'll just end up nose-first in the silt.

Re:Keeping them Up (1)

gyrogeerloose (849181) | more than 4 years ago | (#32115652)

If they're anything like my kites, they'll just end up nose-first in the silt.

Charlie Brown! When did you start posting on Slashdot?

(Obligatory: "Rats!")

10x the speed? (1, Insightful)

Anonymous Coward | more than 4 years ago | (#32115296)

last i checked power wasn't measured in meters/second.
very confused summary.

Re:10x the speed? (2, Informative)

Chris Burke (6130) | more than 4 years ago | (#32115372)

No, power is measured in joules/second. They're both rates. 10x higher speed means 10x higher rate.

It's not the best choice of words, but it works okay I guess. :/

Re:10x the speed? (1)

clone53421 (1310749) | more than 4 years ago | (#32115632)

Assuming the power curve on your generator is linear, which it isn’t.

Re:10x the speed? (1)

Chris Burke (6130) | more than 4 years ago | (#32115834)

Or assuming they're talking about power generated, not angular velocity of the generator.

Re:10x the speed? (1)

clone53421 (1310749) | more than 4 years ago | (#32115982)

I’m assuming they’re talking about the linear “water-speed” of the kite. That makes the most sense to me, at least, after watching the video simulation [ebase.se] .

Re:10x the speed? (1)

Chris Burke (6130) | more than 4 years ago | (#32116038)

Well we were making different assumptions then. BTW that link is busted. :/

Re:10x the speed? (1)

clone53421 (1310749) | more than 4 years ago | (#32116090)

My bad. Somehow or other all the spaces got borked and I didn’t notice it in the preview.

http://www.ebase.se/minesto/Animated movie of Deep Green.mov [ebase.se]

Re:10x the speed? (1)

Chris Burke (6130) | more than 4 years ago | (#32116332)

Thanks, that's pretty neat, though it doesn't exactly answer the question.

Though now that I re-read the sentence in question, it says "capture energy from the tidal currents at ten times the speed of the actual stream velocity", I was missing the "of the actual stream velocity" part. That definitely makes it sound like they're saying the kite (and thus generator) moves at 10x the tidal speed, which for sure doesn't mean an equivalent increase in power generation. Though it can be close.

Re:10x the speed? (1)

t33jster (1239616) | more than 4 years ago | (#32115426)

last i checked power wasn't measured in meters/second.

I'm pretty sure you're right, but I think it's talking about ocean (well, tidal) current, not electrical current.

Re:10x the speed? (1)

asukasoryu (1804858) | more than 4 years ago | (#32115820)

last i checked power wasn't measured in meters/second.

Not directly. But the mass of ocean water is known so if you know it's velocity you can calculate how much kinetic energy is available for conversion. The same can be done for air and windmills.

Another energy-diffuse, capital-intensive system (3, Insightful)

Scareduck (177470) | more than 4 years ago | (#32115324)

Like windmills, PV solar (and arguably, thermal solar), this will use a ton of capital (in multiple dimensions -- energetic, costs, and materials) to harvest very diffuse energy. The cries to subsidize installation -- and possibly operational -- costs will start almost immediately.

Re:Another energy-diffuse, capital-intensive syste (3, Informative)

HeckRuler (1369601) | more than 4 years ago | (#32115520)

Well ok. Anything wrong with that?

Re:Another energy-diffuse, capital-intensive syste (1)

Degro (989442) | more than 4 years ago | (#32115812)

Come on, it's better to just keep digging up and draining the ground until there's nothing left and hope for a bright future. That way when all the economically viable hydrocarbon sources are used up we'll have no backup plan and really be able to commit to sucking the teat of whatever corporations corner the next energy dependencies.

Re:Another energy-diffuse, capital-intensive syste (1)

Anonymous Coward | more than 4 years ago | (#32116110)

Come on, it's better to just keep digging up and draining the ground until there's nothing left and hope for a bright future. That way when all the economically viable hydrocarbon sources are used up we'll have no backup plan and really be able to commit to sucking the teat of whatever corporations corner the next energy dependencies.

Well yes, you're exactly right, it _is_ better to do that. It always makes sense to keep using a cheaper product (as long as you accurately calculate all the costs) than a more expensive one. Some people argue we don't accurately account for the costs of fossil fuels (thus the interest in a carbon tax which is a way of doing so, albeit a tremendously inaccurate one guaranteed to be subject to massive political interference such that it most likely won't serve it's purported purpose in any useful way). But assuming the pricing is accurate, it's not like suddenly one day all the wells are going to run dry and there will be no oil. It will just gradually get harder and harder to extract (i.e. more expensive) and at some point it will make economic sense to evaluate alternatives. Indeed, this process has been going on since the day after the first oil well was drilled. Also, it's not like research into alternatives isn't going to be happening the whole time. Subsidizing economically unviable alternatives distorts this whole process in stupid ways (like germany having a huge installed solar base despite being a relatively inefficient place to actually do solar). In this sense, a carbon tax would be much better than subsidies - if you could actually create a level playing field where all technologies were priced properly, you'd wind up with the best one winning out. Unfortunately, that's a big if, and frankly it's never going to happen, because nobody will ever be able to accurately price these things even if you could keep the politicians from sticking their fingers into the pie and screwing things up. That's why I generally favour the status quo because _even with the unfair advantage fossil fuels have due to not fully accounting for environmental costs_, I think we are still better off than we would be with the massive inefficiencies that would invariably occur when trying to account for them in some artificial way controlled by a massive bureaucracy. And that's not even taking into account that wind and solar have some obvious effects that are not incorporated into the costing for them, and probably have still others that we haven't discovered yet but that will manifest if they are ever deployed on a large enough scale.

What's wrong with it (1, Troll)

Scareduck (177470) | more than 4 years ago | (#32116036)

should be painfully obvious: where does that subsidy come from? Why, yes, from economic activity derived from burning fossil fuels.

We should be looking at truly sustainable energy solutions, not scams.

We will know an energy source is working properly when politicians seek to tax it.

Re:What's wrong with it (2, Insightful)

Chris Burke (6130) | more than 4 years ago | (#32116144)

Why, yes, from economic activity derived from burning fossil fuels.

Yes, like essentially everything we do today, no matter if it is something that is trying to get us off of fossil fuels or not. Our economy is based on burning fossil fuels, ergo all economic activity is based on burning fossil fuels.

Spending some of that activity to stop using fossil fuels is, if you consider using fossil fuels bad, what we would call "intelligent".

We should be looking at truly sustainable energy solutions, not scams.

If they produce more energy in their lifetimes than they take to produce -- which, if the system works, they almost certainly will -- then it's not a scam, it's a viable energy source. The more of these we build, the less of our economic activity will be based on fossil fuels, and the problem in the first part of this post will be resolved.

Up-front costs can prevent the development of new technologies, even if in the longer term they are a net positive. Something can be economically viable (which is what it means to have a net positive return on investment) without necessarily being economically practical for a particular entity at a particular time. Subsidies offset this, and get us to the point where we are using fewer fossil fuels faster. This is a good thing.

Re:What's wrong with it (1)

A. B3ttik (1344591) | more than 4 years ago | (#32116404)

-5 Uncomfortable Truth

Re:Another energy-diffuse, capital-intensive syste (0)

Anonymous Coward | more than 4 years ago | (#32116194)

Yes, forcefully taking money from people is wrong. Charge enough for the energy to cover the costs, if ti's a feasible technology the energy companies will adopt it and it will pay for itself in time.

Re:Another energy-diffuse, capital-intensive syste (0)

T Murphy (1054674) | more than 4 years ago | (#32115598)

Well, if you can design a windmill, solar cell, tidal turbine or other naturally-powered generator so that you can leave it alone for decades (centuries?), it can pay itself off compared to the cost of operating a traditional fuel-burning plant, although the payoff time would be so slow it may need subsidies to get investment going.

I do agree that, beyond research/prototype funding, government shouldn't subsidize these technologies until they are able to compete commercially on their own merits. Until it's cost effective, the money is better spent on clean coal or nuclear.

Re:Another energy-diffuse, capital-intensive syste (1)

h4rr4r (612664) | more than 4 years ago | (#32116360)

Which means they will never be cost effective.

Clean coal does not exist, cannot exist and will not exist. It is just a marketing phrase.

Re:Another energy-diffuse, capital-intensive syste (0)

Anonymous Coward | more than 4 years ago | (#32115782)

You haven't been paying attention to PV development lately, have you?

They've made quite a bit of progress lately. If you shop around your panels can be paid off in 10 years of less (PV lasts 30+ years). In energy costs its even less than that now.

And solar thermal pays off quicker than that and lasts even longer.

As for 'operational costs' you aren't familar with how windmills and panels work at all, are you?

Re:Another energy-diffuse, capital-intensive syste (1, Interesting)

Anonymous Coward | more than 4 years ago | (#32115890)

"this will use a ton of capital (in multiple dimensions -- energetic, costs, and materials)"

Renewables are hardly unique in that. A single-reactor nuclear plant costs over 5 billion euros (see Olkiluoto 3) and takes half a decade to build.

Sea kites for space travel (4, Funny)

T Murphy (1054674) | more than 4 years ago | (#32115356)

Tidal forces are from the moon, and over time the moon is getting farther away. Clearly, if we harvest tidal energy we will force the moon away faster as it makes up for the difference. If NASA times it just right, we could put people on the moon, launch the moon at Mars and have people walking on Mars just months later. Melt the polar icecaps on Mars, use tidal kites there, and repeat as needed to keep using the moon as our Earth/Mars space shuttle. Add Phobos and Deimos into the mix and space tourism can take off.

Next, we use the tide from the sun to travel to Alpha Centauri.

Re:Sea kites for space travel (1)

camperdave (969942) | more than 4 years ago | (#32116424)

Actually, most of the tide comes from the Sun, which is why you get six hour variations (Oh noes! Time cube!).

dem dang numbers (0, Offtopic)

Ancient_Hacker (751168) | more than 4 years ago | (#32115374)

The numbers don't look very promising for this kind of device.

Let's assume you have a 12-meter by 5-meter "kite" and it's moving out with the tide.

And let's assume the tide is a huge one, like 10 meters.

Also let's be generous and assume the kite can sequester an average of one meter of depth of water.

That's 60 cubic meters of water, falling 10 meters, twice a day.

Jut for fun, switching back to English units, about 60 tons falling 63 feet per day.

or 120,000 pounds falling 63 feet per day. That's about 87 ft-lbs/sec, or about 110 watts.
Wholesale electricity is going for about 3 cents a kilowatt-hour, so this kite is at best making .33 cents an hour.

I don't think you can build deploy, and operate, and pay for a kite that size on that kind of income.
Just the interest lone has to be more than that.

Re:dem dang numbers (2, Funny)

HeckRuler (1369601) | more than 4 years ago | (#32115494)

Yeah, it'd be great if they could try to make some sort of proof of concept, or trial version to test it out before investing in it whole-hog....

Re:dem dang numbers (2, Informative)

b0bby (201198) | more than 4 years ago | (#32115630)

My impression is that the tethered kite will fly back and forth in the current, allowing the little turbine strapped to the bottom of it to spin faster (10x, per TFA). I guess they'll just go ahead with their trial to see if it all works out, but it seems like it could be a way to make use of the power of the currents without building huge turbines.

Re:dem dang numbers (4, Informative)

fava (513118) | more than 4 years ago | (#32115676)

Thats not how it works.

The kite is really a steerable sail that moves back and forth across the current, thereby increasing the velocity through the attached turbine.

An animation is available at http://www.ebase.se/minesto/animation.htm [ebase.se]

fava

Re:dem dang numbers (2, Informative)

idji (984038) | more than 4 years ago | (#32115688)

You've got it all wrong. I don't even think you read TFA, because you said "assume... it's moving out with the tide" - you don't get it.

The kite is not moving, it is hovering - tethered - and the energy is generated by the turbine attached to the kite. The "flying" is probably just to lift it to optimal position, drag and angle. The energy is generated by water moving HORIZONTALLY in and out of the bay, not UP and DOWN. You don't need a high tide, you need bay with a lot of horizontal water movement.

The advantage about this method to other sea methods, is you can lift the kite out of the water in a storm or for maintenance, it doesn't have to stay down there. The only infrastructure you need down on the seabed is a hook to hold it, not gates or turbines.

Re:dem dang numbers (0)

Anonymous Coward | more than 4 years ago | (#32115794)

You've got it all wrong. I don't even think you read TFA, because you said "assume... it's moving out with the tide" - you don't get it.

Of course. Naysaying technology by not even trying to understand it is kinda his "thing".

Re:dem dang numbers (0, Offtopic)

Ancient_Hacker (751168) | more than 4 years ago | (#32115924)

Sorry for my oversimplifying things. I just assumed everybody knew basic physics and knew that it matters not one whit whether the kite is slewing, sliding, swooping or gliding, and it matters even less what speed it's achieving, or whether the water is moving horizontally or vertically, or whether the kite is moving and the water is behind it, or the kite is standing still and the water is moving past it or through it. All those fancy scenarios are just different angular projections of the same basic kinematics. You can't make any more energy than is available by the basic fact that water is dropping in a gravitational field.

Even if my assumptions are off by a factor of ten, we are still a very long way from even paying the interest on the capital investment, much less paying off the investment, which is in effect saying that we're going to be going to a lot of trouble to lose energy.

Re:dem dang numbers (2, Informative)

Daniel Dvorkin (106857) | more than 4 years ago | (#32116060)

You're not making simplifying assumptions. You are completely misrepresenting the mechanism, and your numbers are meaningless. You are wrong, the posters who called you on your original post are right, and snarky comments about "basic physics" aren't going to cover that up.

Re:dem dang numbers (1)

Ancient_Hacker (751168) | more than 4 years ago | (#32116376)

Thanks David, for giving us a living example of the lack of knowledge of Physics in the general populance. One learns in first-semester Physics about the equivalence of physical motion and conservation laws. Speeding up the water flow for the turbine is just basic impedance-matching, it's not creating any energy or tapping any hidden font of power.

The basic issues are that there is very limited and diffuse power in tidal flow, and the significant cost and short life of the equipment to capture that energy. For sturdier equipment, like coffer dams, you also have to consider the cost of money. I wish these folks every bit of luck, but they're working in a very difficult and cost-sensitive area.

Re:dem dang numbers (0)

Anonymous Coward | more than 4 years ago | (#32115690)

.33 cents seems to be about 2 orders of magnitude less than my estimates.

Re:dem dang numbers (2, Informative)

snowraver1 (1052510) | more than 4 years ago | (#32115898)

There is a problem with your reasoning. The 60 cubic meters of water is not the total amount of water that would run by this device. The 60 cubic meters figure you quote would be the amount of water acting upon the device *at a single point in time*. As the water flows and the kite moves, much, much more than 60 cubic meters of water will flow by this device.

Re:dem dang numbers (3, Informative)

NeutronCowboy (896098) | more than 4 years ago | (#32116062)

And as with all numbers, the devil is in the detail.

Tide power is generated by water flowing through a turbine. As a result, what matters is the surface of the turbine times the apparent water speed. That gives you a volume over time, which in turn controls how fast the turbine spins. Considering that apparent water speed depends not only on the size of the tide, but the local ocean floor geometry, and the output of the turbines can vary wildly depending on where they're located.

Finally, you made a key mistake in your calculation: a tide turbine doesn't capture the up and down movement of the tide - it captures the horizontal flow of water as it flows from point A to point B. This means that your entire calculation is completely useless. It isn't captured twice a day, it is captured constantly with an oscillating efficiency. The energy captured is only marginally related to a mass of water falling the height of the tide - the falling is translated into horizontal speed, where g is completely overwhelmed by local geometry. And lets not even get into real and apparent water flow, turbine construction, efficiencies, etc...

Really, you could have saved yourself a lot of time and just said "I don't know how this works".

Re:dem dang numbers (1)

canajin56 (660655) | more than 4 years ago | (#32116428)

Your numbers are nonsense. The tide doesn't work by a little cube of water moving downwards, once. It's a flow. You might as well say that wind turbines, by "dem numberz" generate 0 power, because the average height of the atmosphere is fixed, therefore, it can do no work. These are tidal as in having to do with ocean currents. Those don't flow a few minutes a day, then stop. The ocean is always moving. And, these things generate 500 kilowatts at peak, about 5000 times what your made up bullshit indicates. And, the currents most places are pretty steady. I'd bet the average power output over the day is at the absolute minimum, 250 kilowatts.

Renewable Energy Source? (1)

Combatso (1793216) | more than 4 years ago | (#32115442)

Thanks to BP and Transocean its a Fossil Fuel source

Explanation video on YouTube (5, Informative)

phiz187 (533366) | more than 4 years ago | (#32115618)

I was having difficulty visualizing this technology, from the text description. Here is a YouTube video that sheds more light. Spoiler: essentially the tethered kite does figure-8 patterns to continually move the turbine through the water.

http://www.youtube.com/watch?v=1qCDRj8TE9Y [youtube.com]

10 times speed of tidal current. Units? (1)

noidentity (188756) | more than 4 years ago | (#32115694)

The company reports that the kite device allows the attached turbine to harvest energy at 10 times the speed of the actual tidal current.

What units is that measured in? I'm not making sense of this sentence. Since when did the tidal current harvest energy in the first place?

Re:10 times speed of tidal current. Units? (1)

kevinNCSU (1531307) | more than 4 years ago | (#32116266)

The kite is steered so that the turbine on it gathers energy from the motion of the kite through the water. Sort of like when you see those kites doing figure 8 patterns in the sky. Their saying the kite is moving 10 times faster then just the current, therefore able to gather more energy then the turbine just sitting in the current. I don't know if the power generation is 10 times as much, but I'm pretty sure they are saying that the movement of water through the turbine will be 10 times as fast.

Gravity and Energy (1)

antirelic (1030688) | more than 4 years ago | (#32116100)

I know I am a bit off topic here, but I am looking for some insight from someone who has a good understanding of physics to help me understand something.

There is obviously a LOT of energy being exerted by the moon and the sun in the form of gravity on the earth. All of these other solutions rely on harnessing this energy via a third source, such as harvesting the energy transmitted by the waves. Would it be possible to directly harness this gravitational and centripetal energy?

Re:Gravity and Energy (1)

scorp1us (235526) | more than 4 years ago | (#32116336)

We don't know how gravity works. LHC is supposed to provide that answer. But you can imagine it as an exchange of energy, in proportion to the ratio of masses involved. Meaning that the net effect is that Earth expends some kind of energy keeping the moon in orbit. This has been theorized as a exchange of graviphoton, gravitophoton, and other such unproven mechanisms. If you could construct and anti-gravity device (one that blocks or reverses this theoretical exchange) you could harvest energy from the difference of the blocked area vs unblocked area. Cold, spinning superconductors to show a small ability to block gravity locally.

If you want to use to moon for energy via its motion, you'd have to have it orbit in a coil and it would induce a magnetic current. It is 13% ferrous material, so it would be weak. The real money is in blocking gravity.

Not gonna work (1)

e2d2 (115622) | more than 4 years ago | (#32116364)

This is not gonna work. Those kites would be right in the flight path of the rare spotted owl fish. Their mating habits will change and they might rub a dolphin the wrong way.

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