Generating Power From Ocean Buoys and Kites

cheezitmike writes "Researchers at Oregon State University are testing a new type of wave-energy converter to generate electricity from ocean waves: 'Even when the ocean seems calm, swells are moving water up and down sufficiently to generate electricity. ... For decades the challenge has been to build a device that can withstand monster waves and gale-force winds, not to mention corrosive saltwater, seaweed, floating debris and curious marine mammals. ... In the most recent prototypes, a thick coil of copper wire is inside the first component, which is anchored to the seafloor. The second component is a magnet attached to a float that moves up and down freely with the waves. As the magnet is heaved by the waves, its magnetic field moves along the stationary coil of copper wire. This motion induces a current in the wire — electricity.'" Meanwhile, researchers at Stanford are working to design "turbine kites" that operate at 30,000 feet, where air currents flow much faster than they do close to the ground. Ken Caldeira, a Stanford associate professor, said, "If you tapped into 1% of the power in high-altitude winds, that would be enough to continuously power all civilization."

Pumping kite wind generator

[Anonymous Coward]

The simplest idea I've seen uses a kite on the end of a tether. The tether is paid out, generating energy, and then pulled back in, requiring energy. By changing the kite's angle of attack during the recovery phase, a net energy output can be obtained.

The energy output is supposed to be around 20kW per square metre... is there any reason why this wouldn't scale to 20GW for square-kilometre kites?

www.win.tue.nl/casa/meetings/special/ecmi08/pumping-kite.pdf

Re:Boondoggle bait

[Anonymous Coward]

Well, perhaps a nation of 300 million can afford to research more than one thing at a time.

Both these technologies are sound ideas for research because they both seek to use some of the highest power densities that also are widespread.

The motion of the waves typically has a higher power density than the wind that created them, which is perhaps not entirely intuitive.

Re:Consequences

[Ex-MislTech]

Jet Airliners already catch free rides in the jet stream to save fuel,
and as there are thousands of planes up around the world
with likely hundreds of them doing it no problems so far
that we can detect.

Also, there are huge current underwater like the antarctic circumpolar
current that has about 140 times the flow of all the rivers on Earth.

A minor tap on it would power the southern hemisphere most likely.

Re:Consequences

[joe_frisch]

An airliner flying in the jet stream doesn't slow it down significantly. There is a small effect when the airliner enters the jet stream (and accelerates), but I think in cruise flight the effect is very small. A power generating kite extracts energy from the jet stream. The description of enough energy to power civilization is surprising to me (though it may be true), are they sure they have counted that the kites will slow down the jet stream? Also the jet stream moves around and changes direction a lot, it can flow anywhere across the US (I don't know the pattern over the rest of the earth), mostly west to east, but can be due north or south. I don't know how you would move the anchorages for the kites around quickly enough to keep up.

So ridiculous

[Ancient_Hacker]

These well-meaning schemes still founder on the basic problems of working in a salt-water environment and the issue of a very dilute energy source.
You can't make a generator that works directly off ocean-swells-- the swells come by so slowly you'd need a coil inductance of about ten thousand Henries.

  A simple loop of wire, as postulated, has about a millionth of that.

Plus you need considerable iron to channel the magnetic flux. No way around it.

Regarding the kites, figure out what the very lightest generator weighs, per watt. Hint: not under 30 kilos per KW. Now assume you want to power 100 houses, say 50 KW.
  Figure out the size of the kite needed to lift than many tons. Now at a 30 degree kitestring angle, the pull on the string will be twice the weight of the kite. Figure out how
much 60,000 feet of kite string that will take that kind of stress weighs. Now you need another large kite just to hold up the kite string.

And BTW, the "high speed" winds up there are not a panacea. They're high speed but low in density. The energy is, again, very dilute. You need to at least double the size of the kite to get the same amount of lift and pull as you can get at low altitudes.
.

Dual purpose

[zogger]

Most large dams are there also for water storage and flood control, to even the supply out over the year, and we really don't have much in the way of alternatives for that.