Wave power: A buoy that generates electricity from the motion of waves. The clear cylinder in the middle of the buoy (see bottom image) contains a roll of rubberlike material that stretches and contracts as the buoy bobs up and down, separating and bringing together electrodes.
SRI International
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A new technology could generate electricity from waves.
Researchers from SRI International, based in Menlo Park, CA, recently completed the first ocean tests of a system that uses a so-called artificial muscle to generate power from the motion of a buoy riding up and down on the waves. Although the prototype produces very little electricity, the researchers say that wave farms based on the technology could eventually rival wind turbines in power output, providing a significant source of clean energy.
Technology for harnessing the ocean's energy already exists, but it has not been widely adopted, largely because it has trouble withstanding the pounding of the waves. The new system could prove both cheaper and more reliable, the researchers say.
Earlier systems used more-conventional electromagnetic devices, such as dynamos with complex transmissions, hydraulic pistons, and turbines. The gears of a transmission, in particular, are vulnerable to wear and tear from the erratic surging of ocean waves.
In contrast, the SRI system is not much more than a sheet of rubber attached to a weight. It has "the mechanical complexity of a rubber band," says SRI senior researcher Roy Kornbluh. As a consequence, it is better able to absorb the shock of waves, says Yoseph Bar-Cohen, a senior research scientist at NASA's Jet Propulsion Laboratory, in Pasadena, CA. What's more, Bar-Cohen adds, the materials that the system is made from are cheap, which could help it compete in price with other sources of electricity.
The polymer-based system at the heart of the new generator is a variation on an artificial muscle--a device developed as an alternative to electric motors in applications such as robots. An artificial muscle will expand or contract when a voltage is applied to it, but the same process can work in reverse: if the muscle is stretched by an outside force, it can generate electricity. A few years ago, SRI developed a small device that, embedded in the heel of a shoe, enabled the wearer to charge a cell phone simply by walking. The wave-harvesting system is basically a larger version of the same technology.
The SRI researchers built their generator by sandwiching a commercially available rubbery material between two electrodes, which are themselves made of a greasy polymer containing conductive materials. The rubber sheet and electrodes are then rolled up, like a scroll, to form a hollow tube. When the tube is pulled by an outside force, the rubber layer is stretched thin, narrowing the gap between the electrodes. Initially, a small battery applies a voltage across the electrodes; when the rubber springs back into its original shape, it forces the electrodes apart, increasing the voltage between them. This excess energy can be siphoned off to generate a current. Part of that current feeds back into the system, so the battery is used only for the first cycle.
The researchers recently tested the system off the coast of Florida. A couple of square meters of rubber rolled into the shape of a hollow tube were attached to a weight and mounted at the center of a buoy. As the buoy bobs in the water, it causes the weight to rise and fall, repeatedly stretching the rubber and allowing it to rebound, generating electricity.
Underwater turbines could harness a massive amount of energy—but could cause problems for boat navigation.
Ten wave and tidal projects will generate 1.2 gigawatts of power.
It certainly sounds impractical as a green technology to offset the energy used by the average city. Here in Phoenix for instance, SRP services 750,000 subscribers (both residential and business) . SRP generates 5,800MW per year using a combination of coal, oil, nuclear, hydro and solar. If the theoretical buoys produce 1kw, it would take 5.8 million buoys to offset the electricity consumed in the Phoenix Metro area. My thinking might be wrong, but it doesn't sound practical at all. How would you string them together with cables? How would you service a million buoys? Who wants them off their coast?
Maybe it works in other scenarios. How about to power self contained signal buoys, or generate electricity for small remote islands? Maybe... But I'm not sure that solar isn't just easier and more reliable in those applications. Unless it's at the extreme north and south. Maybe it would be great to power a remote station in the Bearing Sea. Or to power something in the North Sea.
-Matt
The buoy itself would be useful to power navigational aids such as a nearby lighthouse, the lights of a bridge, or an oil platform - or anything that needs remote power and has no access to a nearby grid.
Maintenance of ocean observatory platforms is extremely expensive and prohibitive to deployment. If very cheap green power such as this were available then it opens the door for many interesting projects.
Guest (hosro@comcast.net)
Harvesting Power from the Ocean
The sea and other bodies of water are a resource that challenges our ingenuity to find ways and materials to tap into the moon earth motor of the sea. The turbines placed in eastern rivers are not a failure if more suitable materials are found to deal with the stresses encountered. Prototypes and tests are to find weaknesses as well as suitability of designs and materials. The source can not be dismissed if various prototypes do not meet expectations or commercial needs. Limited use may be all that is practical but that use may have advantages over other means.
Life cycle costing and maintenance are costs that should be incorporated into all energy sources and we know that current major systems do not. The cost the customer pays at the pump have no means, yet of incorporating all of the costs associated with providing a gallon of gas to any customer. History is a good source of comparing technologies and problems of development overtime; whether they were considered feasible or not how long into their development it was required to meet needs of cost and
suitability.
Re: Harvesting Power from the Ocean
Unless there is an economical way to convert ocean water to fresh water for human and animal consumption and energy use there will be less of an incentive to pursue the technology.
Greetings,
I remember hearing about a company that already has this sort of power generation in production. Theirs uses magnets to suspend the generation magnet in the cylinder. The AC that is generated is stored on the buoy in a large capacitor, and then an AC inverter sends out a 60Hz (or 50Hz) AC via a cable to shore. These buoys are set up in arrays that generate a lot of power: 150kW for each buoy, with 60 buoys in each array, totaling ~10mW
http://www.sciencefriday.com/program/archives/200708102
Sincerely, Neil
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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SVE
51 Comments
Sounds a little too optimistic
<<A bundle of rubber about a meter long and half a meter thick, with optimized electronics and an improved buoy design, could generate a kilowatt of electricity>>
Compare this to a conventional kilowatt alternator which is about the size of half a shoebox.
<<SRI system produces high voltages, in the range of a kilovolt ... high voltage is an advantage, since it makes it more efficient to transmit electricity>>
By this argument you should rub balloons against carpet and harvest the static electricity. That is high voltage also. Don't fool yourself. If you plan on using semiconductor electronics, kilovolts are terrible.
<<The main challenge moving forward, the researchers say, is to develop a reliable manufacturing process>>
Hah! That's the least of their problems. A couple of square meters to produce 5 watts is like 0.25 milliwatts/cm2. Compare this to a crappy fuel cell that is 25 milliwatts/cm2 and this is 100 times worse.
Move along folks. Nothing to see here.
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Elroch
56 Comments
Re: Sounds a little too optimistic
It is good to be sceptical, but it is not good to use loose arguments.
<< <<SRI system produces high voltages, in the range of a kilovolt ... high voltage is an advantage, since it makes it more efficient to transmit electricity >> >>
<< By this argument you should rub balloons against carpet and harvest the static electricity. That is high voltage also. Don't fool yourself. If you plan on using semiconductor electronics, kilovolts are terrible.>>
The comparison with static electricity is spurious. Static electricity provides very little energy. And if they can manage to deal with the high voltages in a device in a shoe, there may be hope in bouys as well.
<< <<The main challenge moving forward, the researchers say, is to develop a reliable manufacturing process>> >>
<< Hah! That's the least of their problems. A couple of square meters to produce 5 watts is like 0.25 milliwatts/cm2. Compare this to a crappy fuel cell that is 25 milliwatts/cm2 and this is 100 times worse.>>
Fuel cells will be an important power source as time goes by, and the hydrogen economy takes off, but they have an entirely different role: they consume hydrogen and generate electricity. The device in this article is for renewable power generation.
<< Move along folks. Nothing to see here. >>
I can't be as sure, and remain open-minded.
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kearns
30 Comments
Re: Sounds a little too optimistic
Good points on both sides of the argument. I was wondering, however, how this compared with OTEC (Ocean Thermal Energy Conversion) since that technology seems to have disappeared from the discussion. It had the promise of producing a considerable amount of energy from deep water sites with a large thermal gradient.
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SVE
51 Comments
Re: Sounds a little too optimistic
First off, there will be no hydrogen economy. Hydogen is too miserable to make, transport, and store. And too many better alternatives exist in all application areas and at every scale of their contemplated usage.
I have no doubts that energy from the ocean will be viable and play a big part. I just doubt that any piezo-like material, which this is, will play any role. Traditional floats, pumps, turbines, and dynamos just work too well.
As far as OTEC, wind, solar goes they will do well. They will take their place along with other local energy sources like hydro and geothermal as our electric grid decentralizes and becomes radically distributed with many more, smaller suppliers.
By the way, this trend of energy industry decentralization is also what is in store for other industries: the voice/data communications industry, the software industry, mass media, the automobile industry, agribusiness, etc. The world of our children will be much more self-sufficient and self-sustaining.
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alrefaee
2 Comments
Re: Sounds a little too optimistic
Referencing all the suggested points and counterpoints, it seems that, just like we have polluted the air by releasing/converting the energy captured in non-renewable sources into ecologically unsustainable environmental disturbances, we are attempting to do the same in the water. The goal of producing new distributed sources of energy is admirable, but on a larger scale, the disruption to waves and its motion, on which sea life depends, and to which all living things are linked, or the notion of drilling to create smokers to drive OTEC and other marine based energy generation sources, is only the beginning of a wave (no pun intended) of exploitation and erosion of one of the few resources the earth's climate has left to help re-balance itself.
Can you see the tipping point? We've been inadvertently, as a human race, trying to cripple one "branch" so far by polluting it, and the earth is still trying to recover by attempting to heal. If we attack other "organs", at some point, the earth will change focus and attempt to cut those "branches" off instead of trying to heal them, all in the attempt to restore balance - it's evolution in its purest form!
I hope it fights back sufficiently to destroy our ability to transform/force it to adapt...
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paulkoola
2 Comments
Re: Wave versus OTEC
Most renewable energy like wave energy is too fluctuating to provide the steady power levels we are used to consuming. Without an energy storage mechanism it is impractical to use. Most wave energy plants that intend to supply power to mainland use the existing electric grid for storage. I think the way to go for floating wave power plants in deep sea is to provide sensor power initially. This technology already exists. Providing uninterrupted power at sea (think Navy) is economically feasible today. Maintenance at sea is the number one killer of wave power designs. What most wave designers forget is life cycle costs including maintenance are more critical than efficiency of conversion.
Later as the technology matures it can be scaled up and used for islands communities where importing fuel to run power plants is exorbitant.
The other option for wave power is to build the structure as self absorbing breakwaters for harbor protection thereby sharing the costs of energy production and harbor protection, which makes them more attractive. Japan, UK and India have already tested prototypes in the range of 100kW.
OTEC however is one source where the oceans act as the storage medium. However unlike wave power where individual devices could be small, the cost of transferring water between bottom depth of the ocean and the surface dictates larger power plants in the MW range to supply the parasitic power required for pumping. The cold nutrient rich water at the bottom of the ocean might have more value than the OTEC energy we can produce. A self sustaining aquaculture environment with OTEC energy for sustaining this environment would be ideal.
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mkogrady
425 Comments
Re: Wave versus OTEC
Can OTEC technology be enhanced by using a more robust heat source like "Black Smokers" found at the bottom of the ocean where geological cracks in the magma are more accessible? With temps neat 1000F, it seems they may be far more efficient to use. Are there "close to shore or shallow" smokers that can be tapped or better yet - drills and manually created?
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zippo
24 Comments
Re: Re: Sounds a little too optimistic
OTEC could cause dangerous weather changes- how much I have no idea. It seems to me, however, that the cooling of the world's ocean currents is becoming a looming danger these days. I've read a couple articles by a couple scientists who state that that Greenland's ice sheet, one of the world's largest, has already had a considerable amount of its mass melted by rising global temperatures. They said that if the rest of this ice melts, it could raise global sea levels by up to a meter and stop a major ocean current in the northern hemisphere- there wold be too much fresh water floating on top of the salty ocean currents. This would then stop the major component for heat transfer in the northern hemisphere and cause a small ice age.
I know these devices are designed to harvest kinetic energy, but that energy comes from a temperature gradient, so you are removing heat from the system. Wave farms on a small scale certainly wouldn't have a large impact, but since when do humans ever like to do things on a small scale, especially when they have the promise of cheap clean energy? Part of the reason we are in this whole global warming catastrophe is because of the scale of the industrial revolution. Nobody had a clue that we should also be scaling up the envirnment's ability to process those extra emissions or be searching for was to reduce such emissions. Now the damage has been done and it's all because we burned one to many gallons of fuel, or one to many tons of coal, etc.
I'm not a physics expert or anything, but I think I remember that if you remove energy from a system, in this case by transforming it into electricity, then it has to come form somewhere, almost like an energy vaccuum. Even for buoys, I would expect that would result in a decrease in oceanic thermal energy.
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jdm
2 Comments
Re: Re: Re: Sounds a little too optimistic
Oceans are really big ... even if we replaced all of our generating capacity with OTEC systems, I doubt that it would have a significant direct impact on ocean temperature. And even if there was an impact, it would be removing heat from overheated oceans (sounds like a good thing to me). But the big win would be the reduction of the use of fossil fuels for power generation and less global warming which is causing those ice caps to melt and the oceans to heat up.
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barcus1
1 Comment
Re: Re: Sounds a little too optimistic
OTEC is available and another way to harness the oceans, very intrusive, but another way. Haven't we learned yet that the best things in life, the most perfect systems are non-intrusive. How smart is it to drill into the ocean floor and open a vent that we will probably not be able to control. If you want thermal differentiation to create power try using the sun or find a terratherm to exploit, for God's sake don't start creating volcanos. One energy source that doesn't change the ecosystem that it is in is pressure differentiation, and this can be utilized not only in the sea but also in deep landlocked lakes. Think of the tiny bubble that is released at 1000 feet below the surface of the ocean, how large will it be at the surface? The technology is already available for this type of generator. Installation is no more difficult than laying a cable on the ocean floor. This type of generator grid could someday power most of the cities along the coast.
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mbloore
39 Comments
Re: Sounds a little too optimistic
>> A bundle of rubber about a meter long and half a meter thick, with optimized electronics and an improved buoy design, could generate a kilowatt of electricity
> Compare this to a conventional kilowatt alternator which is about the size of half a shoebox.
no, compare this to the alternator and the engine that drives it and the tank that holds the fuel supply.
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