Gear technology helps lower cost of wave energy farming

February 18, 2015, KTH Royal Institute of Technology
Gear technology helps lower cost of wave energy farming
A CorPower buoy in the test environment.

A Swedish company has cracked the challenge of scaling up wave energy, with the help of technology from researchers at KTH Royal Institute of Technology.

CorPower Ocean's new system, which uses a gearbox design that KTH researchers helped develop, generates five times more energy per ton of device, at one third of the cost when compared to competing state-of-the art technologies. Energy output is three to four times higher than traditional wave power systems.

The company's innovation was recently awarded EUR 100,000 at the MIT Building Global Innovators Demo Day.

Wave energy has been held back in part because of the cost of electricity generation. The amount of steel and concrete needed in order to produce each MWh has simply been too great to make it into a profitable business. Even still, the power of waves presents a problem with reliability; and because waves vary greatly in height and timing, it's difficult to create a conversion system that functions across the full wave spectrum.

Known in the wave energy industry as a point absorber type system, the CorPower converter consists of a buoy that absorbs energy from the waves, plus a drivetrain that converts the buoy's motion into electricity. The company's system is based on Swedish cardiologist Stig Lundbäck' patents, some of which are inspired by his research into heart pumping and control functions.

Gear technology helps lower cost of wave energy farming
A close-up of the CorPower wave converter's "cascade gear" system.

CEO Patrik Möller says the CorPower wave energy converter can manage the entire spectrum of waves, unlike competing systems.

Methods for phase control, in which compact wave buoys swing in resonance with ocean waves, have been studied by researchers in Trondheim since 1970s, and the CorPower project works closely with researchers from NTNU. The system tested well in Portugal and France and a driveline scale of 1: 3 has recently been installed in a large test setup at the Department of Machine Design at KTH.

"Unlike other wave power systems, ours actively controls the timing between the buoy and the incoming wave, with the help of a unique drivetrain," Möller says. "We can ensure that it always works in time with the waves, which greatly enhances the buoy's movement and uses it all the way between the wave crest and wave trough and back in an optimal way, no matter how long or high the waves are."

The system also boasts a specially-designed rack and pinion gear solution developed in cooperation with the Department of Machine Design at KTH and gear expert Stefan Björklund, among other partners. The so-called cascade gear provides a robust and efficient way to convert linear motion into rotation, Möller says. The novelty of the invention is its capability to handle heavy loads and high velocities efficiently, with numerous small pinion wheel parts sharing the load.

An artists' rendering of the CorPower wave energy converter. Credit: CorPower
"The cooperation with KTH around gear technology has been crucial to the rapid developments over the last two years, and we hope to deepen cooperation with KTH with more research on gear technology and lubrication," Möller says.

The buoys are compact and lightweight and can be manufactured at a relatively low cost. A buoy with 8 meters in diameter can produce 250-300 kilowatts in a typical Atlantic Environment. A wave energy park with 100 buoys can generate 25 to 30 megawatts.

A pilot installation of the technology (scale 1:2) will be exhibited in the Atlantic in November 2015 in cooperation with the multinational electric utility company Iberdrola.

CorPower Ocean is a Swedish company that developed through the support of the European research effort KIC InnoEnergy, an innovation-promoting collaboration between academia and industry in the context of renewable energy, in which KTH is important partner. Swedish Energy Agency is a co-financier.

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flying_aries3
2 / 5 (1) Feb 18, 2015
Great idea, but just don't suck all the energy out of good surf.
gkam
3 / 5 (2) Feb 18, 2015
Perhaps we can replace the seaside nuke plants with these. The inland Ginna nuke plant has lost $100,000,000 in the last two years, and now the customers have to pay it $17,500,000 every month to keep it open!

After it is closed, what happens to the highly-radioactive plant? What about the waste, which we have no way to store for the long term?

Why do we let corporations do this to us?
Eikka
2 / 5 (1) Feb 18, 2015
what happens to the highly-radioactive plant?


The same thing as happened to the Rancho Seco plant. They'll dismantle it. The most radioactive parts aren't nearly as radioactive for nearly as long as you make believe.

which we have no way to store for the long term?


There's plenty. You just deny the existence of them all for political reasons.
Eikka
1 / 5 (1) Feb 18, 2015
now the customers have to pay it $17,500,000 every month to keep it open!


Considering that it's a 577 Megawatt unit, it will make roughly 430,000 MWh of electricity each month at full output, which puts the cost of electricity at roughly $40 per MWh or 4 cents a kWh. Even if it was off the line half the time, it would still be cheaper than the US average electricity price.

I don't see what your complaint is.

The only problem with the station is that it's really old and in need of repairs, which will cost a lot of money.
gkam
5 / 5 (1) Feb 18, 2015
Your four cents/kWh is the increased cost of the bailout of the utility's monster. It is already uncompetitive. What will this increase do to the cost of power?

The utility put their customers in the position of having to bail out their failing assets. Not good use of funds from consumers, is it?

I wonder what the cost is of the total power per kWh produced by Fukushima Dai-ichi, considering the total costs of that error, which will not be determined for decades.
Eikka
not rated yet Feb 21, 2015
Your four cents/kWh is the increased cost of the bailout of the utility's monster. It is already uncompetitive. What will this increase do to the cost of power?


You should answer that, since you apparently have the information. All I did was go with the numbers you provided.

Don't keep us in the dark.
Eikka
not rated yet Feb 21, 2015
http://www.bloomb...-nuclear

According to this article:

A single-unit reactor like Ginna needs as much as $71 a megawatt-hour to earn an 11 percent return and $56 to $64 to break even, based on 2016 forecasts, Exelon said.


That's still not very much, although clearly not competetive with fossil fuels anymore.

The reason why the nuclear plant is in troubles is because of cheap natural gas selling at $39 per MWh - and if the plant is closed down, the power it produces will be replaced with natural gas.

So, the choice is between more CO2 and cheaper power, or less CO2 and more expensive power.

How much was the New York subsidy for renewable power again? Oh, that's right, $34.95 on top of the going rate: http://guarinicen...bsidies/
Eikka
not rated yet Feb 21, 2015
Perhaps we can replace the seaside nuke plants with these.


Given the figures provided, you'd need about 2,200 units to replace Ginna, but there's no mention of the capacity factor.

If it's assumed to be similiar to wind power at 0.25, then you need about 10,000 units. The biggest issue there would be to find enough space and shallow waters to put them in, and wire them up in a big collector farm so that they won't shade and rob energy off of each other.

The available power per square mile isn't without limit, so the density of these collectors can't be too high. According to Wikipedia, the global resources available with current level of wave power technology is limited to about 500 GW out of 2,700 GW potential, so you'd actually need to cover a significant portion of the earth's seas to replace just a handful of nuclear power stations.

gkam
not rated yet Feb 21, 2015
Why would you want to assume the capacity factor of ocean waves is as variable as wind? Show me.

Of course, I was kidding about the direct replacement of deadly nukes with benign wave harvesters. We need more than that, which is why none of the alternative energy systems will be alone, but integrated into the system as appropriate, each one with its own characteristics, rounding out a diverse and resilient grid.

We probably will not have to hide the residue of wave power from living things for a quarter-million years, like we do with Plutonium-contaminated materials.
Eikka
not rated yet Feb 21, 2015
Why would you want to assume the capacity factor of ocean waves is as variable as wind? Show me.


Ask yourself, what causes ocean waves?

Wind, perhaps?
gkam
not rated yet Feb 21, 2015
There is always wind somewhere. How far do waves travel? How many seashores and offshores do not have continuous waves? String these between the offshore wind turbines, to share infrastructure, and you will have continuous power.
Eikka
not rated yet Feb 21, 2015
We probably will not have to hide the residue of wave power from living things for a quarter-million years


Well, there is the issue that widespread construction of wave power farms will induce permanent ecological damage to reef ecosystems and shallow water fisheries of the world.

Wind and waves induce mixing of water layers, which influences nutrient turnover, and harnessing wave energy reduces this. It may result in oxygen-depleted dead zones where there were previously thriving ocean ecosystems.

But that's just conjecture.
gkam
not rated yet Feb 21, 2015
The massacre of thermally-sensitive organisms near the discharge of thermal powerplants such as nukes is well-understood. Because such plants need to be taken off-line periodically, the temperature of the entire marine area changes, killing much of the biota.

No conjecture.
Eikka
not rated yet Feb 21, 2015
How far do waves travel?


That depends on the wavelenght. There's more energy in shorter wavelenght waves, but they diminish over shorter distances than the long wavelenght ones.

You have a point in that harnessing wave energy is effectively collecting wind energy over a huge surface area of the sea, but then again the established figures show that this isn't a very effective process. If there is a 2,700 GW potential for wave energy in the entire world, that really isn't giving much hope for individual generator farms.

String these between the offshore wind turbines, to share infrastructure, and you will have continuous power.


When was the last time you saw calm seas with high winds on the shore, and calm winds with high seas at the horizon?

The weather is usually the same for at least as far as you can see off the coast.
Eikka
not rated yet Feb 21, 2015
No conjecture.


Only loaded language.

killing much of the biota.


I would like to see some backing for this claim. What exactly constitutes "much" in this context?

And how much is "near" a thermal powerplant, and why is this not an issue for other thermal powerplants that run on things like biogas/biomass burning, or geothermal energy which need even more thermal mass to cool them down due to lower carnot efficiency?

I resent that you're constantly restorting to poor rhetorical propaganda instead of discussing with facts.

gkam
not rated yet Feb 21, 2015
I clearly said "thermal powerplants". Please read the post. Thermal pollution is a factor with ALL thermal powerplants.

Here, we can produce solar power in the daytime, wind in the afternoon and at night, and reduce the burning of fuels.

BTW, compare the thermal efficiency of powerplants such as coal or gas combined-cycle, and compare them to nukes, and get back to us.
gkam
not rated yet Feb 21, 2015
Here you go, Eikka:

http://www.sadgur...2012.pdf
xstos
5 / 5 (1) Feb 22, 2015
Being afraid of nuclear doesn't change the fact that it is the densest clean power source we have at the moment. Fear and political inconvenience continue to marginalize this feasible low-carbon alternative. With fuel reprocessing and modernization of half-century-old reactor designs, we could have it all. Not to knock wind/wave/whatever as this research is useful, but I find it amusing that nukes get all the blame when 20% of world capacity is nuke. If I was king of the world, i'd subsidize and swap out the remaining coal/gas/oil and live happily ever after. Safe nuclear is possible, if there is a will to achieve it.
gkam
not rated yet Feb 22, 2015
xstos, I would like to believe that, but we do not need and cannot afford to build such dangerous technologies just to boil water. It is not safe, and it is not economic, and we STILL have no sure way to even store the deadly waste, but are leaving it for the rest of Humanity to deal with.

Where to start? Chernobyl, Fukushima, Fermi I, Brown's Ferry, Monju, SL-1, TMI II, Hanford, WIPP, . . . shall I go on?
xstos
not rated yet Feb 22, 2015
xstos, I would like to believe that, but we do not need and cannot afford to build such dangerous technologies just to boil water. It is not safe, and it is not economic, and we STILL have no sure way to even store the deadly waste, but are leaving it for the rest of Humanity to deal with.

Where to start? Chernobyl, Fukushima, Fermi I, Brown's Ferry, Monju, SL-1, TMI II, Hanford, WIPP, . . . shall I go on?


Of all those accidents combined, more people have been killed from oil/gas/coal pollutants. Where is the danger my friend? Why doesn't polluting our biosphere scare you more? By burning fossil fuels, we're slowly destroying our planet. I would take clean skies and a few football fields of sequestered active waste (which can be reprocessed) than the garbage dump we have now.
xstos
1 / 5 (1) Feb 22, 2015
Anyway i'm not going to engage in a flame war, as you've made up your mind, and no rational arguments can ever change it. Such indoctrination, like religion, is nearly impossible to penetrate, as your brain has been wired the wrong way. You hear/believe what you wish. So I won't be participating any further...
gkam
not rated yet Feb 22, 2015
No flames required nor intended. Just facts. In case you are unaware, in the late 1970's I tested the safety components of the GE Mark I & II BWRs. I am also a former Senior Engineer in Technical Services for Pacific Gas & Electric. I understand fission power systems.

Do you?

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