Even better: GE started the Haliade-X project as a 12MW turbine, then went to 13MW, which is what the article says, and in some places where it can be appropriately uprated, is now at a 14MW...
Even better: GE started the Haliade-X project as a 12MW turbine, then went to 13MW, which is what the article says, and in some places where it can be appropriately uprated, is now at a 14MW design baseline.
One of the challenges wind is going to need to overcome if we want to make a serious dent in our global CO2 emissions is being able to site the turbines in deeper waters that are further offshore. Right now most offshore wind turbine projects are located in shallow water banks with a silt/clay matrix only 10-20 metres below sea level. This does limit the available area for these farms.
If we can get the nascent idea of floating turbines sited on their own platforms to take off, things get even more interesting. You could go even bigger still (and in the 10MW+ range, even small increases in blade diameter now dramatically increase output due to the swept area of the blades increasing thanks to πr2), and with bigger blades, your turbines are taller, allowing you to tap into faster wind speeds higher-above ground, further increasing power output, which already offer wind speeds that are much higher than near-shore farms. Distance is also your friend: the further off-shore you can site these things, the more atmospheric haze and the curvature of the Earth will obscure the turbines from shore.
So if you can imagine ultra-large 20MW, or even 30MW turbines located 50-100km offshore, suddenly you don't need more than 40-60 turbines to provide the output of a commercial nuclear reactor, and when the wind is blowing strong and you don't need the energy, use electrolysis of water to create hydrogen, which could either be piped elsewhere, or stored as a battery to burn when the wind is less strong.
Higher windspeeds aren't necessarily a wind turbine's friend and the larger the blades, the slower they can spin. Blades don't like tip speeds above mach 0.92, after that point they begin vibrate...
You could go even bigger still (and in the 10MW+ range, even small increases in blade diameter now dramatically increase output due to the swept area of the blades increasing thanks to πr2), and with bigger blades, your turbines are taller, allowing you to tap into faster wind speeds higher-above ground, further increasing power output, which already offer wind speeds that are much higher than near-shore farms
Higher windspeeds aren't necessarily a wind turbine's friend and the larger the blades, the slower they can spin. Blades don't like tip speeds above mach 0.92, after that point they begin vibrate destructively and lose efficiency exponentially with increases in speed. So they'll need to saddle the turbines with braking systems and generators strong enough to slow the blades down. The article lists this new turbine as having a 722 foot diameter, that puts the speed limit of the blades at 27rpm to keep it under mach 0.92. Wind turbines typically spin in the 10-20rpm range.
Of course this is probably all a thought experiment for naught as the maximum theoretical diameter for a wind turbine spinning at 10rpm is 1958 feet, which is far outside the realm of our current manufacturing and engineering capabilities. But if we go with the maximum 20rpm of typical wind turbines we're in the more achievable range of 983 foot diameter. Huge, but not a far cry from GE's 722.
In the case of the Haliade-X, it's worth noting the rated speed at which the turbine produces its nameplate capacity is only 7.8rpm, GE have been pretty careful to not want to push this too high...
In the case of the Haliade-X, it's worth noting the rated speed at which the turbine produces its nameplate capacity is only 7.8rpm, GE have been pretty careful to not want to push this too high because, like you say, they're being cautious about the velocity of the turbine blade tip speed at full power—the downside to this is of course its 600+ tonne, direct-drive nacelle.
Given that only 4 years ago the upper capabilities of offshore wind turbines was in the 6-8MW range, and we're now deploying test articles of 12-14MW turbines, and there's componentry nearly ready to be integrated into turbines with 20MW nameplate capacities in the next few years, I'd say there's still lots of room to grow in the offshore wind market!
The learning curve of this industry is still very clearly underway, I expect the next step will be more localised fabrication of parts near to—or even at—very large projects to continue to push down cost, and new ships designed specifically for the installation of truly enormous, multi-piece blades.
I think I'm missing something in the process here. I get that the blades can't spin too fast because they would shake themselves apart. So given that there is an upper limit on speed, what is the...
I think I'm missing something in the process here. I get that the blades can't spin too fast because they would shake themselves apart. So given that there is an upper limit on speed, what is the advantage of make the blades larger? How is the extra energy captured by that expanded surface area converted into more watts if the speed doesn't go up?
Good question :) To an extent, you can simply make the generator in the nacelle have more resistance by designing it with more magnets, requiring more force from the wind to turn the blades. The...
Good question :)
To an extent, you can simply make the generator in the nacelle have more resistance by designing it with more magnets, requiring more force from the wind to turn the blades. The downsides to doing so are you need a huge amount of permanent magnets to do so—somewhere in the region of 250kg/MW of rated power. Turbines with gearboxes (becoming less and less common because they require so much maintenance, especially as they become larger) will also have higher gearing ratios which accomplishes the same thing. The downsides to this are massive nacelles which are approaching nearly 1000 tonnes in conceptual designs, which affects construction logistics as well as the design of the tower itself.
It's going to take some time before the industry settles into an optimum local maximum, but for now, it looks like the size of the turbines are going to keep rising for a while yet.
The generator becomes more difficult to turn. The turbine is rotating at the same angular velocity, but with significantly more force, thus generating more energy.
The generator becomes more difficult to turn. The turbine is rotating at the same angular velocity, but with significantly more force, thus generating more energy.
Packed with sensors gathering data on wind speeds, electricity output and stresses on its components, the giant whirling machine in the Netherlands is a test model for a new series of giant offshore wind turbines planned by General Electric.
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The prototype is the first of a generation of new machines that are about a third more powerful than the largest already in commercial service. As such, it is changing the business calculations of wind equipment makers, developers and investors.
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A larger turbine produces more electricity and, thus, more revenue than a smaller machine. Size also helps reduce the costs of building and maintaining a wind farm because fewer turbines are required to produce a given amount of power.
These qualities create a powerful incentive for developers to go for the largest machine available to aid their efforts to win the auctions for offshore power supply deals that many countries have adopted. These auctions vary in format, but developers compete to provide power over a number of years for the lowest price.
[...]
On Dec. 1, G.E. reached another preliminary agreement to provide turbines for Vineyard Wind, a large wind farm off Massachusetts, and it has deals to supply 276 turbines to what is likely to be the world’s largest wind farm at Dogger Bank off Britain.
Even better: GE started the Haliade-X project as a 12MW turbine, then went to 13MW, which is what the article says, and in some places where it can be appropriately uprated, is now at a 14MW design baseline.
One of the challenges wind is going to need to overcome if we want to make a serious dent in our global CO2 emissions is being able to site the turbines in deeper waters that are further offshore. Right now most offshore wind turbine projects are located in shallow water banks with a silt/clay matrix only 10-20 metres below sea level. This does limit the available area for these farms.
If we can get the nascent idea of floating turbines sited on their own platforms to take off, things get even more interesting. You could go even bigger still (and in the 10MW+ range, even small increases in blade diameter now dramatically increase output due to the swept area of the blades increasing thanks to πr2), and with bigger blades, your turbines are taller, allowing you to tap into faster wind speeds higher-above ground, further increasing power output, which already offer wind speeds that are much higher than near-shore farms. Distance is also your friend: the further off-shore you can site these things, the more atmospheric haze and the curvature of the Earth will obscure the turbines from shore.
So if you can imagine ultra-large 20MW, or even 30MW turbines located 50-100km offshore, suddenly you don't need more than 40-60 turbines to provide the output of a commercial nuclear reactor, and when the wind is blowing strong and you don't need the energy, use electrolysis of water to create hydrogen, which could either be piped elsewhere, or stored as a battery to burn when the wind is less strong.
Higher windspeeds aren't necessarily a wind turbine's friend and the larger the blades, the slower they can spin. Blades don't like tip speeds above mach 0.92, after that point they begin vibrate destructively and lose efficiency exponentially with increases in speed. So they'll need to saddle the turbines with braking systems and generators strong enough to slow the blades down. The article lists this new turbine as having a 722 foot diameter, that puts the speed limit of the blades at 27rpm to keep it under mach 0.92. Wind turbines typically spin in the 10-20rpm range.
Of course this is probably all a thought experiment for naught as the maximum theoretical diameter for a wind turbine spinning at 10rpm is 1958 feet, which is far outside the realm of our current manufacturing and engineering capabilities. But if we go with the maximum 20rpm of typical wind turbines we're in the more achievable range of 983 foot diameter. Huge, but not a far cry from GE's 722.
In the case of the Haliade-X, it's worth noting the rated speed at which the turbine produces its nameplate capacity is only 7.8rpm, GE have been pretty careful to not want to push this too high because, like you say, they're being cautious about the velocity of the turbine blade tip speed at full power—the downside to this is of course its 600+ tonne, direct-drive nacelle.
Given that only 4 years ago the upper capabilities of offshore wind turbines was in the 6-8MW range, and we're now deploying test articles of 12-14MW turbines, and there's componentry nearly ready to be integrated into turbines with 20MW nameplate capacities in the next few years, I'd say there's still lots of room to grow in the offshore wind market!
The learning curve of this industry is still very clearly underway, I expect the next step will be more localised fabrication of parts near to—or even at—very large projects to continue to push down cost, and new ships designed specifically for the installation of truly enormous, multi-piece blades.
I hadn't looked up GE's new turbine target RPM so thanks for that info! It's certainly and exciting time for the industry and energy as a whole.
I think I'm missing something in the process here. I get that the blades can't spin too fast because they would shake themselves apart. So given that there is an upper limit on speed, what is the advantage of make the blades larger? How is the extra energy captured by that expanded surface area converted into more watts if the speed doesn't go up?
Good question :)
To an extent, you can simply make the generator in the nacelle have more resistance by designing it with more magnets, requiring more force from the wind to turn the blades. The downsides to doing so are you need a huge amount of permanent magnets to do so—somewhere in the region of 250kg/MW of rated power. Turbines with gearboxes (becoming less and less common because they require so much maintenance, especially as they become larger) will also have higher gearing ratios which accomplishes the same thing. The downsides to this are massive nacelles which are approaching nearly 1000 tonnes in conceptual designs, which affects construction logistics as well as the design of the tower itself.
It's going to take some time before the industry settles into an optimum local maximum, but for now, it looks like the size of the turbines are going to keep rising for a while yet.
The generator becomes more difficult to turn. The turbine is rotating at the same angular velocity, but with significantly more force, thus generating more energy.
From the article:
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