A new formula has been devised to help wind farm owners generate energy more cost efficiently.
Charles Meneveau, a Johns Hopkins University (JHU) fluid mechanics and turbulence expert, working with a colleague in Belgium, has devised the new precept through which the optimal spacing for a large array of turbines can be obtained.
‘I believe our results are quite robust,’ said Meneveau, who is the Louis Sardella Professor of Mechanical Engineering in the university’s Whiting School of Engineering. ‘They indicate that large wind farm operators are going to have to space their turbines farther apart.’
According to JHU, the newest wind farms typically use turbines with rotor diameters of about 300 feet.
Currently, turbines on large wind farms are spaced about seven rotor diameters apart. The new spacing model developed by Meneveau and Johan Meyers, an assistant professor at Katholieke Universiteit Leuven in Belgium, suggests that placing the wind turbines 15 rotor diameters apart – more than twice as far apart as in the current layouts – results in more cost-efficient power generation.
Large wind farms – consisting of hundreds or even thousands of turbines – are planned or already operating in the western United States, Europe and China.
‘The early experience is that they are producing less power than expected,’ Meneveau said.
Earlier computational models for large wind farm layouts were based on adding up what happens in the wakes of single wind turbines, Meneveau said. The new spacing model, he added, takes into account interaction of arrays of turbines with the entire atmospheric wind flow.
Meneveau and Meyers argue that the energy generated in a large wind farm has less to do with horizontal winds and is more dependent on the strong winds that the turbulence created by the tall turbines pulls down from higher up in the atmosphere.
Using insights gleaned from high-performance computer simulations as well as from wind tunnel experiments, they determined that in the correct spacing, the turbines alter the landscape in a way that creates turbulence, which stirs the air and helps draw more powerful kinetic energy from higher altitudes.
The experiments were conducted in the Johns Hopkins wind tunnel. Before it enters the testing area, the air passes through an ‘active grid,’ a curtain of perforated plates that rotate randomly and create turbulence so that the air moving through the tunnel more closely resembles real-life wind conditions.
Air currents in the tunnel pass through a series of small three-bladed model wind turbines mounted on posts, mimicking an array of full-size wind turbines.
Data concerning the interaction of the air currents and the model turbines is collected by using stereo particle-image-velocimetry, which requires a pair of high-resolution digital cameras, smoke and laser pulses.
Further research is needed, Meneveau said, to learn how varying temperatures can affect the generation of power on large wind farms.
I cannot believe that these conclusions have not been arrived at years ago before we have destroyed the scenic beauty of the countryside. I am a qualified engineer having worked in the aerospace sector where mistakes like this kill people, is that the difference
So they need to stop every other turbine in a line to get a better effect, interesting!
Not being a mechanical engineer but would it not be possible to re-design the gearing in the turbine so that more turbine generating speed can be obtained for the same turbine blade revolution? If this is possible can the new gearing be added during regular maintenance?
Is it not interesting that, once you have seen or heard a thing it becomes obvious?
I had done some work, never published, on how to manipulate equations to get the ‘characteristic dimensions’ out of them, even if you cannot necessarily solve the set. this situation is normal for interactive aerodynamic devices.
That approach suggests that there are certain characteristic lengths for all processes. I wonder if the equation set that the researchers are using would be able to use that approach.
The advantage of teasing out the characteristic dimensions of a process is that you can often ‘see,’ for the first time, just how nature seems to see the process.
NO FREE LUNCH.
I am very much in favour of wind power but I often wonder what would be the ultimate effect if there were to a significant proliferation of large “wind farms”
The electrical energy we use from this source must obviously reduce the velocity of the wind which drives the turbine.
Is this likely to reach the level where it might create it’s own weather/climate problems?
The learning curve is not a mathematically calculated one and only time will expose the inevitable assumptions that are introduced as academic contribution to the yet unknown. In an ideal world and if nature was not nature the wind velocity could be nicely channeled into feeding each one of the wind generator blades so you would have focussed power channels. This would the stop the imbalance of suction created by each of the wind generators and would stop them from stealing into each of their neighbours air flow, hence the unwanted turbulence between the towers would be eliminated.
Yese, to be really effective the spacing should be considered more carefully, but, this is only one issue.
How about the cost and complications of maintenance, replacement of bearings on the generator and dealing with the ingress of saline moisture in the off shore installations. These costs have yet to hit the owners, the operators and ultimately the consumer. The Nuclear power generation might not be considered by some as being environmentally friendly, but, the few stations we have in the UK are less unsightly and less intrusive than the proliferation of wind farms wherever they are located. Our power conversion products gives us a position in both energy disciplines but our tendency is leaning more towards the Nuclear sector for long term cost effective reasons to upgrade, renew and add new stations to the 8 sites the UK already has.
To Robert White: Note that until circa 1992, diesel-electric locomotives utilized DC current, and at that late date it was discovered AC generation and AC motors were more efficient. Why did it take so long (?fifty years?) to understand this superior efficiency?
Rotor tip vortices are the main cause for the requirement for greater spacing. This was discovered during 1980-2000 in California wind farms as the size (diameter of rotors) of wind turbines progressively increased, and spacing between machines became a required parameter to evaluate. This study is putting laboratory analysis to the real-time observations that have been on-going. Unlike repeatedly rearranging your living room furniture to achieve the optimum configuration, wind turbines pretty much get one-time-sited by geographical considerations.
To Bernard Wallace: your concerns about maintenance, salt corrosion, not to mention siting, erection, and power transmission are areas I have also examined. I have concluded the following parameters need to be met in order to make offshore wind (or tidal, wave) electricity generation practical: (1) no electrical equipment offshore. All conversion of natural forces (wind, waves, tides) should be converted to water pressure, and a “reverse river” of water should come ashore, and flow through land-based (near-shore) hydrodynamic machinery to generate electricity. (2) Only robotic devices should be utilized to transport, site, build, and maintain offshore structures. Men going to sea to do dangerous work means that their safety and well-being overwhelm the design considerations of the build/maintenance equipment. Of course, this means an all-inclusive approach to the design, build, and siting, which requires the ancillary that (3) no expensive megastructure builds. Assembly-line manufacturing, no drill-rig, Ekofisk-size structures and platforms.
I have designed a system that meets all the above requirements. But I am but one person. I have not found a methodology to fund even a demo project.
As far as I am concerned wind turbines ought to be at least 100 miles apart. They are inefficient, unreliable forms of electricity generation and ruin the countryside, being unsightly and causing noise pollution (not to mention that alleged impact on wildlife).
It is about time that the proponents of these machines realise that you cannot obtain energy for nothing and that the increasing numbers of these so-called “environment-friendly” devices are having an impact on the world and its weather patterns. The article makes this clear when it states that “the turbulence created by the tall turbines pulls down (high winds) from higher up in the atmosphere.”
How do we get politicians to see sense and to stop this tilting at windmills and put the emphasis on implementing robust nuclear power programmes?
They would be more efficient in greater amounts- and everyone I have talked to about wind turbines has told me that, if anything, the turbines INCREASE the beauty of the countryside.
Not to mention, you claim to fear for the wildlife, but nuclear energy is a well-known BAD THING- and ruins the environment in a lot of different ways, not even mentioning the destruction that has occurred when one of these sites has FAILED.
Politicians, for the first time in a LONG TIME, are seeing sense- they’re working towards a more permanent and healthy solution in the future. You may not have to worry about it, from your obvious lack of future outlook- but think about the generations down the line and even the children of today.
If you have any compassion or empathy, you’ll see the sense in wind turbines.
This article is somewhat annoying as I have climbed many turbines in my relatively short career in the industry and can see the affects of poor wind farm lay out and god awe full design. Most notably the affect of the turbulence from one turbine in front of another turbine. The current spacing technique does need to be revised, but should have input from those who see the problems on a daily basis. May I suggest that some of the design engineers and wind farm developers actually climb a turbine and see how many mistakes are being made. The guys on the ground (in this case those in the turbines) have to deal with ridiculous design arrangements that give poor efficiency and lead to bad press. There is no substitute for a hands on approach.
And for all those who think wind turbines are unsightly, did you complain when the national grid pylons where erected? I expect you like having electricity at the flick of a switch as well . . . .
Hi, I am not an engineer, just interested… I don’t know how to contact you, so I thought you might reply to this, even if this ‘thread’ is from 8 years ago.. What are the possible effects of a ‘V’ shaped pattern with the turbines on either side turning the opposite way, maybe helping an inner “V” array? Maybe a “teardrop” shape? Just curious. Oh, also, what about all in a line, with an axle runing between them all with clutches that ‘helped’ the one ahead or behind it if it reached a certain speed?
maybe a three dimensional pattern, like a beehive on its side?
What about a circle at the tips of the (impellers?) that helped propell them faster with electro-magnetic current generated by the turbine? Just asking.. interested.