Wind mill spacing

[Notassmartasithought]

A couple of days ago my brother and I drove through the Fowler Ridge Wind Farm ( Fowler Ridge Wind Farm - Wikipedia ) in Indiana. We’d never seen one so large, and we’d never seen one at night. So we wonder about two things.

First, the spacing of the windmills. It seemed the rows were about a quarter mile apart, and I suppose the towers were 300 hundred yards apart, or so. Things were somewhat irregular, which we attributed to land ownership, or other issues. Our question is whether there are aerodynamic factors that might specify an ideal spacing of the windmills.

Second, at night, all the red lights on the windmills blink simultaneously. That must be intentional. What’s the thinking there? Why not have them all blink independently?

[johnpost]

you need no causes of wind turbulence for quite a few distances (based on height) for good functioning.

if the flashing was all independent it would be very disorientating to aircraft and not give a accurate representation of the obstructions. by all flashes synchronized it outlines the whole obstructed area.

[Notassmartasithought]

Well, we got that far speculating on both issues. Perhaps I misstated our questions.

What is the optimum spacing, and why? Blade length? Height? RPM (including gearing)? Average wind speed? Blade pitch? Anything else? Any aerodynamicists out there?

As for the simultaneous blinking, iIs there an FAA ruling on this? Was it a long regulatory fight, or relatively quick? Other red lights around airports don’t blink simultaneously. Are there other things going on?

[DSeid]

Some work on optimizing spacing inspired by biological systems.

Dabiri realized that one major problem on wind farms is interference between neighboring turbines. When placed close together, they funnel wind into each other, reducing energy output and increasing wear and tear. To avoid this, wind farms space turbines hundreds or even thousands of feet apart.

Dabiri found an analogous problem in the ocean. When fish move as a school, they push water against each other, potentially slowing the whole group. But they’ve found ways of moving together more efficiently and with less energy. Dabiri modeled their motion mathematically and used the results to develop software to define the optimal placement of wind turbines. He says his math makes it possible to squeeze more turbines onto a given plot of land and yield 10 times more energy. He started the company Scalable Wind Solutions to commercialize the software and plans to start selling it in the next two years. “He was the first person to think of” modeling wind farms on fish schools, says Alexander Smits, one of Dabiri’s engineering professors at Princeton. “It’s a game-changer.”

[MikeS]

@Notassmartasithought

As for the simultaneous blinking, iIs there an FAA ruling on this? Was it a long regulatory fight, or relatively quick? Other red lights around airports don’t blink simultaneously. Are there other things going on?

I can answer the first question at least: FAA Standards for Obstruction Lighting and Marking (PDF), which includes the standards on marking wind turbines (p. 33 & 34). Basically, the lights do have to be synchronized, and if the turbines are in a line, there has to be at least one light every half-mile along the line.

[MikeS]

Oh hey, here’s a technical report from 2005 on the development of lighting standards for wind farms. Concerning the synchronization:

Operating in the non-synchronous mode, the obstruction lighting array presented a most confusing and unsatisfactory appearance and, in the opinion of all present, did not accomplish the objective of outlining or warning of the presence of dangerous projections (i.e. 345 foot high wind turbines) above the surface of the ridgeline. This result was expected, and was the reason why synchronization of the light flashes was added to the proposed obstruction lighting system design. Photographs and video tapes of the system were taken at that time.

…

[In synchronous mode,] the limits of the turbine farm was immediately evident, since all 14 lighted wind turbines were defined by high intensity red strobes that were flashing simultaneously. The effect was in strong contrast to the previous night’s presentation, in that the simultaneously flashing lights very clearly defined the extent of the entire wind farm, from one end to the other, and also provided a most dramatic warning of the potential hazard.

It’s also noted in the executive summary that bridges and arrays of radio towers also use synchronized lights, and that the wind farm standards were based off of these previous practices.

[hibernicus]

@Notassmartasithought

Things were somewhat irregular, which we attributed to land ownership, or other issues.

I just want to comment on the irregularity. In areas I am familiar with, there are a large number of constraints on the positioning of wind turbines. One such constraint is distance from the site boundary. Others are steepness, distance from dwellings, lines of sight and forested areas. By the time you have overlaid 5 or 6 maps showing areas that are “out of bounds” for various reasons, the number of available locations can be very limited.

[core_dump]

How exactly are the blinking lights syncronized? I live in the middle of a wind farm and noticed that a few of the lights have lost sync and don’t blink with the rest. I’m assuming this is done via communication over the powerline, but if something broke with that one and the light can’t even be controlled, does that also mean the utility has lost control of the turbine?