Power generation is blowing in the wind

Jan 17, 2012 by Anne M Stark
Wind turbines can produce different amount of power due to different "shapes" in the wind. Photos by Jacqueline McBride/LLNL

(PhysOrg.com) -- By looking at the stability of the atmosphere, wind farm operators could gain greater insight into the amount of power generated at any given time.

Power generated by a wind turbine largely depends on the wind speed. In a wind farm in which the turbines experience the same wind speeds but different shapes (such as turbulence) to the wind profile, a turbine will produce different amounts of power.

And this variable power can be predicted by looking at atmospheric stability, according to Lawrence Livermore National Laboratory scientist Sonia Wharton and colleague Julie Lundquist of the University of Colorado at Boulder and the National Renewable Energy Laboratory.

In a paper appearing in the Jan. 12 edition of the journal, Environmental Research Letters, Wharton and Lundquist examined turbine-generated power data, segregated by atmospheric stability, to figure out the power performance at a West Coast wind farm.

"The dependence of power on stability is clear, regardless of whether time periods are segregated by three-dimensional turbulence, turbulence intensity or wind shear," Wharton said.

The team found that power generated at a set wind speed is higher under stable conditions and lower under strongly unsteady conditions at that location. The average wind power output difference is as high as 15 percent less when the atmosphere is unstable.

While turbulence is a relatively well-known term in assessing turbine efficiency, wind shear -- which is a difference in wind speed and direction over a relatively short distance in the atmosphere -- also plays an important role when assessing how much power a turbine generates over certain time scales.

Wharton and Lundquist said that wind farm operators could better estimate how much power is generated if the wind forecasts included atmospheric stability impact measurements.

Though earlier research looked at atmospheric stability effects on power output, few studies have analyzed power output from modern turbines with hub heights of more than 60 meters.

In the new research, Wharton and Lundquist gathered a year of power data from upwind modern turbines (80 meters high) at a multi-megawatt wind farm on the West Coast. They considered turbine power information as well as meteorological data from an 80-meter tall tower and a Sonic Detection and Ranging (SODAR), which provided wind profiles up to 200 meters above the surface, to look at turbulence and . Looking at upwind turbines removed any influence that turbine wakes may have on power performance.

The team found that wind speed and power production varied by season as well as from night to day. Wind speeds were higher at night (more power) than during the day (less power) and higher during the warm season (more power) than in the cool season (less power). For example, average power production was 43 percent of maximum generation capacity on summer days and peaked at 67 percent on summer nights.

"We found that experienced stable, near-neutral and unstable conditions during the spring and summer," Wharton said. "But daytime hours were almost always unstable or neutral while nights were strongly stable."

"This work highlights the benefit of observing complete profiles of and turbulence across the turbine rotor disk, often available only with remote sensing technology like SODAR or LIDAR (Laser Detection and Ranging,)" Lundquist said. "Wind energy resource assessment and forecasting would profit from this increased accuracy."

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nixnixnix
2.6 / 5 (5) Jan 17, 2012
What no petroleum industry funded astro-turfing climate-change-denying trolls? For shame! :)
nixnixnix
not rated yet Jan 17, 2012
Nice find!

It is past Jan 12. Can we get a reference and hyperlink to the article, even if it is pay for access?

antialias_physorg
3.7 / 5 (3) Jan 18, 2012
Good news that wind is more stable during the night. With solar only available during the day (and with molten salt storage during the first part of the night) this should make for a more stable alternative grid.

Also the numbers lay to rest the urban myth that wind farms only, on average, generate 20% of their peak capacity.
For example, average power production was 43 percent of maximum generation capacity on summer days and peaked at 67 percent on summer nights.

Looks more like 55%, which is surprisingly good. Though we probably have to detract a few percent for turbines which are not directly upwind and also a few percent for winter operation where winds are a bit lower.
SiBorg
5 / 5 (1) Jan 18, 2012
@nixnix http://iopscience...1/014005

The paper is free access.
ShotmanMaslo
4 / 5 (4) Jan 18, 2012
antialias: Maybe they picked a wind farm with more favorable location than the average. Its not an urban myth but a fact that average capacity factor of wind farms is cca 30%:
http://www.umass....ctor.pdf

http://www.bwea.c...hree.pdf
Eikka
1 / 5 (2) Jan 18, 2012
Good news that wind is more stable during the night. With solar only available during the day (and with molten salt storage during the first part of the night) this should make for a more stable alternative grid.


Too bad the majority of electricity it used during the day.
antialias_physorg
5 / 5 (1) Jan 18, 2012
Too bad the majority of electricity it used during the day

Certainly. But solar really only works during the day. So anything that works night or day is a good complement to other powerplant types.

If all alternative power sources only worked during the day then we'd have a problem.

tadchem
5 / 5 (2) Jan 18, 2012
Given the poor publicity from raptor deaths, drying up of subsidies, catastrophic equipment failures, and improved understanding of high maintenance costs for turbines, it would be more appropriate to say that power generation is 'spinning in the wind.'
Eikka
not rated yet Jan 18, 2012

Certainly. But solar really only works during the day. So anything that works night or day is a good complement to other powerplant types.


But there's still the problem that most of the energy is consumed during the day. Increasing the amount of wind power just decreases the fraction of wind power you can utilize, because there's no-one to use it during the night. It helps little to nothing in the overall scheme of things, considering all the other flaws like random and highly variable production.

It's not a case against renewable energy, it's just an argument against wind power.
MarkyMark
5 / 5 (1) Jan 28, 2012
@ Eikka at night power genorators use power as do....

Hospitals
Lighting
Heating
Pumps filters etc from water supply
Millitary installations
Radio stations
T.v stations
Settop boxes such as Sky ones when left on standby
Computers from night shift and standby computers
Buisnesses that stay open all hours
Police networks
CCTV cameras
The goverment groupthink emmiters ( need to be on almost all the time to work)
Firestations
All night boozers
Mining facilaties
Smelters ( a lot here )
The anti Reptilian defence grid (A.R.D)
Petroll stations
The stock markets
Farms
Any Manufacturing buisness that operates 24 hours (i.e. pretty much all of them).

Loads more i am sure but i hope you get the idea???