HOW GOOD CAN WIND GET?

Research uses “stereo particle-image-velocimetry”: A “smoke” of particles in a 40 mph wind is illuminated by laser light double pulses and photographs are made of the particles in the wind.

The head researcher (Charles Meneveau of Johns Hopkins) explains how the photos are used: “When the images are processed, we see that there are two dots for every particle…Because we know the time difference between the two laser shots, we can calculate the velocity. So we get an instantaneous snapshot of the velocity vector at each point…[this] allows us to calculate how much kinetic energy is flowing from one place to another…”

Meneveau’s point: “We’d better know what the effects are in order to implement wind turbine technology in the most sustainable and efficient fashion possible.”

In other words, they follow the dots. Dylan was right. You don’t need a weatherman to know which way the wind blows. You need a physicist.

Wind Turbines Produce “Green” Energy And Airflow Mysteries
December 15, 2007 (Johns Hopkins University via ScienceDaily)

WHO
Johns Hopkins University and Rensselaer Polytechnic Institute researchers (Charles Meneveau, team leader and Raul B. Cal, Hopkins postdoc fellow); The National Science Foundation (NSF)

The Hopkins toy wind tunnel where grown-up research is done. (click to enlarge)

WHAT
Despite wind energy’s remarkable growth, there are ways it can become more efficient if research can pin down certain still-unclear aspects including how best to position turbines in large arrays and whether the large arrays will affect local weather. An NSF $321,000 grant will push the research along.

WHEN
The NSF grant was awarded recently.

WHERE
- Denmark produces 20% of its electricity from wind energy.
- The research team is collecting data at a Hopkins campus wind tunnel.

WHY
- Questions to be answered by the research: Could large wind farms, whipping up the air with massive whirling blades, alter local weather conditions? Could changing the arrangement of these turbines lead to even more efficient power production?
- The research wind tunnel is built to include turbulence simulating live conditions. The 40 mph wind generated by wind tunnel fans is passed through model airplane propellers on posts, meant to be simulated wind turbines. Using the “particle” wind and photographs illuminated by double laser pulses, the researchers will obtain data for computer modeling.

An Arnold Air Force Base wind tunnel w/ stereo particle-image-velocimetry being calibrated. (click to enlarge)

QUOTES
- Meneveau, research team leader/turbulence expert, Whiting School of Engineering(Hopkins): “With diameters spanning up to 100 meters across, these wind turbines are the largest rotating machines ever built…There’s been a lot of research done on wind turbine blade aerodynamics, but few people have looked at the way these machines interact with the turbulent wind conditions around them. By studying the airflow around small, scale-model windmills in the lab, we can develop computer models that tell us more about what’s happening in the atmosphere at full-size wind farms.”
- Cal, Hopkins research team: “What happens when you put these wind turbines too close together or too far apart? What if you align them staggered or in parallel? … All of these are different effects that we want to be able to comprehend and quantify, rather than just go out there and build these massive structures, implementing them and not knowing what’s going to happen.”