Wind Turbines Can Generate Lightning Via Movement Of Turbine Blades
Given the right conditions, wind turbines can generate lightning (for reasons other than simply being elevated), new research from the Universitat Politècnica de Catalunya (UPC) has found. The relatively fast movement of the wind turbine blade tips directly triggers electrical discharges, according to the work.
The researchers think that their new findings will be useful in the creation of protocols and systems to help limit the damage caused by such phenomena. Millions of euros of damage are caused to wind turbines every year by lightning, according to the researchers — primarily to the blades, which are typically made of a composite material sensitive to the effects of electric discharges and lightning.
Image Credit: Universitat Politècnica de Catalunya (UPC)
The press release from the UPC provides more:
The UPC Lightning, Atmospheric Electricity and High Voltage Research Group’s (LRG) new work relied on its lightning mapping array located in the Terres de l’Ebre region of Tarragona — and via this array the researchers were able to detect periodically recurring electrical discharges from the wind turbines that we’re being monitored. The duration of these discharges varied from around every few minutes, to over an hour, depending on the storm conditions at the time.
Researchers have made high-speed video recordings of lightning flashes caused by wind turbines on the Rubió wind farm. The LRG, which is a European benchmark in lightning studies, has recorded several upward lightning flashes caused by rotating wind turbines under clouds. These recordings were made at a distance of one kilometre from the wind turbine, with the camera set at a speed of 6668 frames per second and a resolution time of 150 microseconds.
With regard to why this work is important, as stated before, lighting can be quite damaging to wind turbines. “Depending on the region in which the farm is located, the damage can be severe. On the west coast of Japan, for example, winter lightning is far more harmful than summer lightning. In fact, some wind farms have been forced to close because of storm damage.”
I’m not sure what will be done about the issue, especially given that the problem comes from the (very necessary) movement of the blades, but characterization of the phenomena is no doubt a good first step.
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“I’m not sure how much can really be done…” For starters, they could talk to aircraft engineers. These folks have been dealing for a number of years with building airplanes from both aluminum and composite materials while minimizing sensitivity to lightning damage.
If the coditions where this occurs are both rare and easily predictable, perhaps the turbines could be run in some sort of safe mode. To go along with the aircraf analogy, flight paths are frequently altered to reduce the lightning threat.
Turbines are on hilltops and are connected to the ground, presenting a very appealing target for lightning. Worse, the high points are designed to rotate, so there’s no low impedance path to ground. Even worse, they are made of material that can’t conduct thousands of amps without damage. To top it off, they are rotating which disturbs the electric field quickly. Aircraft wings have sharp bleeder points on the wings that dissipate charge by corona as they fly. I haven’t seen any on turbine blades, but maybe they would help.
Here’s the abstract from the academic paper titled: “Lightning discharges produced by wind turbines,” by Joan Montanyà, Oscar van der Velde, and Earle R. Williams. Published in Journal of Geophysical Research.
It looks like one simple solution is to turn them off when atmospheric conditions are at the right (or wrong) conditions.
“New observations with a 3-D Lightning Mapping Array and high-speed video are presented and discussed. The first set of observations shows that under certain thunderstorm conditions, wind turbine blades can produce electric discharges at regular intervals of ~3 s in relation to its rotation, over periods of time that range from a few minutes up to hours.
This periodic effect has not been observed in static towers indicating that the effect of rotation is playing a critical role. [separated by me for emphasis]
The repeated discharges can occur tens of kilometers away from electrically active thunderstorm areas and may or may not precede a fully developed upward lightning discharge from the turbine. Similar to rockets used for triggering lightning, the fast movement of the blade tip plays an important role on the initiation of the discharge. The movement of the rotor blades allows the tip to “runaway” from the generated corona charge. The second observation is an uncommon upward/downward flash triggered by a wind turbine. In that flash, a negative upward leader was initiated from a wind turbine without preceding lightning activity. The flash produced a negative cloud-to-ground stroke several kilometers from the initiation point. The third observation corresponds to a high-speed video record showing simultaneous upward positive leaders from a group of wind turbines triggered by a preceding intracloud flash. The fact that multiple leaders develop simultaneously indicates a poor shielding effect among them. All these observations provide some special features on the initiation of lightning by nonstatic and complex tall structures.”
How about extending the tower to a height just above the highest point of the blades when they’re pointing straight up and putting a normal lightning conductor on it.
Would that work?
I haven’t a clue. I just cut and pasted the abstract from the research paper, since it was written very well. Researchers due a good job at defining problems. Manufacturers and those with a performance contract are good at fixing them. That’s a great question for Cleantechnica to ask someone in the supply chain.
Or simply running a conductor along the back of the blade? Then conducting it down the tower?
Then maybe somewhere done the time line, someone will come up with a way to push all that charge into a super capacitor and then into a flow battery. 😉 And they be added to all the tall buildings in the world that gets storms also.
There was actually a study being done in China on that – They were using lightning to charge a capacitor (I don’t remember if it was a super cap or just a cap) which was then being used to charge an electric bus IIRC… not sure whatever came of that.
A tall lightning rod should help but would actually be difficult to do. It would have to be strong enough so that it wouldn’t be bent by strong winds enough to come in contact with the blades and would add significant extra weight and wind loading to the turbine. The extra cost may be more than what just repairing the lightning damage would be.
This is just lightening striking the wind turbines; and many lightening bolts actually flow from the ground up to the atmosphere. The turbines are not generating the lightening.
Either way, the lightening is just traveling on the outside of the turbine. You could be inside a metal trash can and be struck by lightening and live. You’d be deaf, but otherwise unharmed. Lightening stays on the outside surfaces.