How efficient are mitigation measures for bird-friendly wind power?

As more and bigger wind-power plants are built, we expect the number of birds killed by wind turbines to increase. This comes in addition to other challenges, such as habitat loss and degradation.

"Luckily, there are cost efficient measures that can be put into use to reduce the risk of bird collisions", says Roel May, researcher in Norwegian Institute for Nature Research (NINA).

Together with his colleagues he has researched and documented the effect of several such mitigation measures.

Increased contrast leads to reduced mortality

"In one of our studies in the Smøla wind-power plant we saw that mortality decreased by 70% after painting one of the three rotor blades black. Increased contrast makes the wind turbines more visible for birds, so that they can avoid collision", May says.

This measure will have great significance when it comes to reducing the risk of collisions for white-tailed eagles, a species Norway has a special responsibility to protect, and a number of other species.

"In this case it was resource demanding to paint the rotor blades, since the wind turbines were already installed. If the painting is done before construction, however, both the cost and the bird mortality will be reduced", May says.

Painted towers cut the risk in half for ptarmigans

It is well known that birds collide with the rotor blades. There has been far less attention to the risk of birds colliding with the turbine towers, and how to mitigate this risk. At the wind-power plant at Smøla, researchers from NINA looked at the effect of painting parts of the turbine towers.

"We painted the lower part of ten turbine towers black. This reduced the mortality for willow ptarmigan by almost 50% compared to unpainted wind turbines in the same area", says Bård Stokke, researcher in NINA.

Do birds in flight respond to ultraviolet lighting?

Unlike humans, many birds are able to see ultraviolet lighting. In a pilot study outside the wind-power plant, May and his colleagues tested if strong lamps with ultraviolet and violet light, respectively, could deter the birds from the lit area. They monitored the area from dusk till dawn.

"The birds were less active and increased their flight altitude. Ultraviolet light had most effect, but the flight altitude was only 7 meters higher than usual, which is not much given the size of a rotor blade (40-50m)."

May underlines that even if the results are promising, there is still some more work to do until they have a fully functional design that can be applied on a wind turbine, with documented effect in the field.

Birds are attracted to updrafts – micro-siting of wind turbines is important

Wind-power plants can also be made more bird friendly by avoiding installation of the wind turbines within strong updraft areas, to which soaring raptors are attracted. Raptors collide more frequently with wind turbines installed in such areas, like ridges with high orographic uplift or flat terrain with high thermal uplift.

To identify landscape elements with increased collision risk, Frank Hansen (NINA) developed a GIS-micro-siting tool to identify updraft areas and calculate the updraft velocities based on open source terrain models, climate data and remote sensing data. The tool, which has been tested and verified in existing wind-power plants both in Gibraltar (Spain) and on the island of Hitra (Norway) makes it possible to determine where it is best to install the wind turbines in order to minimize the risk of bird collisions.

"As expected, our studies at Hitra and Spanish Gibraltar confirms that orographic updrafts are more dominant than thermal updrafts at northern latitudes, whereas thermal updrafts are more dominant than orographic updrafts at southern latitudes . The GIS micrositing tool can contribute to a more bird friendly siting of wind turbines", Frank Hanssen says.

Must be knowledge-based and apply the mitigation hierarchy

The path towards a more sustainable future leads to a continued demand for wind power. A goal of as low as possible environmental costs per kWh from wind power suggests that wind power development in general should focus on larger locations with good wind conditions, sufficient infrastructure, and with minimal conflict with environmental considerations. This requires that planning, establishment and operation of wind-power plants to a larger degree is knowledge-based and applies the mitigation hierarchy to all steps from planning to decommissioning of the wind-power plant. This hierarchy suggests that you should first avoid, thereafter minimize and reduce, then restore and, as a last resort, compensate for negative impacts. The government will enforce stricter demands for environmental surveys when reviewing new concessions in the time ahead.

"I think thorough pre- and post-construction monitoring, and actively applying mitigating measures, will make it possible to avoid potentially conflict-ridden areas and minimize the negative effects in the plan areas", says Roel May. "Both the industry and the government should take responsibility and make “natural wind power” the Norwegian standard."