Wind farms to trial painted blades in bid to prevent bird strikes

A relatively simple solution may be on the horizon to help prevent South Africa’s threatened bird species from colliding with wind turbines — painting or patterning wind turbine blades to improve their visibility.

Experience in Norway suggests that painting (patterning) wind turbine blades can enhance their visibility and reduce bird fatalities, according to BirdLife South Africa and the South African Wind Energy Association (SAWEA). 

This has spurred the two non-profits to join forces to encourage similar experiments at local wind farms to test, and prove, the effectiveness of this solution.

The vision of birds, particularly those that hunt from the air such as birds of prey, has not evolved to perceive large, moving structures in their environment, such as wind turbines. 

This is largely because of their physiological limitations, such as low-colour contrast detection abilities, combined with motion smear created by moving, unpatterned turbine blades. This leaves these species vulnerable to blade collisions, which is a particular concern for threatened species.

In July 2020, a study by BirdLife South Africa, found that more than 800 birds were killed after colliding with turbines at 20 wind energy facilities between 2014 and 2018 in South Africa. The fatalities included species of conservation concern such as endangered Cape vultures and black harriers.

One tool in the toolbox

Wind-generated power has many positive benefits for the economy and the environment compared to fossil-fuel power generation methods, according to a briefing document on blade patterning, which was compiled by BirdLife South Africa and SAWEA, to encourage wind farms to trial blade patterning as a means to conserve birds.

“However, it also presents some environmental challenges, one of which includes the collision of avifauna with wind turbine blades. In particular, fatalities of threatened raptor species are of considerable concern because raptors play an important ecological function — many species are already threatened due to other sources of anthropogenic [human-caused] pressure.” 

The risk wind turbines pose to birds can negatively affect conservation efforts and limit areas available for development. 

“Most measures available to minimise turbine collisions are expensive and rarely completely effective,” it said. 

Simpler and more cost-effective solutions are needed. “Our experience in decades of monitoring the impacts of wind farms on birds suggests that no one measure will completely eliminate fatalities in every situation. At this point, we rather strive to accumulate a set of tools that allows us to adapt to different situations to reduce fatalities to sustainable levels.” 

Case of Smøla

One potential method of preventing bird collisions or “strikes” is to pattern a single blade in a high contrast colour — preferably black — to make it more visible to birds, with the end goal that “these species would be able to see and thus avoid the turbine and its moving blade altogether”.

A blade patterning experiment at the Smøla wind power plant in Norway showed a significant reduction in annual fatality rates. In this experiment, about two-thirds of a single wind turbine blade was painted black. 

There were 70% fewer fatalities of all bird species recorded at the four turbines with a painted blade, relative to the neighbouring (unpainted) control turbines, and a 100% reduction in white-tailed eagle fatalities recorded at marked turbines. 

“The Smøla experiment has continued for more than seven years and the experimental turbines continue to show no eagle fatalities, while the white-bladed controls continue to kill, on average, six eagles per year,” the document noted. Similar tests are being undertaken in Denmark, the US and the Netherlands.

First of its kind

Earlier this year, a first-of-its-kind pilot project was initiated at the Umoya Energy Wind Farm in the Western Cape. Between January and March, four “problematic turbines” were initially painted with two broad signal-red stripes on a single blade. The 16 nearest remaining turbines will act as controls, with no patterning. 

Dr Rob Simmons of Birds & Bats Unlimited, consultant ornithologist, recommended a total of 10 turbines be painted, while 10 turbines were used as controls, but because of financial constraints, the “painting of the remaining turbines and the blades will take a phased approach over time (likely next year).” 

According to the briefing document, the selection of “signal red” was taken forward in consultation with the South African Civil Aviation Authority as it falls within the permissible colours for structures as contained in its technical standards. 

“Theoretically, black is the best colour but CAA rejected this. Red is, however, perceived well by raptorial birds in good light conditions and is seen as the second-best option.”

Painting blades at the Umoya Energy Wind Farm is a “proactive measure to reduce fatalities” because, despite the low fatality rates recorded at the facility, fatalities included the endangered black harrier, a species which “cannot afford additional anthropogenic fatalities”.

A few other operational wind farms in the country are considering implementing this approach as part of their adaptive management strategies, and have begun the process of obtaining the necessary approvals. “Marking blades is also now often included as a potential mitigation measure in environmental impact assessments for proposed wind farms in South Africa.”

Technical challenges 

Several technical challenges exist with painting blades. These include whether a particular turbine supplier is willing to allow the painting of blades when considering warranties and working on the turbine blades for operational turbines.  

“However, several well-known turbine suppliers do undertake the painting of blades at the factory, as some countries, (for example, India), have a mandatory requirement to paint the blades with red tips for civil aviation safety.” 

In addition, the extra weight of the paint (approximately 60kg for a 40m blade that had roughly 75% of its area painted) may also have a physical impact on the blades. 

The rotational balancing of all three blades needs to be achieved to prevent strain on the drivetrain and associated operational and energy production issues. 

“However, this can be overcome by counterbalancing the other two blades by painting the same additional quantity of white paint,” the briefing document noted.

The actual painting of the blades, too, can present a technical and “somewhat costly challenge” for operational wind farms. Painting under windy conditions can be challenging and present health and safety risks to workers.

“This can have cost implications for the wind farm if they need to fund and procure the necessary professional services to paint the blades. There will also be operational costs and losses if the turbines need to be stopped for any amount of time when energy production is required.”

These costs are likely to be minimal compared to alternative measures to prevent avifaunal collision impacts, such as shutdown-on-demand using manual observers, radar, or cameras, the briefing document explained. 

“If the blades can be painted at the factory before erection at the wind farms, the cost should be negligible.”

Promising results 

While the research results are promising, the in situ effectiveness of marking turbine blades black has only been demonstrated at one wind farm — Smøla. 

The organisations said that further research is required to test whether the results from this study will be “generalisable to other environments and to assess the effectiveness for different species or groups of species”. 

They are hopeful that blade patterning will be demonstrated as effective in mitigating bird strikes and will become standard practice.

Santosh Sookgrim, senior technical adviser at the South African Wind Energy Association, said the project has the potential to be the leading form of bird-strike mitigation as it is the first of its kind in the country. 

“There is a lot of interest from multiple IPPs to begin to implement this measure at other wind farms and have it form part of the research study, which began at Umoya Energy Wind Farm. If approved, it can be done at a much lower cost if the blades are painted during manufacture as opposed to the removal and painting on site.”