The shocking image of a vulture colliding with the blade of a wind turbine filmed by a home video enthusiast on the Greek island of Crete and posted on Youtube has raised controversy and fuelled the case against wind power among public opinion makers in several countries. It is a sad case – a story that has put doubts in our minds and which will undoubtedly hurt many people's feelings. However, we wanted to publish this story to ensure efforts are doubled to reduce the wind industry’s impact on bird life.
Many researchers and organisations have spent time and resources over the last few years examining this problem and therefore, Renewable Energy Magazine decided to find out what the current status of bird mortality is. According to José Santamarta, director of the Spanish language version of WorldWatch Institute, there are many studies showing that bird mortality around wind farms is minimal compared to bird deaths caused by pest control substances and collisions with telecommunications towers or motor vehicles.
Wind turbines not the primary cause of bird deaths
Santamarta, economist and wind energy expert, states that only 0.0005% of bird deaths in the US – the country that has conducted the most research into the causes and effects of this problem – are due to wind turbines. This expert, who is also in charge of the electronic publication REVE, has prepared the following data on bird deaths in the US based on several studies performed there:
– Collisions with windows: 976 million birds
– Cat attacks: 110 million birds
– Ingestion of pest-control substances: 72 million birds
– Collisions with telecommunications towers: 4 to 50 million birds
– Hunting: over 100 million birds
– Collision with high-voltage power cables: 175 million birds
– Road traffic collisions: 50 to 100 million birds
– Coal or gas-fired power stations: 14.5 million birds
– Nuclear power stations: 327,000 birds
– Wind farms: 7,000 birds
Santamarta concludes that US wind farms are responsible for “less than 0.0005% of bird deaths caused by man", specifying that this figure represents “one bird for each latest generation wind turbine every decade” and that “the death rate caused by wind turbines is 0.269 deaths per GWh”. The author also adds that the death rate “for fossil fuel-powered electricity plants is 5.18 per GWh and for nuclear power plants, 0.416 per GWh”. He also says that “the collision of a bird with a wind turbine is nothing compared to the effect on wildlife of acid rain or climate change”.
EU law (which is similar to that in the US), stipulates that bird movements must be monitored for at least a year as part of the environmental impact assessment (EIA) presented as a pre-requisite to a wind farm being developed. Santamarta explains for example that of the 72 sites included in the Navarre Wind Power Plan in Spain, 50 were refused planning permission for environmental reasons.
A few months ago, the Regional Government of Valencia also ordered the closure of two wind farms in the region – Arrielo and Folch I, totalling 60 MW – after confirming that Griffon vultures in the area had changed their flight patterns due to the closure of a man-made feeding point in Teruel, which caused them to look for food in the Vilafranca municipal rubbish dump close to the two wind farms. It is claimed, depending on the source, that 260 or over 300 vultures died from collisions with wind turbine blades as a result of this. The wildlife organisation SEO/Birdlife focused its attention on the "quality" of the EIA performed prior to building the wind farms and on the lack of inter-province coordination when locating feeding points for birds, but not specifically on the wind industry.
Despite this incident, SEO/BirdLife published a report earlier this year entitled "Guidelines for assessing the impact of wind farms on birds and bats", which concluded that "it appears that the direct death rate from collisions with wind turbines is lower than that caused by other human infrastructures". According to SEO, “the death rate due to wind turbine collisions varies between 0.63 and 10 birds per annum in the United States (National Wind Coordinating Collaborative, 2004)". In Spain – added the organisation - this rate "varies between 1.2 in Oiz (Vizcaya; Unamuno et al., 2005) and 64.26 in the El Perdón wind farm (Navarra; Lekuona, 2001)”.
Solutions available
While evidence shows that wind turbines are not the primary cause of bird deaths, public authorities and companies alike have set out to minimise the impact of wind farms on bird populations. Thanks to calls by SEO and other wildlife groups, a number of projects have been set up to analyse this issue, including the project led by the Spanish National Research Council (Consejo Superior de Investigaciones Científicas de España ). This research focused firstly on determining the ideal location for turbines installed on new wind farms (i.e. something similar to an EIA), and secondly, on developing a system that can be retrofitted to an existing turbine to avoid bird collisions.
The system devised comprises installing a video camera on a turbine to detect the presence of birds within its vicinity. It works by calculating to what extent the pixels of the camera image grow. Project leader, Miguel Ferrer, explains that computers are capable of analysing the data “and determining whether the image of the bird closing in on a turbine grows in one way or another to predict its trajectory”.
In tests, the software connected to the camera was able to detect a Griffon vulture approaching at a distance of 2,000 metres and precisely calculate its flight path 750 metres from the turbine. “This gives a working margin of 67 seconds – the time it takes the bird to travel the 750 metres - to reduce the blade speed,” explains Ferrer, who is a biologist. Reducing the turbine’s speed from 16 to 20 revolutions per minute to just three, “is more than enough to ensure the vulture can avoid the turbine’s spinning blades”.
The company DTBird has also developed a bird avoidance system, whish is already on the market. It involves a similar sensor: a video camera, which stays on stand-by until it automatically detects the presence of a bird close to a turbine. The system can detect birds flying towards machines or merely circling and once a possible threat has been identified, software processes data in real time to calculate the probability of collision according to the distance, flight path and air speed. If there is a danger of collision, an acoustic signal is emitted to dissuade the bird from approaching and if it continues on the same flight path, DTBird can order a turbine to stop. According to its inventors, the system works even in the rain and extreme weather conditions.
A similar system, the Merlin Avian Radar System, is already in use on Iberdrola’s Peñascal wind farm in Texas (US). Comprising 84 2.3 MW turbines, the wind farm uses a radar originally developed for NASA and the US Air Force to detect approaching birds from as far as four miles away, analyse weather conditions, and then determine in real time whether they are in danger of flying into the rotating blades. “If they are, the turbines are programmed to shut down, restarting once the birds are safely on their way”, said Gary Andrews, the chairman of DeTect, Inc, the Florida company that developed the technology.
These are just some of the systems the wind industry is developing to reduce the impact of wind turbines on birds and bats flying overhead and help avoid tragic accidents like the one filmed in Greece.
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