The assertion that the Model 33M-VS is safer for raptors is contained in the first written update in over a year by Kenetech's team of bird researchers. It is based on the results of ground searches made over a period of a year beneath both types of turbines. Although a single newer, variable-speed Model 33M-VS still kills as many birds as the 56-100, its rotor diameter is 3.4 times greater so preliminary data suggest the kills per kWh of power are lower, the report concludes.
The finding, although based just on the Altamont Pass in California and its particular terrain and species of birds, could be significant for any area of wind development and especially Spain where 56-100 turbines are blamed for numerous bird deaths. Still, it is not clear if the finding is scientifically significant -- if enough turbines were studied over a long enough period of time.
In the report, the Kenetech avian researchers also suggest Altamont Pass may have one of the world's largest concentrations of golden eagles. The research team states, too, that a new type of perching guard, a wire placed above a tower spar, at a bird's chest height if it stood on the spar and so far installed on 54 turbines in northern California, may cut fatalities by over 50%.
Some researchers hope also that the new Kenetower, just unveiled by the company, will significantly cut avian injuries and deaths. The decrease in fatalities could be by as much as half, although proper studies will take years, says Richard Curry, Kenetech's manager of avian research and policy development, who oversaw the report. "It's hard to speculate. It could be higher (than 50%). It could be lower," he says.
New patterned blades, possibly with a contrast in the ultraviolet range so the markings cannot be discerned and do not interfere with questions of aesthetics, may be installed as soon as early next year. Other visual devices, such as pylons or markers to guide birds around the end of a string of turbines or through a gap, are also being tested in a project to be completed in 1995. This year, Kenetech has spent $130,000 on bird research and the US Department of Energy (DOE) has allocated $300,000. Funding should be of a similar order next year, says Curry.
Three pronged strategy
The report, the Avian Research Program Update, is the outcome of a twice-yearly meeting of Kenetech's team, established in 1992 after the first reports of bird problems were widely publicised. So far, Kenetech has spent a total of more than $2 million on the matter. Its strategy is three-pronged:
¥ to site wind farms so the problem is minimised
¥ to fund supporting pro-bird programmes to offset inevitable injuries and deaths
¥ and to discourage birds from getting injured once in the wind farm by design changes to individual turbines or entire plants.
Bird kills is the single most damaging environmental problem for the wind industry. It is estimated that each year, 156 million birds die in the US after colliding with vehicles, windows, and structures. But for wind turbines, the issue is especially thorny. Not only does wind have to live up to high standards to maintain its green credentials, the damage caused to birds by wind technology often involves eagles, a species both highly symbolic and legally protected. Sites are also in windy, remote areas where birds flourish. And avian collisions are a highly visual problem, easy to perceive and relatively easy to document, compared with the seemingly subtle, long-term issues of, say, nuclear power.
In April 1992 a two-year bird study of Altamont Pass wind farms, east of San Francisco, was commissioned by the California Energy Commission (CEC). It identified 43 bird carcasses in the study area, leading consultants to speculate that as many as 567 raptors may have been killed during the two years in the whole Altamont Pass, which has more than 7000 wind turbines. Of those killed, some 78 may have been golden eagles, suggest the consultants.
Lattice tower link
Kenetech is the largest avian researcher amongst wind companies, in part because of the company's size and the link between truss towers and bird kills. It has been doing bird research since the mid-80s, but its research accelerated after the CEC study identified the size of the problem and when Kenetech hired Dr Tom Cade of the World Center for Birds of Prey.
Cade concluded that neither the CEC study nor Kenetech efforts were based on enough data to be scientific. As a result, a six man expert avian task force was formed. Even so, Kenetech notes data is hard to gather. In its on-going programme, which focuses on wild kestrels, golden eagles and red-tailed hawks, few incidents have actually been observed. A three-dimensional tracking device has been developed so both wild and trained birds can be watched in the field as they manoeuvred along a string of turbines. Since the incidents remain rare, new military technology might even be used so that the video cameras would only switch on when a bird flies past.
In 6000 homing pigeon flights, only three pigeons have been observed colliding with a turbine, says the report. Still, it appears that fog, not surprisingly, makes a bird more likely to collide. Birds also seem to have more time to avoid a blade if flying upwind towards a turbine. With a strong tail wind, they have less time to react.
In controlled tests with homing pigeons, the birds have not flown through the blade swept area of a 56-100, although they do seem willing to attempt to negotiate a 33M-VS. There has been speculation that birds might be killed more often by the 33M-VS turbine because of there willingness to approach it and because of its larger rotor swept area. The report asserts, however, that this is not the case. It says searches for carcasses suggest that the 33M-VS may in fact be no more fatal per turbine, which means that power can be produced that kills fewer birds overall.
The 'before' tests of arrays of turbines was completed this autumn, says Curry. The next phase is to see if mitigation measures make any difference. Possibilities include coloured bands or pylons to guide birds through a gap in a string or at the end of a row, to prevent them from cutting the corner too much. Laboratory research also continues, both in Boise, Idaho, at Boise State University, and at Kenetech's site in Livermore near the Altamont. Visual stimuli are being scrutinised, and in the summer of 1995 field tests will be conducted using trained raptors.
As a result of the research so far, six types of patterned blades with a high contrast to deter birds have been studied. One pattern has now been selected and blades will be painted with it in early 1995, says the report. So-called perch guards, developed by Kenetech with its wind experts, are installed on some turbines now and their effectiveness for keeping wild birds away from towers is being observed. They consist of a thin wire, one-eighth of an inch in circumference, above the horizontal I-beam. It seems they reduced perching by 54%, says the report. "Our goal is to eliminate [the problem]," says Curry. "But we've found birds are very determined."
The native eagle population in the Altamont Pass has also been monitored for the past year to try and determine the area's population and the impact of wind development in the long-term. Start-up funds were initially provided by Kenetech, with the remainder coming from the DOE through the National Renewable Energy Laboratory. A total of 54 nests have been found in the area, but there is no baseline data to determine whether the population is growing or declining. The reports says ground squirrels do seem to be the nesting eagles' preferred diet, and that many of the birds entering the wind plant are adolescents or adult "floaters" without a territory.