Wind farms vs. neighbors - Solar, Wind and Land: Conflicts in Renewable Energy Development - page 32

throw snow or ice across the property line, causing injury or property
damage. Like skyscrapers, utility poles, and most other large structures,
wind turbines can accumulate snow and ice on them on during wet, chilly
days. In some instances, rotating wind turbine blades have thrown large
chunks of this ice hundreds of meters from turbine towers. 74 High winds
can also strip ice from a turbine blade and carry it a significant distance
from the turbine on its descent to the ground . 75 In colder climates or high-
elevation areas, this risk of thrown or fallen ice can be yet another reason
for locals to oppose a proposed wind energy project.
Several researchers have studied the ice-related risks of wind turbines
over the past decade. In 2007, a group of researchers disseminated an
article describing their mapping of ice throws and falls below a 600 kW
wind turbine near a ski resort in the Swiss Alps. 76 The researchers inspected
the ground below the turbine after every “icing event” for two consecutive
winters, documenting the weight, size and location of every chunk of fallen
ice. They found 94 ice fragments over the course of just one winter during
the test period, and some of the fragments they found were as long as 100
centimeters and weighed as much as 1.8 kilograms.
Siting turbines an adequate distance away from buildings and residential
areas is the most basic way to prevent damage or injury from ice throws.
Although wind speed and the shape of the ice fragment can also affect the
distance that ice travels when thrown from a turbine blade, 77 the following
general formula has been offered by some as a means of calculating
minimum setback distances for protection from ice throws: 78
Minimum setback distance = 1.5 * (hub height + rotor diameter)
Although utility-scale wind turbines are often set back at least this distance
from residential buildings, they are sometimes sited closer to roads and
other public areas where people could be put in danger. Additional setback
requirements from these other land uses may be warranted in climates and
settings where turbine blade ice is likely to be a problem. For example, in
the case of the wind turbine studied in the Swiss Alps, operators placed
additional restrictions on public access to the area near the turbine as a
precaution against injury to the public.
It is worth noting that turbine ice throws could theoretically pose a
threat to livestock grazing near wind turbines as well. Since only a very
small percentage of the total surface area involved in a wind energy project
is physically occupied by turbine towers or supporting infrastructure,
ranchers often continue to allow cattle or other animals to graze on land
that has been developed for wind energy. Although this practice allows
for more overall productivity of range land, it can result in cattle grazing
directly under the enormous rotating blades of commercial wind turbines
where ice could fall and cause injury. Fortunately, risks associated with
ice throws are often allocated between developers and landowners in wind