When an offshore wind turbine is built, there is a phase of construction that is tailored to the environmental noise issue. The turbines provide a vital renewable energy source while leaving a constantly low noise level when operating.
from DHI Frank Thomsen talked about how this constant noise can affect wildlife in his seminar. Operational underwater noise from future offshore wind turbines could affect the behavior of marine mammals.” The session took place on 26 May. At the Sheraton Denver Downtown Hotel, East USA, as part of the 182nd Meeting of the Acoustic Society of America.
Thomsen and colleagues studied sound levels broadcast from operational wind farms to identify trends regarding turbine size. In general, the larger the turbine, the higher the noise emissions.
How Do Wind Turbines Work?
Wind turbines work on a simple principle. Wind turbines use the wind to generate electricity. Wind turns a turbine's propeller-like blades around a rotor, which turns a generator and generates electricity.
Wind is a form of solar energy that results from a combination of three simultaneous events:
- The sun heats the atmosphere unevenly
- irregularities of the earth's surface
- world turn
Wind flow patterns and speeds vary widely in various parts of the world. Differences in water bodies, vegetation and terrain affect winds. Humans use this wind flow or motion energy for many purposes. Examples of these are sailing, kite flying and even electricity generation.
The terms “wind energy” and “wind power” both describe the process by which wind is used to generate mechanical power or electricity. This mechanical power can be used for certain tasks (such as grinding grain or pumping water), or a generator can convert this mechanical power into electricity.
A wind turbine converts wind energy into electricity using the aerodynamic force from the rotor blades, which work like an airplane wing or helicopter rotor blade.
When the wind blows across the wing, the air pressure on one side of the wing decreases. The difference in air pressure on either side of the blade creates both lift and drag. The lift force is stronger than the friction and this causes the rotor to turn. The rotor is connected to the generator either directly (if it is a direct drive turbine) or via a shaft and a set of gears (a gearbox) that speeds up the rotation and allows for a physically smaller generator. This conversion of aerodynamic force into the rotation of a generator produces electricity.
If we go back to our article;
However, newer wind farms using quieter driving technology can offset the impact of larger turbines to some extent. Older gearbox technology reaches devastating levels for marine mammals up to 6,3 kilometers away. In contrast, newer direct drive turbines are only expected to affect animal behavior within a 1,4 kilometer radius.
“Work noise is unlikely to cause any injury or even hearing impairment, but behavioral changes can be a concern, as our study shows,” Thomsen said. “It is possible for the impact zones of individual turbines to overlap, but this still does not mean that the wind farm is an area where marine life is prohibited. We often see dolphins swimming near the turbines.”
The long-term consequences of this noise on wildlife are still largely unknown. The impact may depend on the number of turbines and their overlapping affected areas.
In theory, the sound could lead to behavioral changes in marine mammals and mask calls from whales, but harbor dolphins are often seen swimming near wind farms in Europe, so it may not be as simple as it sounds.
“As offshore wind farms have a relatively long lifespan and there will be many, the potential impacts should not be ignored,” Thomsen said. “The purpose of our work is to raise awareness.”