Zero Is The New Black

Countries around the world are turning towards more environmentally friendly means of power generation. Wind power may just be the answer to a lot of problems we face today. Since it emits no greenhouse gases and does not adversely affect the environment, it is aggressively being developed and put to use. Also, since wind turbines do not depend on fuel for operation, variations in fuel and oil supplies and prices do not have any impact on the system. Wind farms, however, are definitely not subtle additions to a landscape. There have been fears in the past about noise levels or visual impacts in a given location; however, these issues are slowly being mitigated thanks to newer designs, better engineering, and a heightened level of awareness.

In order to understand what the potential noise levels could be, it is vital to understand the mechanics of the wind turbines constituting a wind farm. Wind turbine towers run anywhere from 25 to a 100 meters in height. On top of the tower we find a nacelle, which contains the generator and the gearbox. This nacelle is somewhat like the apparatus found in an aircraft engine. Generally, three turbine blades of considerable size and height project from the nacelle, and rotate on a horizontal axis trapping the wind to harness its energy; this is in the case of the commonly used horizontal axis wind turbines. Thus, there can be a couple of probable sources for noise generation, namely mechanical noise created in the nacelle due to the generator and gearbox and an aerodynamic noise created with the movement of the blades.

Mechanical noise: Mechanical noise refers to the noise created by the generator and gear box within the nacelle. Due to technological advancements, this noise is now constrained to a bare minimum. In the last decade, wind turbine designers and manufacturers have managed to negate this problem almost entirely with the use of an efficient insulation system. In any case, this mechanical noise is generally audible only when a person is standing right next to the wind turbine, if at all.

Aerodynamic noise: Aerodynamic noise is more audible than mechanical noise and has been considered more of a problem. Aerodynamic noise is basically the noise created by the turbine blades as they cut through the air and its rotational action. The level of noise created depends on the design of the blades, the angle they are set at, and the speed of the wind they are coming into contact with.  The sound resembles that of a ceiling fan, but obviously on a larger scale. People have also noticed a thudding sound, which could occur when turbines are positioned too close to one another on a given site. This sound is magnified when downwind turbine blades are faced with additional turbulent effects transmitted by the upwind turbines. Although modern engineering is being used to downplay these problems, bigger turbine blades do tend to produce more noise than their smaller counterparts.

Low frequency noise: When faced with higher winds and turbulence, the action of the blade cutting through the air and their interaction with the wind could create a low frequency noise. This is more common in high altitude areas.

Like all devices with parts in motions, wind turbines do produce noise. Noise levels are normally quantified in decibels (dB). A 10 dB change in general noise level would be considered as double or half of the present level, whereas a 1dB change would be just about discernible. The noise in a quiet room would be approximately 30 dB, a bustling office would be around 60 dB; whereas the noise level at the base of a wind turbine tower would be around 80-90 dB, not much more than a busy commercial area. That said, the noise level from a wind farm would drop to a very tolerable 30-40 dB from 350 meters away.  Residential areas are generally located at a far enough distance from wind farm projects that the sound isn’t disruptive and intrusive. The noise level at the periphery of a wind farm is not much louder than atmospheric sounds like the sound of the blowing breeze or a stream. In majority of the cases, the sound from the normal traffic on the road tends to drown out any noise from the wind project. Therefore, the question of noise being a problem is alleviated if turbines are erected a mere 1,000 feet away from residential properties.