Interesting article in my opinion:
The dull hum that emanates from many wind turbines could soon become a thing of the past thanks to a group of German researchers who claim to have developed a new sound muffling technology capable of cutting noise levels by an estimated 50 per cent.
Engineers at the at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden claim to have developed an automated noise absorber designed to stop vibrations from a wind turbine's gear box reaching the surrounding tower and being amplified. They are now looking to talk to turbine manufacturers about undertaking field tests for the technology.
Speaking to BusinessGreen.com, Holger Kunze, one of the researchers working on the project, said that many turbines already use some form of sound dampener, but these typically only prove effective at muffling one frequency of sound.
In contrast, the device the IWU team has developed measures the vibrations in the gear box and then feeds electricity into piezo actuators, small devices that convert an electric current into mechanical vibrations. The vibrations feed into a "mesh" around the bear box and are set at a level to cancel out the sound vibrations emanating from the gear box, creating what Kunze refers to as "anti noise". Read more
Source: Business Green
Apart from aesthetics and the potential impacts on birds, noise seems to be some of the most frequently cited objections to wind turbines. Developments like those referred to in the above article would probably help in addressing the issues related to noise associated with wind turbines...
However, the main issue that restricts the use of wind energy (using existing methods of harvesting) is its relatively low efficiency and more important - the unreliable nature of the resource.
Unlike tide energy (which can be predicted accurately) the wind "supply" is extremely intermittent and shows considerable variability in wind speed, intensity, duration (and even wind direction).
The video below shows a possible consequence of the wind being too strong, but more often the problems occur when it is not strong enough (to move and/or power the turbine generator).
YouTube - A Vestas wind system fail and crashes.
The intermittency of the wind is what rules out many locations from having wind turbines, and even where the (measured) wind patterns demonstrate its feasibility, there will always be "down time" when the wind is insufficient (and these are difficult if not impossible to accurately predict).
As a result of its intermittent poorly predictable nature, wind can make a useful contribution as a supplementary electricity source, but using the current turbine designs, it could never be dominant.
These problems of intermittency are less likely for wind farms in offshore locations, since the lower friction associated with the sea surface (in comparison to wind blowing over the land surface) results in less problems with source variability; however, the installation and maintenance costs are higher for the offshore windfarms, and they are likely to be located further away from existing electricity grids.
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An article on some recent research to address one of the issues associated with wind power generation – “voltage dips”…
> New techniques to protect wind generators during voltage dips « Technology For Life
The objective of Jesús López Taberna was to provide a solution to the problems caused by sudden dips in voltage in the electric grid. The fruit of his research is a rotor model which enables anticipating how the wind power unit will behave in these situations. This system allows the generator to remain in operation during these voltage dips and thus prevent the wind energy converter from ceasing to function.
A voltage dip is a sudden reduction in potential in the electric grid, followed by a rapid return to its normal value…
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However, the main issue that restricts the use of wind energy (using existing methods of harvesting) is its relatively low efficiency and more important - the unreliable nature of the resource.
Unlike tide energy (which can be predicted accurately) the wind "supply" is extremely intermittent and shows considerable variability in wind speed, intensity, duration (and even wind direction).
Laser Sensors Improve Efficiency of Wind Turbines
World of Wind Energy - November 06, 2008
A system that detects gusts before they arrive reduces wear, boosts output.
A new fiber-optic laser system can measure wind speed and direction up to 1000 meters in front of a wind turbine, giving the massive machines enough precious seconds to proactively adapt to gusts and sudden changes in wind direction. The device, developed by Catch the Wind, a startup based in Manassas, VA, could improve the efficiency of wind turbines and keep them from breaking down. The device could help lower the cost of renewable electricity from wind. Wind turbines lose roughly 1% of their operating efficiency for every degree their blades are out of alignment with the oncoming wind. Catch the Wind claims that its laser system can boost turbine power output by 10% by improving orientation accuracy. The pitch of the blades can also be adjusted in advance of the wind to reduce wear and tear on turbine gearbox components and blades, lowering repair and maintenance costs by up to 10 percent and extending the operating life of a wind farm, the company says.
Current wind-energy measurement systems--both mechanical anemometers and more advanced LIDAR (light detecting and ranging) devices--are used primarily to determine if a location is suitable for a wind farm. The systems are also kept as part of on-site weather stations used for longer-term wind forecasting. Real-time data can also be gathered by mounting a small anemometer on the back of a turbine's nacelle, Kourtoff says. The problem with this setup is that the air is so disturbed after passing by the turbine blades that measurements are often skewed and unreliable. Also, the turbine can only respond to wind changes after its blades have been hit, leaving them vulnerable for a few seconds to a range of punishing forces caused by wind shear, gusts, and turbulence.
Catch the Wind has adapted LIDAR so that it can be mounted on wind turbines and used to measure wind changes in time to make adjustments to the turbine. It pulses three invisible laser beams in front of the turbine that can simultaneously measure both vertical and horizontal wind speeds at different distances, as well as sudden changes in direction. Like conventional LIDAR, it does this using the Doppler principle: when the laser bounces off small dust particles carried in the wind, it changes color. The color of the laser is directly proportional to the speed of the particle. The device uses proprietary algorithms to convert this data into measurements of wind speed and direction before communicating a course of action to the turbine's control system. The device provides 20 seconds' advance notice--enough to turn the nacelle and angle the blades so that the turbine can catch more of the wind energy while reducing strain on its parts.
Read Full Article: World of Wind Energy.com - News - Laser Sensors for Wind Turbines
Related: Laser Sensor Boosts Wind Turbine Efficiency
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