EK132 Intro to Wind Energy
Wind energy is one of the fastest growing electric power sources in the United States. Massachusetts alone produces over 90MW of land-based wind power capacity and plans to install wind turbines to produce 2000MW of energy by 2020. 1000MW of wind power can offset 2.6 million tons of CO2 (5). Wind energy is also now competitively priced, offering an advantage over coal solutions because of its clean-burning nature. Despite the obvious environmental benefits of using wind turbines to produce energy, the potentially dangerous health effects of placing these turbines within public view and hearing have raised social unrest and concern. One negative health effect of wind turbines is ice throw; however, the risks of ice throw are preventable. I believe that the government should continue to support wind turbine construction despite ice throw possibilities.
Ice throw is a possible risk that poses a threat to surrounding residents of a wind turbine field. In areas of cold climate, ice can accumulate on turbine blades and break off the machine with drops in temperature, unexpectedly. In the small town of Whittlesey, England December 2008, “lumps of three or four feet long flew through the air,” into a carpet showroom and parking lot due to wind turbine ice throw. Residents described ice shards as “javelins” (2). The wind industry, however, rebuts with the fact that all tall structures such as skyscrapers, trees, utility poles, roofs and cell phone towers will develop ice that can fall and injure observers down below (7). The case of Whittlesey wind turbines is abnormal and could have been prevented with proper safety measures.
The effects and amounts of ice throw produced by a wind turbine are predictable, depending on its location, height, and blade length. In most cases, ice falls within a radius of the tower equal to the tower height, and rarely exceeds total height (tower height plus blade length) (4). Also, wind power generation facilities in southern regions have warm climates that preclude the issue of ice (3). The energy company GE lists specific guidelines that must be implemented in order to reduce dangers of ice throw, such as using the formula (1.5 * (hub height + rotor diameter)) to calculate a safe distance, place warning signs near wind turbine range, remotely switch off turbine site personnel detect ice accumulation, and restricting direct physical access to turbines by workers and the public (9).
In Wisconsin, precautions have been implemented for determining the risk of turbine location. An estimate should be made of the time (days per year) in which icing conditions occur at the turbine site to determine the risk of construction in that area. In Wisconsin, they categorized “heavy icing” as more than 5 days, less than 25 days, “moderate icing” as more than 1 day, less than 5 days, “light icing” as less than 1 day per year, and “no icing” as warm climate areas where no icing would occur (7). Sites for wind turbines can then be chosen from the “light” to “no icing” categories.
The town of Arkwright in New York has taken precautions against ice-shedding such as turbine-shut-down, in which ice that accumulates on rotor blades will cause a weight imbalance, automatically turning off the turbine motors. Once the ice melts, the turbine can only be turned back on by a worker (10). Turbine shut-down mechanisms can prevent issues of ice throw.
Heating the blade’s surface is another option. Active anti-icing systems include electrical resistance heating (heating a membrane on the blade’s surface) and indirect heating of the surface (using a radiator from the inside of the blade). In 1996, Yukon Energy painted their blades with a Teflon-like material called StaClean, a highly slick substance that ice tended to fall off of. This is an example of a passive anti-icing system (1).
Remote monitoring and operating is now required in the wind energy industry; all commercial machines have ultrasonic vibration sensors which automatically shut down turbines when ice is detected at a pre-set level (detecting 40-70kHz frequencies). Devices having heating elements that switch on at shut-down level are also desirable. Icing rate is important to take into account to note the efficiency of location and long-term usage of the turbine (8).
Successful wind turbine sites in Wisconsin and New York, as well as anti-icing mechanisms have worked in the past, an indication that ice throw issues can be mitigated. The government should allow for the construction of wind turbines, as long as they maintain safety measures and precautions such as guidelines as to calculate a safe distance from residential areas, determining the risk of ice accumulation at the site region, shut-down mechanisms, remote monitoring and operating systems and active/passive anti-icing systems. The benefits of implementing wind energy for the sake of the environment and clean energy usage are worth taking the extra precautions.
1. Carriveau, R; Dalili, N; Edrisy, A. “A Review of Surface Engineering Issues Critical to Wind Turbine Performance.” Elsevier. Vol. 13 Issue 2, February 2009, pages 428-438.
2. Galbraith, Kate. “Ice-Tossing Turbines: Myth or Hazard?” The New York Times. December 9, 2008. http://green.blogs.nytimes.com/2008/12/09/ice-tossing-turbines-myth-or-hazard/.
3. “Ice Throw.” Blue Highlands Citizens Coalition. 2004. http://www.bhcc.ca/ice_throw.htm.
4. Independent Expert Panel of Massachusetts Government. “Wind Turbine Health Impact Study” MassGov. January 2012.
5. “Land-based Wind Energy: A Guide to Understanding the Issues and Making Informed Decisions.” CLF Ventures. June 2011.
6. “Noise and Health Effects of Large Wind Turbines.” National Wind Watch, Inc. Oct. 25, 2006. http://www.wind-watch.org/ww-noise-health.php.
7. Sangrillo, Mike. “Home-Sized Wind Turbines and Flying Ice.” Windletter. Volume 22, Issue No. 6, June 2003.
8. Seifert, Henry. “Assessment of Safety Risks from Wind Turbine Icing.” Dutch Wind Energy Institute. April 2, 1998.
9. Wahl, David. “Ice-Shedding and Ice Throw – Risks and Mitigation.” GE Energy. April 2006.
10. “Wind Turbine Ice Blade Throw.” Tetra Tech EC, Inc. December 2007.