Wind Energy - a new challenge to the fall protection industry
Wind power is the conversion of wind energy into another, useful form. Originally it was as mechanical motion used to crush grain or pump water, but now the majority of collected wind power is converted to electricity. Most large scale wind farms are connected to electrical grids, and at the end of 2007, worldwide capacity of wind-powered generators had reached 94.1 GW (gigawatts).
Although wind currently accounts for only about 1% of world-wide electricity production, it represents approximately 19% in Denmark, 9% in Spain and Portugal and 6% in Germany and the Republic of Ireland (2007 data). Globally, wind power generation increased more than fivefold between 2000 and 2007. There is no reason to believe that this growth will slow significantly in the coming years.
The first commercial wind farm in the UK, opened December in 1991 at Delabole in Cornwall, used ten 400 kilowatt (kW) turbines - the world's largest wind farm, the Horse Hollow Wind Energy Centre in Texas, has 421 wind turbines that generate enough electricity to power 230,000 homes per year.
All parts of the system need regular attention. The blades, for example, have good fatigue resistance but they need a much more maintenance in hostile locations such as tropical sunshine and mountain tops - exactly the places where it is hardest to get to them. To fix them you need to reach them, which means either cranes or towers.
Erecting a tower involves the use of the ladder system installed in the individual sections of the tower. Some towers have a vertical fall protection system in place, but others do not, so workers can use the ladder system, along with a full body harness and lanyard, as a means of fall protection. If the work is on the nacelle (the structure located at the top of the tower and behind the hub of the wind turbine motor) it often involves the installation of electrical control units, which requires cabling to be installed through the length of the tower. So at a minimum, a full body harness and lanyard will be required. But once the worker needs to go outside or on top of the nacelle to access the hub or blades, the risks increase hugely and they have to use an anchorage, either permanent or temporary, such as a self contained vacuum anchor. Blade cleaning, an essential part of ongoing maintenance routines, can be an extremely difficult job, and requires specialist access equipment and rope access techniques.
Tower construction workers will spend long periods of time working on the tower, so fall protection equipment has be lightweight and comfortable with multiple anchor points. The ability to house tools as well as be easy to wear for extended periods makes it more likely that it will be used properly and consistently.
Once working in the upper reaches of the tower, however, rescue can be almost impossible from the ground by conventional methods. So self-rescue, personal evacuation and easy to use casualty evacuation equipment is vital. Time is of the essence in rescue situations, so the capacity for controlled, rapid descent for multiple users in the event of a fire or complete mechanical failure, for example, is an absolute must for personnel constructing and maintaining towers. All rescue and evacuation equipment should be lightweight, fast to deploy and easy to use in a relatively confined areas.
Wind turbine operations and maintenance are a significant part of the overall ‘cost of energy’ and as such wind farm operators are looking for new ways of working to reduce costs. The majority of lifting in the wind industry is now performed by large cranes designed to be used across a range of industries for construction and maintenance applications.
However, given that wind farms are often sited on remote hill top locations, they can be difficult to access with heavy cranes that can also cause substantial damage to the ground and access roads. Large cranes are inherently costly, difficult to transport, deploy, operate and demobilize. In addition they can, perhaps ironically, only be deployed when there isn’t much wind.
Because more power is generated by higher wind speed, much of the energy comes in short bursts. The 2002 Lee Ranch sample is telling; half of the energy available arrived in just 15% of the operating time. Over the course of a year, a turbine will generate about 30% of their theoretical maximum output, compared to 50% for conventional power stations. It has been suggested that enormous wind farms that could be used to produce energy carriers such as hydrogen, soda or ammonia which can then be tankered to markets be located in remote and windy locations such as the Gobi Desert. Considerations of construction, repair and maintenance in such remote locations are a huge factor in the viability studies for such projects. Self rescue would be the only realistic option.
Wind energy is plentiful, renewable, widely distributed, clean, and reduces greenhouse gas emissions when it displaces fossil-fuel-derived electricity. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand, but it presents extra costs when wind is to be used for a large fraction of demand. But by its very nature the issues surrounding the construction, maintenance, repair and ultimately disassembly will continue to create ever more complex challenges to height safety specialists around the world.
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