Information about wind energy industry
Maximum possible utilization of renewable energy resources is one of the key points of the EU energy policy, under which the EU has set a goal to increase the share of gross energy consumption from renewable resources to the level of 20 % in 2020.
World energy situation
The modern wind power industry development in the world is primarily evaluated according to the installed capacity in particular countries. It has been growing continuously in the last 10 years and at the end of 2011 all wind power plants in the world had more than 238 GW.
Production costs per one kilowatt hour from wind power have fallen from 15 - 20 eurocents to 6 – 8 eurocents in the last 20 years. It was also due to new composite mateirals used for blades of high-capacity turbines (over 1 MW), enhanced management and control systems and primarily the subsolution of the critical problem of air vessel utilization during very weak or strong winds. Turbines with a capacity over one MW have already become a standard, and first five-megawatt machines were built in 2003. As a result, the new types of wind power stations installed currently achieve excellent results in terms of increasing wind power efficiency.
Fundamentals of Wind Power Plant Design
Wind is formed in the atmosphere as a result of different atmospheric pressures due to uneven heating of the Earth´s surface. Hot air goes up and is replaced by cold air. The rotation of the Earth turns air currents; they are further influenced by landscape morphology, ground cover, water sheets. The aerodynamic forces act on the rotor blades and a turbine placed on the utility pole transforms the wind energy into rotary mechanical energy. Through a generator, it becomes a source of electrical energy. In the area along the rotor blades there are present aeorodynamic forces; the blades, therefore, have to have a specially shaped profile, similar to the profile of aircraft wings. Buoyancy forces increase as a square of the coming air current speed, and the energy produced by a generator as a cube of it. For this reason it is necessary to ensure effective and quickly working rotor output regulation to avoid overloading of mechanical and electrical components of a wind power plant.
How does a wind power plant work?
A tube of the plant must be high enough to bring a wind turbine above the atmospheric turbulences near the ground, and solid enough to resist the weight of all the equipment and forces that are formed by wind currents. Generally, the height of the pole and the rotor diameter affect fundamentally the achievable efficiency of a wind power plant.
A gondola contains a gearbox – the 8 to 17 rotations per minute are not sufficient for electricity generation, to drive an electric generator the speed must be increased to over 1,500 rotations per minute. So called generators without gearbox are an alternative. They use a slow, multi-pole generator and do not need a gearbox. Further, the gondola contains a generator, shaft bearings, a system of turning and control system. There is a system absorbing vibrations between the gondola nad the tube.
Wind which can be used for energy generation mus have a speed of 3 to 25 m/s. Using a physical equation, it is possible to calculate that the achieved output is a cube of the speed of the wind. In case the wind speed exceeds 25 m/sec, the wind power plant automatically stops due to safety reasons. In such a case, the rotor stops and the blades turn their thinnest profile to face the wind.
Modern wind power plants usually have double-blade or triblade fixed blades with a diameter of 80-100 m. The rated capacity around 2 – 3 MW is achieved when the wind speed is around 13 m/s, so called start-up wind speed is 3 m/s.
The wind energy industry is really environmentally friendly. It does not produce solid or gas emissions or exhaust heat, there is no burden of waste storage, it does not need water for its operation. It even does not bring any important occupation of agrucaltural land and building sites occupy a minimum area. The cost of wind electricity falls along with the development of this technology. One Vestas V90-3.0 MW wind power plant operating for 20 years can generate roughly 37 time as much energy as has been used not only for its production, but also for its operation and liquidation.
Frequently discussed questions
The structure of modern wind power plants is so advanced now, that sound levels in the distance of 500 m from a 2 MW wind power plant´s pole meet the standard, which is 40 dB. Negative experience with noise is mainly connected to older constuctions from the first half of the 90s in the last century.
Bird threatening and animal frightening
According to a research carried out in Wales by the British Royal Society for the Protection of Birds, there is only one mortal collision per each ten thousand birds. Birds are far more endangered by, for example, automobile traffic.
A research by the at the department of wild animal research at Hannover College of Veterinary compares areas with wind power plants with areas without them. The research does not confirm the worries that wind power plants might cause migration of wild animals (hares, roe-deers, foxes and other animals).
Impact on TV and radio signal reception
This problem might occure if poles of wind power plants were located in an immediate vicinity of a broadcast antenna. Ordinary radio, TV and GSM mobile operator nets reception is not hampered.
Impact of a rotating blade (so called disco effect)
This phenomenon appears only during sunny weather, in case the sun is low in the sky at sunrise or sunset. Already the project stage of the wind power plants location process is prepared so that a possible hampering effect on residences is avoided as much as possible.
Impact on tourism
Data in a British study on wind farms´ impact on tourism carried out by a commission of the British parliament in May 2006 do not notice any decreasy in the visit rate in places with wind power plants. The reality is contrary, visit rates in such places were higher.