TECHNICAL AREA Running

As a most renewable energies, wind power origin is the sun. Between 1 and 2% of the energy coming from the sun is turned into wind, because of the movement of the air caused by the uneven warning of the earth´s surface.

Except the areas with environmental value, this fact supposes a wind power potency of 53 Twh/year five times more than the annual electric consumption in the world. So, theoretically, wind power would allow us to widely attend the energetic necessitres of the world.

The machines used in order to transform the kinetic force of the wind into electricity are called wind turbines. These are divided into two groups: horizontal axle and vertical axle. The horizontal axle wind turbine, considered the most efficient, is the most used nowadays.

The turbines extract the energy from the wind using a technology similar to that of plains and helicopters. The main systems of a wind turbine are:

• System of capture. (open-air)¹
  • Rotor: It includes the bushing and the blades (generally three).
  • Blades: They capture the wind and transmit the power to the bushing. They could be:
  • Variable step: they capture wind power all the time. The reduction of the mechanic power supplied to the turbine
    is controlled through the modification of the angle of blade.
  • Fixed step: this type of blades has not modification of the angle of blade. Consequentty, when the wind goes beyond the margin, it is a necessary a system which limits the mechanical thrust of the wind to the generator. This limitation is reached through the entrance into aerodynamic loss from a certain wind spead on (aprox. 15 m/s), bringing about turbulences in the air stream, reducing this way the pair supplied to the stow axle.
  • Bushing: it joins the solidarity blades and the slow axle. It is connected to the low speed axle of the wind turbine.
• System of transmission. 
  • Slow axle. The low speed axle of the wind turbine connects the bushing of the rotor to the multiplier. Inside the axle there are leads of the hydraulic or electricity system, in order to activate the aerodynamic brakes, variable step or to control the sensors of the rotor.
  • Multiplier. The low speed axle is at an entrance and through some meshings, it makes the axle of outlet round more speedly (between 79 and 50 times more) depending on the power of the turbine.
  • High speed axle. It rounds approximately at 1500 revolutions per minute (r.p.m.) and this fact allows the running of the electric generator. It is equipped with a mechanical disc brake of emergency.
• System of direction.
  • Engines of turn. In big wind turbines it is necessary a mechanism that place the turbine in front of the wind. This circular movement is reached through some engines and reductives fixed to the engine casing and engaging with a cog of the higher part of the tower called crown of direction. The signal of correct positioning is received from the turbine´s controller with the readings of the weather vane and anemometer placed in each turbine.
  • Brakes in direction. Their mission is to avoid radical displacements of the engine casing because of the unwanted effect of the influential wind or the turn of the rotor. In the same way, they reduce the wear of the direction gear teeth. Their operation can be hydraulic or electric, acting in pliers of brake or electric engine respectively.
• Generation system.
  • Electric generator. The electric generators of the turbine are the elements that turn the mechanical power into electric power. The electricity produced in the generator circulates through some wires to the database of the tower, in order to be transformed and sent to the network.
  • Power wining. It transports the electric power generated from the alternator to the transformer, passing through the different protections of maximum or minimum tenssion, about intensity or frequency: avoiding damages to the network or to the own turbine in the case of being produced contingencies in the wind turbine or the network of distribution.
  • Internal transformer. The power of generation is boasted from 690 to 20 KV, reducing this way the strength in order to bring down the heating of the wearing and to reduce leakages.
• Control system.
  • Controller of turbine. The controller of the wind turbine is made up of some computers that supervise the conditions of the wind turbine and collect statistics of its running. The controller, as its own name indicates, controls a great number of switches, hydraulic bomb, valves and engines into the turbine.
  • Control sensors. They are used in order to measure the physic parameters of operation and supervision of the turbine. The electric signals are used by the electronic controller of the wind turbine in order to connect the wind turbine when the signal received is correct. The computer will stop the wind turbine automatically if the information received from the sensors is erroneous with the end of protecting the turbine.
  • Control and regulation outlet. From the controller of turbine, based on the information analyzed of the sensors of the state of the turbine, they come some orders that affect the operation and running of the turbine.
• System of support.
  • Tower. It supports the casing engine and the rotor. It can be tubular or latticework shaped (these ones, although cheaper, are not used nowadays because tubular towers are much more secure). They have different sections in order to make the transportation easier. The different sections are bolted.
  • Base or foundations. It is the part that secures the vertical tower, and take up the efforts of the rotor and casing engine and transmit them to the land. It is calculated depending on the type of soil and the size of the wind turbine.
• Hydraulic system.
  • Group of pressure. It supplies hydraulic flow at a certain pressure in order to allow the running of the systems of capture, direction or transmission.
  • Hydraulic pipes. They pipe the hydraulic flow to the point of use.
  • Control valves. They adapt the pressure and the volume of flow.
• Cooling systems.
  • Fans. They work if the controller request them in order produce a circulation of air.
  • Heat exchanger. They dispel the heat of the component that will be refrigerated (generator, multiplier or hydraulic station).

• STARTING MECHANISM OF THE WIND TURBINE.

  When the turbine detects wind in any direction, through the sensors of wind speed (anemometer of turbine) the controller send the following orders to the wind turbine, through the respective engines:

  • Between 2 - 3 m/s. It sents the order of positioning in front of the wind. This order is called direction of turbine.
  • From 3 m/s on. The order of stopping the application of the brakes in order to let the turbine go round.
  • Variable step. It also sends the order of position of the blades progressively 90º ® 0º.
  • Rpm=>1500. When it gets the required speed of synchronism of the generator (depending on the wind, it selects one generator or aother, with different speed), the generator is connected to the network in a soft way, wing power electronics through "tiristores" (a type of continuous switch of semiconductor that can be controlled electronically) directly connects the generator to the network.
  • Direct connection to the network. From this moment the generator is directly connected to the general electricity network, supplying the energy to the national system. The speed is constant and limited only by the frequency of the network. When the wind is strong, it exists a limit of power in the blades if the turbulences increase the flow of air.
  • Variable step. The control of the wind turbine is done acting on the angle of step, capturing or limiting the power ablained from the wind. The generation speed can be variable.
  • Double winding turbines. If they detect that the flow of air is not suffcient to a generator, they can connect other smaller one in order to take the most of its output.
• WIND TURBINES STOP.
  • High wind. When the wind goes beyond a certain margin (> 25 m/s or 90 km/h), or when a failure is detected based on the reading of the sensors of wind to the controller.
  • Running failure. It has been detected a running failure through the information of the sensors.
  • Stop because of low wind. The sequence starts if it detects a low generation with very low wind.
  • Manual stop. It is made under the supervision of the personnel of operation and maintenance.

  The stop of the turbine has the following procedures:

  • Soft stop.
  • Fixed step. The controller sends an order to the system of capture in order to deploy the wind-brakes, disconnects the generator, checks the decrease of rpm and applies brakes in a soft way. After some seconds it applies brakes in a soft way. After some seconds it applies a pressure of braking in order to get the complete stoppage.
  • Variable step. The order is sent to the pitch increasing the grades to 90º. Simultaneously, it disnonnects the generator and applies a gradual increasing of pressure in the secondary circuit of braking.
  • Emergency stop. It is produced by important failures or danger for people or the turbines. They are applied brakes at the higher pressure from the first moment.
  • Change of winding generator. It is not a stop , it is only decrease of speed of round in the case of changing from the big to the small generator. On the contrary, the turbine is joined and it allows the packing with the wind to the new spped of synchronism.

At the following address, we can simulate the running of a wind turbine in a simple way. It is an address of the web page WindPower:

http://www.windpower.org/es/kids/intro/build.htm

Video de energía eólica. Página WindPower:

http://www.windpower.org/movies/uabl/uables.htm

¹ The rest of the systems are into the engine casing. The engine casing contains the key components of the wind turbine, including the multiplier and the electric generator. The staff can go into the engine casing from the tower of the wind turbine.