The offshore wind availability is much higher than on shore. In consequence, twice as much power can be generated at sea.
However, the operation of turbines at sea is a much more challenging affair. The offshore operations and maintenance involve more costs, since the sea conditions are much more awkward and irregular, a higher level of specialist expertise is required, stricter security requirements must be met and longer travel times are involved, as the electricians have to travel to the turbine by sea.
The offshore turbines are faced with harsh conditions, including sea-water,
waves, currents, salt and strong wind. Various sections of the turbines
have been modified for offshore use. For instance, the required corrosion
protection factor for the tower (both its interior and exterior) and
all the components that are in direct contact with outdoor air has been
adjusted upwards. The proportions within the gear-boxes have also been
modified because the offshore turbine is more heavily laden.
Two types of turbine maintenance are distinguished: preventive and corrective maintenance.
Corrective maintenance is required if a failure has occurred. In some cases, it will be possible to remedy the failure remotely. In other cases, a visit to the turbine will be required.
Preventive maintenance comprises planned turbine maintenance. These activities will take place in the event of specific circumstances and according to a fixed maintenance schedule at intervals of 4 to 6 months. A survival kit is present in the turbine for the visiting maintenance staff in case electricians are unable to leave the turbine as a result of a sudden spell of bad weather.
How do wind turbines work?
The wind that flows along the wind turbine is caught by the rotor blades. As a result of the intelligent design of these rotor blades, which are shaped like the wings of an airplane, the wind energy flowing along the turbine is transformed into a rotating movement. The blades are attached to the principal axis.
The rotating movement of the principal axis is accelerated through a gear-box. In its turn, the quickly revolving output shaft of the gear-box drives a power generator. This process is comparable to the workings of a bicycle dynamo. The axes, gear-box and generator have been accommodated in the nacelle. This nacelle is able to revolve, which makes it possible to optimally direct the turbine to the wind. A transformer at the base of the turbine increases the voltage to 22 kV for transport to the offshore high-voltage substation.
Finally, the turbine has been equipped with a computer that can be used to control the turbine from a remote location. This computer ensures that the wind turbine is able to generate power in a safe way.