Environmental Engineering Reference
In-Depth Information
Since onshore wind energy converters are in most cases optimised with regard
to minimum noise creation, and as blade tip speed is the deciding parameter re-
garding noise emissions, the maximum number of rotor revolutions is subject to
certain restrictions with increasing rotor diameters. If noise characteristics are less
important, as it is likely for offshore wind energy converters, a higher numbers of
rotor revolutions should be admissible. These would result in decreased tower
head mass (i.e. power train mass) due to the reduced driving torque and would
also help cut costs. However, considerably enhanced blade tip speeds may dam-
age rotor blades due to erosion at high concentrations of particulate matter in the
air. A high content of water drops and salt particles in conjunction with a rela-
tively high air humidity and throw of spray, as it can be expected for offshore in-
stallations, additionally require effective protection of all offshore wind power
converter components against corrosion and detrimental deposits.
Electric and electronic system components (such as operating control, sensors,
generator, and transformer) require special protection against spray and deposits.
For this purpose hermetic protection against ambient air or an installation under
slight excess pressure, ensuring appropriate air-conditioning, appear suitable.
However, the climate has to be controlled with regard to temperature and humid-
ity to prevent overheating and moisture condensation.
The design of offshore wind energy converters includes the installation of
hoisting equipment on board to remove and insert all major components, such as
generator, gearbox, if applicable, etc. without expensive external hoisting equip-
ment, from and into the nacelle. Furthermore, each offshore wind energy con-
verter needs to be provided with a landing platform to enable personnel landing
and material provision.
To ensure plant safety and a safe start-up in the case of power failure, an emer-
gency power generation unit must be provided. Available options include batteries
or power stand-by units for electro-mechanical systems, hydraulic accumulators
for hydro-mechanical systems and spring brakes for exclusively mechanical sys-
tems. However, such short-term accumulator units only secure shut-off of wind
energy converters. Special stand-by units are required for prolonged power fail-
ures.
To achieve the same plant availabilities as for onshore converters, in spite of
the meteorologically more difficult plant accessibility, particularly during winter
months, quality and robustness of all plant components need to be ensured over
long periods under hard environmental conditions. For this purpose a highly so-
phisticated operating control system is required. The system should allow for an
early detection of damages, start itself after possible grid damages and revert the
wind energy converter to normal operation. Remote complete reprogramming and
re-initialisation should also be possible from the onshore control panel. For this
purpose, effective tele-monitoring and reliable communication technologies are
required. Furthermore, the converter should be adequately equipped with all major
sensors (such as vibration monitors and temperature sensors) and all indispensable
system components.
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