The need for the development of renewable energy in
2.2
The
Benefits of Development
2.2.1
Climate Change and Air Quality
Over the past decade, the fuel used for electricity
generation in
The target for
In 2005, the First Sustainable Energy Strategy for
Hong Kong ([2])
set a target of 1-2%
electricity consumption from renewables sources by
2012 in
·
The
annual use of 62,000 Tonnes (T) of coal;
·
The
annual emission of 150,000T of carbon dioxide;
·
The
annual emission of 520T of sulphur dioxide; and
·
The
annual emission of 240T of nitrogen oxide.
2.2.2
Security and Diversity of Supply
The electricity generated from the proposed wind farm
would be adequate to meet the consumption for 50,000 households in
2.2.3
Socio-economic
Employment
The opportunity to source materials and expertise for
the construction and operation of the wind farm from
Detailed decisions on the management of the offshore
wind farm have not been finalised.
However, it is anticipated that a number of positions for the operation
will be required, including maintenance staff and management staff. In addition, ongoing maintenance needs
will need the supply of materials.
Tourism
Experience at other international wind farm indicates
that a number of visitors will come to view the wind farm once
constructed. This could have
positive implications for the local economy.
2.3
Background to the
Components of an Offshore Wind Farm
Wind farm technology has advanced rapidly over the
last 10 – 20 years with European countries acting as the technological hub of
development. In general, a wind
farm is comprised of the following main components:
·
Wind
turbine units, including foundations.
·
Submarine
electricity cables that connect turbine units to the offshore substation and an
onshore grid network.
·
An
offshore substation.
·
A
meteorological monitoring mast to monitor atmospheric and sea conditions.
The following provides a summary of these
components, with further detail presented in Sections 4 and 5.
2.3.1
Wind Turbines
Wind turbines generally consist of rotor
blades, a nacelle (the housing that sits at the top of the wind farm mast that
contains the gearbox, generator etc), mast and foundation. Large-scale modern turbines are usually
designed with three blades, which rotate around a horizontal hub at the top of
a steel tower. Wind turbines vary
in size depending upon the level of energy output and the supplier (see Section 4).
Most wind turbines start generating
electricity at wind speeds of around 3-4 metres per second (m/s); generate
maximum ‘rated’ power at around 15 m/s; and shut down to prevent storm damage
at 25 m/s or above. When the wind
blows the blades rotate. This leads
to the turning of a shaft located inside the turbine nacelle. This shaft goes into a gearbox, which increases
the rotation speed for the generator also located in the nacelle.
Foundations are required to support the
turbine mast, nacelle and blades and also to provide a platform above sea level
for ongoing maintenance access.
2.3.2
Subsea Cables
Wind turbines will be inter-connected by subsea
cables to provide both power and telemetry links. 22kV, 33kV or other voltage rating
according to the proprietary design of wind turbine manufacturers will be used
for the windfarm internal grid and connection to the
offshore sub-station. 132kV cables
will be used to connect the substation to the onshore grid.
2.3.3
Sub-station
An offshore sub-station will be required to transform
the voltage of the electricity generated at the wind turbine to a high voltage
suitable (132kV) for transmission of power within HK Electric’s onshore grid
network. As an alternative, an
onshore sub-station may also be considered at a later stage subject to detailed
engineering design.
2.3.4
Monitoring Mast
A monitoring mast will be required to measure wind,
wave and current information for operational purposed. These structures generally consist of a
steel lattice mast and foundation. Anemometry equipment is installed on the
mast and wave and current sensors are installed on the foundation structure.