The way in which wind energy has developed has been
influenced by the nature of the support mechanisms.
Early developments in California and subsequently in
the UK, for example, were mainly in the form of wind
farms, with tens of machines, but up to 100 or more
in some instances. In Germany and Denmark the arrangements
favoured investments by individuals or small cooperatives
and so there are many single machines and clusters of
two or three. Economies of scale can be realised by
building wind farms, particularly in the civil engineering
and grid connection costs and possibly by securing "quantity
discounts" from the turbine manufacturers. Economies
of scale deliver more significant savings in the case
of offshore wind farms and many of the developments
involve large numbers of machines. Figure 13.6 gives
an indication of typical parameters for offshore and
onshore wind farms. It may be noted that the offshore
project uses machines with three times the power rating
of the onshore project.
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Figure
13.6: Key features of an onshore and an offshore
wind farm
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Onshore
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Offshore
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Project name
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Hagshaw Hill
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Middelgrunden
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Project location
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50 km S of Glasgow in the Southern Highlands
of Scotland
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Near Copenhagen, Denmark
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Site features
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High moorland surrounded by deep valleys.
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Water depth of 2-6 metres
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Turbines
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26, each 600 kW
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20, each 2 MW
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Project rating
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15.6 MW
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40 MW
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Turbine size
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35 m hub height, 41m diameter
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60 m hub height, 76 m rotor diameter.
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Special features of turbines
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Turbine structure modified for high extreme
gust wind speed; special low-noise features
of blades.
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Modified corrosion protection, internal climate
control, built-in service cranes.
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Turbine siting
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Irregular pattern with two main groups, typical
spacing 3 rotor diameters.
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180 m apart in a curve and a total windfarm
length of 3.4 km.
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Energy production (annual)
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57 000 MWh
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85 000 MWh (3% of Copenhagen's needs)
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Construction period
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August to November 1995
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March 2000 to March 2001
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Source: Bonus Energy A/S, Denmark
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