7:39 PM
Following figure shows trends by year
of the typical largest turbine sizes targeted for mainstream commercial production.
Megawatt turbines existed in the 1980s but almost all were research prototypes.
An exception was the Howden 1 MW design (erected at Richborough in the UK), a
production prototype, which was not replicated due to Howden withdrawing from the
wind business in 1988. Although there is much more active consideration of
larger designs than indicated in figure, no larger turbines have appeared since
2004.
To read more about new wind turbine trends see: Wind Turbine Trends
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| To enlarge the figure click |
Up until around 2000 an
ever-increasing (in fact mathematically exponential) growth in turbine size
over time had taken place among manufacturers and was a general industry trend.
In the past three or four years, although there is still an interest in yet
larger turbines for the offshore market, there has been a slowdown in the growth
of turbine size at the center of the main, land-based market and a focus on
increased volume supply in the 1.5 to 3 MW range.
The early small sizes, around
20-60 kW, were very clearly not optimum for system economics. Small wind turbines
remain much more expensive per kW installed than large ones, especially if the
prime function is to produce grid quality electricity. This is partly because towers
need to be higher in proportion to diameter in order to clear obstacles to wind
flow and escape the worst conditions of turbulence and wind shear near the
surface of the earth. But it is primarily because controls, electrical
connection to grid and maintenance are a much higher proportion of the capital
value of the system in small turbines than in larger ones.
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| To enlarge the figure click |
Onshore technology is now
dominated by turbines in the 1.5 and 2 MW range. However, a recent resurgence in
the market for turbines of around 800 kW is interesting and it remains unclear,
for land-based projects, what objectively is the most cost-effective size of
wind turbine. The key factor in continuing quest for size into the
multi-megawatt range has been the development of an offshore market. For
offshore applications, optimum overall economics, even at higher cost per kW in
the units themselves, requires larger turbine units to make up for the
proportionally higher costs of infrastructure (foundations, electricity
collection and sub-sea transmission) and number of units to access and maintain
per kW of installed capacity.
Following figure shows the
development of the average sized wind turbine for a number of the most
important wind power countries. It can be observed that the average size has
increased significantly over the last 10-15 years, from approximately 200 kW in
1990 to 2 MW in 2007 in the UK, with Germany, Spain and the USA not far behind.
As shown, there is a significant difference
between some countries: in India, the average installed size in 2007 was around
1 MW, considerably lower than in the UK and Germany (2,049 kW and 1,879 kW,
respectively). The unstable picture for Denmark in recent years is due to the
low level of turbine installations.
To learn more about Germany wind energy see: Germany wind energy potential
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| To enlarge the figure click |
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