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In recent years, three major trends have dominated the development of grid-connected wind turbines:
- Turbines have become larger and taller – the average size of turbines sold on the market has increased substantially;
- The efficiency of turbine production has increased steadily; and
- In general, the investment costs per kW have decreased, although there has been a deviation from this trend in recent years.
Figure 1.3 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 annual 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 US 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 levels 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.
Figure 1.3: Development of the Average Wind Turbine Size Sold in Different Countries
In 2007, turbines of the MW-class (with a capacity of over 1 MW) had a market share of more than 95 per cent, leaving less than 5 per cent for the smaller machines. Within the MW-segment, turbines with capacities of 2.5 MW and upwards are becoming increasingly important, even for on-land sites. In 2007, the market share of these large turbines was 6 per cent, compared to only 0.3 per cent at the end of 2003.
The wind regime at the chosen site, the turbine hub height and the efficiency of production determine power production from the turbines. So just increasing the height of turbines has resulted in higher power production. Similarly, the methods for measuring and evaluating the wind speed at a given site have improved substantially in recent years and thus improved the site selection for new turbines. However, the fast development of wind power capacity in countries such as Germany and Denmark implies that, by now, the best wind sites in these countries have been taken and that new on-land turbine capacity will have to be erected at sites with a marginally lower average wind speed. The replacement of older and smaller turbines with modern versions is also becoming increasingly important, especially in countries which have been involved in wind power development for a long time, as is the case for Germany and Denmark.
The development of electricity production efficiency, owing to better equipment design, measured as annual energy production per square metre of swept rotor area (kWh/m2) at a specific reference site, has correspondingly improved significantly in recent years. With improved equipment efficiency, improved turbine siting and higher hub height, the overall production efficiency has increased by 2-3 per cent annually over the last 15 years.
Figure 1.4 shows how these trends have affected investment costs, exemplified by the case of Denmark, from 1987 to 2006. The data reflects turbines installed in the particular year shown (all costs are converted to 2006 prices); all costs on the right axis are calculated per square metre of swept rotor area, while those on the left axis are calculated per kW of rated capacity.
The number of square metres covered by the turbine’s rotor – the swept rotor area - is a good indicator of the turbine’s power production, so this measure is a relevant index for the development in costs per kWh. As shown in Figure 1.4, there was a substantial decline in costs per unit of swept rotor area in the period under consideration, except during 2006. So from the late 1990s until 2004, overall investments per unit of swept rotor area declined by more than 2 per cent per annum, corresponding to a total reduction in cost of almost 30 per cent over these 15 years. But this trend was broken in 2006, when total investment costs rose by approximately 20 per cent compared to 2004, mainly due to a significant increase in demand for wind turbines, combined with rising commodity prices and supply constraints.
Looking at the cost per rated capacity (per kW), the same decline is found in the period 1989 to 2004, with the exception of the 1,000 kW machine in 2001. The cause is related to the size of this specific turbine: with higher hub height and larger rotor diameter, the turbine is equipped with a slightly smaller generator, although it produces more electricity. This fact is particularly important when analysing turbines built specifically for low and medium wind areas, where the rotor diameter is considerably larger in comparison to the rated capacity. As shown in Figure 1.4, the cost per kW installed also rose by 20 per cent in 2006 compared to 2004.
Figure 1.4: The Development of Investment Costs from 1989 to 2006, Illustrated by the Case of Denmark.
Note: Right axis: Investment costs divided by swept rotor area (€/m2 in constant 2006 €). Left axis: Wind turbine capital costs (ex-works) and other costs per kW rated power (€/kW in constant 2006 €).
In addition, the share of other costs as a percentage of total costs has generally decreased. In 1989, almost 29 per cent of total investment costs were related to costs other than the turbine itself. By 1997, this share had declined to approximately 20 per cent. This trend towards lower auxiliary costs continues for the last turbine model shown (2,000 kW), where other costs amount to approximately 18 per cent of total costs. But from 2004 to 2006 other costs rose almost in parallel with the cost of the turbine itself.
The recent increase in turbine prices is a global phenomenon, which stems mainly from a strong and increasing demand for wind power in many countries, along with constraints on the supply side (not only related to turbine manufacturers but also resulting from a deficit in sub-supplier production capacity of wind turbine components). The general price increases for newly installed wind turbines in a number of selected countries are shown in Figure 1.5. There are significant differences between individual countries, with price increases ranging from almost none to a rise of more than 40 per cent in the US and Canada.
Figure 1.5: The Increase in Turbine Prices from 2004 to 2006 for a Selected Number of Countries
Note: Preliminary data shows that prices for new turbines might continue to rise during 2007.
Source: IEA (2007)
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