In general, three major trends have dominated the development
of grid-connected WTs in recent years:
• The WTs have grown larger and taller – thus, the average
size sold has increased substantially.
• The efficiency of WT production has increased steadily.
• In general, investment costs per kW have decreased.
Figure 2.1 shows the growth in average size of WTs sold
each year in a number of the most important wind power
countries. The annual average size has increased significantly
within the last 10-15 years, from approximately
200 kW in 1990 to almost 1.5 MW in Germany and
Denmark in 2002. But, as shown, there is quite a difference
between the individual countries. In Spain, the US
and the UK, the average size installed in 2002 was
approximately 850-900 kW, significantly below the levels
of Denmark and Germany of 1,450 kW and 1,400 kW
respectively. The large increase in Denmark from 2001 to
2002 was mainly caused by the Horns Reef offshore wind
farm which came onstream in 2002 equipped with 80
WTs of 2 MW each.