Furthermore, preparatory work started in 2011 on nine other wind power projects, seven in Germany and two in the UK. These wind farm projects have a cumulative capacity of 2,910 MW, 2,272 in Germany and 638 in the UK.
With these 18 wind power projects completed, total installed offshore wind farm capacity in Europe would reach 9 GW. Furthermore, EWEA has identified 18 GW of fully consented wind energy projects in 12 European countries.
Since 2009, the average size of offshore wind farms has been increasing steadily. In 2011, the average size of the projects, once fully completed, is just under 200 MW, 45 MW (+29%) more than in 2010.
This trend is expected to continue and, indeed, accelerate as the average size of offshore wind farms currently under construction is almost 300 MW, and the average size of projects consented – but where construction has not yet started – is 344 MW, 72% bigger than 2011 projects.
As the technology matures and it is expected that wind farms will continue to grow in size, the UK offshore wind “round 3” is an example of this. The average size of projects being planned by developers increases to 555 MW.
The average capacity of offshore wind turbines was 2 MW at end 2011. Average size of wind turbines grid connected during 2011 was 3.6 MW up from 3 MW in 2010.
The first offshore wind turbines deployed in the nineties were not of the MW scale. In 2000 a first offshore wind farm using 2 MW wind turbines was built and grid connected.
Since, the average size of offshore wind turbines has been increasing, albeit not linearly, and in the middle of the last decade wind turbines in the 3+ MW range were being deployed.
The first 5 MW wind turbines were used in 2007 at Beatrice in the UK and 2008 at Hooksiel in Germany. This size turbine has, since, become more common and, by 2011 the average size of offshore wind turbines was 3.6 MW, 20% more than in 2010 (3 MW) and over 6 times more than the turbines used in the early nineties.
Moreover, in 2011 REpower installed the first wind turbines with a rated capacity above 5 MW (5.075 MW) at Ormonde in the UK.
Looking at the under construction offshore wind farm pipeline (4,583 MW), the Siemens 3.6 MW wind turbine will continue to be used extensively. However, roll-out of 5 –6 MW wind turbines means that the under construction pipeline averages 3.9 MW.
Five different types of substructures were used in fully connected offshore wind farms in 2011. Excluding floating concepts that are still at experimental or demonstration stage, four types of substructures have been used in offshore wind farms to date: monopile, gravity, jacket and tripile.
Monopiles are by far the most common substructure used in offshore wind farms. Looking at wind farms that are currently under construction, the trend remains the same with monopiles maintaining an over 60% share. Jackets and tripiles make up the rest with similar shares (20% and 18% respectively). Currently, no gravity based foundations have been identified in the under construction pipeline. The latter are generally used in wind farms closer to shore.
Offshore wind farms are increasingly being built further from the coast and in deeper waters. Analysis of the planned projects pipeline shows that this trend will continue. In 2011 average water depth of wind farms was 22.8m and average distance to shore 23.4km. For projects under construction, average depth is 25.3m and distance to shore 33.2km.