increase energy produced because more wind goes through the turbines. The exact position of each turbine matters, because a difference of 30 metre could potentially double output. This careful placement is referred to as 'micro-siting'. Offshore Europe is the leader in offshore wind energy, with the first offshore wind farm (Vindeby) being installed in Denmark in 1991. As of 2010, there are 39 offshore wind farms in waters off Belgium, Denmark, Finland, Germany, Ireland, the Netherlands, Norway, Sweden and the United Kingdom, with a combined operating capacity of 2,396 MW. More than 100 GW (or 100,000 MW) of offshore projects are proposed or under development in Europe. The European Wind Energy Association has set a target of 40 GW installed by 2020 and 150 GW by 2030. , The Walney Wind Farm in the United Kingdom is the largest offshore wind farm in the world at 659 MW, followed by the London Array (630 MW) also in the UK. Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise is mitigated by distance. Because water has less surface roughness than land (especially deeper water), the average wind speed is usually considerably higher over open water. Capacity factors (utilisation rates) are considerably higher than for onshore locations. The province of Ontario in Canada is pursuing several proposed locations in the Great Lakes, including the suspended Trillium Power Wind 1 approximately 20 km from shore and over 400 MW in size. Other Canadian projects include one on the Pacific west coast. In 2010, there were no offshore wind farms in the United States, but projects were under development in wind-rich areas of the East Coast, Great Lakes, and Pacific coast; and in late 2016 the Block Island Wind Farm was commissioned. Installation and service / maintenance of off-shore wind farms are a specific challenge for technology and economic operation of a wind farm. , there are 20 jackup vessels for lifting components, but few can lift sizes above 5MW. Service vessels have to be operated nearly 24/7 (availability higher than 80% of time) to get sufficient amortisation from the wind turbines. Therefore, special fast service vehicles for installation (like Wind Turbine Shuttle) as well as for maintenance (including heave compensation and heave compensated working platforms to allow the service staff to enter the wind turbine also at difficult weather conditions) are required. So-called inertial and optical