Construction of an offshore wind farm
The construction of an offshore wind farm is challenging due to the conditions in the marine environment and the great size and weight of the turbine components. The construction of an offshore wind farm is also demanding on the port used because the turbine components are stored temporarily in the port. The turbines are also pre-assembled as much as possible in the port. In the construction of offshore wind power, diligent preliminary planning and various studies of the seabed are key to the success of the project.
Construction is determined by the weather conditions
Before installing the turbines, the seabed is prepared for the foundations, for example, by dredging and levelling. The foundation of an offshore wind turbine is manufactured on shore and transported by ship to the installation place. There are many different types of foundation. According to current knowledge, the gravity foundation installed on the sea bed (caisson foundation) and the so-called monopile foundation that is driven into the seabed are the most suitable in the Finnish conditions. The wind conditions and waves in the area pose a challenge to construction: both of them have their own limits, and exceeding these limits makes it impossible to lay the foundations on the seabed or lift turbine components in place on top of the foundations. Therefore, the weather conditions have a significant impact on the project schedule, and strengthening winds in the autumn and winter also put a limit to a suitable timeframe for construction.
In an offshore wind farm, a network of power cables runs between turbines on the seabed and a longer sea cable from the wind farm to the shore. Depending on the size of the wind farm, one or several substations are also built at sea on a large offshore wind farm located far from the shore. Careful planning of the substation and the location of the cable network and electricity transmission cable, taking into account, e.g. marine traffic and ice conditions, is extremely important in terms of secure electricity production.
Icing of the sea area
Despite the diminishing of sea ice, there is still ice in the Finnish sea areas every year. Therefore, the ice conditions and the impact of ice on offshore wind farms must be taken into account in the planning and construction of the project. Ice loads on the foundation and tower of the turbine must be assessed and taken into account when designing the structures. The depth, location and landing of power cables must also be designed so that the amassed ice cannot damage them.