Offshore wind farms

Offshore areas have great potential for wind power generation in Northern Europe. However, construction of foundations for offshore wind turbines facing heavy ice conditions has been considered to be a challenge. The cost of the foundation should be reasonable. Tens of foundations should be installed in a single construction season.

A new foundation concept has been developed in order to meet the challenge in water depths up to 24 meters with firm to hard bottom conditions. It features a thin walled cylindrical steel shell with a conical upper part and a ring footing. The shell is filled with granular material giving the composite structure the necessary stability. Compared to a traditional caisson foundation the shell is much lighter weighting 200 – 400 tons, does not have compartments and has an open bottom.

The shells are fabricated at a workshop and lifted to water where they can be floated by help of the entrapped air and set down on the prepared bottom by releasing air. The option is to use a barge and offshore lifting. By overlapping different work phases (bottom preparations, installation of shells, filling of shells, placement of erosion protection, erection of towers, turbines and rotors, laying of cables, hook up and commissioning) one set of working groups can install 100 MW wind power capacity in a single construction season.

The Pori offshore 100 MW wind power project is a practical application of the foundation concept. Some key aspects of the design, construction and economics are discussed in an article you can download by clicking here.

The construction sequence

The Baltic Sea area offers great potential for wind power generation. Wind conditions are much better and environmental concerns smaller offshore than onshore. Furthermore, suitable shallow water areas are available with easy access to the grid.

The techno-economically and environmentally best offshore wind power areas have been identified in Finland based on the cost of electricity production. The total capacity of the areas shown in the map below is 6500MW. The capacity of comparable areas elsewhere in the Baltic Sea is one order of magnitude larger.

The Baltic Sea and shallow water areas showing best feasibility for large
scale offshore wind power generation in Finland