Mankind has always sought ways to harness the power of the sea and the wind. Today, the wind blowing across the sea is also a source of electricity, the kind produced by offshore wind farms. What is an offshore wind farm? An offshore wind farm is an electricity generation facility that uses wind turbines placed offshore, in the open sea, usually at a distance of several kilometers from the coast. This also makes the part of the earth's surface occupied by seas and oceans, which is more than 70% of the total surface area, productive. Even though for practical reasons offshore farms are built at distances not too far from the coast, it adds a significant area devoted to electricity generation to the area available on land. If a wind farm is located a short distance from the coast, it’s called ‘near-shore’. In some cases, offshore wind farms are also built in lakes. How does an offshore wind farm work and what are the components of a wind turbine? Offshore wind farms can be divided into two broad categories depending on the technique adopted. The first consists of wind turbines attached to the seabed: this is used for near-shore plants, in lakes and the open sea at shallow depths; the second (floating) is more suitable to the deep sea and uses turbines placed on floating platforms. The operation of an offshore wind farm is similar to that of onshore wind farms: electricity is generated by turbines driven by rotating blades that are moved by the wind. The major difference between offshore and onshore parks is their location. The main components of a wind turbine are: the tower, which is the structure that supports all the others and is between 30 and 120 meters high; the rotor, which is the set of blades that rotate around a hub, moved by the wind; the nacelle, to which the rotor is welded and which contains the devices that convert the kinetic energy of the rotor's motion into electricity. The electricity produced by an offshore wind farm is transported to the mainland via underwater cables and then channeled onto the distribution grid. The advantages of offshore wind energy Offshore wind farms have many advantages, some of which it has in common with onshore wind energy: little space since most wind turbines extend vertically; Added to these advantages are those specific to offshore farms: the main advantage is that winds are generally stronger at sea, partly because they do not encounter natural or man-made obstacles; wind speeds at sea are also more constant, so the supply of energy is more consistent and the structures are subjected to less mechanical stress; it’s also easier to estimate a facility's electricity production in advance; Environmental and economic challenges As on land, the construction and operation of wind turbines must take into account environmental factors, particularly animal life: in this case, the protection of birds is complemented by the protection of fish – partly with a view to keeping resources intact for fishing, an important economic activity for many communities living in coastal areas. In general, offshore parks present additional challenges compared to onshore parks, mainly related to cost. Given the greater logistical difficulties, the costs of constructing, operating, and maintaining offshore wind turbines are higher, especially in parks located in deep water. On the other hand, the ability to use a high number of very large turbines results in lower generation costs per kWh. The challenge, therefore, is to continually reduce costs so as to shrink the margin of difference between offshore and onshore wind farms. Offshore wind farms around the world The renewables industry is already dealing with this challenge successfully: according to data from the International Renewable Energy Agency (IRENA), between 2010 and 2020 the average cost of new installations fell globally by 48%, and estimates predict a further decline. As a result, the construction of offshore farms is also increasing: between 2010 and 2020 the installed capacity of offshore wind worldwide increased more than tenfold to a total of 34 GW. Growth is also accelerating: by 2021 the total exceeded 55 GW, an increase of more than 60% over the previous year. As the International Energy Agency (IEA) reports, although offshore farms made up only 7% of total wind capacity in 2021, new capacity installed during the year was 22% of the total: a record high, triple the average figure for the previous five years. Eighty percent of this growth is due to China, which is making very rapid increases: installed capacity doubled between 2018 and 2020. However, it is Europe that still plays the role of global leader, hosting more than 70% of the world's installed capacity. This is a long-standing record: the first commercial-scale offshore wind farm, with a capacity of 160 MW, opened in Denmark in 1991. Currently the largest in the world is Hornsea 1 in the United Kingdom, with a capacity of 1.12 GW. Future prospects Like Italy, many other countries plan to significantly increase (or start from scratch) their offshore wind capacity.
