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Offshore wind power

Offshore wind farms have advantageous characteristics which differ from those of land-based installations

Offshore wind farms have advantageous characteristics which differ from those of land-based installations, namely:

The wind resource offshore is higher than over the nearby coasts.

Due to the offshore location, the visual and acoustic impact is lower than that of wind farms on land, which allows a greater use of the existing wind resource, with larger machines and the use of more efficient blade geometries. Likewise, the lower variation in the surface height for installations in the sea favours the use of lower towers.

It creates higher employment levels in the phases of construction, assembly and maintenance, due to the greater complexity of installation and operation.

There is opportunity for integration in mixed marine complexes.

However, compared to those based on land, these offshore installations also have significant disadvantages which are limiting their development: lack of electrical infrastructure; more severe environmental conditions; evaluation of the most complex and expensive wind resource; and above all, higher investment ratios and operating expenses, requiring specific technologies for construction and foundations, transportation and assembly on the high seas, laying of submarine electrical networks and operation and maintenance tasks.

The unit power of offshore wind turbines is higher than that of land-based turbines. While on land, due to limitations associated with terrain and transport, unit powers have been consolidated around 3 MW for wind turbines, with a clear tendency to increase the rotor diameter for a better use of the sites; at sea, new developments in wind farms result in unitary powers of more than 5 MW, and prototypes exist of up to 10 MW.

The average depth of offshore wind farms operating around the world at the end of 2016 (mostly in the seas of Northern Europe) is less than 25 m. Exceptionally, a few wind farms slightly exceed the depth of 45 m - 50 m, which can be considered as the bathymetric limit for current technology, and for almost all commercial wind farms installed in Spain up to 2020.

Possibly the biggest challenge for offshore installations continues to be reducing the cost of foundations, of which there are four variants: monopile, tripod, gravity and floating. Monopiles are the most commonly used for waters of average depth (up to 25 metres), gravity are used for shallower waters (less than 5 metres) and tripods are used for greater depths (up to 50 metres). Considering the other option, the commercial viability of floating platforms for the implementation of wind turbines in deep waters is still unknown, although there is already an experimental installation that has demonstrated their technical viability.

Energía eólica, aerogenerador