Renexia, Med Wind and offshore wind

1. The energy of the future

1. Making wind the energy of the future: Renexia’s grand vision, from Beleolico to Med Wind

Wind energy is clean, renewable, affordable and abundant. Wind power projects have been under development in Italy for many years to contribute to the country’s energy transition.

Renewables are also a source of continuous innovation, and Renexia has gained unique experience in Italy in this sector, thanks to the construction, in just 10 months, of the Mediterranean’s first marine wind farm: Beleolico in Taranto. Starting from this first step, Renexia is convinced that more can be done in Italy, on a different scale and using the most innovative technologies on the market: we are talking about offshore wind, designed in the open sea, far from the coasts, where large-scale plants are possible, invisible from land and, above all, capable to spur the achievement of the objectives set by the PNIEC (National Integrated Energy and Climate Plan). The Med Wind project represents the most important project for the production of large-scale clean energy, moored but not anchored to the seabed, in the open sea, at a great distance from the Sicilian coast, preserving Italy’s tourist vocation.

What are floating offshore wind farms

Offshore means at a great distance from land, where winds are stronger and more constant. Offshore wind power makes it possible to develop much larger plants than on land, relying on much taller turbines with larger blades, capable of capturing the wind’s energy more stably and efficiently. The strength of the wind on the high seas is also much greater than that of the wind on land.

Floating means that wind towers are not embedded in the seabed, but float on the surface without drifting, by means of a system of moorings and anchorages that does not involve invasive work on the seabed.

The turbines can be up to 250 metres high and thanks to the nacelle (the part of the wind turbine that houses the motor that transforms the rotor’s kinetic energy into electricity), they can orient themselves according to the direction of the wind, optimising the production of clean energy.

Using this technology plants can be built tens of kilometres from land, where the Mediterranean Sea reaches depths of hundreds of metres and where wind towers are invisible from the coast, as in the Strait of Sicily.

2. What are floating offshore wind farms

Within the area occupied by an offshore wind farm, all human activities involving the exploitation of the sea are not allowed. This will favour the reconstitution of habitats on the seabed, now severely scarred by years of aggressive fishing practices and pollution, phenomena that have compromised the biodiversity of delicate ecosystems. The same area will also represent a fish restocking zone, with undoubted benefits for the ecosystem and for fishing activities themselves.

An offshore wind farm has an ‘expiry date’. In the case of Med Wind, the concession of the maritime area will last 25 years, at the end of which it will be dismantled and largely recycled, to make way for new technologies in a rapidly developing sector.

Before construction of the wind farm begins, the local marine fauna and flora must be carefully classified and monitored to avoid any possible negative impact, with particular regard to protected species, including cetaceans. Particular attention shall also be paid to migratory routes, taking all necessary measures to avoid interference with avifauna. Each study phase must be monitored and validated by independent research institutes.

Med Wind is the perfect example of the floating offshore wind farm: it will cover an area of around 800 km2, where it will be possible to install up to 190 turbines, capable of generating, once fully operational, an amount of energy unthinkable for other renewable energy plants, enough to meet the annual needs of millions of households.

3. The ‘long journey’: from wind to energy

3. From wind to energy

3.1 The basic layout of an offshore wind farm

The operation of an offshore wind farm is similar to that of onshore farms.
Wind turbines capture the energy of the wind and trigger the movement of the blades. These activate the rotor enclosed within a frame, called nacelle, which transmits the movement to a gearbox.

The rotation then reaches the alternator, whose task is to transform the mechanical energy into electricity.

The electrical energy thus produced is transferred via the cable to a transformer, which collects all the electricity generated by the wind farm’s blades, raises its voltage to the required levels, and feeds it into the national transmission grid.

3.2 How wind energy reaches the coast

The electricity produced by offshore wind turbines is transferred to land via submarine cables.

Submarine cables are an essential part of the development of offshore wind farms. They are able to transport the electricity produced by offshore wind farms to the coast, where it can be used to power homes and businesses.

Submarine cables:

  • are made of copper or aluminium,
  • can have lengths of up to 100 kilometres and transport up to 1,000 Megawatts of electricity,
  • are coated with an insulating material that protects the electricity from water infiltration,
  • are laid in the open sea using special ships. The ships lay the cables on the seabed using a roller system. They are then fixed to the seabed using anchors or other anchoring structures,
  • are a safe and reliable technology capable of transporting electricity over long distances without significant losses,
  • are resistant to stress in the marine environment and can operate in rough sea conditions.

3.3 From coast to shore: the collection substation

A substation, for an offshore wind farm, is a structure that collects the electricity produced by offshore wind turbines and transfers it to the onshore electricity grid, where it can be used to power homes, businesses and industries. It is a complex and expensive structure to build and maintain, but essential for the production and distribution of electricity generated by offshore wind farms.The substation is usually located offshore, close to the offshore wind farm, and consists of a series of transformers that lower the voltage of the electricity from 380 kilovolts to 220 kilovolts, and a system of cables that connect the substation to the onshore grid. Here are some of the main components of a substation for an offshore wind farm:

  • Transformers: the transformers lower the voltage of the electricity from 380 kilovolts to 220 kilovolts, making it compatible with the onshore power grid.
  • Cables: cables connect the substation to the onshore power grid. They can be submarine cables or terrestrial cables.
  • Control cabins: control cabins house the electrical equipment needed to operate the substation.
  • Cooling systems: the cooling systems keep the temperature of the transformers within operating limits.
  • Structure: the substation structure is designed to withstand marine conditions, such as waves, currents and storms.

4. What an offshore wind farm looks like: materials

The materials used for the construction of offshore wind farms must be able to withstand even extreme marine conditions, such as waves, currents and storms, as well as the corrosion process typical of a high salinity environment, and must be able to transport large amounts of electricity. Offshore wind farms are constructed from a variety of materials, which are corrosion-resistant and can be machined into a variety of shapes, including:

  • Steel: steel is the most commonly used material for the construction of offshore wind turbines and the floating platforms that support them.
  • Fibreglass: fibreglass is a light and strong material that is used for the construction of offshore wind turbine blades.
  • Aluminium: aluminium is a light and strong material that is used for the construction of offshore wind turbine towers.
  • Copper: copper is an electricity-conducting material that is used for the construction of power cables. Offshore wind farms may require hundreds of kilometres of cables.

4. What an offshore wind farm looks like
5. Floating technology

What is floating technology in an offshore wind farm

Floating technology is a technology that allows wind turbines to be installed in water many hundreds of metres deep, where fixed foundations on the seabed would not be possible. Floating wind turbines are positioned through floating structures, which can be of two main types:

  • floats: floats are boat-shaped structures that support the wind turbine. They are made of lightweight materials, such as steel or fibreglass, and can be of different sizes;
  • platforms: platforms are larger structures that floats and can support multiple wind turbines. They are made of heavier materials, such as steel or concrete, and are anchored to the seabed.

Floating technology is a relatively new technology, but it is the solution that all new projects worldwide are moving towards. For the Mediterranean, floating wind farms offer a number of advantages over traditional wind farms:

  • our seas are characterised by reaching great depths even at short distances from the coast. The floating solution therefore allows wind farms to be moved away and their impact on the landscape to be reduced to zero;
  • being able to position wind farms offshore allows the winds to be used where they are strongest and most constant, with the advantage of guaranteeing greater electricity production for the same installed power;
  • they guarantee a negligible impact on the seabed and the ecosystems it hosts, being much less invasive than traditional technological solutions;
  • they are more flexible, as they can be installed in a variety of marine conditions.

6. The advantages of offshore wind farms

First and foremost, the construction of a wind farm generates many jobs, requires infrastructural improvements in the site area, the activation of industrial sectors such as port logistics, and the creation of new professional skills related to the construction and maintenance of the facilities for the duration of the concession, 25 years in the case of Med Wind. Offshore wind will create and sustain highly qualified national and local jobs: engineers, electrotechnicians, electrical and mechanical component manufacturers, maritime transport and logistics workers. Offshore wind projects can help revitalise multiple manufacturing sectors and ports in the areas concerned, provide an incredible boost for the creation of entire value chains, and are a prerequisite for securing stable and skilled employment for decades.

6. The advantages of offshore wind farms