Experts say that in a couple of decades offshore wind power could meet the entire world’s electricity demands. Indeed, the International Energy Agency (IEA) also has this renewable energy source in its sights. In a report published at the end of 2019, the agency analysed a range of data and drew a road map that is taking ever clearer shape as new projects are launched and developed all around the world.

The basic condition for achieving this goal is political and financial support. The sector has huge potential for development and a propensity for constant, scientific evolution that researchers and sector analysts see as very promising.

It’s well known that decarbonization, the goal of international treaties and guidelines on the climate from the world’s most industrialised countries, is plunging traditional energy industries into a historic, and some say irreversible, crisis. Covid-19 was another blow to industries that rely purely on fossil fuels to produce energy. The answer from many sides is to go to renewable sources. It’s no overstatement to say that we’re living through a historic moment; in many areas the only solution is reconversion. Without doubt, this would benefit the environment more than anything else. Both land and sea would become more inhabitable and less polluted. 

The analysis done by the IEA estimates that 1,200 billion dollars of investment is needed to build wind turbines offshore and set up undersea transmission systems, to bring the electricity grid up to international standards. This should mean all the climate goals we’ve now set ourselves are achieved by 2040. Consider that, according to the report, offshore wind power generated 22 GW in 2018, and that production should go up by another 20 GW in the coming years and eventually even double.
It’s an impressive feat when you think that the big energy companies could use their expertise and the technologies they’ve created by offshore hydrocarbon extraction, reconvert or find synergies to get themselves through the energy transition.

Fatih Birol, the executive director of the IEA, says that in the last decade two large areas of technological innovation have been game changers for the energy system, prompting a sharp decline in costs: the revolution in shale and the rise of solar photovoltaics.

Among renewable sources, offshore wind energy is a promising alternative, although certain conditions are needed if it’s to be used. Offshore wind turbines are normally built on seabeds that are low but, of course, also near the coast. Blades longer than 100 m can’t spin above a seabed deeper than 50-60 m. This restriction has repercussions on land, marring the landscape (imagine turbines higher than a block of flats just a few miles off the coast), the environment (ecosystems) and the economy (fishing and tourism).

Deep, flat seabeds near the coast are few and far between in the world, and many of them are concentrated in the North Sea. Two examples. Until a few weeks ago, the world's largest offshore wind farm by size and production capacity was off the island of Walney, in the Irish Sea. But it was recently overtaken by Hornsea One, 120 miles off the Northern English coast. This new wind farm covers 150 square miles and will have 1.2 GW of power at full capacity, which is more than a reactor in a nuclear power station. It will satisfy the energy needs of more than a million families.

The site of the project has already seen a lot of experiments in the field. It’s just the first of four neighbouring wind farms for which the contract has already been signed. Altogether they will reach a total potential of at least 8 GW. Although it still accounts for less than 1% of the world’s electricity production, offshore wind power has a key role in Northern Europe. That said, building a 1 GW offshore wind farm today will set you back a good 4 billion dollars.

The Mediterranean is not as lucky as the North Sea in this field, as it doesn’t have the same characteristics. Two cases, at Rimini and Taranto, show as much. They’ve been thinking about installing a turbine off the coast of Rimini, in Romagna, for the last 15 years. To see if that could be feasible, the provincial government built an anemometer 9 miles from the beach. Today the project can go ahead with 59 wind turbines off the coast. The turbines, each with 5 MW, will be mounted on masts 125 m high and the propeller blades will have a radius of 81 m. They’ll be built as far away from the beach as possible, to make them harder to see from it.

The nearest will be about 6 miles offshore, where the Adriatic is about 12 m deep, and the furthest will be 14 miles off, on the outskirts of Italian waters, where the depth is about 30 m. The propeller masts will be placed in long semi-circles and there will be a distance of more than 500 m between them, so the whole area is not fenced off and there’s no impediment to fishing and sailing. The total cost of the project is 1 billion euros. Meanwhile, there’s something similar going on off the coast down in Taranto. There are plans to produce 30 MW of wind energy at the offshore sites within a year and a half, although the blades aren’t spinning just yet.

From a technical point of view, floating turbines are an important breakthrough in offshore wind power, because they can be installed very far off the coast, where the great depths rule out traditional turbines. And again we can turn to Italy for an example, off the coast of Marsala in Sicily. A group of Danes put the project forward to the Ministry of Environment and the Ministry of Infrastructure before the pandemic broke out. They were backed by funding from Copenhagen Infrastructure Partners, which specialises in large renewable energy projects around the world.

The farm is called 7SeasMed and it will be composed of 25 floating turbines with 10 MW each. It will lie 22 miles off both the Sicilian coast and the Aegadian Islands (meaning it will be practically invisible), in a stretch of sea about 300 m deep (quite different, you’ll note, from the 30 m depth of the Rimini project). The overall costs will be in the order of 740 million euros and it shouldn’t take very long to build. It will use a significantly different technology to its competitors, going by the name of TetraSpar. It’s the brainchild of Henrik Stiesdal, the granddaddy of Danish wind power. Born in 1957, he built the first multi-megawatt commercial wind turbine in 1978 and now dedicates his time to research and offshore wind projects. Just think that Siemens Gamesa’s latest turbine, which will be tested in the coming months in Denmark, is 260 m tall. That’s almost as high as the Chrysler Building in New York.

As Luigi Severini, the engineer who drew up the plans and is also responsible for designing the wind farm in Taranto, explained in an interview with IlSole24Ore: “Using floating components based on the same metal cylinders used to build wind turbines means not having to produce them ad hoc. They will form a great triangle, 80 metres on each side, at the base of each tower. This brings a huge advantage when it comes to economies of scale and industrialisation. In fact, Stiesdal’s turbines are much cheaper than other floating turbines used in projects until now.” The offshore wind sector in Italy is at a fever pitch. That much is clear from another project which is opening up big vistas.

It’s taking place in the sea about 19 miles off the south-west coast of Sardinia, where a structure of 42 floating wind turbines, each with 12 MW, will be installed. Its total electrical power will therefore be 504 MW. The total cost will be around 1.4 billion euros. Offshore wind power is still a costly business. But the IEA seems convinced that costs fall by over 40% in the next 10 years. Moreover, if the European Union goes on with its current environmental and economic policies, the bloc should be generating 20-130 GW more energy by 2040. Reaching the threshold of 180 GW should be enough to achieve neutrality in carbon emissions and get more electricity from offshore wind than from gas. Generally, if the IEA’s estimates are correct and investment in offshore wind stays constant, the world could save itself 7 million tonnes of CO₂ emissions.

Magazine of digital culture, director Maria Pia Rossignaud