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Battle at Sea

Constructing offshore wind farms are highly complex and risky operations, especially when considering that these colossal installations are taking place further and further out at sea, where conditions are anything but friendly.

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Battle at Sea

Out at ocean, when the wind is howling around your ears and rain whipping into your face, constructing an offshore wind park can be a tough business. “There are times when it’s very hard work,” confirms Eduard Lopkov, “but it’s also a fascinating job. I think you need something of a pioneering mindset. And despite the challenges, the satisfaction on completing a job is immense.”

Lopkov is an offshore installation manager for wind turbine generators at Denmark’s largest energy company, DONG Energy. His job has him oversee development, planning and construction of offshore wind parks, which means there are periods when he spends two consecutive weeks at sea. It’s certainly not a job for everyone, the Bulgarian admits, although he believes that attracting talent to what is a young and dynamic industry is not a problem. Indeed, with the global focus on renewable energy continuing to grow, the offshore wind market is a sector with increasing appeal.

A recent study by Roland Berger, entitled Offshore Wind Toward 2020, found that the worldwide offshore wind industry will reach a market volume of €130 billion by 2020. The bulk of this will be located in Europe, which will generate around 4,500 megawatts, while Asia-Pacific is expected to produce 1,500 megawatts and the Americas 500 megawatts. The reasons behind these geographical differences are numerous. European climate and energy targets aim to have 35 percent of all electricity produced by renewable sources by 2020, with 12 percent of this coming from wind energy. And while areas such as the United States have large uninhabited areas to install logistically simpler onshore wind farms, Europe’s higher population density means wind farms must increasingly be located at sea.

Within Europe, the focus is very much on the North and Baltic Seas. “Northern Europe represents the most mature offshore market, with the United Kingdom leading the way and Belgium,  Holland, the Scandinavian countries and Germany also all expanding capacities,” explains Robert Maurer, Head of Engineering, Germany & Central Europe at Allianz Global Corporate & Specialty (AGCS). And with good reason: “Offshore wind has 40 percent higher energy efficiency than onshore wind.” What it also has, however, are more challenging conditions. Strong, gusty winds, waves and very salty water and air can all cause significant wear and tear on the equipment used in offshore wind parks.

A further challenge to the industry is presented by a developing trend towards constructing larger wind parks further away from the shore. “In the past, wind parks were usually built at a depth of about 20 meters and 20 kilometers away from the coast,” says Gerhard Müller, Senior Engineering Risk Consultant at AGCS. “But as coastlines start to become more crowded, we are beginning to see parks constructed further out to sea. This is particularly so in Germany, where environmental laws restrict nearshore construction and local residents simply don’t want 100-plus-meter high turbines in the vicinity of their houses – they see it as an eyesore.”

Tackling complex logistics

Building wind parks further away from the coast has a major impact on both the logistics of and the foundation required for the turbines. These support elements on which the wind turbines are built weigh up to 900 tons, while the turbines themselves are growing ever bigger, requiring larger and more powerful cranes to lift them into place. These factors are driving up the cost of investment and making an already lengthy process more complex.

One major bottleneck for this still fledgling industry is the lack of specialized turbine installation vessels, a problem that is only now being addressed. In the past, it was common to use platforms that had been adapted from the offshore oil and gas industry, which had to be maneuvered into position by separate vessels – a time-consuming process. But as wind parks make their way out into deeper and more exposed waters, more flexible and efficient solutions are required.

Enter ships such as the INNOVATION of HGO InfraSea Solutions, one of a new generation of turbine installation vessels built recently to cope with the changing demands of the industry. It is a loading, transport and installation vessel in one, with four massive jack-up legs that can extend down to the seabed and lift the ship out of the water, providing a completely stable base from which to lay both the foundation pieces and carry out the turbine installation. As Eduard Lopkov explains, however, very few of these ships are currently in service, meaning they are much in demand. “We try to secure these vessels at least two years in advance of the actual installation works.” With projects sometimes subject to delays in the preparatory phase on land, not to mention potential weather-induced downtime when out at sea, it can be a challenge to synchronize project timings. “Sticking to the schedule can be the hardest part of this job,” Lopkov admits.

The actual construction process for an offshore wind park begins with a geotechnical investigation of the seabed to precisely locate the best positions for installing the turbines. Based on this data, there then follows a fine-tuning of the foundation setup. The most widespread type of foundation currently in use is a monopile; a giant steel pipe that is hammered into the seabed.

On top of this sits the transition piece, which connects the foundation and the turbine tower. For larger turbines in deeper water, the cost of monopiles rises significantly, however, which is  leading to the growth in popularity of a jacket foundation. Made of three or four main legs joined by bracings, jacket foundations offer greater flexibility and lower weight in comparison with monopiles, with the Roland Berger study predicting a sharp rise in their use over the coming years.

Once the foundations are in place, the turbine installation team takes over. It’s here that ships such as the INNOVATION come into their own as they are able to transport up to seven 6-megawatt turbines from the port, carry them out to sea and take care of installation. “Using a vessel like this simplifies the process considerably,” says Lopkov. “It removes the need for feeder barges, dangerous and time-consuming sea towing, and anchor handling operations. You can load, transport and install a number of turbines with just one port visit, which is not only more economically viable, it also reduces the risk of weather downtime.”

It takes between one and two days to install a single turbine – precision work that requires perfect coordination between all team members. “Everything is planned extremely thoroughly, so we have exact measurements in terms of what needs to go where,” says Lopkov. “There’s no margin for error, which isn’t easy when you’re moving pieces that weigh hundreds of tons.

Installation engineers work two weeks on followed by two weeks off, while for the marine crew on the installation vessel – experienced seamen – the period is double. “It’s hard work, but conditions onboard modern ships are very good,” Lopkov explains. “And to be honest, after a 12-hour working day, you tend to sleep like a log wherever you are! It’s the periods when the weather is too bad to work – that’s when you appreciate the TVs, fitness rooms and canteens.”

Once the turbines have been successfully installed, with more than 100 used in some of the larger wind parks, then the electricity generated must be transported back to the grid on land. This is another area in which the newest generation of wind parks further away from the coast is facing challenges. “Over shorter distances, electricity can be transported to the shore via alternating current (AC) cables and fed directly into the grid,” says Gerhard Müller. “But over longer distances, this results in huge electricity losses, so you need an offshore high-voltage direct current converter (HVDC), which transmits the electricity to shore, where it is then converted back to AC and fed into the grid.”

Offshore Wind Toward 2020 points out that there are only three suppliers currently capable of producing HVDCs, with delivery time running into years. And at 10,000 tons, only a few  installation vessels around the globe are currently capable of installing them. “This is one of several significant challenges in the German market right now,” comments Müller. “In general, there isn’t the same level of experience with offshore wind parks as there is in the UK. When you consider that it’s all being attempted at a scale which hasn’t really been done elsewhere, then delays are almost inevitable. This is unproven technology.”

Striving for cost-competitiveness

The relative infancy of the offshore wind sector also means that it has struggled to attract major external investment, with wind park ownership still dominated by utilities companies. It’s an industry that still has a considerable degree of risk involved, says Maurer, and until now has only been prevalent in countries offering significant government subsidies. In particular, offshore electricity generation must become more competitive on a financial level to ensure its sustainability. “There’s a clash with the more traditional forms of energy generation. The price of CO2 certificates is so low at the moment that renewables just can’t compete.”

With so many changes afoot in the industry, it’s an exciting time to be involved, believes Maurer, although it may take several years for some stability to enter the market and technology to mature.

While offshore still won’t be able to match competitive cost levels for more conventional means of energy production by 2020, Roland Berger believes it is on the right path, although the study highlights the need for greater cooperation between governments and the industries involved. “One thing is for sure, you cannot escape the fact that wind power is vital in our energy transition,” Maurer says. “We need it and in the future we will need it even more.”