Offshore wind energy is pushing the boundaries of construction

Andries Hofman, Project Manager at Gusto MSC

The next generation of offshore wind turbines is pushing engineers to think more creatively and cost-effectively about construction.

According to the International Energy Agency’s (IEA) latest report, global energy demand rose by 2.1% in 2017, more than twice the previous year’s rate. While 70% of this demand is still being met by oil, natural gas and coal, renewable energy sources are of increasing importance. Wind Europe believe that the record 14GW provided by wind energy in the EU in 2017 could continue at an average of 12.6 GW for the next four years, with offshore farms representing a quarter of installations.

Such is the rate of innovation that individual turbines with the capacity to deliver 12MW or even 15MW of power could easily be in use in the near future. But installing these increasingly colossal structures in harsh deep water environments is a huge challenge faced by installation contractors.

Incremental improvements

“If we look at the current fleet of vessels we can use, they may still be used in the nearby future if properly upgraded. However, their capabilities cannot be stretched up forever”,” explains Andries Hofman, Project Manager at GustoMSC, a design and engineering company that specialises in mobile offshore units and equipment. “Radically new technologies or methods would be nice to dream of, but it’s relatively difficult to bring to market. So what we are mainly doing now is extending the current technologies, with incremental improvements.”

The current state of the art wind turbine installation jack-ups typically feature a crane with a reach well above 100 m above sea level, revolving around one of the jack-up legs and a jacking system optimised for frequent jacking operations. Only the most capable installation jack-ups, such as the Scylla, are able to install the larger offshore wind turbines. The Scylla has recently completed installation of wind turbines in world’s largest offshore windfarm (Walney Extension) with 7 MW and 8 MW turbines.

Vessels such as the Oleg Strashnov, with its unique hull shape and a 5,000 tonne revolving crane, are representative of the technology engineered to support the installation of much heavier  turbine foundation structures. The Oleg Strashov was recently used to manoeuvre foundations weighing between 1,000 and 1,500 tonnes into place at the Beatrice offshore wind farm in the Moray Firth off the coast of Scotland.

Inspired by current solutions

It’s key that this new generation of technology is not only able to carry larger loads, but also has the capacity to enable higher hoisting heights. Heavy duty cranes, with increased lifting capacity and outreach are being developed to meet these requirements in a wide range of offshore construction markets. The very latest innovations even include telescopic leg cranes.

“Installing something 150m above the water level is even beyond my imagination and sailing around with a crane that will reach these heights is not practical,” says Hofman. “So we have designed a novel telescopic crane solution suitable for the offshore environment. We now can design and deliver cranes that enable installation of 12-15MW turbines, and when they’re retracted they become sturdy and strong and can add capacity for foundation installation.”

A major contributor

One major benefit of enhancing current technologies rather than inventing new ones, is that the processes involved in deploying them are familiar to the industry. This not only helps with streamlining planning and fulfilment, but also supports financial efficiency. Even those crane and jack-up vessels developed only few years ago that are no longer fit for purpose aren’t going to waste. Some are being deployed in other regions of the world in upcoming offshore wind sectors, where the turbine sizes still tend to be somewhat smaller. In addition, they can be repurposed to support the upkeep and maintenance of the wind farms they helped to install.

The rapid developments currently taking place within the sector certainly aren’t confined to Europe either, with China and the United States contributing around 50% of the increase in renewables-based electricity generation in 2017, according to the IEA. What was once a highly subsidised sector is now becoming increasingly competitive and many, like Hofman, are excited about its future. “Offshore wind energy is now a serious contributor to the energy landscape,” he concludes.