Hywind and the use of the Flange Clamp tool

Although floating technology for wind farms is relatively new, it is rapidly gaining interest among developers due to its potential to overcome the limitations of conventional offshore turbines and meet challenging climate targets. Floating projects, anchored to the seabed by mooring lines, are more suitable for countries with limited access to shallow waters, or where the geology of the seabed makes it impossible to install conventional ‘fixed-bottom’ turbines. These are difficult to install beyond depths of 60m, which makes them unsuitable for waters further from shore, where wind speeds are higher. The UK – home to Hywind, the world’s first commercial floating wind park – has a 1GW floating target out of a total 40GW offshore wind goal by 2030. Countries such as France, Norway, Spain, the USA and Japan – surrounded by deeper waters than the North Sea – are now actively pursuing floating technology.

Connection challenges

The installation of floating wind turbines presents numerous challenges for those active in the industry, including IQIP, a partner to many of its leading contractors. One such hurdle on the Hywind project was how to provide an efficient method for mating two structures, namely the tower section with the floating substructure, without human interaction. While the industry is constantly seeking to improve safe working practices, the need for a solution arose due to changes to UK legislation stipulating that people must not work under suspended loads. For the Hywind project, five turbines were first assembled at a quay in a Norwegian fjord before being towed into position 29 km off the Scottish coastline. Due to the challenges of wave conditions and movements, it was decided to build the turbines onshore and install them on the fjord. The use of floating substructures means that the longer equipment stays connected with a vessel, the greater the safety risks, and the higher use of fuel through the dynamic positioning of the vessel. So time, money and sustainability are also significant factors. Many things are involved in the installation and if the process can be expedited, several issues can be eliminated. It’s important to consider that there are several sequences in the process, from securing the turbine before lift-off, remote release and then connection to the floating structure, transit from installation to the floating quay, and securing the turbine during bolting. As five turbines were required, making a series installation without the interference of (manual) bolting actions (which can take two to three hours) was the optimum solution. There is also a limited timeframe for the installation and contractors must wait for good weather with no waves. Time is a major influence.

Winds of Change

Innovative thinking from IQIP

IQIP’s solution for the quick ‘hands-free’ connection of the tower and floating substructure of the Wind Turbine Generator (WTG) was its Flange Clamp Tool (FCT). This hydraulic clamp installation extends and clamps the flanges to make a fail-safe connection. Used prior to and during the installation of permanent bolting, it can be remotely operated by radio control, therefore eliminating the need for personnel within the wind turbine and ensuring a safe process. A predetermined number of preinstalled FCTs were mounted around the circumference of each WTG tower flange. Each FCT system is connected to a termination panel, and operated and controlled by means of a remote HPU, which is connected to the termination panel by an umbilical.

Safety, speed and customer satisfaction

After safety, accuracy and speed are the next two benefits. A perfect fit for both structures is required, and it’s important to have a quick connection and disconnection. It’s also vital to disconnect the crane vessel as soon as possible, for safety and to make it available for the next installation. After the temporary connection of the two structures, the bolts can be placed safely by personnel and the FCTs can be removed once all the bolts are fixed and tensioned. The FCT can therefore be used on other projects, and for both installation and decommissioning. The FCT prototype was used 40 times on Hywind – without any issues – and the customer was extremely satisfied. Furthermore, after 25 years of service, the wind park may be decommissioned and IQIP will be able to use the same tool again. The FCT can also be applied to other lifting and installation requirements as it can be adapted to all kinds of flange combinations. This includes the flange between a monopile and transition piece, and between the tower section and transition piece, for example.

Proven technology

Following its successful utilisation on the Hywind project, the unique FCT has proven its technological capabilities to perform sequences rapidly, repeatedly and reliably. It joins IQIP’s growing portfolio of equipment for floating wind farm installation, including combi-lifting and internal lifting tools, established over 35 years of working in the industry. The implementation of IQIP’s innovative FCT to build the world’s first commercial floating wind farm contributed to a safe and reliable execution, with a reduced installation time and at a lower total cost for the customer. Ultimately, this contributes to the levelised cost of energy for the total product. According to figures released in 2021, Hywind Scotland is the UK’s best performing offshore wind farm, reaching the highest average capacity factor of 57.1% in the 12 months to March 2020. It provides sustainable energy to 20,000 Scottish homes and is providing data to help advance the technology globally and drive the industry forward.