Heave compensation for offshore wind turbine installations

In the offshore wind sector, heave compensation refers to technology designed to counteract the vertical motions caused by wave activity. Compensating for these movements prevents equipment from being damaged when lifted onto foundations or transferred between vessels. Heave compensation is critical for the safe installation of offshore wind turbines.

Heave compensation systems are traditionally categorised as either active or passive, each with their own distinct mechanisms and applications.

Passive heave compensation (PHC) systems rely on mechanical elements, such as springs and hydraulic pistons, to absorb and counteract wave-induced motion. They have fewer moving parts, making them simpler and less costly than active systems. However, passive systems lack real-time adaptability, which can limit their effectiveness in highly dynamic sea conditions.

Active heave compensation (AHC) systems use sensors and control mechanisms that adapt in real time to wave motion. These systems employ sophisticated algorithms and actuators(hydraulic or electric) to precisely match the heave of the vessel or lifting platform. As a result, AHC systems can perform precision lifts under harsher conditions and are particularly beneficial for offshore wind installations.

A heave-compensated crane involves the use of an active heave compensation winch. It uses real-time data from motion sensors to adjust the line speed and tension of the winch in response to wave height data. In offshore wind applications where turbine parts are heavy and require precise placement, heave-compensated cranes enable safer lifts by preventing sudden shifts or “re-hits” when components swing back towards the deck.

With conventional solutions, offshore wind installations must be stopped when waves exceed a height of 1.5 m. AHC systems like those by Seaqualize keep heavy loads virtually motionless even while the crane vessel is subjected to waves of up to 3 m. Norwegian engineering company Safelink has developed a pioneering hook-based AHC system which makes lifting conditions almost as stable as on land, greatly decreasing installation time. In this competitive market, reduced wait times are crucial, as projects often require hundreds of lifts.

With ongoing improvements in heave compensation technology, the offshore wind industry will see faster, safer and more cost-effective installation, bringing renewable energy solutions closer to meeting global demand.