Rosie Barnes, founder of Pardalote Consulting, visits SeaTwirl in Sweden to explore why the company is reviving the largely abandoned vertical axis wind turbine (VAWT) design specifically for floating offshore applications.
Key insights:
VAWTs place heavy generators and gearboxes near the waterline rather than atop a tall tower, lowering the center of gravity and reducing structural steel requirements, which is a significant advantage for floating platforms.
SeaTwirl’s rotating spar design integrates the turbine and floating foundation into a single structure, simplifying installation and maintenance compared to conventional floating turbines.
A shift from three blades to two blades in their 2025 design reduces extreme storm loads, lowers weight, and enables the turbine to be assembled horizontally and upended, dramatically simplifying offshore installation.
The main engineering trade-off is a lower power coefficient of around 0.42 compared to 0.5 for horizontal axis turbines, though the rectangular swept area partially compensates.
The closer turbine spacing due to faster wake recovery could allow denser farm layouts, potentially offsetting the efficiency gap. Shortly after filming, SeaTwirl was awarded a €15 million Horizon Europe grant to accelerate development.