The focus of this latest Infra Dig podcast turns once again to technology in the offshore wind sector as listeners are treated to a deep dive into SeaTwirl, its history and the ambitions for a new method of harnessing energy in waters your average offshore wind turbine just cannot reach.

IJGlobal content director Angus Leslie Melville sits down with Johan Sandberg, chief executive of SeaTwirl, to hear about his company's truly fascinating innovation in turbines for the offshore wind industry.

You can access this latest episode on Apple Podcasts and through Google Podcasts. It is also available across a number of other platforms.

Having had a pilot unit in the water since 2015, SeaTwirl rates as one of the most established players in the floating offshore wind space and is all the more exceptional for not relying on traditional “windmill” design – the horizontal axis wind turbine.

Based on a vertical axis design (see image below), it was reinvented from an on-land version to one that could compete with horizontal axis models, able to operate in deep water.

SeaTwirl’s wind turbines use a vertical axis wind turbine with a tower connected to the sub-sea structure, consisting of a floating element and a keel. As the energy of the wind makes the turbine rotate, the structure maintains its stability by using the keel and the counter turning moment, similar to the function of a keel on a sailboat.

The wind turbine, the tower and the sub-sea part are assembled and rotate as one unit. Around the tower, above the water surface – but below the wind turbine – is an enclosed, stored generator housing that is static (non-rotating). The generator housing and the wind turbine are anchored to the seabed by several catenary mooring lines.

SeaTwirl turbines can be sited in sea depths of much more than 50-60 metres – unlike offshore wind turbines on the market today – allowing units to be sited where winds are stronger and more reliable.

Johan says: “The first prototype was installed in 2015. It’s a small machine – only 30kW – but it has been out there since then and it has been working very well, validating models and all sorts of tests on that little machine there.

“It was planned to install a much bigger pilot in 2020, but Coronavirus came about and things were a bit delayed. As we came out of Corona, you had the war and inflation, interest rates going up and so-forth. So, the project is somewhat delayed, but the turbines are in production still.

“We have made the blades. We have made the struts. We are procuring all the generators and so on. There are a few components left to build, but the plan is to install this turbine in the next 1-2 years.”

This model will be installed in Norway at the Marine Energy Test Centre (Metcentre) alongside 2 other floating offshore wind pilots – the HyWind turbine from 2009 and the TetraSpar demonstrator that has been in place since 2021.

To hear all about this fascinating company and its plans for the future, tune into this latest Infra Dig podcast…