A new 1MW vertical axis wind turbine could change offshore wind farms forever, dramatically reducing the cost of offshore wind power

Swedish company SeaTwirl says its vertical axis floating wind turbines have what it takes to significantly reduce the cost of offshore wind energy. They will deploy a 1 MW turbine on a commercial scale in Norway.

Current offshore wind turbines, built based on land-based designs, are not cost effective in the deep ocean. There is a huge opportunity for fundamentally different designs to modernize a rather sickly looking industry, provide much cheaper energy from offshore wind farms and in doing so, greatly contribute to the clean energy revolution.

We talked about Swedish company SeaTwirl earlier in the year, building on an idea first tested in 2007, the company has a small 30kW test version of its floating turbine technology, called S1, installed off Lysekil (Sweden) since 2015. With a height of 13 m above the waterline and a span of 18 m below, it is connected to the network and produces energy from seven years, and has demonstrated its ability to withstand hurricane-force winds and waves.

Simple and robust design.

It is a vertical axis wind turbine, a rotating cylinder, unlike the horizontal axis wind turbines used today. VAWTs are a promising technology for floating offshore wind for several reasons.

First, they can accept and use wind from all directions, so they don’t need heavy and expensive systems to direct them to the breeze, as HAWTs do. Second, they can run their generators at or below the waterline. HAWTs must mount this heavy equipment atop their support towers where the main shaft is, creating a very heavy design that requires extreme tower strength and massive counterweights below the surface to keep them upright. More strength means more materials and more costs.

Third, they can be deployed much closer than HAWTs because they create minimal downwind wake effect. HAWTs must be further apart, which reduces performance for a given project area.

The SeaTwirl design rigidly mounts three VAWT blades on a long, floating mast with a low center of gravity and heavy underweight that acts as a keel. This pole rests on a ring that generates static electricity, anchored to the seabed. The entire pole rotates, propelled by the blades as they catch the wind, and the generator collects the energy and sends it to earth via cables.

Since the main tower is floating and held more or less vertical by the keel, the bearings of the generator do not have to support the weight of the entire structure. That’s why they can be smaller, lighter and cheaper. As with other VAWT designs, maintenance should be much easier and cheaper than with HAWTs, because the parts that need work are near sea level rather than on top of the huge towers. In this way, maintenance can be carried out without resorting to monstrous and expensive cranes.

SeaTwirl is about to build its first 1 MW version, a pilot for its first commercial product. The company has signed a letter of intent with offshore, energy and marine supplier Westcon to build and deploy its first Model S2x turbine near Bokn in Norway.

It should be commissioned in 2023, for a trial period of about five years.

SeaTwirl S2x

It is 30 times larger than the S1. It will reach a height of around 55m above the surface, and its weighted central mast will dive to a depth of 80m.

As such, it will need deep water to function; SeaTwirl suggests at least 100m if you don’t want to touch the bottom of the sea. It will shut off the power if the wind speed exceeds 25m/s (90km/h), but it is designed to withstand extreme winds up to 50 m/s (180 km/h), which would correspond to the upper limits of a category 2 hurricane.

According to the company, it should have a useful life of between 25 and 30 years.

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More information: seatwirl.com

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