Energy

Pivoting arms could stabilize massive floating offshore wind turbines

View 4 Images
Gazelle says its innovative floating wind platforms can handle enormous offshore turbines up to 20 MW in a stable and cost-effective manner
Gazelle Wind Power
Gazelle says its innovative floating wind platforms can handle enormous offshore turbines up to 20 MW in a stable and cost-effective manner
Gazelle Wind Power
The Gazelle system (center) is a sort of cross between semi-submersible and tension leg designs
Gazelle Wind Power
Large pivoting mechanical arms link three sea floor tethers to a counterweight slung underneath the Gazelle platform
Gazelle Wind Power
Wave tank testing in Spain confirmed the company's claims on an earlier design at small scale, keeping pitch movement below one degree
Gazelle Wind Power
View gallery - 4 images

Irish company Gazelle has announced the third generation of a fascinating new floating wind platform design it says can stabiliize massive offshore turbines up to 20 MW in capacity, while radically reducing weight, cost and sea floor cable tension.

As we've discussed many times before, offshore wind represents an enormous opportunity for clean energy, but some of the best resources are out in deep water, where sinking a shaft straight into the sea bed becomes prohibitively expensive and difficult.

Floating offshore platforms offer an alternative, but the engineering challenges here are enormous. A typical 14-megawatt offshore turbine, for example, might place a 500-ton nacelle on top of a 130-meter (427-feet) tower, spinning three 108-meter (354-feet) long carbon blades into the full force of a gale out at sea.

Balancing a monster pinwheel like that on a floating base is no mean feat, and doing it in a way that can easily be manufactured, installed and deployed at low cost? Well, that's a billion-dollar problem that many companies are racing to solve.

The Gazelle system (center) is a sort of cross between semi-submersible and tension leg designs
Gazelle Wind Power

Gazelle reckons it's got a solution. The company says its odd-looking platform is somewhat of a cross between two other approaches to floating wind, those being semi-submersible and tension leg platform designs.

Gazelle's third-gen floating wind platform tethers to the sea floor on three sides. Cables reach up from the sea floor tethers and come up over the floating structure, running over pivoting arms before dropping down to attach to a heavy counterweight suspended below the platform.

This, says the company, creates a passive system capable of balancing wave and tidal motions as well as the enormous forces wind exerts through the giant lever of the turbine tower, reducing pitching motions and improving efficiency. Gazelle claims the resulting platform is much smaller and lighter than a typical semi-submersible design – thus reducing steel use by as much as 70%, and costing around 30% less. Its "dynamic mooring" system also places some 80% less load on the sea floor tethers than a typical tension leg platform, keeping tilt under one degree while allowing some up and down movement.

Large pivoting mechanical arms link three sea floor tethers to a counterweight slung underneath the Gazelle platform
Gazelle Wind Power

Gazelle says this relatively lightweight, cheap structure can scale to handle turbines up to 20 MW in size – bigger than anything currently deployed in the offshore category. It says it's modular and easy to manufacture, tow and deploy, requiring no specialist equipment, cranes or port facilities.

It's verified the above claims in small-scale model testing in a wave tank at the University of Cantabria's Environmental Hydraulics Institute in Spain, and has received the first "Statement of Feasibility" for an offshore wind platform from DNV, a classification service provider specializing in lifecycle analysis of offshore installations, particularly in renewable energy, oil and gas.

Wave tank testing in Spain confirmed the company's claims on an earlier design at small scale, keeping pitch movement below one degree
Gazelle Wind Power

The company raised some US$14.1 million in 2021. It's signed an MoU, whatever that's worth, to develop a 2 MW pilot plant with Maersk Supply Service in the Canary Islands, although according to that MoU, this project's due to be completed by Q2 this year, and it's unclear exactly how far this project has advanced. Likewise, the company has announced it's "teamed up" with WAM Horizon on another pilot project in Portugal, but has thus far given no information on size, timelines, or even what this amorphous partnership really means. So it's hard to assess where things stand in terms of progress.

Either way, it's a mechanically interesting design targeting a low (but as yet unpublished) Levelized Cost of Energy (LCoE), and we'll be interested to see where this technology goes in the coming months. Check out the company's innovative design in the video below.

Source: Gazelle, via Recharge News

View gallery - 4 images
  • Facebook
  • Twitter
  • Flipboard
  • LinkedIn
4 comments
Pupp1
While I love seeing technology like this, I am concerned this is yet another money-pit associated with the green movement. Concerning environmental impact, there has been some evidence that the building of offshore wind farms increase wale deaths, in addition to the bird-wacking associated with all turbines. This design may at least solve, or reduce, the wale problem.

The other issue is that wind turbines have been pretty consistent in proving that they are much less reliable, and generate much less energy than the manufacturers claim. This design is definitely more mechanically complex than a typical turbine. It depends on pivoting weights, and very large cables that are constantly being bent over the pulleys. And of course, the ocean is notoriously hostile to any mechanism.
TechGazer
Small-scale wave tank testing doesn't really tell much about long-term reliability in full-scale real life conditions. Maybe barnacles will abrade the moving parts quickly. Maybe fish or other aquatic creatures will get pulled into the cable/pulley gap. Maybe some failure mode that isn't so obvious. A way to reduce costs would be good, but complicated moving parts in the marine environment tend to be unreliable.

Do blade-killed birds noticeably boost fish production in offshore wind farms? The protein is probably wasted in on-shore wind farms.
DaveWesely
Excellent development! It seems to embody the essentials of KISS (Keep It Simple, *). There are no hydraulics, actuators or electronics to keep it upright and stable. Puppy seems to think the cables go up and over the pivoting arms on pulleys. Nope. Look again, the cables are attached to pivot points. So no cable bending and excessive wear points on the cables.
The counterweight doesn't really pivot, as there is no axle or pivot point. Swings may be more descriptive, since it is hanging from the pivoting arms. This is rather ingenious, as the counterweight is lifted up and lowered with the sea level rise and fall due to tidal effects - as opposed to increasing tension on the cables with sea level rise. This explains why tension load on the tethers is so much lower. Shock forces should be reduced as well, as the counterweight can absorb those better than cable tension.
I don't know what a wale is, perhaps it is related to a snipe. Whales are marine mammals. Cats literally kill 1000 to 10,000 times more birds than wind turbines. Time to euthanize kitty!
The LCOE for land wind turbines is half that of natural gas, and a fourth that of nuclear. It is the most cost effective energy generation method. Off shore turbine LCOE is higher, but the wind is more consistent. Having a cost effective deep sea method is important as that dramatically increases the area wind turbines can be installed.
Adrian Akau
No harm in trying it out. Since it is a moving device, perhaps energy might also be extracted from the cables.