A Boston startup, T-Omega Wind, is challenging the conventional wisdom about how best to capture the potential for offshore windfarms by focusing on a radical new way to design floating platforms. Their goal is to drop the costs of offshore wind 70-80%.
The trend in offshore and onshore wind farms has been to just take the land-based designs and put them on base fixed on the ocean floor. To get power cost per MWh down, the designs have trended toward increasing the height and blade length in the typical pinwheel-on-a-stick designs. The biggest individual wind turbine is now the 13 MW offshore Haliade-X from GE (260 m high—like an 80-story building—with 220 m blades). But this approach has led to the need for thick-walled (3 inch thick) steel towers to carry the weight and resist the force of the wind plus husky bearings to support the turning shaft between the blades and the generator assembly. These are placed on an offshore mounting base in the deep sea that is also very costly. As a result, it is not clear that the increased scale is really achieving the intended results in lower cost of electricity, except in the windiest offshore locations. The sheer size brings its own complications in maintenance. The DOE reported that the average cost was $84/MWh with a range of $61-116/MWh.
The US is by no means a leader in offshore wind with only 42 MW currently operating and 932 MW under construction compared to 50 GW operating currently worldwide. To meet renewable resource goals, offshore wind capacity is going to have to increase dramatically. President Biden has set a goal of 30 GW by 2035 with a cost reduction to $45/MWh. Some of the best wind sites are in deep waters off the West Coast and Maine. In those areas, the sea floor drops off so quickly, sinking a fixed base for offshore turbines is likely to be economically unrealistic.
The major alternative has been to use a floating platform, but with the tall turbines the floating base needs to be quite large and tethered to the seafloor with cables and a number of heavy concrete and steel anchors. The CEC has adopted an aggressive goal of 5 GW of offshore wind by 2030 and 25 GW by 2045. To meet that goal with competitive power costs, it is likely some innovation is going to be needed.
The T-Omega approach is very different. It uses a stable, lightweight, four-leg structure that is allowed to float with slack (in order to turn into the wind). It looks like a Ferris wheel, with the wind turbine and the generator supported on each side rather than trying to balance everything on top of a tower.
This design takes the load off the bearing, means the steel legs can be much lighter weight, and the mass of the floating structure below water is virtually eliminated. In the standard design, there may be 1500 tons above water, and 6000 tons underwater to keep it upright. T-Omega is not far enough along to make any credible claims on cost, but just from the elimination of thousands of tons of steel their goal of a massive cost reduction is likely to be achieved.
If the CEC goal for offshore wind is to be achieved, it is going to take dramatic innovation in the design of floating systems. T-Omega may be only one of many ideas, but it is one of the best we have seen.
Here is a good article with more details if you are interested. In particular, the test of a 1:60 scale model in a wave tank at the end of the article is a good demonstration of the viability of their idea.
ABOUT THE AUTHOR
Gary Simon is the Chair of CleanStart's Board. A seasoned energy executive and entrepreneur with 45 years of experience in business, government, and non-profits.