b'THE UNCONTAINEDDR. HABIB DAGHER ANDAJOT: Taking offshore wind power as a whole,Dagher: Every technology has its pros and cons where in the technology curve are we?where you are in the world, what manufacturing THE POTENTIAL OF Dagher: There are two types of offshore windinfrastructure you have, what port facilities, what technologies, fixed-bottom turbines, and floatinggeophysical conditions you have offshore. how deep turbines. And theyre quite different.the water is, what kind of soil conditions you have.All In the fixed bottom world, Europe built thedetermine which technology may or may not be better than first offshore wind farm in 1991. They built a verythe other. Theres really no single solution fits all. But you significant industry. They have over 5,000 turbinescant make the Spar-buoy in the US, there is no port facility US OFFSHORE WIND POWER installed in Europe already. where you can make it. When you talk about fixed-bottom turbines, youAJOT: Do the blades and the nacelle, the turbine are also talking about what goes along with it. So,itself, present technological challenges in floating that are for example, the turbine designs and manufacturingdifferent from fixed? are all in Europe. There is no offshore wind turbineDagher: When you go to floating technologies, you have manufacturer in the United States today. different vibration characteristics, motion characteristics AJOT:What about floating turbines? of the hull. The hulls are moving around a lot more when Dagher: When the water exceeds roughly 150theyre floating than when theyre fixed. Theyre moving feet, floating becomes the technology you lookat different frequencies. You want to make sure that the at, because building 150-foot foundation down tomotions of the hull, as the hull moves around in the waves the seabed will cost you a lot of money. [In 2009]and the winds, dont eventually damage the turbine from a Equinor built a single two-megawatt unit off thefatigue perspective or strength perspective. You dont want coast of Norway, and that became the very firstto over-stress the blades or over-stress the gears inside the floating turbine in the world. Since then, they built aturbine nacelle.project off Scotland, using five, six-megawatt units.AJOT: Will it be necessary for a totally new blade design And now theyre doing one in an oil and gas field [inor nacelle design? Or is it likely to be an adaptation of what the Norwegian North Sea] that is even bigger thanis now being produced?that, but not really commercial scale yet. Dagher: Weve worked with all the turbine OEMs. Right With floating technology, its a wide-open field.now, weve been able to adapt the current turbines to the There are over 40 technologies in the floating worldhull that we have. We can accept turbines from almost any right now. Proposed solutions for floating windsupplier. turbines fit into three different major categories:What we would have to do from an adaptation Spar buoy, semi-submersible and tension-legperspective is really optimizing the turbine for the hull. How platform. And there are also hybrids of these designs. This is where we have focused our research at the University of Maine for the last 14 years and have built the leading research team in floating technology in the United States.The design that U Maine has developed is the semi-submersible, and thats the most common technology being proposed across the world today. The one that Equinor designed is called the Spar-buoy, but this requires a very, very deep draft, 250-to-300-foot drafts for these units. So, its very difficult to fabricate them dockside because you dont have port facilities with 300 feet of water unless youre in Norway. What weve developed is a semi-submersible that has less than a 25-foot draught dockside, so you can actually make the hull in a lot of places around the US.Also, the hulls are stable without tension legs, without the mooring lines. The mooring lines just keep them on station, so they dont fall away.So, the advantage of the semi is its stable on its own and has a relatively small draft. You can actually fabricate it onshore and throw it out to sea. AJOT: Are there cost advantages of the semi-submersible as well? 19'