"When Vincent Schellings started designing wind turbines two decades ago, he frequently polled his colleagues about what they thought was the biggest turbine they could build. “We didn’t get much further than a 3-megawatt machine with a 100-meter rotor,” he recalls. “But even that seemed too big.”Schellings, 44, never stopped asking that question. Today, he leads the team at GE Renewable Energy developing the world’s largest wind turbine, one that dwarfs his youthful musings. This veritable behemoth will loom 260 meters tall from base to blade tips — 1 meter taller than New York’s famous 30 Rockefeller Plaza tower. With blades as long as a football field, the rotor will measure a beefy 220 meters in diameter.These turbines come with a 12-megawatt generator sitting 150 meters above the waves. Each will be capable of powering 16,000 homes and producing 67 gigawatt-hours per year, based on wind conditions on a typical German North Sea site — that’s 45 percent more energy than any other offshore wind turbine available today. “We asked ourselves ‘What is the biggest rotor we would still feel comfortable with?’ and then we pushed ourselves some more,” Schellings recalls. “From a technology perspective, it seems like a stretch. But we know it’s doable. The beauty of the turbine is that it gives an edge over the competition. There’s nothing like this. Not even close.”Today, the largest wind turbine has a rotor with a 180-meter diameter, but that is a prototype. The biggest operating turbines have rotors topping 164 meters and generators rated up to 9.5 megawatts. “We decided to leapfrog the competition,” Schellings says.The size matters. The huge rotor allows the engineers to catch a lot more wind and ramp up what the industry calls “capacity factor.” This number describes the amount of power the turbine can produce per year at a given site, versus the energy it could have generated had it run full power all the time. GE’s Haliade-X clocks in at 63 percent, “five to seven points higher than the competition,” Schellings says. “Basically, every point of capacity factor is worth $7 million per 100 megawatts for our customers. That’s a nice upside.”

Top and above: “We asked ourselves ‘What is the biggest rotor we would still feel comfortable with?’ and then we pushed ourselves some more,” says wind turbine engineer Vincent Schellings. Images credit: GE Renewable Energy.

The current model of the Haliade turbine can generate 6 megawatts. These machines are destined for Germany's huge Merkur offshore wind farm. Image credit: Tomas Kellner for GE Reports.

There are other benefits. The new 12-megawatt design will allow operators to build wind farms with fewer turbines, lay fewer cables, reduce construction, maintenance and other capital costs, and recoup their investment faster. “This helps the customers when they are competing at auctions to build offshore farms and enter the lowest bid per kilowatt-hour,” says John Lavelle, the CEO of GE Renewable Energy’s Offshore Wind unit. He and his team are starting to talk to companies interested in building wind farms in the next few years using equipment that will start shipping in 2021. “We are trying to target those bidders, so they can factor in the value we can bring. If they win, we win.”Offshore wind is the fastest-growing renewable energy segment. “The renewables industry took more than 20 years to install the first 17 GW of offshore wind,” said Jérôme Pécresse, president and CEO of GE Renewable Energy. “Today, the industry forecasts that it will install more than 90 GW over the next 12 years. This is being driven by lower cost of electricity from scale and technology. The Haliade-X will set a new benchmark for cost of electricity and drive more offshore growth.”Huge wind turbines like the Haliade-X will play a key part, but how do you build one? GE, which is investing $400 million in the project, started exploring the idea two years ago. After deciding on the diameter of the rotor, Schellings’ team worked backwards to calculate the magnitude of the generator and the size of the tower supporting both.Each step presented its own challenge. It’s hard to mass-produce blades in the first place, let alone ones that are 107 meters long each. “There’s a lot of manual labor involved,” Schellings says. “You need as many as 250 workers working on a single machine, and all kinds of scaffolding and tooling to properly handle the material.” “Building a blade of this size requires a lot of people with strong team synchronization and collaboration to handle materials and tooling.”The team reached out to experts at LM Wind Power , the Danish blade manufacturer GE acquired last year. LM Wind is now seeking to “industrialize” the production of the largest blades.The next element was the size of the rotor itself. “You catch a lot of wind, which is good for energy production, but the downside is that you need the support structure to keep the rotor up in the wind,” Schellings says. “It’s kind of unfortunate that as you scale the rotor size, the turbine costs will go up quicker than the incremental yields you get from the larger rotor.”The team solved the problem with software, using algorithms to process data from the turbine and offset the high forces the wind produces. “We use software to control the pitch of the turbine and keep it in the wind,” Schellings says. “It helps us keep the size and the weight of the support structure under control.”When Schellings’ team did its early calculations, it reached out to engineers across the company to help it validate and improve the design. Schellings calls this approach “the best of GE.” His team worked closely with Vic Abate, GE’s chief technology officer who also runs GE Global Research, to help identify experts in diverse fields to review the designs. “The foundation loading, the aerodynamics, the structural weight — we’ve worked these things through with scientists at GE Global Research,” Lavelle says. “We’ve called in experts from GE Aviation, Power, LM Wind and other GE businesses to set up peer reviews. It gave us confidence that we are going in the right direction. It’s amazing what we can accomplish when we collaborate and bring the best talent available.”The engineers are far from done. Teams working in Barcelona, Spain, Nantes, France, Hamburg, Germany, and elsewhere in Europe and the U.S. will spend the next few months perfecting their designs and getting ready for the first component tests. GE plans to erect the first complete test turbine in the second quarter of 2019.But Lavelle is already thinking ahead and looking for ways to include the latest technologies, like 3D printing, into the design, keep improving it, and reduce costs. GE Aviation is already printing entire blocks of aircraft engines, and GE Additive built a beta version of a 3D printer for metals that can print parts as large as 1 meter in diameter. “We can’t limit our thinking,” Lavelle says. “What is our limit today may not be our limit in 2020.”Lavelle should know. He spent 35 years at GE developing technologies for power plants. “All those were fun and they mattered and they were important, but the things that help improve the environment, I think those are the things that you can go home and tell your kids and your family and they’re proud of what you are doing.""