Fit To Print: GE plans to 3D print wind turbine towers from concrete for more efficient wind farms

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As you drive across the eastern end of New York State, you cannot fail to notice the clusters of wind turbines that have sprung up over the past decade on rolling fields and remote ridges. As in other parts of the world, these wind farms are a manifestation of America’s growing adoption of renewable energy.

But wind power in this part of the country is more than just big rotors bobbing around in the constant breeze off Lake Ontario. Just step inside a cavernous warehouse in Bergen, a village just south of Rochester, where GE Renewable Energy engineers and their partners are working on innovations that could help the renewable energy industry capture even more wind in the future. .

Inside the warehouse, around 20 workers use one of the world’s largest 3D printers to form the bases of wind turbine towers from high-tech concrete. Their success could help the wind industry overcome the bottlenecks that limit the size and power of onshore wind turbines today and also lead to more efficient wind farm designs.

Christopher Kenny, senior engineering manager for emerging technologies at GE Renewable Energy and facility manager, says the wind industry has evolved tremendously over the past few decades. But there are physical limits to the power of onshore wind turbines. “Bigger generators will require taller, stronger, bigger towers,” he says. “If we do nothing, we will hit a roadblock.”

To make a wind turbine tower today, builders bring pre-fabricated steel tubes to the site on flatbed trucks and weld them together on site. But as anyone who’s tried to move a piece of furniture in a New York walk-up apartment knows, there are limits that can’t be exceeded. For turbine towers, this limit is approximately 14 feet in diameter. Scale them up and they become too wide to fit many roads. (Wind blades face a similar problem with length. But GE found an ingenious way to split the blades into two pieces and fit them together at the wind farm.) “It’s a real hurdle, but there’s a way around it,” Kenny says.

The solution is 3D printing, also known as additive manufacturing. By 3D printing the base of the tower from concrete on site, wind farm builders will be able to make it wider and strong enough to support a taller and more powerful wind turbine. The method could also unlock new locations for wind generation.

The printer Kenny and his team are testing in Bergen consists of long trusses and beams connected at right angles in a way that resembles a concert stage at a music festival. Electric motors attached to the beams move the print nozzle in three directions and allow it to print concrete structures up to 20 meters high – about 66 feet.

Kenny says attaching a pre-engineered steel tower to a concrete base 20 meters high could help wind farm designers build turbines with towers reaching 140 meters – 450 feet. Taller and more powerful wind turbines could help increase a wind farm’s annualized energy output (AEP), an important industry figure that describes the efficiency of a wind turbine. The number represents the actual amount of power the turbine produces per year and depends on the design of the turbine, the wind speed at a specific location and the number of windy days. “Hub height is critical to gaining AEP, and today it’s usually not fully optimized,” says Kenny, adding that the wind is generally stronger and more stable higher off the ground.

Since the printed concrete base can vary in height, the print could allow turbine heights optimized for the local terrain. “When you think of very large wind farms where the terrain and the wind change, we are limited on how we can vary the height of the turbine to maximize the site layout,” says Kenny.

The US Department of Energy is funding the research with $5 million, underscoring the importance of the project. “We appreciate the support of the U.S. Department of Energy for the research we are conducting here and are confident it will help make tomorrow’s wind farms even more efficient, economical, and environmentally friendly,” said Danielle Merfeld. , chief technology officer of GE Renewable Energy. . She said “Innovation will continue to be a key driver to accelerate the energy transition”.

The establishment will hold an “open house” on Thursday. Visitors will include Matteo Bellucci, head of advanced manufacturing technologies at GE Renewable Energy; Henrik Lund-Nielsen, founder and CEO of COBOD, the Danish company that designed the 3D printer; Edelio Bermejo, global head of R&D, innovation and intellectual property at Holcim, the partner helping GE develop high-tech concrete for printing; and representatives from Optimation, a New York engineering company that helps develop and standardize the printing process.

GE has been studying 3D printed wind turbine towers for several years. In collaboration with COBOD and Holcim, it printed concrete towers in Denmark in 2020.

Kenny, who was at the first print test in Denmark, says GE has spent the past two years working with COBOD on the evolution of the printer design and with Holcim on new compositions for concrete. In Bergen, for example, GE uses local stone and sand to provide a process that can help adapt the recipe to different locations. “Rather than trucking stones across the country, using local materials makes economic and environmental sense,” says Kenny.

The collaboration also identified and built the basic components that mobile printing operations will need in the field. They include the large printer, a mobile concrete batching plant on a trailer, a cement storage tank, also on wheels, and an assembly for forming circular rebar rings that penetrate the concrete and support the towers. “All the tools and equipment we develop to support the process will fit in custom modules that can travel from site to site, and we’re testing prototypes here right now,” says Kenny.

Don’t be fooled by the fact that the main building material here is concrete. It is high tech work. The mobile concrete plant, for example, is loaded with sensors that weigh sand, stone and cement, measure the moisture content of ingredients, and monitor mixing torque, rheology – the flow rate of the printing mix – and other factors for each individual lot. Operators monitor and adjust factors from a computer inside a glass cabin in the middle of the trailer. “Once we’ve mixed it and made the concrete, we only have a short time to be able to print it,” says Kenny. “Based on a combination of testing, computer modeling and simulation work, the concrete is designed to develop its strength at a certain rate to support the layers above and the weight of the rebar. This allows us to build the structure within the targeted time frame.”

The whole system is designed to work like this: The concrete plant mixes the cement from the storage tank and the stone, the sand and the water, and sends the concrete to the printer. The printer then extrudes layers of concrete into the desired shape through a special nozzle. Each layer is several centimeters thick. As at the concrete plant, the process is monitored by sensors and cameras.

The team faces many engineering challenges. Concrete mix, for example, must harden quickly so that the layer covering it does not deform it. But if the concrete hardens too quickly, it can clog the printer and destroy the material. “It’s a good balance,” Kenny says.

This monitoring is also important for quality control and certification. Naturally, the government will have to approve the process before GE can roll it out. “That’s a big part of the focus of this facility,” Kenny says.

GE will test the indoor printing process in 2022 and plans to start printing outdoors next year, aiming to demonstrate a full-scale outdoor tower segment. The ultimate goal is to demonstrate the ability to deliver high, cost-effective towers, and to do this, the GE team is looking for a viable site to install a prototype turbine that will generate 2-3 megawatts.

Some builders have already started 3D printing houses, but 3D printing a wind turbine tower requires solving challenges of a different magnitude. “Our loads and structural requirements are significantly higher than in a 3D printed house you see today,” says Kenny. “We learn to take advantage of the opportunities the additive opens up for us.”

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