Large swathes of the United States have yet to be tapped for wind power, partly because of politics and partly because wind speeds in these areas are not optimal. Only the voting public can deal with the political end. Meanwhile, engineers and innovators are tackling the problem of wind speed, which can be solved by building taller wind turbine towers. It’s not as simple as it sounds, but GE Renewable Energy is banking on 3D printing to overcome the hurdles.
Why not taller wind turbines?
Taller wind turbines have several advantages over their shorter cousins. They can reach heights where the winds are stronger, without interference from trees, topography or buildings. The greater height also allows for longer blades, which means a single turbine can harvest more energy. The cost savings can also add up for taller and longer wind turbines, at least on paper.
Since a free lunch does not exist, the cost factor can also add up, and not in a good way. Transporting long sections of conventional steel towers can be a deciding factor solely due to logistics, making it impossible to build taller towers where the curvature of the road and other infrastructure pose obstacles. Similar obstacles are present on the precast concrete bases that would be large enough to support a taller tower.
Pouring the concrete on site would solve the transportation problem, but it raises new headaches for project managers who are tasked with assembling a team in a remote location and keeping it there for as long as it takes to build the round.
Higher wind turbines and 3D printing
One solution to the problem is modular construction. Global wind energy company Vestas has applied this approach to the nacelle, which is the energy transfer system that sits atop the turbine tower.
The modular approach has also taken hold in the turbine tower arena, and GE is taking things up a notch by adding 3D printing to the mix. The idea is to transport the printer to a site and print the concrete base there. With only a few people needed to operate the printer during this stage, labor costs become more manageable.
GE recapped its previous work on the 3D printing project in 2020 and was very excited to partner with 3D printing leader COBOD and Holcim (formerly LafargeHolcim), the sustainable construction company.
“Since Charles Brush built the first wind generator in Cleveland, Ohio, in 1887, engineers have searched for a practical way to extract more power from wind turbines, stretch their blades and make them grow. Now, a combination 3D printing, materials science and robotics could trigger a new growth spurt for the industry,” GE enthused.
The repowering solution
Given the hurdles faced by wind turbine developers in many US states, one wonders why GE bothers to push for taller wind turbines. The answer could be quite simple. Even though some states stubbornly resist new wind turbines, there are many opportunities to be seized in re-powering old wind farms.
Thousands of existing wind turbines in the United States are already beginning to age, and wind energy players are already beginning to retrofit them with more powerful turbines.
The trend towards wind turbine renewal is affecting even wind farms that are still in the planning stage, allowing developers to reduce costs by reconfiguring their networks to accommodate fewer wind turbines.
Add taller towers to the mix, and the power boost for revitalizing old wind farms could be irresistible.
According to GE’s figures, the improvement is significant even without a turbine upgrade. The company calculates that an average 5 megawatt turbine generates 15.1 gigawatt hours per year at 80 meters high. The same turbine could generate 20.2 gigawatt hours at 160 meters high
Wind turbines: how high can they go?
In 2020, GE noted that the tallest onshore wind turbine reached 178 meters. They were referring to a “water battery” that pumped hydroelectric power storage into a concrete wind tower base. This is an interesting concept for taking advantage of more cost-effective renewable energy in hydroelectric sites, although its application would be limited to sites with water resources.
GE is betting that 3D printing will expand the range of sites while reducing costs, considering a height of 150 to 200 meters.
COBOD’s contribution is the design of a transportable 3D printing system on site.
“Once there, the system will suspend a printhead from an elevated track like a magic marker with a tip the size of a gallon milk jug. printing as it follows its programmed path,” says GE.
Holcim came up with the concrete mix that stiffened quickly, but not fast enough to clog the nozzle.
The world’s largest 3D printer of its kind
To be clear, GE’s tower design isn’t concrete everywhere. Key to the design is a concrete base, which will support a longer section of steel tubing. The steel part is flexibly designed to absorb the wind, like a modern skyscraper.
GE also designed the steel tower to be customizable. Its height can be adjusted according to the needs of the wind developer.
As early as 2020, GE and its partners achieved one of their major milestones, which was the 3D printing of a 10 meter high concrete base. The next goal is 20 feet, and they just announced the grand opening of a new 3D printing facility that will take them there.
The new 3D printer is no small potato. It is the height of a three-story building and it is considered the tallest of its kind in the world. Here, let Henrik Lund-Nielsen, the founder and CEO of COBOD, explain:
“The printer we delivered is second to none: not only can it print more than 10 tons of real concrete per hour, but it is also the first concrete 3D printer in the world with two X axes on the printer. With the multiple functions of the printer, the printer can best be described as a multi-functional construction robot than a printer.
GE is not shy about testing new ideas to increase the efficiency of wind turbines. Some of these did not have a widespread impact, such as the new siding of the grid towers and the windbreak covers for the nacelles. However, its mega-size offshore wind turbines have set the offshore industry in turmoil. If all goes according to plan, 3D printing could also be a game-changer for onshore wind development.
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Photo: 3D printing for wind turbines courtesy of GE (via email).
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