Concrete towers will be increasingly important to the wind energy industry because they offer the advantages that project owners and developers need: higher hub heights, longer equipment life spans and, most importantly, a lower cost of energy.
There are a wide variety of commercial and experimental concrete tower designs in operation today. Nordex/Acciona Windpower was an early adopter of concrete tower technology, going back to the company’s first installation in 2006, and after having installed more than 500 concrete towers around the globe since, we’ve seen the advantages of concrete firsthand. We expect concrete tower technology will become more common in the North American market and around the globe.
Although there will never be a single solution that’s perfect for every project, and shorter steel towers will continue to play an important role for many sites and wind conditions, concrete towers could be one of the key components that will make the next generation of wind farms succeed.
Taller towers and broader rotors have been key factors in driving down the cost of wind energy in recent years, which, in turn, has helped spur the continued growth of wind power. As this trend continues, tower heights will need to grow beyond the limitations of steel. Concrete towers will be an important tool for the wind industry to further drive down the cost of energy and open up new areas for development.
Going higher typically allows a project to access a stronger wind resource and increase energy production. Concrete is generally a better option than traditional steel for constructing towers of 100 meters-120 meters and above. For very tall towers, concrete can be a lower-cost option that also offers benefits for durability, transportation and local employment.
Under the right conditions, a 120-meter concrete tower can reduce the overall cost of energy by a few percentage points compared with a conventional steel tower, creating a major financial advantage over the life of a project.
By tapping into a stronger wind resource, taller concrete towers can make wind development viable at many sites where conventional steel towers won’t work. As the U.S. Department of Energy explained in a 2015 report, “The deployment of taller wind turbines [already prevalent in Germany, with average hub heights at 116 m] will expand U.S. land area available for wind deployment by 54 percent. Further innovation and increasing heights to 140 m will increase that further to 67 percent.”
The U.S. has lagged behind other countries in deploying taller towers, partially because of the short-term production tax credit (PTC) renewals that were in place from 2010-2015. These one- and two-year PTC windows forced U.S. wind developers to keep their project timelines extremely tight and avoid any innovations that could extend the planning and permitting process.
Going forward, the industry should have a more stable policy outlook that will help developers plan and permit accordingly for taller heights.
The maturing wind industry is focused not just on building new projects, but also on lowering wind farms’ operations and maintenance costs and extending their operating lives. Because concrete towers have a long life span and minimal maintenance requirements, they can reduce operating costs over the long term.
Concrete towers are virtually maintenance-free, with no risk for corrosion or fire, high resistance to impact, and a fatigue loads profile that is lower than steel towers, which could extend the life and even allow for potential repowering. Concrete towers are better able to absorb vibration, which is a source of wear on components inside the nacelles. Concrete is also more rigid than steel, which decreases the deflection (or sway) at the top of the tower, thereby reducing fatigue on the structure.
The durability and low maintenance of concrete towers will make them an attractive option as operators look to extend the life of turbines to 30 years and beyond.
There are a limited number of facilities that can produce steel wind turbine towers, which means that steel towers usually need to travel long distances to reach a project. Concrete, on the other hand, can be built anywhere. The concrete tower sections used by the Nordex Group can be cast locally or even at the project site using a mobile batch plant.
Reducing the distance towers need to travel is only one way concrete towers can lower logistics costs. Concrete tower sections are also less complicated to transport than steel because concrete towers are cast in smaller, modular sections as opposed to steel cylinders. These concrete sections can usually be delivered on trucks with conventional extensible platforms rather than the customized trailers required to deliver steel tower sections. The concrete sections can also be trucked through highway overpasses that don’t accommodate larger steel towers.
The local production of concrete towers can also increase the local economic benefits of a project. Although some markets such as Brazil have legal requirements for local turbine production, every community will welcome the increase in jobs and local investment that concrete tower production can bring.
The North American market has an opportunity to take advantage of tall concrete towers to develop new and more efficient wind farms. The advantages of concrete towers have been demonstrated around the globe in a wide variety of sites. Now it’s up to original equipment manufacturers, developers and investors to work together to embrace concrete tower technology that will deliver more affordable clean energy to consumers and help the wind industry continue to grow.
Scott Baron is head of product strategy at Nordex/Acciona Windpower. He can be reached at SBaron@nordex-online.com.