An expandable wind tower that could make wind farms more competitive has been successfully demonstrated by a Spanish-Dutch consortium. The innovative technology saves on materials and cuts installation costs.
Wind power is a growing part of Europe’s energy infrastructure. To further boost the sector by streamlining wind plant set-up costs, Spanish engineering company Esteyco S.a.p. and heavy lifting specialists ALE B.v. have developed a telescopic wind turbine tower in the Eurostars EE-ALE TWT project, applicable to both offshore and onshore wind farms.
Designed to be transported in a compact collapsed state then expanded on-site, the tower is easier to install than traditional equivalents. It also uses concrete, a low-cost material that can be moulded by non-specialist companies, which takes pressure off production costs.
This technology makes wind more competitive, which is critical for clean energy goals.
Potential demand for the technology is huge. “There is a robust market for clean, affordable energy and wind is the next biggest renewable power source after hydro power,” says Esteyco’s Chief Technology Officer José Serna. He adds that the tower can save 35-40% of the substructure and installation costs of new offshore wind turbines, which are roughly 50% of the cost of an offshore wind plant project.
The tower is made of pre-cast concrete segments that are placed inside each other. A nacelle and blades are added when the structure is ready to be installed, then the segments are lifted on top of each other using a system of standard heavy-lift strand jacks. Once each level is in place, it is supported by pre-structured bolted joints.
This technology could make it easier to add wind generation capacity to an energy system. EE-ALE TWT’s towers need only readily-available equipment for transport and installation, even for the increased hub heights of the next generation of larger wind turbines. In contrast, standard wind towers – made of steel tubes – must be transported to a site on long vehicles, lifted into place by tall cranes and have greater limitations in terms of turbine size and height.
Further costs savings are from the manufacturing process. “Concrete is cheaper than steel,” says Serna, “and with the right moulds, construction companies – including many SMEs – can produce the parts.” This gives a free-flowing supply chain, unlike steel towers, which require specialist construction and where there are often bottlenecks.
EE-ALE TWT allowed Esteyco to develop a test tower to prove that it works and is cost effective. “We are the first in the world to install towers without cranes,” says Serna. “We invested in the technology ourselves but it took a lot of money and time to develop - a 100% investment would have been too risky for us.”
Although the tower uses simple concepts, its stability depends on precise engineering. Researchers had to accurately model the forces working on the structure during installation and when the turbine blades turn.
Esteyco has taken out international patents on the lifting process and other elements not already in the public domain. It plans to engineer specific towers for customers, making the technology available to generation, turbine or construction companies. The company is already achieving the 20% growth target it set for itself at the beginning of the project and expects the towers to double its turnover by 2020, says Serna.
Since EE-ALE TWT ended, Esteyco has taken part in two EU-funded projects demonstrating the tower offshore. The latest (ELICAN) supports a 5MW turbine and is scalable to 12 MW says Serna. “We have developed a European technology that can be exported. It makes wind more competitive, which is critical for Europe’s clean energy goals.”