Segmented towers most cost-effective as turbines edge past 120 metres, study shows

Segmented turbine towers offer the best technical feasibility and cost effectiveness for high hub heights among alternatives to traditional steel-tubed towers, according to a new analysis of several tall tower solutions. Other options scored high on some criteria, such as maintenance, but not as well overall.

Tall tower vendors are few and far between, but US firm Northstar produces segmented towers
Tall tower vendors are few and far between, but US firm Northstar produces segmented towers

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Segmented towers currently account for only 0.5% of the global market, while traditional steel-tubed towers take a majority share at 61.5%, according to IntelStor research.

Lower fabrication costs are the main advantage of segmented towers, as they use less material and require less rolling of steel plates.

They also have substantially reduced logistics and transportation costs because they can be transported on conventional flatbed trucks, IntelStor CEO Philip Totaro explained.

New solutions will be needed for cost-efficient turbine towers offering both height and transportability as turbines increase in size and power, the advisory firm pointed out.

Most turbine manufacturers now have 4MW and 5MW turbines under production, and some have plans for 6.XMW. 

These turbines will need hub heights greater than 120 metres to prevent blades striking the ground as they rotate. The global average hub height already exceeds 110 metres as towers get taller, according to IntelStor data.

This increased size can make towers difficult to transport and install, so new solutions are needed.

“In a time where net installed cost savings is key for OEMs and project developers, the acquisition of technologies which can present a significant advantage is of critical importance,” Totaro said.

As well as analysing segmented towers, IntelStor also looked at tripod, cable-stayed, concrete and hybrid concrete-steel towers as alternatives to traditional steel-tubed towers.

  • Segmented towers were ranked as "good" for transportation and installation costs and erection time, and "decent" for maintenance costs and field-assembly time. Overall, it ranked segmented towers levelised cost of energy (LCoE) as the "best";
  • Tripod towers were ranked as "poor" for transportation and installation costs, as well as field-assembly time, but "fair" for erection time and "good" for maintenance costs. Overall, it ranked tripod towers’ LCoE as "poor";
  • Cable-stayed towers scored "fair" for maintenance costs and erection time, but "poor" for transportation and installation costs, and field-assembly and erection time. Overall, it ranked cable-stayed towers’ LCoE as "fair";
  • Concrete towers were judged "good" for maintenance and transportation costs, as well as erection time, and "fair" for installation costs and field-assembly time. Overall, concrete towers’ LCoE was seen as "good";
  • Hybrid concrete-steel towers were evaluated as "good" for maintenance costs, "fair" for transportation and installation costs, but "poor" for field-assembly and erection time, with overall LCoE as "fair".

Tall tower vendors are few and far between, with most companies currently favouring hybrid concrete and steel tube versions due to the capital invested in transportation, logistics and erection of the steel tube towers that sit on top of the concrete base.

However, projects using hybrid technology have found it expensive as the contractor is effectively installing two towers — a concrete base that extends beyond the pedestal foundation and the steel upper section, Totaro explained.

Meanwhile, concrete towers can require co-located batch plants at a construction site, which necessitates large wind turbine orders to justify the Capex, he added.

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