JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 52

wind
Modular blade technologies
Over the past two decades, many patents and papers have discussed the optimum design of a wind turbine modular blade. In the last few years, several blade manufacturers have worked on R&D projects, built prototypes or introduced modular blade designs for future WTG’s that cover many of the different options under discussion. The main discussion is centred on the “bonded-or-bolted” issue: what is the best method for joining two massive composite parts subjected to high static and fatigue loads: a bonded joint or a bolted joint? A bonded joint would provide excellent mechanical properties at reduced extra weight and cost, but the reliability of such a structural bonding process, performed in external environmental conditions, is hard to ensure. On the other hand, bolted connections between thick composite parts are simple and reliable, but provide a lower-load carrying capacity that

gies (Innoblade®) was developed to comply with the ambitious characteristics that were required for the G10X-4.5MW wind turbine: - To fulfil the logistic objectives, G10X blades are divided into two modules, which are manufactured and transported separately and assembled on site (see Figure 2).

The initial prototype of the G128-4.5MW has been running since 2009; other prototypes were built in 2010 and 2011 and serial production started in 2012. The G128-4.5MW is currently the world’s largest wind turbine for the onshore wind energy market.

More information ...

can be insufficient for the extreme conditions of an intermediate joint, and require an intensive maintenance programme due to the creep of the composite material under permanent load. The Innoblade® modular joint (see Figure 4) combines bonded connections between the metallic parts and the composite laminates – a process that is performed in the blade factory, in special clean environment conditions – and bolted connections between metallic parts, that are made on site, including an automated preload control, as described later. This combination of processes ensures maximum load-carrying capacity and process reliability.

Fig. 2: A set of G128 blades ready for assembly on site

- To fulfil the cost of energy objectives, the internal structure of G10X blades uses new laminate and material configurations that are up to 40% lighter than the average tendency on the current multimegawatt blade market (see Figure 3).

G10X blade systems
Traditionally, wind turbine blades have been just a component with aerodynamic and structural performance. As blade size increases, new opportunities for extra functions may be explored. Following this approach that leads to “smart blades”, G10X blades include several new systems that provide new capabilities to the wind turbine: - Strain sensors are embedded in the blade laminates as part of a system to reduce the loads transferred to the wind turbine, detect abnormal situations (such as the presence of ice) and improve energy production. - Preload sensors in the bolts of the intermediate joint ensure that all blades are properly assembled on site, eliminating uncertainties regarding the reliability of the bolted connection process.

Fig. 3: Multimegawatt blade market weight comparison

52 jec composites magazine / No74 July 2012

JEC COMPOSITES MAGAZINE - Issue #74 - July 2012

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #74 - July 2012