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The TENTORTUBE: an innovative improvement of a passive tip mechanism



Most present wind turbines are equipped with actively controlled tips as a safety system. For variable speed wind turbines passive controlled tips can be utilised for both power control and as a safety system, as has been demonstrated on a rotor equipped with a tip mechanism, consisting of a metal screw cylinder and a spring. The main problems with this mechanism are the large mass and complexity and high maintenance costs, but these can be solved with a TenTorTube combining the functions of the spring and the screw cylinder. The TenTorTube is a long, slender tube made of composite material in which the anisotropic behaviour of fibre reinforced material is utilised. The objective is to reach an aeroelastic stable configuration of a blade with a TenTorTube tip mechanism and to deliver reliable information on its costs and applicability.

Technical Approach

For rotor structures with a low torsional frequency aeroelastic stability is a potential problem which may lead to blade loss. For a TenTorTube blade an additional coupling occurs. The aeroelastic behaviour will be evaluated using available prediction tools in terms of aeroelastic stability boundaries. From this information a wind tunnel test specimen will be specified and manufactured and a test plan will be formulated to explore the boundaries. During the test different parameters will be varied to define their influence. This may be followed by improvements of the prediction codes and, if necessary, additional tests. The full scale blade and TenTorTube will be designed to meet the draft IEC regulations. After manufacturing acceptance tests will be carried out to ensure the functionality and safety of the rotor configuration. During the full scale test different properties will be monitored to enable evaluation of the power curve, dominant loads acting on the blade and the hub and the strains in the TenTorTube. The behaviour and applicability of the TenTorTubes will be evaluated. For this evaluation the knowledge gathered during the tests and technical evaluations will be used as well as the economical results.

Expected Achievements and Exploitation

Preceding national studies, carried out by SPE, have shown the feasibility and the mechanical durability of the proposed tip mechanism. Within this project the last technical problems can be solved, concerning the aeroelastic behaviour and the durability in a full scale outdoor test. Tip controlled variable speed wind turbines are likely to have a better cost/benefit ratio compared to constant speed wind turbines. Application of a TenTorTube will result in a tip controlled blade with a simple, durable, inherent safe, low weight and maintenance free tip mechanism. The possibility to use the axial force as a control input creates the possibility to achieve a smoother tower loading and thus diminish the tower costs and total turbine costs. The above leads to an improved reliability and improved cost/benefit ratio of the wind turbine.
TenTorTubes are likely to be produced within commercial wind turbine blades by one of the project partners (Aerpac).

Funding Scheme

CSC - Cost-sharing contracts


229,Czaar Peterstraat 229
1000 AJ Amsterdam

Participants (4)

Aerpac Special Products BV
96,Bedrijvenpark Twente
7602 KD Almelo
Westerduinweg 3
Ipa NV
9160 Lokeren
United Kingdom
Mayfield Road Kings Buildings
EH9 3JZ Edinburgh