Precast Concrete Wind Towers – The Rise to the Next Level in Hub Height and Support Capacity for Large Turbines
a report by José Serna1 and Jorge Jimeno2 1. Managing Director, Esteyco Energía; 2. Head of Sales, Inneo Torres
Concrete is generally the most common and competitive material for all types of high-rise pylon-type structures (see Figure 1), such as large chimneys, communication towers, bridge piers, etc.1
The wind energy
sector, in which tower construction has been practically monopolised by tapered tubular steel towers, is therefore an exception. Two main reasons help explain this singularity: the critical need for fast erection of towers, for which steel structures are very well suited, and the extremely high optimisation level of steel tower design and logistics. This optimisation has been achieved with the construction of many thousands of towers, which has resulted in a very cost-competitive solution. Steel tower tubes are formed from seam-welded rolled plates with no stiffeners and delicate but well-solved L-flange connections at terminations. The price per kilogram of erected steel of one such tower can be roughly one-third of the reference prices for other steel structures, such as bridges. This gives a good idea of the level of cost optimisation achieved. However, the erection speed and cost-efficiency of the conventional tubular steel tower solution are very dependant on the inland transportation of complete tubes to the site. This limits the maximum tower diameter2
4.3m and dramatically constrains the capacity of this concept to keep up with the global market trend towards higher and larger wind turbines, which allow for a lower cost of energy.
Alternative Concepts
Practically all existing wind turbines with >100m hub height and rated power above 2–3Mw have used a modified tower solution. Moreover, the main turbine manufacturers have all launched strategic platforms to find and test new industrially feasible tower concepts. These
José Serna is Managing Director of Esteyco Energía, a company which provides advanced engineering services related to infrastructures in the energy sector, with a 15-year track record in wind energy. He has worked and directed projects and consultancy services for over 100 wind farms worldwide, with particular focus on geotechnical and structural engineering. In particular, he has been responsible for the research and design engineering teams behind the Inneo
Torres precast concrete towers, a proven concept for higher performance towers which has been pioneer worldwide. He has written papers and held conferences on the matter in several congresses and post-graduate courses. He received an MSc in Civil Engineering, and he has worked in the design and construction of all types of building and civil structures. Mr Serna’s book Los Puentes del Tren (Bridges for the Railway) was published in 2006.
E:
jserna@esteyco.es
Jorge Jimeno is Head of Sales and on the Board of Directors of Inneo Torres, which is a company that manufactures precast concrete towers for multimegawatt wind turbines. He has over 10 years of experience in the precast concrete sector, focusing on the development of systems to industrialise precast large concrete pieces.
E:
jorgejimeno@inneo.es
concepts need to take towers to the next level in terms of hub height and support capacity for the present and future multimegawatt turbine developments. Precast concrete towers have already proved to be one such concept. Although initially developed to reach where conventional tubular steel towers could not, precast concrete towers have turned out to be a profitable option for conventional turbines and hub heights. This is particularly true in rapidly emerging markets where the infrastructure for steel tower manufacturing and transportation is more limited. Here the potential advantages for close-to-site mobile manufacturing of concrete elements become increasingly beneficial.
Many of the main turbine manufacturers have already taken steps in their search for tower concepts that can overcome the transport- related diameter constraints related to conventional tubular steel towers. Truss steel towers for hub heights well over 100m have, for instance, been used by Nordex or Fuhrländer.3
However, the erection to roughly
times, visual appearance and need for maintenance of truss tower concepts have restrained their use. Different applications of concrete to provide higher and more capable towers have been used for several years by many manufacturers. General Electric, Nordex, WinWinD and Alstom-Ecotecnia have all used hybrid towers with in situ concrete tower bases of different heights combined with steel tubes for the upper part of the tower. These positive experiences have, however, been limited to prototypes or small-scale projects. Although adequate from a technical point of view, in situ concrete solutions imply a lot of qualified labour on site and require very long and weather-dependant construction times. This prevents in situ construction from becoming viable as an industrial solution for full-scale tower production. On the other hand, well-conceived precast concrete solutions can provide the structural capacity of large-diameter concrete towers together with industrial manufacturing and high-speed tower erection. Gamesa, Siemens and WinWinD have all recently installed testing prototypes using precast concrete technology for increased hub height towers carrying large multimegawatt turbines.
Two turbine manufacturers – Acciona Windpower and Enercon – have progressed furthest with the use of precast concrete towers. The Inneo Torres tower concept used by Acciona Windpower, with the first prototype built in February 2006, has a track-record of nearly 100 towers. Enercon’s concept leads the way with many hundreds of operating precast concrete towers,4
world at the time of publication, with a rated power of 7Mw.5
including the largest turbine in the Both
(Enercon and INNEO) are the only two technologies used for large industrial projects (see Figure 2). Enercon use smaller pieces than INNEO (also precast concrete pieces).
Main Challenges
The extensive existing experience with all types of high-rise concrete structures is of course valuable and proves the suitability and versatility
52 © TOUCH BRIEFINGS 2010
Wind
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124