Design and analysis of small scale wind turbine support structures

[摘要] ENGLISH ABSTRACT:A technology that has advanced immeasurably as a result of the necessity for green energy production is theharnessing of wind energy. One of the most important aspects of a wind turbine is its supporting structure.The tower of a wind turbine needs to be sufficiently reliable and structurally sound to ensure that the designlife of the wind turbine machine is unaffected. The tower also needs to be of the correct height to ensure thatthe full potential of energy capture is realised.The supporting structure of a wind turbine constitutes up to as much as 30% of the total costs of a windturbine. The most common wind turbine supporting structures seen worldwide today are Steel MonopoleTowers. The large cost proportion of the tower compels the industry to investigate the most feasiblealternative supporting tower structures and thus prompted the research developed in this thesis. In this thesisthe focus is on small scale wind turbines (<50kW), more specifically, a 3kW Wind Turbine. The proposedalternative design the support structures of small scale wind turbines to the presently used Steel Monopoletower was a Steel Lattice tower.Both a Steel Lattice and Steel Monopole Tower was designed for a 3kW Wind Turbine using rational designmethods determined from pertinent sections of the South African design codes. The Tower designs needed toincorporate the details of the element connections, so as to encompass all of the cost parameters accurately.The foundation design of each of the towers was also required from the point of view of cost analysiscompleteness, and ended up playing a critical role in the feasibility analysis.To validate the design methods, the two towers were modelled in the finite element package Strand7 and anumber of different analyses were performed on the two towers. The analyses included linear static, nonlinearstatic, natural frequency and harmonic frequency analyses. The towers were assessed for a number ofdifferent load case combinations and were examined in terms of stress states, mass participation factors anddeflections, to mention a few, for the worst loading combination cases that were encountered.Once a final design was reached for both the Steel Lattice and Steel Monopole Towers, each element fromwhich they were made was assessed from a structural viewpoint to determine manufacturing and constructioncosts.The cost analysis was conducted by means of asking a number of leading construction companies for unitprices for each of the identified elements to be assessed.The fabrication and construction of each of the Towers was then compared to determine which one was morefeasible, in terms of each design aspect considered as well as looking at the complete end product.It was found that the Steel Lattice Tower was more feasible from the points of view of fabrication, andconstruction, as well as having a far more cost effective foundation. This was a positive conclusion from theperspective of the proposal for a more feasible alternative to the presently used Steel Monopole Towers.The outcome of the research conducted here could certainly prove to be worth considering from a wind farmdevelopment perspective, with particular focus on the up and coming Wind Industry developments in SouthAfrica.

[发布机构] Stellenbosch University