Loading, modelling and costing of concrete and steel support structure designs : large wind turbines in South Africa

[摘要] ENGLISH ABSTRACT: Wind energy has the potential to be a strong contributor to a more sustainable future.Globally it is a major player in the market and is expected to become more influential in the future. In South Africa the potential exists and major development is under way. Amodern wind turbine has a horizontal axis orientation, three rotor blades, active pitchand face into the wind using yaw control. It has a steel monopole tower between 60m and80m high with a reinforced concrete foundation. However, this design presents variousproblems for structural integrity, manufacturing and viability at heights above 80m.These constraints has led to a movement towards steel-concrete hybrid and full concretetowers. Such designs present an alternative and possibly more optimal solution for towerheights over 100 m.This hypothesis was tested for South African conditions. Steel and prestressed concretetower designs were acquired for a 3MW reference wind turbine with 100m hub height.Towers were loaded according to local conditions and the structural soundness thereofwas tested and proved. Structural parameters were optimized and material mass andvolume were determined for each. A cost estimation and sensitivity analysis was performedfor the following life-cycle phases: manufacture, construction and installation;transport; and disposal and recycling.Margins of cost between the tower designs were low enough for all three to be consideredcompetitive alternatives at 100m in height. The cast-in-place prestressed concretedesign was estimated to be the most affordable solution. However, its high sensitivity tovariation in erection cost causes uncertainty and a higher financial risk. Furthermore,the steel tower was the most viable for low steel prices and high erection costs. For alarger foundation size it still remained a competitive alternative to the concrete towers.Overall the prestressed precast design was the most expensive. However, for high erectioncosts it was more affordable than the cast-in-place tower. For disposal and recyclingthe steel solution was a much more favourable financial alternative to the concrete design.However, salvage income does not contribute a significant gain compared to overallcost.

[发布机构] Stellenbosch University