Browsing by Author "De Kock, Conrad Jeanne"

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    Loading, modelling and costing of concrete and steel support structure designs : large wind turbines in South Africa
    (Stellenbosch : Stellenbosch University, 2015-12) De Kock, Conrad Jeanne; Van der Klashorst, Etienne; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    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. A modern wind turbine has a horizontal axis orientation, three rotor blades, active pitch and face into the wind using yaw control. It has a steel monopole tower between 60m and 80m high with a reinforced concrete foundation. However, this design presents various problems for structural integrity, manufacturing and viability at heights above 80m. These constraints has led to a movement towards steel-concrete hybrid and full concrete towers. Such designs present an alternative and possibly more optimal solution for tower heights over 100 m. This hypothesis was tested for South African conditions. Steel and prestressed concrete tower designs were acquired for a 3MW reference wind turbine with 100m hub height. Towers were loaded according to local conditions and the structural soundness thereof was tested and proved. Structural parameters were optimized and material mass and volume were determined for each. A cost estimation and sensitivity analysis was performed for 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 considered competitive alternatives at 100m in height. The cast-in-place prestressed concrete design was estimated to be the most affordable solution. However, its high sensitivity to variation 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 a larger foundation size it still remained a competitive alternative to the concrete towers. Overall the prestressed precast design was the most expensive. However, for high erection costs it was more affordable than the cast-in-place tower. For disposal and recycling the steel solution was a much more favourable financial alternative to the concrete design. However, salvage income does not contribute a significant gain compared to overall cost.