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Research articles 04 Oct 2018

Research articles | 04 Oct 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).

Comparison between upwind and downwind designs of a 10 MW wind turbine rotor

Pietro Bortolotti, Abinhav Kapila, and Carlo L. Bottasso Pietro Bortolotti et al.
  • Wind Energy Institute, Technische Universität München, D-85748 Garching, Germany

Abstract. The size of wind turbines has been steadily growing in the pursuit of a lower cost of energy by an increased wind capture. In this trend, the vast majority of wind turbine rotors has been designed based on the conventional three-bladed upwind concept. This paper aims at assessing the optimality of this configuration with respect to a three-bladed downwind design, with and without an actively controlled variable coning used to reduce the cantilever loading of the blades. A 10MW wind turbine is used for the comparison of the various design solutions, which are obtained by an automated comprehensive aerostructural design tool. Results show that, for this turbine size, downwind rotors lead to blade mass and cost reductions of 6% and 2%, respectively, compared to equivalent upwind configurations. Due to a more favorable rotor attitude, the annual energy production of downwind rotors may also slightly increase in complex terrain conditions characterized by a wind upflow, leading to an overall reduction in the cost of energy. However, in more standard operating conditions, upwind rotors return the lowest cost of energy. Finally, active coning is effective in alleviating loads by reducing both blade mass and cost, but these potential benefits are negated by an increased system complexity and reduced energy production. In summary, a conventional design appears difficult to beat even at these turbine sizes, although a downwind non-aligned configuration might result in an interesting alternative.

Pietro Bortolotti et al.
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Pietro Bortolotti et al.
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Short summary
The paper compares upwind and downwind three-bladed configurations for a 10 MW wind turbine in terms of power and loads. For the downwind case, the study considers also a load-aligned solution with active coning. Results indicate that downwind solutions are slightly more advantageous than upwind ones, although improvements are small. Additionally, pre-alignment is difficult to achieve in practice, and active coning solution is associated with very significant engineering challenges.
The paper compares upwind and downwind three-bladed configurations for a 10 MW wind turbine in...