Abstract
Wind energy is a vital resource for meeting international climate change targets. A key industry challenge is integrating wind power plants within the electrical grid, especially as we move towards a more renewable energy mix. Supplement to this challenge, however, is developing new turbine technologies that produce cheaper energy across a range of geographical and economic climates. Multi-disciplinary optimisation (MDO) methods enable improvements in turbine technology because they can provide rapid and insightful concept evaluations, leading to innovative inter-disciplinary synergies.A promising research field for wind turbines is aeroelastic tailoring. By embedding directional stiffness in the blades, e.g. bend-twist coupling, reductions in levelised cost of energy (LCoE) can be made through a synergistic balancing of loads, sizing costs, and power production. Aeroelastic tailoring is a prime candidate for MDO. However, the potential LCoE-benefits, and the mechanisms by which they are made, remain crudely understood. Thus, the aim of this PhD is threefold:
1) To develop an MDO framework, suitable for aero-servo-elastic tailoring of a next-generation wind turbine platform (20 MW);
2) To discern and illustrate the mechanisms by which LCoE improvements are made. Due to its large effect on cost and power, blade length is fixed for these optimisation studies;
3) To quantify the maximum LCoE improvements available by expanding the design space to include blade length and aeroelastic tailoring techniques.
To meet the aforementioned aims, various methods have been developed within the tool known as ATOM (Aeroelastic Turbine Optimisation Methods). These methods are united in a monolithic optimisation architecture which, through its collective properties, represents a step forward in the scope of wind turbine MDO. The architecture performs turbulent simulations at every design evaluation, enabling the optimiser to utilise realistic design synergies. Load envelopes from these simulations enable a uniquely comprehensive set of constraints to be enforced, including strength, buckling, fatigue, tower clearance, and aeroelastic stability. Additional contributions of note include validation studies and novel methods to improve optimisation performance with turbulent simulations.
Optimisation results demonstrate successful sizing of aerodynamic, structural and operational parameters. Mass-competitive 20 MW blade designs are attained (71-79 tonnes), displaying favorable LCoE reductions (-2.3% relative to the reference turbine). The fixed-length studies offer insight into numerous mechanisms by which energy gains, load reductions, and cost reductions are made. A central theme displayed is the preference for a strong bend-twist coupled response, induced by a novel combination of spar cap location and distance from the leading edge to the pitch axis. Lastly, studies with fibre rotations and sweep show similar LCoE improvements but their uptake is limited, possibly due to local optima or drawbacks such as stiffness knockdowns and torsional load increases.
| Date of Award | 25 Jan 2021 |
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| Original language | English |
| Awarding Institution |
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| Sponsors | Offshore Renewable Energy Catapult |
| Supervisor | Terence Macquart (Supervisor), Alberto Pirrera (Supervisor), Paul M Weaver (Supervisor) & Peter Greaves (Supervisor) |