Redesign of an upwind rotor for a downwind configuration: design changes and cost evaluation

Abstract

Abstract. Within this work, an existing model of a Suzlon S111 2.1 MW turbine is used to estimate potential cost savings when the conventional upwind rotor concept is changed into a downwind rotor concept. A design framework is used to get realistic design updates for the upwind configuration, as well as two design updates for the downwind configuration, including a pure material cost out of the rotor blades and a new planform design. A full design load basis according to the standard has been used to evaluate the impact of the redesigns on the loads. A detailed cost model with load scaling is used to estimate the impact of the design changes on the turbine costs and the cost of energy. It is shown that generally lower blade mass of up to 5 % less than the upwind redesign can be achieved with the downwind configurations. Compared to an upwind baseline, the upwind redesign shows an estimated cost of energy reduction of 2.3 %, and the downwind designs achieve a maximum reduction of 1.3 %.

Multidisciplinary aeroelastic optimization of a 10MW-scale wind turbine rotor targeting to reduced LCoE

“…The current trend in the design of modern wind turbines is to apply integrated aeroelastic optimization methods [1], which consider both the aerodynamic performance of the rotor and the structural characteristics of the system components within the same optimization loop. They are aiming at the simultaneous design of the aerodynamic shape and the inner structure of the blades as well as of all other load carrying components, using as objective function of the optimization process specific cost parameters [2], [3] or more recently even the overall levelized cost of electricity (LCoE) [4]. In the present paper, an upgraded version of the thin-walled method presented in [5] is combined with an inhouse, state-of-the-art, hydro-servo-aero-elastic design and analysis tool for wind turbines [6], within a multi-disciplinary optimization framework based on publicly available Python libraries.…”

Comparison of 25 MW downwind and upwind turbine designs with individual pitch control

“…Downwind blades bend away from the tower under load, offering cost-savings by allowing lighter, flexible blades due to eased tower clearance constraints; however, they also pose several challenges limiting their wide-scale adoption. Their rotor-swept area contracts under aerodynamic loading, reducing power production [2,3]. Additionally, downwind turbine towers endure higher fore-aft bending moments from the combined effect of the rotor thrust and the gravitational loading due to rotornacelle-assembly (RNA) center of mass, prompting the need for heavier towers or non-trivial RNA redesign to reduce tower cost [4].…”

Influence of tower shadow on downwind flexible rotors: Field tests and simulations

“…Downwind turbine designers should generally consider three critical issues: Aerodynamic performance and rotor mass: Downwind turbines (compared to upwind turbines) tend to have lower rotor masses due to flapwise load alignment but can have a reduction in annual energy production due to a decreased swept area caused by downwind aeroelastic deflections 5,6 Low‐frequency noise: Downwind turbines have been known to emit a low‐frequency “thumping” noise that is louder than upwind turbines 7 ; this can be an important issue for onshore wind farms (but may be less of an issue for offshore wind farms). Fatigue: Increased structural fatigue for downwind turbines due to tower shadow has been identified as a potential issue that should be considered in structural design, 5 but it is unclear if the current wake deficit models for tower shadow can capture the unsteady blade load impact for field conditions. There has been little experimental data to analyze the tower shadow effect on downwind turbines. Previously, the only publicly available data set from a downwind turbine field test was from the Unsteady Aerodynamics Experiment (UAE) turbine developed and tested by the National Renewable Energy Laboratory (NREL).…”

“…Aerodynamic performance and rotor mass: Downwind turbines (compared to upwind turbines) tend to have lower rotor masses due to flapwise load alignment but can have a reduction in annual energy production due to a decreased swept area caused by downwind aeroelastic deflections. 5,6 2. Low-frequency noise: Downwind turbines have been known to emit a low-frequency "thumping" noise that is louder than upwind turbines 7 ; this can be an important issue for onshore wind farms (but may be less of an issue for offshore wind farms).…”

“…3. Fatigue: Increased structural fatigue for downwind turbines due to tower shadow has been identified as a potential issue that should be considered in structural design, 5 but it is unclear if the current wake deficit models for tower shadow can capture the unsteady blade load impact for field conditions.…”