Wind Turbine Design: Multi‐Objective Optimization

Within the last 20 years, wind turbines have reached matured and the growing worldwide wind energy market will allow further improvements. In the recent decades, the numbers of research papers that have applied optimization techniques in the attempt to obtain an optimal design have increased. The main target of manufacturers has been to minimize the cost of energy of wind turbines in order to compete with fossil‐fuel sources. Therefore, it has been argued that it is more stimulating to evaluate the wind turbine design as an optimization problem consisting of more than one objective. Using multi‐objective optimization algorithms, the designers are able to identify a trade‐off curve called Pareto front that reveals the weaknesses, anomalies and rewards of certain targets. In this chapter, we present the fundamental principles of multi‐objective optimization in wind turbine design and solve a classic multi‐objective wind turbine optimization problem using a genetic algorithm

OPTIMAL DESIGN AND STRESS/STRAIN ANALYSIS OF WIND TURBINE BLADE FOR OPTIMUM PERFORMANCE IN ENERGY GENERATION VIA SIMULATION APPROACH

The blade is a significant part of a wind turbine, due to its role in the conversion process of the wind energy into mechanical energy. The blade during operation is being acted upon by different forces and pressures on high humidity, which gives rise to a high rate of failure of the blade. There is a great need to study these forces and constraints on the design shape of the material blade via a simulation approach. This research focusses on the optimal design and stress/strain analysis of a wind turbine blade for sustainable power generation. This is to enable the manufacturer and end-users of the wind turbine blade to understand how the blade material withstand the forces and pressures acting on the blade during operation in the form of displacement, stress, and strain in high humidity. The design and simulation software employed in this study is Solid Works Visualize 2018. The wind turbine blade is made of AL6061 alloy material. The blade is simulated under two forces, 1 N and 5 N, with the pressure at zero degree. The result from this analysis shows the maximum stress that causes the blade to experience failure during operation, and this failure occurs at 285.377 N/m^2 and 1426.83 N/m^2, respectively. The result from the simulation analysis shows the specific area were the deformation process, and possible failure will occur on the blades. This paper also gives reasonable suggestion for reinforcement of the wind blade during the maintainer's section, which can be applied to achieve optimum performance of the wind turbine blade

Intelligent approach on sensorless control of permanent magnet synchronous generator

In this paper, a standalone permanent magnet synchronous generator (PMSG) system is designed to generate power at maximum power point (MPP). The variable speed operation of wind energy conversion system consists of PMSG, controlled rectifier and voltage source inverter co to the load. Proportional integral (PI), sliding mode (SM), and feed forward neural network (FFNN) control strategies are applied in field oriented control (FOC) at generator side converter. A comparative study on power generated at maximum power point (MPP) is done with these controllers using simulation. Hill climb search (HCS) method is applied to attain MPP. Load side inverter control strategy involves the PI and SM controllers in order to maintain the unity power factor and to control the active and reactive power for nonlinear load. The control strategies are modelled and simulated with MATLAB/Simulink. The effectiveness of proposed control method is demonstrated using simulation results

Design and economic analysis of a hydrokinetic turbine for household applications

Social and political concerns on climate change have made renewable energy an essential component of government's work plans. Grid-connected horizontal-axis hydrokinetic turbines are promising eco-friendly power sources for electrical energy supply to households near middle-to-high discharge rivers, while providing an opportunity to sell the energy surplus. In this work, a rotor design analysis of a hydrokinetic turbine with a 1 m nominal radius is performed based on blade element momentum theory. Then, an economic analysis is presented in terms of the discounted payback period and the internal rate of return. The numerical results show that three-bladed hydrokinetic turbines with a nominal tip speed ratio of 5 and state-of-the art high lift-to-drag ratio hydrofoils (∼100) lead to maximum performance with a power coefficient around 0.45. Performance can be further improved in an affordable manner using diffuser-augmented hydrokinetic turbines. The use of hydrokinetic energy in household applications can be profitable in leading economic countries with a discounted payback period of 4-6 years. In energy developing countries, this technological solution can be cost effective accompanied by economic subsides and implementation of a local industry, resulting in similar payback periods.This work was supported by projects PID2019-106740RB-I00 and EIN2020-112247 of the Spanish Agencia Estatal de Investigación . Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022)

The impact of pitch-to-stall and pitch-to-feather control on the structural loads and the pitch mechanism of a wind turbine

This article investigates the impact of the pitch-to-stall and pitch-to-feather control concepts on horizontal axis wind turbines (HAWTs) with different blade designs. Pitch-to-feather control is widely used to limit the power output of wind turbines in high wind speed conditions. However, stall control has not been taken forward in the industry because of the low predictability of stalled rotor aerodynamics. Despite this drawback, this article investigates the possible advantages of this control concept when compared to pitch-to-feather control with an emphasis on the control performance and its impact on the pitch mechanism and structural loads. In this study, three HAWTs with different blade designs, i.e., untwisted, stall-regulated, and pitch-regulated blades, are investigated. The control system is validated in both uniform and turbulent wind speed. The results show that pitch-to-stall control enhances the constant power control for wind turbines with untwisted and stall-regulated blade designs. Stall control alleviates the fore-aft tower loading and the blades flapwise moment of the wind turbine with stall-regulated blades in uniform winds. However, in turbulent winds, the flapwise moment increases to a certain extent as compared to pitch-to-feather control. Moreover, pitch-to-stall control considerably reduces the summed blade pitch movement, despite that it increases the risk of surface damage in the rolling bearings due to oscillating movements with a small amplitude

Modeling the induction, thrust, and power of a yaw misaligned actuator disk

Collective wind farm flow control, where wind turbines are operated in an individually suboptimal strategy to benefit the aggregate farm, has demonstrated potential to reduce wake interactions and increase farm energy production. However, existing wake models used for flow control often estimate the thrust and power of yaw misaligned turbines using simplified empirical expressions which require expensive calibration data and do not accurately extrapolate between turbine models. The thrust, wake velocity deficit, wake deflection, and power of a yawed wind turbine depend on its induced velocity. Here, we extend classical one-dimensional momentum theory to model the induction of a yaw misaligned actuator disk. Analytical expressions for the induction, thrust, initial wake velocities, and power are developed as a function of the yaw angle and thrust coefficient. The analytical model is validated against large eddy simulations of a yawed actuator disk. Because the induction depends on the yaw and thrust coefficient, the power generated by a yawed actuator disk will always be greater than a $\cos^3(\gamma)$ model suggests, where $\gamma$ is yaw. The power lost by yaw depends on the thrust coefficient. An analytical expression for the thrust coefficient that maximizes power, depending on the yaw, is developed and validated. Finally, using the developed induction model as an initial condition for a turbulent far-wake model, we demonstrate how combining wake steering and thrust (induction) control can increase array power, compared to either independent steering or induction control, due to the joint dependence of the induction on the thrust coefficient and yaw angle.Comment: 22 pages, 9 figure

Implementation of multi-criteria decision method for selection of suitable material for development of horizontal wind turbine blade for sustainable energy generation

The material selection process for producing a horizontal axis wind turbine blade for sustainable energy generation is a vital issue when using Nigeria as a case study. Due to the challenge faced with the low wind speed variations. However, this paper focuses on implementing MCDM for the material selection process for a suitable material for developing a horizontal wind turbine blade. This paper used a quantitative research approach using AHP and TOPSIS multi-criteria decision method. The study put into consideration the environmental conditions for the material selection process when designing the questionnaire. The authors extracted the data used for the selection process from the 130 research questionnaire distributed to materials engineers and renewable energy professionals. This research considered four alternatives that is, aluminum alloy, stainless steel, glass fiber, and mild steel to determine the best material for the wind turbine blade. Also, the model has four criteria and eight sub-criteria used for developing the pair-wise matrix and the performance score used for the ranking process of the alternatives. The result shows that a consistency index of 0.056 and a consistency ratio of 0.062 gotten via the AHP method is workable for material selection practice. 78%, 43%, 67%, and 25% are the performance scores for the four alternatives via the TOPSIS techniques. In conclusion, aluminum alloy is the best material, followed by glass fibre. Therefore, the decision-makers recommended aluminum alloy; hence, manufacturers should apply aluminum alloy to develop the wind turbine blade for sustainable energy generation

Wind tunnel study on power output and yaw moments for two yaw-controlled model wind turbines

In this experimental wind tunnel study the effects of intentional yaw misalignment on the power production and loads of a downstream turbine are investigated for full and partial wake overlap. Power, thrust force and yaw moment are measured on both the upstream and downstream turbine. The influence of inflow turbulence level and streamwise turbine separation distance are analyzed for full wake overlap. For partial wake overlap the concept of downstream turbine yawing for yaw moment mitigation is examined for different lateral offset positions.Results indicate that upstream turbine yaw misalignment is able to increase the combined power production of the two turbines for both partial and full wake overlap. For aligned turbine setups the combined power is increased between 3.5&thinsp;% and 11&thinsp;% depending on the inflow turbulence level and turbine separation distance. The increase in combined power is at the expense of increased yaw moments on both the upstream and downstream turbine. For partial wake overlap, yaw moments on the downstream turbine can be mitigated through upstream turbine yawing. Simultaneously, the combined power output of the turbine array is increased. A final test case demonstrates benefits for power and loads through downstream turbine yawing in partial wake overlap. Yaw moments can be decreased and the power increased by intentionally yawing the downstream turbine in the opposite direction.</p

Hydrodynamic performance optimization of semi-submersible floaters for offshore wind turbines

Floating structures have become viable alternatives for supporting wind turbines as offshore wind projects move deeper into the water. The wind is prevalent in deep water (depths > 60 m) all around the world. Because of the amount of potential at these depths, wind turbines will require the design of a floating platform, as current wind turbines are usually fixed at the bottom and rely on ordinary concrete with a gravity base, which is not practical at these depths. Floating offshore wind offers a huge potential for green energy production offshore and the overall energy transition to zero carbon emission in general. With the development of even larger wind turbines in the range beyond 15 MW, the floating concepts become more attractive and competitive from a cost perspective. However, larger turbines and cost optimization also require a re-thinking of established solutions and concepts. New ideas and innovations are required to optimize floating offshore wind farms further. An approach for the optimization of semi-submersible floaters using different surrogate models has been developed in this thesis. A semi-submersible floater is selected and designed to support a 15-MW wind turbine in the North Sea. The optimization framework consists of automatic modeling and numerical simulations in open-source tools as well as obtaining the Pareto fronts using surrogate models and the Genetic Algorithm in CEASES software. A Python-SALOME-NEMOH interface is used to obtain the hydrodynamic properties for geometries defined by various variables. The geometries are subjected to three performance constraints: the static platform pitch, metacentric height, nacelle acceleration, and wind. Loads in operating and parked conditions are considered. Finally, the geometries are optimized using two objective functions related to material cost and nacelle acceleration, and the results are discussed. This work contributes to developing efficient design optimization methods for floating structures

Simulating the Effects of Floating Platforms, Tilted Rotors, and Breaking Waves for Offshore Wind Turbines

Offshore wind energy is a rapidly expanding source of renewable energy worldwide, but many aspects of offshore wind turbine behavior are still poorly understood and are not accurately captured by low-cost engineering models used in the design process. To help improve these models, computational fluid dynamics (CFD) can provide valuable insight into the complex fluid flows that affect offshore wind turbine power generation and structural loads. This research uses CFD simulations to examine three main topics important to future offshore wind development: how breaking waves affect structural loads for fixed-bottom wind turbines; how platform motions affect power generation, wake characteristics, and downwind turbine behavior in floating wind turbines; and how rotor tilt angles affect wake characteristics when interacting with earth\u27s surface. These high-fidelity simulations can help inform future improvements to engineering models like wake models, power prediction models, and breaking wave models, which are integral to designing and financing both offshore turbines and offshore wind farm arrays. First, breaking wave limits and slam force models are evaluated using CFD simulations of shoaling and breaking waves impacting monopile foundations, for environmental conditions representative of U.S. East Coast offshore wind sites. Second, floating turbine wakes are characterized by the velocity deficit, turbulent kinetic energy, and wake centerline location using large eddy simulations (LES) coupled via an actuator line model to the multidynamics turbine modeling tool OpenFAST. These wake metrics are compared for different floating platform types, atmospheric stability types, and environmental conditions. Third, the power generation of spar and semisubmersible floating turbines is simulated using OpenFAST with LES inflow, with different platform motions isolated. These power results inform a new analytical model for power generation in floating turbines. Fourth, downwind turbines with different platforms are simulated in OpenFAST using an upwind floating turbine\u27s LES wake as inflow, to study how floating-turbine wakes affect a downwind turbine\u27s power, blade loads, and towertop displacements. Finally, LES with an actuator disk model of a tilted wind turbine are performed for different tilt angles and blade-to-surface gaps, to characterize tilted rotor wakes and how they interact with the sea or ground surface