12 research outputs found
Organic field-effect based sensors for body parameters monitoring
No full textIn this paper we propose totally flexible organic field effect transistors (OFETs) assembled on plastic films as sensors for physiological parameters monitoring. In the first part, mechanical sensors for pressure and bending detection are presented and some biomedical sensing applications are illustrated. A sharp and reversible sensitivity of the output current of the device to an elastic deformation induced by means of a mechanical stimulus on the device channel is observed. In the second part, the possibility of using similar devices for bio- and chemo-detection is described. By exploiting the properties of the basic structure, the device can be combined with any kind of substrate to detect for instance the 3D bending of a flexible surface and/or for detecting pH of sweat. Robot skin and wearable electronics seem to be promising applications for this emerging technology
A Comparative Study to Assess the Accuracy of the Lifting Line Code AWSM for Simulating Winglets on Wind Turbines
No full textWind turbine power output has grown massively over the past few decades, and this has been achieved in part by increasing the size of rotors. But the size of rotors is now limited by structural constraints as well as space constraints in wind farms. It is therefore important to use other innovative methods to increase wind turbine capacity without increasing size. One way to achieve this is by the use of winglets. Winglets increase power output by reducing tip effects, thereby producing a more efficient distribution of forces over the blade. The art of designing winglets is to find the best trade-off between the increase in profile drag of the winglet itself and the reduction of induced drag that the winglet provides. To do this, it is very important to fully understand the aerodynamics of winglets on wind turbine blades.High-fidelity methods like CFD are capable of producing accurate and detailed flow fields and are able to offer greater insight into the complex aerodynamics of winglets on rotors. However, this comes at great computational cost which might be infeasible in the design and optimization of winglets. More common and cheaper models like the BEM method are incapable of modelling winglets and other out-of-plane features. The Lifting Line Method is a middle ground that is capable of simulating winglets but is also comparatively inexpensive. The goal of this thesis is to study the performance of the Lifting Line method, in particular, ECN Aeromodule's AWSM Free-Wake Vortex Lifting Line code in simulating the case of winglets mounted on wind turbines. AWSM results are compared with results of normal and tangential forces and circulation distribution from a validated OpenFOAM model. The results show that over the outboard section of the blade and over the span of the winglet, AWSM performs well in predicting the performance of the blade-winglet configuration. This study shows that AWSM is a reliable tool for the design and optimization of winglets on wind turbine blades at a much lower cost than higher fidelity methods like CFD.Aerospace Engineerin
Offshore Airborne Wind Energy TKI Sea-Air-Farm Aerodynamic Performance, Installation and Operation and Maintenance
No full textAuthor Correction: Cross sectional evaluation of the gut-microbiome metabolome axis in an Italian cohort of IBD patients
No full textCorrection to: Scientific Reports https://doi.org/10.1038/s41598-017-10034-5, published online 25 August 2017
Integrated design of a semi-submersible floating vertical axis wind turbine (VAWT) with active blade pitch control
No full textA semi-submersible Tri-Floater has been designed to support a 6 MW vertical axis wind turbine (VAWT) with active blade pitch control. Due to the low centre of gravity and large allowable floater tilt angle, a relatively small floater can be used to support a VAWT. Coupled simulations including hydrodynamics, mooring system, aerodynamics and control system have been performed to analyse the strongly coupled dynamics of floater and wind turbine. Software tools have been developed or upgraded to enable these simulations. Based on typical extreme operational and survival design load cases, it is illustrated that the active blade pitch control system can be successfully used to minimize the governing loads on the floater. Whereas for a VAWT with fixed blades, the parked survival conditions are typically design driving for the floating support structure, this is not the case if blade pitch control is applied. It is concluded that, compared to a horizontal axis wind turbine (HAWT) with the same rated power, a 20 percent lighter floater can be used as support structure for the VAWT with active blade pitch control.Wind Energ
Vortex-model-based Multi-objective Optimization of Winglets for Wind Turbines using Machine Learning
No full textIn order to reduce the levelised cost of energy, the rotors of wind turbines are increasing in size. To increase the energy yield, wind turbine rotors need to have an innovative tip design; such as winglets. Winglets are used widely in aircraft design; however, they remain mostly absent in state-of-the-art wind turbine design. The low-fidelity wind turbine design models used by industry, such as BEM, are insufficient to capture the full 3D flow physics in such an innovative design. Therefore, high-fidelity methods, such as vortex methods, are becoming more and more important in such a design phase in wind energy research. Single-objective optimisation has been applied in earlier works to maximise power production. Winglets have shown the potential of increasing power production while simultaneously increasing the design-driving loads (DDLs), for example, the thrust or flapwise bending moment. This work focuses on optimisation using machine learning of a winglet that increases power production without increasing DDLs. A parameterised design for a winglet on a wind turbine is created. Different design constraints, such as DDLs or a diameter constraint, are explored to determine under which constraints and conditions a winglet can have an added value to the wind turbine blade design. Multi-objective Bayesian optimisation is used to maximise the rotor's power production and minimise DDLs. Surrogate models, created using machine learning techniques such as Gaussian Processes and Bayesian Neural Networks, are used in combination with an acquisition function, to determine what designs should be evaluated by the lifting line model AWSM. This has the goal to obtain designs that lie on the Pareto front of two or more objectives. The recent Bayesian Neural Networks were able to find the Pareto front most effectively in this work. Furthermore, the results show that different DDL constraints led to different winglet designs, with noticeable differences between upwind and downwind winglet designs obtained by the optimiser. Both a downwind and upwind winglet were found to be able to increase power without increasing the thrust, root flapwise bending moment and flapwise bending moment at 80% of the rotor radius.European Wind Energy Masters (EWEM
Vortex-model-based Multi-objective Optimization of Winglets for Wind Turbines using Machine Learning
No full textDifferent Design Driving Load constraints (DDLs), are explored in this work to determine under which constraints and conditions a winglet can have an added value to the wind turbine blade design. Multi-objective Bayesian optimization is used to maximize the rotor's power production while minimizing the flapwise DDLs. Surrogate models, created using machine learning techniques such as Gaussian Processes and Bayesian Neural Networks, are used in combination with an acquisition function, to determine what designs should be evaluated by the lifting line model AWSM, with the goal to obtain designs that lie on the Pareto front of two or more objectives. The recent Bayesian Neural Networks as surrogate model were able to find the Pareto-front most effectively in this work. Furthermore, the results show that different DDL constraints led to different winglet designs, with noticeable differences between upwind and downwind winglet designs. Winglet designs were found to be able to increase power without increasing the thrust, root flapwise bending moment and flapwise bending moment at radial locations on the blade. A noticeable increase in power was found when introducing sweep to the winglet design. Aerospace EngineeringWind Energ
A probabilistic rainfall model to estimate the leading-edge lifetime of wind turbine blade coating system
No full textRain-induced leading-edge erosion of wind turbine blades is associated with high repair and maintenance costs. For efficient operation and maintenance, erosion models are required that provide estimates of blade coating lifetime at a real scale. In this study, a statistical rainfall model is established that describes probabilistic distributions of rain parameters that are critical for site-specific leading-edge erosion assessment. A new droplet size distribution (DSD) is determined based on two years’ onshore rainfall data of an inland site in the Netherlands and the obtained DSD is compared with those from the literature. Joint probability distribution functions of rain intensities and droplet sizes are also established for this site as well as for a coastal site in the Netherlands. Then, the application of the proposed model is presented for a 5 MW wind turbine, where the model is combined with wind statistics along with an analytical surface fatigue model that describes lab-scale coating degradation. The expected lifetime of the blade coating is found three to four times less for the wind turbine operating at the coastal site than for the inland site - primarily due to rainfall at higher wind speeds. Further, the robustness of the proposed model is found consistent with varying data periods used for the analyses.</p
A probabilistic long-term framework for site-specific erosion analysis of wind turbine blades: A case study of 31 Dutch sites
No full textRain-induced leading-edge erosion (LEE) of wind turbine blades (WTBs) is associated with high repair and maintenance costs. The effects of LEE can be triggered in less than 1 to 2 years for some wind turbine sites, whereas it may take several years for others. In addition, the growth of erosion may also differ for different blades and turbines operating at the same site. Hence, LEE is a site- and turbine-specific problem. In this paper, we propose a probabilistic long-term framework for assessing site-specific lifetime of a WTB coating system. Case studies are presented for 1.5 and 10 MW wind turbines, where geographic bubble charts for the leading-edge lifetime and number of repairs expected over the blade's service life are established for 31 sites in the Netherlands. The proposed framework efficiently captures the effects of spatial and orographic features of the sites and wind turbine specifications on LEE calculations. For instance, the erosion is highest at the coastal sites and for sites located at higher altitudes. In addition, erosion is faster for turbines associated with higher tip speeds, and the effects are critical for such sites where the exceedance probability for rated wind conditions are high. The study will aid in the development of efficient operation and maintenance strategies for wind farms.Aerospace Manufacturing TechnologiesAerospace Structures & Computational Mechanic
