Development of an experimental methodology for appraising the dynamic response of tethered tidal turbines

This thesis makes a comparison of different station keeping structures to support tidal energy converters. It was observed that the use of flexibly tethered turbines would be beneficial due to low material costs and the capability to permit the turbine’s self alignment to the flow regime. However, because of the uncertainties over their dynamic behaviour, it was considered that an analysis of response in a range of conditions was essential before they could be considered as practical station keeping system. Firstly, a static analysis was carried out for both rigid and flexible foundations. Thereafter, the thesis presents the development of an experimental methodology to study the dynamic response of tethered tidal energy converters. In this methodology, the alignment and oscillations of the three main rotational angles (i.e. roll, pitch and yaw), estimated over a period of time, were taken as the fundamental metrics of system behaviour. The analysis was extended into the frequency domain in order to estimate the intensity of the parameters that affect the turbine and its condition (e.g. blade failure, excessive backlash or misalignment, vortex shedding, etc.) Within the methodology development a series of steps were specified, based on established protocols related to similar concepts (for example EquiMar) where parameters such as the selection of test facilities, blockage ratio limits or safety factors in applied loads were discussed. Instruments to measure the dynamic motion of turbines were specified, along with other instruments to measure power, thrust, angular velocity and flow speed. The final steps in the methodology denoted methods to analyse the acquired signals. In order to verify the feasibility of the methodology, a series of experiments were carried out at various turbine models scales. Firstly, small turbine models were installed on a zero turbulence tow tank and a flume tank with significant levels of turbulence, under controlled conditions and at similar flow velocities. To compare the dynamic responses, studies were undertaken for a larger turbine deployed in the natural turbulence of an open tidal site and in a turbulent river stream affected by marine traffic. This thesis concludes that the methodology proposed is suitable to characterise the dynamic response of tethered devices at various model scales. The results presented showed the advantages and disadvantages of using various turbine configurations. Therefore, this methodology can be used develop and validate analytical models that predict the dynamic response of flexibly moored turbines

MARE-WINT: New Materials and Reliability in Offshore Wind Turbine Technology

renewable; green; energy; environment; law; polic

Numerical Simulation of Wind Turbines

The book contains the research contributions belonging to the Special Issue "Numerical Simulation of Wind Turbines", published in 2020-2021. They consist of 15 original research papers and 1 editorial. Different topics are discussed, from innovative design solutions for large and small wind turbine to control, from advanced simulation techniques to noise prediction. The variety of methods used in the research contributions testifies the need for a holistic approach to the design and simulation of modern wind turbines and will be able to stimulate the interest of the wind energy community

Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems

The electrical power system is undergoing a revolution enabled by advances in telecommunications, computer hardware and software, measurement, metering systems, IoT, and power electronics. Furthermore, the increasing integration of intermittent renewable energy sources, energy storage devices, and electric vehicles and the drive for energy efficiency have pushed power systems to modernise and adopt new technologies. The resulting smart grid is characterised, in part, by a bi-directional flow of energy and information. The evolution of the power grid, as well as its interconnection with energy storage systems and renewable energy sources, has created new opportunities for optimising not only their techno-economic aspects at the planning stages but also their control and operation. However, new challenges emerge in the optimization of these systems due to their complexity and nonlinear dynamic behaviour as well as the uncertainties involved.This volume is a selection of 20 papers carefully made by the editors from the MDPI topic “Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems”, which was closed in April 2022. The selected papers address the above challenges and exemplify the significant benefits that optimisation and nonlinear control techniques can bring to modern power and energy systems

The aerodynamic control of the v-type vertical axis wind turbine

The V-type vertical axis wind turbine (V-VAWT) is of simple design and construction, has a low aerodynamic efficiency, yet its originators consider that it will be a cost effective configuration in electricity generation applications. However, the quality and reliability of its power output must be ensured; this necessarily requires continual control of rotor speed and power. The initial V-VAWT investigations of Sharpe and Taylor, and methods of wind turbine control are reviewed. Partial-span pitch angle variation is considered the most promising option, and the systematic investigation of this control method in V-VAWT applications is reported. This work includes the design, construction and performance testing of a small V-VAWT with pitching blade tips. The tests showed that rotor power can be regulated with small blade tip areas, however, correlation between the measured and theoretical results was not good. Wind tunnel test were undertaken to determine the characteristics of the NACA0025 aerofoil used for the model blades. Performance predictions using this data showed better correlation between experimental and- theoretical results. This has allowed the theoretical model to be used with confidence for predicting the performance of larger V-VAWTs with partial-span pitch control. A theoretical model of the dynamic behaviour of a V-VAWT generator integrated with an electricity supply network has been developed and embodied in the computer program DYNVAWT. This program has allowed the dynamic behaviour of a 5kW sized V-VAWT to be simulated, and an active control strategy developed. The simulation studies show that active partial-span pitch control ensures the quality and reliability of the electricity supply can be maintained even when the V-VAWT is operating in turbulent wind conditions

Control of a swept wing tailless aircraft through wing morphing

Inspired by flight in nature, work done by Lippisch, the Hortens, and Northrop offered insight to achieving the efficiency of bird flight with swept-wing tailless aircraft. Tailless designs must incorporate aerodynamic compromises for control, which have inhibited potential advantages. A morphing mechanism, capable of changing the twist of wing and that can also provide pitch, roll and yaw control for a tailless swept wing aircraft is the first step to a series of morphing techniques, which will lead to more fluid, bird-like flight. This research focuses on investigating the design of a morphing wing to improve the flight characteristics of swept wing Horten type tailless aircraft. Free flight demonstrators, wind tunnel flow visualization, wind-tunnel force and moment data along with CFD studies have been used to evaluate the stability, control and efficiency of a morphing swept wing tailless aircraft.;A wing morphing mechanism for the control of a swept wing tailless aircraft has been developed. This new control technique was experimentally and numerically compared to an existing elevon equipped tailless aircraft and has shown the potential for significant improvement in efficiency. The feasibility of this mechanism was also validated through flight testing of a flight weight version.;In the process of comparing the Horten type elevon equipped aircraft and the morphing model, formal wind tunnel verification of wingtip induced thrust, found in Horten (Bell Shaped Lift distribution) type swept wing tailless aircraft was documented. A more complete physical understanding of the highly complex flow generated in the control region of the morphing tailless aircraft has been developed.;CFD models indicate the possibility of the presence of a Leading Edge Vortex (LEV) on the control section morphing wing when the tip is twisted between +3.5 degrees and +7 degrees. The presence of this LEV causes a reduction of drag while lift is increased. Similar LEVs have been documented in use by birds and insects

Aeronautical engineering: A special bibliography with indexes, supplement 80

This bibliography lists 277 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1977

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Aeronautical Engineering: A continuing bibliography with indexes

This bibliography lists 529 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in May 1980

Aeronautical engineering: A continuing bibliography with indexes (supplement 315)

This bibliography lists 217 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics