Showing papers on "Wave power published in 2018"

Stalling-Free Control Strategies for Oscillating-Water-Column-Based Wave Power Generation Plants

Abstract: The rising use of renewable power generation plants is highlighting the need for an integrated research combining multiple disciplines in order to achieve a commercially competitive technology stage. The demonstrative NEREIDA wave power plant installed in the northern coast of Spain constitutes a good example of this effort. This paper deals with the design, modeling, and control of the oscillating-water-column-based wave energy converter in order to maximize the power output of the NEREIDA power plant. The power optimization relies on two control strategies proposed to avoid the stalling behavior, a characteristic drawback of the Wells turbine, which limits the system's power. The first control strategy is an airflow control using a PID controller tuned by the particle swarm optimization algorithm and its recent memetic variant called fractional particle swarm optimization memetic algorithm. This controller will control a throttle valve to regulate the airflow in the turbine duct. The second one consist of adequately controlling the rotational speed of the generator by means of the rotor-side converter of the back-to-back converter connected to the doubly fed induction generator to provide a swift way to respond to the rapid variations in the turbine speed. The results show that both controls provide a higher power generation compared to the uncontrolled case.

ULF wave activity in the magnetosphere: resolving solar wind interdependencies to identify driving mechanisms

Abstract: Ultra-low frequency (ULF) waves in the magnetosphere are involved in the energisation and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind-magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine fifteen years of dayside ground-based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to $L \sim 6.6 R_E$). We determine the relative contribution to ULF wave power from instantaneous non-derived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground-based ULF wave power are solar wind speed $v_{sw}$, southward interplanetary magnetic field component $B_z < 0$ and summed power in number density perturbations $\delta N_p$. Together, the subordinate parameters $B_z$ and $\delta N_p$ still account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin-Helmholtz instability, formation and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.

Application of numerical wave models at European coastlines: A review

Abstract: Significant advancements have been made in the past few decades (since the 1980s) on detailed evaluation and quantification of wave resources globally. Larger availability and advances of computational resources have contributed to the utilisation of numerical wave models as powerful tools in climatic and energy studies. This review presents current state-of-the-art numerical tools and their status in the process of wave power assessments. We focus on the evolution of studies undertaken at the European coastline regions and the Black Sea. Although, a number of studies have been successfully developed and implemented in the past contributing to our understanding of the resource, this paper discusses the benefits, limitations and potential for improvement of numerical tools. From the literature, it is evident that different applications and scale may require different models, however, it is also the experience and knowledge of the user, applied in the tuning of a number of parameters that govern the process of wave generation, propagation, and the quality of input parameters that are the cornerstones of a successful model. This review depicted that the use of numerical wave models, depending on specific region and application, offers significant benefits on quantification of coastal zone wave resources which benefit multiple offshore applications and the energy industry.

Studies on Wave and Tidal Power Extraction Devices

Abstract: Electric power from wave and tidal power is a form of pollution free and echo-friendly renewable energy which has a huge potential. This potential has not been realized high capital costs and environmental concerns. This paper discussed how the two problems could be resolved utilizing small scale technologies, innovative financing, and involving local communities of the coastal areas to ensure that all key impacts are manageable. Bangladesh has 710 km long coast line and long coastal area with 2~8 m tidal head/height rise and fall, most of which is protected against flooding by embankment and sluice gates. Therefore, the potential for wave and tidal power in the country is significant because the barrages necessary for creating controlled flow through turbines (to tap tidal power) are also needed for flood control. The wave climate has been studied for a long time at the coastal belt of Bangladesh. It has been shown that it is feasible to generate electricity using the Bay of Bengal. Our research study showed that all twelve months of the whole year are not feasible for wave and tidal power production but 8 months of the year (from the late March to October) are most suitable, feasible and viable for power production

Assessment of the Potential of Energy Extracted from Waves and Wind to Supply Offshore Oil Platforms Operating in the Gulf of Mexico

Abstract: Offshore oil platforms operate with independent electrical systems using gas turbines to generate their own electricity. However, gas turbines operate very inefficiently under the variable offshore conditions, increasing fuel costs and air pollutant emissions. This paper focused on investigating the feasibility of implementing a hybrid electricity supply system for offshore oil platforms in the Gulf of Mexico, both for the United States and Mexico Exclusive Economic Zones. Geographic Information Systems methodologies were used to analyze the data from various sources. Three different scenarios were studied, including wind power only, wave power only, and wind and wave power combined. The results showed that all the offshore locations were within accepted feasible distance to the coast for connecting to the onshore grid. Most of the locations had acceptable power levels of either wind or wave energy while the combination of both resources can improve the overall energy harvesting efficiency and reduce the variability in a significant number of locations. The proposed methodology can be applied for specific locations with finer spatial and time resolution, which will allow stakeholders to improve the decision making process, generate important savings on the normal operation, reduce pollution, and potentially increase income by selling surplus energy from renewable sources.

Flow Control in Wells Turbines for Harnessing Maximum Wave Power

Abstract: Oceans, and particularly waves, offer a huge potential for energy harnessing all over the world. Nevertheless, the performance of current energy converters does not yet allow us to use the wave energy efficiently. However, new control techniques can improve the efficiency of energy converters. In this sense, the plant sensors play a key role within the control scheme, as necessary tools for parameter measuring and monitoring that are then used as control input variables to the feedback loop. Therefore, the aim of this work is to manage the rotational speed control loop in order to optimize the output power. With the help of outward looking sensors, a Maximum Power Point Tracking (MPPT) technique is employed to maximize the system efficiency. Then, the control decisions are based on the pressure drop measured by pressure sensors located along the turbine. A complete wave-to-wire model is developed so as to validate the performance of the proposed control method. For this purpose, a novel sensor-based flow controller is implemented based on the different measured signals. Thus, the performance of the proposed controller has been analyzed and compared with a case of uncontrolled plant. The simulations demonstrate that the flow control-based MPPT strategy is able to increase the output power, and they confirm both the viability and goodness.

Influences of Wave Climate and Sea Level on Shoreline Erosion Rates in the Maryland Chesapeake Bay

Abstract: We investigated spatial correlations between wave forcing, sea level fluctuations, and shoreline erosion in the Maryland Chesapeake Bay (CB), in an attempt to identify the most important relationships and their spatial patterns. We implemented the Simulating WAves Nearshore (SWAN) model and a parametric wave model from the USEPA Chesapeake Bay Program (CBP) to simulate wave climate in CB from 1985 to 2005. Calibrated sea level simulations from the CBP hydrodynamic model over the same time period were also acquired. The separate and joint statistics of waves and sea level were investigated for the entire CB. Spatial patterns of sea level during the high wave events most important for erosion were dominated by local north-south winds in the upper Bay and by remote coastal forcing in the lower Bay. We combined wave and sea level data sets with estimates of historical shoreline erosion rates and shoreline characteristics compiled by the State of Maryland at two different spatial resolutions to explore the factors affecting erosion. The results show that wave power is the most significant influence on erosion in the Maryland CB, but that many other local factors are also implicated. Marshy shorelines show a more homogeneous, approximately linear relationship between wave power and erosion rates, whereas bank shorelines are more complex. Marshy shorelines appear to erode faster than bank shorelines, for the same wave power and bank height. A new expression for the rate of shoreline erosion is proposed, building on previous work. The proposed new relationship expresses the mass rate of shoreline erosion as a locally linear function of the difference between applied wave power and a threshold wave power, multiplied by a structure function that depends on the ratio of water depth to bank height.

Determining the Mode, Frequency, and Azimuthal Wave Number of ULF Waves During a HSS and Moderate Geomagnetic Storm.

Abstract: Ultra-low frequency (ULF) waves play a fundamental role in the dynamics of the inner-magnetosphere and outer radiation belt during geomagnetic storms. Broadband ULF wave power can transport energetic electrons via radial diffusion and discrete ULF wave power can energize electrons through a resonant interaction. Using observations from the Magnetospheric Multiscale (MMS) mission, we characterize the evolution of ULF waves during a high-speed solar wind stream (HSS) and moderate geomagnetic storm while there is an enhancement of the outer radiation belt. The Automated Flare Inference of Oscillations (AFINO) code is used to distinguish discrete ULF wave power from broadband wave power during the HSS. During periods of discrete wave power and utilizing the close separation of the MMS spacecraft, we estimate the toroidal mode ULF azimuthal wave number throughout the geomagnetic storm. We concentrate on the toroidal mode as the HSSs compresses the day side magnetosphere resulting in an asymmetric magnetic field topology where toroidal mode waves can interact with energetic electrons. Analysis of the mode structure and wave numbers demonstrates that the generation of the observed ULF waves is a combination of externally driven waves, via the Kelvin-Helmholtz instability, and internally driven waves, via unstable ion distributions. Further analysis of the periods and toroidal azimuthal wave numbers suggests that these waves can couple with the core electron radiation belt population via the drift resonance during the storm. The azimuthal wave number and structure of ULF wave power (broadband or discrete) have important implications for the inner-magnetospheric and radiation belt dynamics.

Studies on Wave and Tidal Power Converters for Power Production

Abstract: Wave and Tidal energy is a predictable, environmentally desirable source of power. The use of water to create electricity comprises a number of technologies, primarily wave power. The long-term potential of wave power is estimated to be between 10-15% of global electricity consumption. Wave power captures energy generated by the waves, by using the rise and fall of waves to activate pumps and generators. Wave power is more predictable than wind power, as waves normally continue for six to eight hours after the wind drops. This allows wave power to smooth out some of the volatility of wind-generated power. Wave power installations are not only less visible and less noisy; they also positively influence the living conditions of fish by providing sheltered areas. Hence, as the technology matures further and costs are brought down, wave power can be one of the intelligent energy sources of the future.

Wave Climate Study for Ocean Power Extraction

Abstract: To harness the Wave power it is needed to study the wave climates. In order to assess an area for wave energy development, the wave climate must be defined. The wave climate describes an Area’s wave height (H) distribution, Wavelength (L) distribution, and Total mean water depth (d). From these parameters, one can compute wave power levels. A significant piece of data to gather from study is that the waves present on the western edge of the continents contain more energy because of the west-to-east winds. An important fact not shown in study is that average wave power is cyclical with winter bringing energy levels up to six times greater than summer.

Model Predictive Control of a Wave Energy Converter with Discrete Fluid Power Power Take-Off System

Abstract: Wave power extraction algorithms for wave energy converters are normally designed without taking system losses into account leading to suboptimal power extraction. In the current work, a model predictive power extraction algorithm is designed for a discretized power take of system. It is shown how the quantized nature of a discrete fluid power system may be included in a new model predictive control algorithm leading to a significant increase in the harvested power. A detailed investigation of the influence of the prediction horizon and the time step is reported. Furthermore, it is shown how the inclusion of a loss model may increase the energy output. Based on the presented results it is concluded that power extraction algorithms based on model predictive control principles are both feasible and favorable for use in a discrete fluid power power take-off system for point absorber wave energy converters.

Sizing of IPM Generator for a Single Point Absorber Type Wave Energy Converter

Abstract: In this paper, a wave energy converter (WEC) is designed for a wave climate condition and its interior permanent magnet (IPM) generator is dimensioned for minimum life cycle cost (LCC). The single point absorber movement is simulated and the harnessed annual energy is determined to be 325 MWh. Possible IPM generator sizes are investigated using finite element calculations. Tradeoffs between the generator cost and the annual energy efficiency is performed in order to find the best economical solution. For the economical evaluation, the net present value method is utilized in order to obtain the LCC of the electric generation system of the WEC. Increasing the axial length of the machine 1.6 times results in the lowest LCC, with a $2.5\%$ efficiency increase, which means an increment of approximately 1000 € in the investment cost. Despite the higher investment cost, the LCC of the WEC generator decreases from 8070 € to 6450 €, due to the lower losses.