A Comparative Analysis of Self-Rectifying Turbines for the Mutriku Oscillating Water Column Energy Plant

Oscillating Water Column (OWC) based devices are arising as one of the most promising technologies for wave energy harnessing. However, the most widely used turbine comprising its power take-off (PTO) module, the Wells turbine, presents some drawbacks that require special attention. Notwithstanding different control strategies are being followed to overcome these issues; the use of other self-rectifying turbines could directly achieve this goal at the expense of some extra construction, maintenance, and operation costs. However, these newly developed turbines in turn show diverse behaviours that should be compared for each case. This paper aims to analyse this comparison for the Mutriku wave energy power plant.This work was supported by the MINECO through the Research Project DPI2015-70075-R (MINECO/FEDER, UE) and in part by the University of the Basque Country (UPV/EHU) through PPG17/33. The authors would like to thank the collaboration of the Basque Energy Agency (EVE) through Agreement UPV/EHUEVE23/6/2011, the Spanish National Fusion Laboratory (EURATOM-CIEMAT) through Agreement UPV/EHUCIEMAT08/190, and EUSKAMPUSCampus of International Excellence

Output Power Improvement in Oscillating Water Column-based Wave Power Plants

[ES] Las centrales de aprovechamiento de la energía proveniente de las olas, y particularmente los dispositivos de columna de agua oscilante, resultan una alternativa factible para reducir la dependencia de los combustibles fósiles y frenar el creciente problema del calentamiento global. Así, los nuevos esquemas de control pueden jugar un papel importante a la hora de aportar mejoras de rendimiento y competir de igual a igual desde un punto de vista comercial con las fuentes de energía tradicionales. En este sentido, el presente artículo propone un nuevo método de control basado en el seguimiento de la curva de máxima potencia, mediante el establecimiento de los valores óptimos de los coeficientes de flujo y de par que permiten maximizar la potencia generada en cada instante. El esquema de control ha sido implementado sobre un modelo completo desde la ola hasta la red de potencia a fin de demostrar la viabilidad del método propuesto y la bondad de sus resultados.[EN] Wave energy power plants, particularly Oscillating Water Column devices, become a feasible alternative to reduce the dependence on fossil fuels and slow down the growing problem of the global warming. Thus, new control schemes can play an important role, providing performance improvements to compete from a commercial point of view with the other traditional energy sources. In this sense, this paper proposes a new control technique based on the maximum power point tracking, by establishing the optimal values of the flow and torque coefficients that allow the maximum power generation at each moment. The proposed control scheme has been implemented on a complete wave-to-wire model in order to demonstrate both the goodness and the viability of the proposed method.Este trabajo ha sido realizado parcialmente gracias al apoyo de la Universidad del País Vasco (UPV/EHU) a través del Proyecto PPG17/33 y del Gobierno Vasco a través de la beca predoctoral PRE_2016_2_0193, además del MINECO a través del Proyecto de Investigación DPI2015-70075-R (MINECO/FEDER, EU)Lekube, J.; Garrido, AJ.; Garrido, I.; Otaola, E. (2018). Mejora de la Potencia Obtenida en Plantas de Generación Undimotriz basadas en Columna de Agua Oscilante. Revista Iberoamericana de Automática e Informática industrial. 15(2):145-155. https://doi.org/10.4995/riai.2017.8831OJS145155152Alberdi, M., Amundarain, M., Garrido, A.J., Garrido, I., Casquero, O., De la Sen, M., 2011. Complementary control of oscillating water column-based wave energy conversion plants to improve the instantaneous power output. 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Ocean Engineering 125, 248-260. https://doi.org/10.1016/j.oceaneng.2016.08.017Correia da Fonseca, F.X., Gomes, R.P.F., Henriques, J.C.C., Gato, L.M.C., Falcao, A.F.O., 2016. Model testing of an oscillating water column spar-buoy wave energy converter isolated and in array: Motions and mooring forces. Energy 112, 1207-1218. https://doi.org/10.1016/j.energy.2016.07.007Cui, Y., Hyun, B., 2016. Numerical study on Wells turbine with penetrating blade tip treatments for wave energy conversion. International Journal of Naval Architecture and Ocean Engineering 8, 456-465. https://doi.org/10.1016/j.ijnaoe.2016.05.009Delmonte, N., Barater, D., Giuliani, F., Cova, P., Buticchi, G., 2016. Review of oscillating wáter column converters. IEEE Transactions on Industry Applications 52, 1698-1710.Falcao, A.F.D.O., 2002. Control of an oscillating-water-column wave power plant for máximum energy production. Applied Ocean Research 24, 73-82. https://doi.org/10.1016/S0141-1187(02)00021-4Garcia, E., Correcher, A., Quiles, E., Morant, F., 2016. Recursos y sistemas energéticos renovables de entorno marino y sus requerimientos de control. Revista Iberoamericana de Automática e Informática industrial 13, 141-161. https://doi.org/10.1016/j.riai.2016.03.002Garrido, A.J., Garrido, I., Alberdi, M., Amundarain, M., Barambones, O., Romero, J.A., 2013. Robust control of oscillating water column (OWC) devices: power generation improvement. Proceedings of the OCEANS-San Diego, 1-4.Garrido, I., Garrido, A.J., Alberdi, M., Amundarain, M., Barambones, O., 2013. Performance of an ocean energy conversion system with DFIG sensorless control. Mathematical Problems in Engineering 2013. https://doi.org/10.1155/2013/260514Garrido, I., Garrido, A.J., Sevillano, M.G., Romero, J.A., 2012. Robust sliding mode control for tokamaks. Mathematical Problems in Engineering 2012. https://doi.org/10.1155/2012/341405Garrido, A.J., Garrido, I., Amundarain, M., Alberdi, M., De la Sen, M., 2012. Sliding-mode control of wave power generation plants. IEEE Transactions on Industry Applications 48, 2372-2381. https://doi.org/10.1109/TIA.2012.2227096Garrido, A.J., Otaola, E., Garrido, I., Lekube, J., Maseda, F.J., Liria, P., Mader, J., 2015. Mathematical modeling of oscillating water columns wave-structure interaction in ocean energy plants. Mathematical Problems in Engineering 2015. https://doi.org/10.1155/2015/727982Lekube, J., Garrido, A.J., Garrido, I., 2017. Rotational speed optimization in oscillating water column wave power plants based on maximum power point tracking. IEEE Transactions on Automation Science and Engineering 14, 681-691. https://doi.org/10.1109/TASE.2016.2596579Le Roux, J.P., 2008. An extension of the Airy theory for linear waves into shallow water. Coastal Engineering 55, 295-301. https://doi.org/10.1016/j.coastaleng.2007.11.003López, A., Somolinos, J.A., Nú-ez, L.R., 2014. Modelado energético de convertidores primarios para el aprovechamiento de las energías renovables marinas. Revista Iberoamericana de Automática e Informática Industrial 11, 224-235. https://doi.org/10.1016/j.riai.2014.02.005Marei, M.I., Mokhtar, M., El-Sattar, A.A., 2015. MPPT strategy based on speed control for ASW-based wave energy conversion system. Renewable Energy 83, 305-317. https://doi.org/10.1016/j.renene.2015.04.039Murakami, T., Imai, Y., Nagata, S., Takao, M., Setoguchi, T., 2016. Experimental research on primary and secondary conversion efficiencies in an oscillating water column-type wave energy converter. Sustainability 8, 756-766. https://doi.org/10.3390/su8080756Murari, A.L.L.F., Sguarezi Filho, A.J., Torrico Altuna, J.A., Jacomini, R.V., 2016. Una introducción al ajuste de parámetros de controladores PI utilizados en el control del generador de inducción con rotor bobinado. Revista Iberoamericana de Automática e Informatica Industrial 13, 15-21. https://doi.org/10.1016/j.riai.2015.11.001M'zoughi, F., Bouallègue, S., Ayadi, M., 2015. Modeling and SIL Simulation of an oscillating water column for ocean energy conversion. International Renewable Energy Congress (IREC). https://doi.org/10.1109/IREC.2015.7110880Rusu, E., Onea, F., 2016. Estimation of the wave energy conversion efficiency in the Atlantic Ocean close to the European islands. Renewable Energy 85, 687-703. https://doi.org/10.1016/j.renene.2015.07.042Rusu, E., Onea, F., 2015. Assessment of the performances of various wave energy converters along the European continental coasts. Energy 82, 889-904. https://doi.org/10.1016/j.energy.2015.01.099Sameti, M., Farahi, E., 2014. Output power for an oscillating water column wave energy conversion device. Ocean and Environmental Fluid Research 1, 27-34.Sevillano, M.G., Garrido, I., Garrido, A.J., 2011. Control-oriented automatic system for transport analysis (ASTRA)-Matlab integration for Tokamaks. Energy 36, 2812-2819. https://doi.org/10.1016/j.energy.2011.02.022Torre-Enciso, Y., Marqués, J., López de Aguileta, L.I., 2010. Mutriku. Lessons learnt. 3rd International Conference on Ocean Energy.Uihlein, A., Magagna, D., 2016. Wave and tidal current energy - A review of the current state of research beyond technology. Renewable and Sustainable Energy Reviews 58, 1070-1081. https://doi.org/10.1016/j.rser.2015.12.284Veigas, M., López, M., Romillo, P., Carballo, R., Castro, A., Iglesias, G., 2015. A proposed wave farm on the Galician coast. Energy Conversion and Management 99, 102-111. https://doi.org/10.1016/j.enconman.2015.04.03

Performance of an Ocean Energy Conversion System with DFIG Sensorless Control

The 2009/28/EC Directive requires Member States of the European Union to adopt a National Action Plan for Renewable Energy. In this context, the Basque Energy Board, EVE, is committed to research activities such as the Mutriku Oscillating Water Column plant, OWC. This is an experimental facility whose concept consists of a turbine located in a pneumatic energy collection chamber and a doubly fed induction generator that converts energy extracted by the turbine into a form that can be returned to the network. The turbo-generator control requires a precise knowledge of system parameters and of the rotor angular velocity in particular. Thus, to remove the rotor speed sensor implies a simplification of the hardware that is always convenient in rough working conditions. In this particular case, a Luenberger based observer is considered and the effectiveness of the proposed control is shown by numerical simulations. Comparing these results with those obtained using a traditional speed sensor, it is shown that the proposed solution provides better performance since it increases power extraction in the sense that it allows a more reliable and robust performance of the plant, which is even more relevant in a hostile environment as the ocean

Real Time Hybrid Model Predictive Control for the Current Profile of the Tokamak a Configuration Variable (TCV)

Plasma stability is one of the obstacles in the path to the successful operation of fusion devices. Numerical control-oriented codes as it is the case of the widely accepted RZIp may be used within Tokamak simulations. The novelty of this article relies in the hierarchical development of a dynamic control loop. It is based on a current profile Model Predictive Control (MPC) algorithm within a multiloop structure, where a MPC is developed at each step so as to improve the Proportional Integral Derivative (PID) global scheme. The inner control loop is composed of a PID-based controller that acts over the Multiple Input Multiple Output (MIMO) system resulting from the RZIp plasma model of the Tokamak a Configuration Variable (TCV). The coefficients of this PID controller are initially tuned using an eigenmode reduction over the passive structure model. The control action corresponding to the state of interest is then optimized in the outer MPC loop. For the sake of comparison, both the traditionally used PID global controller as well as the multiloop enhanced MPC are applied to the same TCV shot. The results show that the proposed control algorithm presents a superior performance over the conventional PID algorithm in terms of convergence. Furthermore, this enhanced MPC algorithm contributes to extend the discharge length and to overcome the limited power availability restrictions that hinder the performance of advanced tokamaks

Mathematical Modeling of Oscillating Water Columns Wave-Structure Interaction in Ocean Energy Plants

Oscillating Water Column (OWC)-based power take-off systems are one of the potential solutions to the current energy problems arising from the use of nuclear fission and the consumption of fossil fuels. This kind of energy converter turns wave energy into electric power by means of three different stages: firstly wave energy is transformed into pneumatic energy in the OWC chamber, and then a turbine turns it into mechanical energy and finally the turbogenerator module attached to the turbine creates electric power from the rotational mechanical energy. To date, capture chambers have been the least studied part. In this context, this paper presents an analytical model describing the dynamic behavior of the capture chamber, encompassing the wave motion and its interaction with the OWC structure and turbogenerator module. The model is tested for the case of the Mutriku wave power plant by means of experimental results. For this purpose, representative case studies are selected from wave and pressure drop input-output data. The results show an excellent matching rate between the values predicted by the model and the experimental measured data with a small bounded error in all cases, so that the validity of the proposed model is proven

Low Effort Nuclear Fusion Plasma Control Using Model Predictive Control Laws

One of the main problems of fusion energy is to achieve longer pulse duration by avoiding the premature reaction decay due to plasma instabilities. The control of the plasma inductance arises as an essential tool for the successful operation of tokamak fusion reactors in order to overcome stability issues as well as the new challenges specific to advanced scenarios operation. In this sense, given that advanced tokamaks will suffer from limited power available from noninductive current drive actuators, the transformer primary coil could assist in reducing the power requirements of the noninductive current drive sources needed for current profile control. Therefore, tokamak operation may benefit from advanced control laws beyond the traditionally used PID schemes by reducing instabilities while guaranteeing the tokamak integrity. In this paper, a novel model predictive control (MPC) scheme has been developed and successfully employed to optimize both current and internal inductance of the plasma, which influences the L-H transition timing, the density peaking, and pedestal pressure. Results show that the internal inductance and current profiles can be adequately controlled while maintaining the minimal control action required in tokamak operation

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Scaly green flagellates from Spanish Atlantic coastal waters: molecular, ultrastructural and pigment analyses

24 páginas, 3 tablas, 86 figurasSeven scale-bearing species of prasinophyceans (Chlorophyta) were studied in light and electron microscopy, pigment analysis, and molecular analysis of the small subunit (SSU) rDNA. Unialgal cultures were obtained from samples collected in the Nervión River estuary, Gulf of Biscay, Spanish Atlantic coast. Five of the species belong to the genus Pyramimonas (Prasinophyceae, Pyramimonaceae) and one each to the genera Mamiella (Mamiellophyceae, Mamiellaceae) and Nephroselmis (Nephroselmidophyceae, Nephroselmidaceae). The morphological features of all the strains analyzed agreed closely with the phylogenetic analysis, which in the case of the genus Pyramimonas presented several clusters corresponding to the subgenera Vestigifera (Pyramimonas orientalis, Pyramimonas moestrupii), Punctatae (Pyramimonas robusta), Pyramimonas (Pyramimonas propulsa), and Trichocystis (Pyramimonas grossii). Even though the phylogenetic relationship among these subgenera remains unclear, the results suggested that the Punctatae should remain an independent clade at least until more sequences or genes are analyzed. According to their accessory pigment composition, three groups were distinguished after their pigment ratios were calculated: prasinoxanthin-containing (Mamiella gilva), loroxanthin ester-containing (P. grossii and P. moestrupii), and siphonaxanthin- containing strains (Nephroselmis pyriformis and remaining Pyramimonas species). A high intraspecific variability was found, which highlights the need of an indepth analysis and multiple technique approach to ensure accurate identification of nanoplanktonic microalgaeSpanish Ministry of Economy and Competitiveness, (Grant/Award Number: ‘projects CGL2010-19016 and GIC07/111-417-07’), Spanish Ministry of Education and Science, (Grant/Award Number: ‘CMT2006-04570/MAR’), University of the Basque Country (UPV/EHU)Peer reviewe

Real-Time Control for the EHU Stellarator

At present, two main magnetic confinement fusion devices exist: tokamaks and stellarators. Moreover, stellarators have been demonstrated to be a good alternative to tokamaks, due to their ability to operate in continuous mode, which eventually translates into a higher commercial profitability. In stellarators, the magnetic confinement of the plasma is achieved exclusively by the coils, thus no electric current through the plasma is needed. In particular, this article presents the Columbia Non-Neutral Torus stellarator that is located in the Automatic Control Group of Euskal Herriko Unibertsitatea (EHU). This EHU stellarator maintains symmetry in its structure due to the topology of the mesh that is formed by its coils. A cornerstone of future fusion reactors is to obtain real-time control that enables a sustained reaction. In this article, a control-oriented model for the installed magnetic confinement coils is presented. The model is based on matrices that preserve symmetry, which is defined from physical principles and then validated by different sets of experimental data. Then, based on this model, a novel predictive control suited to this particular model with symmetric objective function is implemented in the numerical simulations, and its response is compared to that of traditional controllers. Finally, this control is implemented in a real plant and the satisfactory experiment results provide validation of both the numerical model and proposed controller