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

Variable Speed Control In Wells Turbine-Based Oscillating Water Column Devices: Optimum Rotational Speed

The effects of climate change and global warming reveal the need to find alternative sources of clean energy. In this sense, wave energy power plants, and in particular Oscillating Water Column (OWC) devices, offer a huge potential of energy harnessing. Nevertheless, the conversion systems have not reached a commercially mature stage yet so as to compete with conventional power plants. At this point, the use of new control methods over the existing technology arises as a doable way to improve the efficiency of the system. Due to the nonuniform response that the turbine shows to the rotational speed variation, the speed control of the turbo-generator may offer a feasible solution for efficiency improvement during the energy conversion. In this context, a novel speed control approach for OWC systems is presented in this paper, demonstrating its goodness and affording promising results when particularized to the Mutriku's wave power plant.This work was supported in part by the University of the Basque Country (Universidad del Pais Vasco UPV/Euskal Herriko Unibertsitatea EHU) through Project PPG17/33 and by the MINECO through the Research Project DPI2015-70075-R (MINECO/FEDER, EU), as well as to the Basque Government through Ph.D. Grant PIF PRE_2016_2_0193. 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 EUSKAMPUS - Campus of International Excellence. They would also like to thank Yago Torre-Enciso and Olatz Ajuria from EVE for their collaboration and help

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. IEEE Transactions on Energy Conversion 26, 1021-1032. https://doi.org/10.1109/TEC.2011.2167332Amon, A., Brekken, K.A., Schacher, A., 2012. Maximum power point tracking for ocean wave energy conversion. IEEE Transactions on Industry Applications 48, 1079-1086. https://doi.org/10.1109/TIA.2012.2190255Amundarain, M., Alberdi, M., Garrido, A.J., Garrido, I., 2009. Neural control of the Wells turbine-generator module. Proceedings of the IEEE Conference on Decision and Control, 7315-7320.Amundarain, M., Alberdi, M., Garrido, A.J., Garrido, I., 2011. Modeling and Simulation of Wave Energy Generation Plants: Output Power Control. IEEE Transactions on Industrial Electronics 58, 105-117. https://doi.org/10.1109/TIE.2010.2047827Bailey, H., Robertson, B.R.D., Buckham, B.J., 2016. Wave-to-wire simulation of a floating oscillating water column wave energy converter. 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

Flow Control in Wells Turbines For Harnessing Maximum Wave Power

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.This work was supported in part by the University of the Basque Country (UPV/EHU) through Project PPG17/33, by the MINECO through the Research Project DPI2015-70075-R (MINECO/FEDER, EU) and by the Basque Government through Elkartek. 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 EUSKAMPUS - Campus of International Excellence. They would also like to thank Yago Torre-Enciso and Olatz Ajuria from EVE for their collaboration and help. The authors would also like to thank the anonymous reviewers that have helped to improve the initial version of the manuscript

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

Influence of season-depending ecological variables on biomarker baseline levels in mussels (Mytilus trossulus) from two Baltic Sea subregions

Highlights • Baltic Sea presents regional and seasonal changes that condition responses in mussels. • Food supply dictated reproductive cycle and consequently biomarker response. • Seasonal variability unequally reflected at different biological organization levels. • Combination of biological and ecological data necessary for biomarker approach.For reliable mussel monitoring programmes based on biomarkers, regionally relevant reference values and their natural variability need to be known. The Baltic Sea exhibits high inter-regional and seasonal variability in physical factors such as salinity, temperature and primary production. The aim of this pilot study is to depict the effects of season-related environmental factors in a selected battery of biomarkers in two environmentally different subregions of the Baltic Sea to help establishing reference data for biochemical, cellular and tissue-level biomarkers. In order to achieve that, mussels were collected from reference sites in Kiel (Germany) and Tvärminne (Finland) during three seasons: summer and autumn 2016, and spring 2017. Finally, in order to characterize the ecological situation, analysis of the chemical tissue burden was performed and chlorophyll‑a and particulate organic carbon concentration and temperature changes were analyzed at each sampling locality using satellite remote sensing images. An integrated biomarker response index was performed to summarize the biomarker responses of each locality and season. The biochemical endpoints showed seasonal variability regulated by temperature, food supply and reproductive cycle, while among the cellular endpoints only lipofuscin accumulation and lysosomal structural changes showed slight seasonal variation. Seasonal changes in tissue level biomarkers were observed only at the northern Baltic Sea site Tvärminne, dictated by the demanding energetic trade-off caused by reproduction. In conclusion, the characterization of the ecological variables and physico-chemical conditions at each site, is crucial to perform a reliable assessment of the effects of a hypothetical pollution scenario in the Baltic Sea. Moreover, reference levels of biomarkers and their responses to natural environmental conditions must be established

Mutrikuko olatu zentralaren azterketa eta potentzia maximoko puntuaren jarraipena

Susperraldian dauden energia iturri berriztagarri berriak berebiziko garrantzia izatera iritsi dira gaur egungo gizartean. Petrolioarekiko menpekotasuna eta berotegi efektua direla medio, energia lortzeko bide berriak miatu beharra nabarmendu da. Ozeanoek eta itsasoek energia kantite handia pilatzen dute bere baitan. Hala ere, gizakia oraindik ez da gai izan energia honetaz egokiro baliatzeko. Ur-zutabe oszilatzailean oinarritutako metodoa da gaur egun itsasotik energia ateratzeko sistema guztien artetik gehien ikertuenetako bat. Alabaina, lorturiko efizientzia baxuek zaildu egiten dute teknologia honen erabilera. Gaur egungo kontrol-metodo berriek, aldiz, efizientzia hau hobetzea ahalbidetzen dute. Metodo hauen artean badago potentzia maximoko puntuaren jarraipena, batez ere energia eolikoan asko erabilia.

State-space Coil Modelling in Plasma Magnetic Confinement Devices

The need of robust and optimal control schemes is a key factor for the development of future fusion reactors. This paper has dealt with the state-space modelling of the Ultra-Low Iota Super Elongated Stellarator of the UPV/EHU, using a physical lumped parameter equivalent circuit approach. The model obtained has been validated by means of experimental output data showing an excellent matching with the real system. Besides, it has been designed a MPC scheme that has been successfully implemented both in simulation and experimentally using a real-time control platform

State-space Coil Modelling in Plasma Magnetic Confinement Devices

The need of robust and optimal control schemes is a key factor for the development of future fusion reactors. This paper has dealt with the state-space modelling of the Ultra-Low Iota Super Elongated Stellarator of the UPV/EHU, using a physical lumped parameter equivalent circuit approach. The model obtained has been validated by means of experimental output data showing an excellent matching with the real system. Besides, it has been designed a MPC scheme that has been successfully implemented both in simulation and experimentally using a real-time control platform