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Bipolar plates are an essential component of electrochemical cells and are used in fuel cells for media supply and electrical contacting, for example. The media supply is realized by flow fields, which are introduced into the plates by shaping processes. Metallic bipolar plates are coated to increase their electrical conductivity and service life. There is a considerable need for research into materials, processes and manufacturing strategies in order to develop cost-effective solutions that are suitable for mass production. Manufacturing strategies based on roll-to-roll processes offer considerable potential and are being further developed for this purpose. The latest developments in this area were addressed within a Fraunhofer project. Both the coating of steel strip with carbon-based coatings and the subsequent forming of the steel strip were investigated. It was shown that PVD coatings from strip processes and batch processes are electrically and electrochemically comparable. Furthermore, it was shown that the coated steel strips are formable and that the production of bipolar half-shells is possible.

A mixed time‐domain/frequency‐domain method is proposed for modelling dense wave energy converter (WEC) arrays with non‐linear power take‐off (PTO). The model is based on a harmonic balance method which describes the system response in the frequency domain, while evaluating the non‐linear PTO force and solving the system equations of motion in the time domain. The non‐linear PTO force is computed with Lagrange multipliers. In order to apply the proposed method for WEC array responses in real sea states, the time series is split into time windows and the simulation is carried out individually per window. The method is demonstrated by investigating the dynamics of the Ocean Grazer WEC array (OG‐WEC) with an adaptable piston pumping system. The key parameters thought to possibly influence model accuracy, including the number of harmonic components, the length of the time window and overlay, are discussed. It is shown that the proposed model can significantly reduce the computational cost with an acceptable accuracy penalty.

Distinct from conventional energy‐harvesting (EH) technologies, such as the use of photovoltaic, piezoelectric, and thermoelectric effects, betavoltaic energy conversion can consistently generate uniform electric power, independent of environmental variations, and provide a constant output of high DC voltage, even under conditions of ultra‐low‐power EH. It can also dramatically reduce the energy loss incurred in the processes of voltage boosting and regulation. This study realized betavoltaic cells comprised of p‐i‐n junctions based on silicon carbide, fabricated through a customized semiconductor recipe, and a Ni foil plated with a Ni‐63 radioisotope. The betavoltaic energy converter (BEC) includes an array of 16 parallel‐connected betavoltaic cells. Experimental results demonstrate that the series and parallel connections of two BECs result in an open‐circuit voltage Voc of 3.06 V with a short‐circuit current Isc of 48.5 nA, and a Voc of 1.50 V with an Isc of 92.6 nA, respectively. The capacitor charging efficiency in terms of the current generated from the two series‐connected BECs was measured to be approximately 90.7%.

Wave energy can be used to power oceanographic buoys. A new switching control strategy is developed in this paper for a two-body heaving wave energy converter that is composed of a floating cylinder and two rigidly connected submerged hemispheres. This control strategy is designed to prevent excessive displacement of the floating buoy that may occur due to the actuator force. This control strategy switches the control between a multi-resonant controller and a nonlinear damping controller, depending on the state of the system, to account for displacement constraints. This control strategy is developed using a one-degree-of-freedom dynamic model for the relative motion of the two bodies. Estimation of the relative motion, needed for feedback control, is carried out using a Kalman filter. Numerical simulations are conducted to select the proper mooring stiffness. The controller is tested with stochastic models of irregular waves in this paper. The performance of the controller with different sea states is discussed. Annual power production using this control strategy is presented based on real data in 2015 published by Martha's Vineyard Coastal Observatory.

Wave energy has the potential to play an important role in the UK's electricity mix in the coming years and it is important to understand the interactions of wave energy converters with the environment before considering them viable alternatives for other technologies. The aim of this study was to identify the environmental impacts of the deployment of the Oyster wave energy converter to the EMEC test site at Orkney, UK over its lifetime across three general categories: resource use, human health and ecological consequences. A full life cycle assessment was performed on two different models of the Oyster wave energy converter: Oyster 1 and Oyster 800. It was found that the latter is a fitting upgrade for its predecessor as it has lower environmental impacts in all categories; however, the high infrastructural needs of the Oyster technology makes its environmental performance worse than most other wave energy converters. Key sustainability indicators for energy converters include carbon footprint and energy payback period, and these were found to be 79 and 57 gCO2 eq/kWh and 45 and 42 months for the Oyster 1 and Oyster 800, respectively. Although these are significantly higher than most estimates for other types of renewable energy converter, the carbon impacts are still significantly lower than for conventional fossil-fuelled power generation.

Vortex-induced oscillations offer a potential means to harness hydrokinetic energy even at low current speeds. In this study, we consider a novel converter where a cylinder undergoes angular oscillations with respect to a pivot point, in contrast to most previous configurations, where the cylinder undergoes flow-induced oscillations transversely to the incident free stream. We formulate a theoretical model to deal with the coupling of the hydrodynamics and the structural dynamics, and we numerically solve the resulting nonlinear equation of cylinder motion in order to assess the performance of the energy converter. The hydrodynamical model utilizes a novel approach where the fluid forces acting on the oscillating cylinder are split into components acting along and normal to the instantaneous relative velocity between the moving cylinder and the free stream. Contour plots illustrate the effects of the main design parameters (in dimensionless form) on the angular response of the cylinder and the energy efficiency of the converter. Peak efficiencies of approximately 20% can be attained by optimal selection of the main design parameters. Guidelines on the sizing of actual converters are discussed.

This paper aims to investigate electric dynamics and improve electric power generation of an isolated wave energy converter that uses a linear permanent magnet generator as the power take-off system, excited by regular or irregular waves. This is of significant concern when considering actual operating conditions of an offshore wave energy converter, where the device will encounter different sea states and its electric load needs to be tuned on a sea-state-to-sea-state basis. To that end, a fully coupled fluid-mechanical-electric-magnetic-electronic mathematical model and an optimization routine are developed. This proposed time-domain wave-to-wire model is used to simulate the hydrodynamic and electric response of a wave energy converter connected to specific electric loads and also used in an optimization routine that searches optimal resistive load value for a wave energy converter under specific sea states. Sample results are presented for a point-absorber type wave energy converter, showing that the electric power generation of a device under irregular waves can be significantly improved. Keywords: wave energy converter, wave power system, wave-to-wire model, linear permanent magnet generator, electric load optimization., Comment: Accepted by Energy

In this paper a system for experiments on redox flow batteries is presented, giving the operator the possibility of dealing independently with advantages and challenges of this innovative energy converter, in particular with regard to testing new, in this case recycled, materials. The recycling aspect is included due to the permanent requirement of reducing cost of especially as far as bipolar plates is concerned. In addition the hole recycling discussion, it is necessary to use the material recycling in different stages of system development and evaluation. Included in the tests was the development of a four-part series of experiments, in the framework of which the operators will treat intensely the cell structure, its characterization as well as testing of the electrolytes and the challenge of the crossover.

The influence of the central platform on hydrodynamic performance of a wave energy converter (WEC) has remained elusive. To approach this dearth of relevant theoretical research, this paper presents a semi-submerged multi-buoy WEC and the results of the numerical analysis at different dimension parameters of the central platform of the WEC. The WEC consists of three oscillating buoys hinged with a central platform through multiple actuating arms. Numerical analysis revealed that there exists a relationship between the hydrodynamic performance of device and the geometry of the central platform. At the given wave condition, different central platform size would obviously affect the hydrodynamic performance and wave energy capture width ratio of the semi-submerged multi-buoy WEC. Additionally, appropriately increasing central platform draft would help to improve the wave energy capture capability of the oscillating buoys.

The floating structure problem describes the interaction between surface water waves and a floating body, generally a boat or a wave energy converter. As shown by Lannes in [18] the equations for the fluid motion can be reduced to a set of two evolution equations on the surface elevation and the horizontal discharge. The presence of the object is accounted for by a constraint on the discharge under the object; the pressure exerted by the fluid on this object is then the Lagrange multiplier associated to this constraint. Our goal in this paper is to prove the well-posedness of this fluid-structure interaction problem in the shallow water approximation under the assumption that the flow is axisymmetric without swirl. We write the fluid equations as a quasilinear hyperbolic mixed initial boundary value problem and the solid equation as a second order ODE coupled to the fluid equations. Finally we prove the local in time well-posedness for this coupled problem, provided some compatibility conditions on the initial data are satisfied.

The analysis of electromechanical energy converters based on metal-thin film ferroelectric (with a large specific capacitance)-nanogap-moving electrode structures was performed. It was shown that the density of the energy being converted and its absolute value increase with the decreasing gap value between the surfaces of the ferroelectric and the metallic moving electrode up to nanometer values. The effects limiting the growth of this energy were established, and the limiting value of the energy density transformed in the nanogap of these structures was determined to be about 1.6 &times, 1010 J/m3, which is 4 orders of magnitude higher than the energy density in inductive converters. The experimental verification of this model based on the data for micromotors fabricated on these structures is given.

The potential of wave power as an alternative energy resource is being studied to address problems associated with fossil fuel exhaustion and environmental pollution. In this paper, to improve the power generation efficiency of a floating-type wave-energy converter that has an activating body, the effects of the positions of a connecting bridge and different connecting methods between a main body and the activating body of the wave-energy converter were studied. In order to research the activating body’s motion characteristics that are caused by the changes of connecting bridge’s position and connecting methods; hinged or fixed connector, the wave-energy converter was modeled and simulated by using a commercial software. The moment and angular velocity of the axis of power generation were measured from the results of simulations and then the power outputs were calculated based on the moment and angular velocity. The outputs, which were analyzed under several regular wave conditions, were compared to each other.

OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples.

Significant research efforts have been invested in the automotive industry on alternative fuels and new hybrid electric powertrain in attempt to reduce carbon emissions from passenger cars. Fuel consumption of these hybrid powertrains strongly relies on the energy converter performance, the vehicle energetic needs, as well as on the energy management strategy deployed on-board. This thesis investigates the potential of new energy converters as substitute of actual internal combustion engine in automotive powertrain applications. Gas turbine systems is identified as potential energy converter for series hybrid electric vehicle (SHEV), as it offers many automotive intrinsic benefits such as multi-fuel capability, compactness, reduced number of moving parts, reduced noise and vibrations among others. An exergo-technological explicit analysis is conducted to identify the realistic GT-system thermodynamic configurations. A pre-design study have been carried out to identify the power to weight ratios of those systems. A SHEV model is developed and powertrain components are sized considering vehicle performance criteria. Energy consumption simulations are performed on the worldwide-harmonized light vehicles test cycle (WLTC), which account for the vehicle electric and thermal energy needs in addition to mechanical energy needs, using an innovative bi-level optimization method as energy management strategy. The intercooled regenerative reheat gas turbine (IRReGT) cycle is prioritized, offering higher efficiency and power density as well as reduced fuel consumption compared to the other investigated GT-systems. Also a dynamic model was developed and simulations were performed to account for the over fuel consumption during start-up transitory phases. Tests were also performed on some subsystems of the identified IRReGT-system. Results show improved fuel consumption with the IRReGT as auxiliary power unit (APU) compared to ICE. Consequently, the selected IRReGT-system presents a potential for implementation on futur SHEVs.; D'importants efforts de recherche ont été investis dans l'industrie automobile sur les nouveaux carburants et les nouvelles chaînes de traction hybride électrique afin de réduire les émissions de carbone des véhicules. La consommation de carburant de ces groupes motopropulseurs hybrides dépend des performances du convertisseur d'énergie utilisé, des besoins énergétiques du véhicule, ainsi que de la stratégie de gestion énergétique déployée à bord. Cette thèse examine le potentiel de nouveaux convertisseurs d'énergie comme substitut du moteur thermique à combustion interne (ICE). Les systèmes de turbines à gaz sont considérés comme des convertisseurs d'énergie potentiel pour les chaînes de traction hybride série (SHEV), car ils offrent de nombreux avantages intrinsèques à l'automobile, tels que la capacité de fonctionner avec plusieurs carburants, la compacité, la réduction du nombre de pièces mobiles, la réduction du bruit et des vibrations. Une analyse exergo-technologique explicite est proposée pour identifier les configurations thermodynamiques réalistes. Une étude préconceptionnelle a été réalisée pour déterminer les rapports puissance/poids de ces systèmes. Un modèle SHEV est développé et les composants du groupe motopropulseur sont dimensionnés en fonction des critères de performance du véhicule. Des simulations de consommation sont effectuées sur le cycle d’homologation WLTC, en prenant en compte les besoins en énergie électrique et thermique du véhicule en plus des besoins en énergie mécanique, et en utilisant une méthode innovante d'optimisation comme stratégie de gestion de l'énergie. Le cycle turbine à gaz (avec compression refroidie, régénérateur et réchauffe durant la détente (IRReGT)) est priorisé car il offre un rendement et une densité de puissance plus élevés ainsi qu'une consommation de carburant réduite par rapport aux autres systèmes investigués. De plus, un modèle dynamique a été développé et des simulations ont été effectuées pour tenir compte de la surconsommation de carburant pendant les phases transitoires du démarrage. Des essais ont également été mis en œuvre sur certains sous-systèmes du cycle IRReGT identifié. Les résultats montrent une amélioration de la consommation de carburant avec l'IRReGT comme groupe auxiliaire de puissance par rapport à l'ICE. Par conséquent, le système IRReGT sélectionné présente un potentiel, non négligeable, qui remplacerait le moteur thermique à combustion interne dans les futures chaînes de traction hybride électriques.

The Tupperwave device is a wave energy converter based on the Oscillating Water Column (OWC) concept. Unlike conventional OWC devices, which are opened to the atmosphere, the Tupperwave device works in closed-circuit and uses non-return valves and accumulator chambers to create a smooth unidirectional flow across a unidirectional turbine. The EU-funded OceanEraNet project called Tupperwave was undertaken by a consortium of academic and industrial partners, aimed at designing and modelling the Tupperwave device. The device was numerically modelled using two different methods. It was also physically modelled at the laboratory scale. The various modelling methods are discussed and compared. An analysis of the dependence of the device efficiency on the valves and turbine aerodynamic damping is carried out, using both physical and numerical approaches.

The exploitation of sea wave represents an important frontier for the energy sustainability in the next future. Despite the proposal of several techniques and solutions, commercial devices are not available. In this context, the Department of Engineering is investigating an innovative solution based on linear energy generators. This machine can be adopted as the main component in a wave energy converter, that is the device for the energy extraction of sea wave. Starting from an existing prototype, the paper examines the replacement of the iron stator with a non-magnetic material, in order to solve several common problems of linear generators, such as the cogging force. Results are reported, considering the no-load voltages and the cogging force produced by the generator in both cases.

Unidad de excelencia María de Maeztu MdM-2015-0552 Current narrative on biofuels is backed up by a large number of studies published in the scientific literature that address second-generation bioethanol only through a single topic approach, nonetheless in the vast majority of cases transition to this energy carrier is evaluated as a generally 'promising' technology. This paper presents a first attempt in proposing an integrated evaluation of the actual benefits expected from bioethanol in the transport sector, by applying the Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) to the prospective realization of a local system of bio-refinery in Campania Region (Southern Italy). MuSIASEM is a multi-criteria analysis enabling to deal with the complexity of a territorial energy system. Since the unavoidable intrinsic uncertainty, the study does not focus on predictions, but adopts a strategy of Quantitative Story-Telling about some relevant results underlying the limits and critical issues about the energy converter fabric, the economic profitability, environmental constraints and the questionable concept of marginal land. The findings suggest concluding toward falsification of key points in the current narrative: (i) the system is not an efficient solar energy converter; (ii) it fails to realize many of the expectations for a renewable energy carrier producer; (iii) the contribution to decarbonization strategies is not as high as desired and other environmental impacts could not be neglected; (iv) the very large land requirement is hardly compatible with conversion of truly marginal land in Campania region; (v) compared to alternate land uses it does not seem an actually promising strategy to regain value from rural economy.

This article presents a permanent magnet planar translational generator which is able to exploit multiple modes of sea wave energy extraction. Linear electrical generators have recently been studied for the exploitation of sea wave energy, but, to the best of our knowledge, no synchronous planar translational generator has been proposed. In this article, to maximize the energy extraction, we have considered all the potential modes of motion due to wave excitation and included them within the mathematical model of the proposed system. The principle of operation of the generator can be summarized as follows: the moving part (translator) of the generator is driven from the sea waves and induces and electromotive force (EMF) on the windings mounted to the armature. The movement of the translator is 2-D and, therefore, all the movement modes of the wave, except heave, can be exploited. The proposed mathematical model includes the dynamic equations of the translator and the electric equations of the windings. The coupling parameters (inductances and fluxes) have been determined by finite element method analysis. Optimization of the device has been performed by considering both, the parameters of the electromagnetic circuit, and, the parameters associated with the stochastic features of the wave.

This paper presents a wave energy converter which is based on a sliding mass coupled to a linear generator. In order to maximize energy extraction, the stochastic features of the energy source has been included in the mathematical model of the system in order to satisfactorily tackle the problem. The results of several simulations are presented.

In this paper we introduce a pitch wave force predictor for a wave energy converter. The designed predictor is composed of two subsystems. First, we design a virtual sensor in order to provide a real-time estimate of the pitch wave force acting on the converter, from measurements provided by a set of on-board sensors. Then, we build an autoregressive predictor on such a virtual measurement to predict the future value of the wave force over a finite prediction horizon length. Simulation results, performed by applying the proposed algorithm on a first-principles based Simulink model of the considered sea wave energy converter, demonstrate the effectiveness of the proposed approach.

In this study, a series of modules is integrated into a wave-to-wire (W2W) model that links a Boundary Element Method (BEM) solver to a Wave Energy Converter (WEC) motion solver which are in turn coupled to a wave propagation model. The hydrodynamics of the WECs are resolved in the wave structure interaction solver NEMOH, the Power Take-off (PTO) is simulated in the WEC simulation tool WEC-Sim, and the resulting perturbed wave field is coupled to the mild-slope propagation model MILDwave. The W2W model is run for verified for a realistic wave energy project consisting of a WEC farm composed of 10 5-WEC arrays of Oscillating Surging Wave Energy Converters (OSWECs). The investigated WEC farm is modelled for a real wave climate and a sloping bathymetry based on a proposed OSWEC array project off the coast of Bretagne, France. Each WEC array is arranged in a power-maximizing 2-row configuration that also minimizes the inter-array separation distance d x and d y and the arrays are located in a staggered energy maximizing configuration that also decreases the along-shore WEC farm extent. The WEC farm power output and the near and far-field effects are simulated for irregular waves with various significant wave heights wave peak periods and mean wave incidence directions &beta, based on the modelled site wave climatology. The PTO system of each WEC in each farm is modelled as a closed-circuit hydraulic PTO system optimized for each set of incident wave conditions, mimicking the proposed site technology, namely the WaveRoller&reg, OSWEC developed by AW Energy Ltd. The investigation in this study provides a proof of concept of the proposed W2W model in investigating potential commercial WEC projects.

Assessment of wave power potential at different water depths and time is required for identifying a wave power plant location. This study examines the variation in wave power off the central west coast of India at water depths of 30, 9 and 5 m based on waverider buoy measured wave data. The study shows a significant reduction ( ∼ 10 to 27 %) in wave power at 9 m water depth compared to 30 m and the wave power available at 5 m water depth is 20 to 23 % less than that at 9 m. At 9 m depth, the seasonal mean value of the wave power varied from 1.6 kW m−1 in the post-monsoon period (ONDJ) to 15.2 kW m−1 in the Indian summer monsoon (JJAS) period. During the Indian summer monsoon period, the variation of wave power in a day is up to 32 kW m−1. At 9 m water depth, the mean annual wave power is 6 kW m−1 and interannual variations up to 19.3 % are observed during 2009–2014. High wave energy ( > 20 kW m−1) at the study area is essentially from the directional sector 245–270° and also 75 % of the total annual wave energy is from this narrow directional sector, which is advantageous while aligning the wave energy converter.

Energy harvested from a Wave Energy Converter (WEC) varies greatly with the location of its installation. Determining an optimal location that can result in maximum output power is therefore critical. In this paper, we present a novel approach to predicting the output power of a nearshore WEC by characterizing ocean waves using floating buoys. We monitored the movement of the buoys using an Arduino-based data collection module, including a gyro-accelerometer sensor and a wireless transceiver. The collected data were utilized to train and test prediction models. The models were developed using machine learning algorithms: SVM, RF and ANN. The results of the experiments showed that measurements from the data collection module can yield a reliable predictor of output power. Furthermore, we found that the predictors work better when the regressors are combined with a classifier. The accuracy of the proposed prediction model suggests that it could be extremely useful in both locating optimal placement for wave energy harvesting plants and designing the shape of the buoys used by them.

Um den aktuellen Herausforderungen von Zuverl��ssigkeit f��r erneuerbare Energiesysteme gerecht zu werden, sind ausgekl��gelte Fehlerrobustheitsvalidierungen und Lebenszeitprognosen von Leistungselektronikger��ten notwendig. Diese Diplomarbeit hat einen weiteren Beitrag zum Fortschritt geleistet, indem neue Umsetzungen erarbeitet wurden, unter Ber��cksichtigung von drei wesentlichen Aspekten: ein Mission Profil von speziell auf den Einsatzbereich abgestimmten physikalischen Umgebungsdaten und Lastprofilen, eine Charakterisierung des festgelegten Systems und Module basierend auf allgemein bekannten Fehlermechanismen. Diese Untersuchung hat sich speziell auf das AIT Smart Grid Converter (ASGC) Leistungselektroniksystem bezogen. Die Systemcharakterisierung wurde evaluiert und daraus ein thermisches Modell erstellt, da die betrachteten Fehlermechanismen, sowohl der Elektrolyt Kondensatoren als auch der IGBT Halbleiterbauteile, vor allem von der Bauteiltemperatur abh��ngen. Besonders innovativ war in diesem Zusammenhang die Entwicklung des Modells f��r die Erm��dung der Halbleiterchips-Bauteilansch��sse, unter Verwendung des Rainflow-Algorithmus zur Berechnung von thermischen Zyklen. Unter Verwendung eines Mission Profiles aus dem Jahre 2017 mit offline Daten eines Photovoltaik Wechselrichters, Standort in Wien, ��sterreich, hat sich f��r das ausgearbeitete Modell die kosmische Strahlung als dominanter Ausfallsgrund gezeigt. Allerdings beinhalten diese Daten nur sehr geringe Belastungen f��r die Systembestandteile. Die Anwendung von weiteren Profilen und Messungen zur Systemcharakterisierung k��nnten daher zu einem Informationszuwachs f��hren., To meet the challenges of nowadays reliability for renewable energy systems, the advancements of robustness validation and lifetime prediction for power electronic devices is an important subject. This thesis has done further progress by developing an implementation and considering three relevant aspects: an operation specific mission profile containing physical environment data as well as load and stress profiles, a system specific characterization and universal failure mechanism sourced modules. The study has focused on the AIT smart grid converter (ASGC) power electronic system. System characteristics have been evaluated and thermal models prepared since the investigated failure mechanisms of electrolytic capacitors and IGBT semiconductors are primarily driven by their temperature. A particularly innovation is the development of the bond-wire fatigue failure model with the use of the rainflow algorithm for the computation of thermal cycles. Based on the mission profile considering 2017's offline data of Vienna, Austria as the operation area for a photovoltaic converter, the results show the dominance of cosmic radiation failures of semiconductors for the prepared models. Nevertheless this mission profile contains only small loads and therefore provides slight stresses to the components. The use of further applications profiles would yield worthwhile information.