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This paper proposes an original model for supercapacitors that takes into account both calendar aging and cycling aging. A state variable is used to quantify the state of aging. This model is based on a series of recent experiments conducted in various research laboratories on the same technology (Maxwell Technology) and serves to represent the degradation of equivalent series resistance and capacitance. This model is particularly useful in an aging-aware life-cycle cost analysis. We show that an accurate aging model is critical to the design of an energy storage system that optimizes the economic life-cycle cost. Such an optimization is particularly applicable for smoothing in offshore systems such as direct wave energy converters, which require both cost reduction and high reliability. The influence of an aging model in the sizing process is investigated toward the end of this paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on the sizing optimization of a thermoelectric generator, combined with a potential heatsink, that harvests heat from the human body. To ensure success, energy models describing a thermoelectric module and a heatsink are introduced; these two models are then simplified for small temperature differences while respecting the continuity between them (both with and without the heatsink). In order to maximize the power produced by such a system, the dual thermal and electrical matching of the generator with its environment is studied in detail. Lastly, to optimize the sizing, a set of optimization parameters are defined, namely leg length, the capture surface area of the thermoelectric generator and, if a heatsink is present, its height. The results derived help draw a conclusion on the pertinence of adding a heatsink, for the purpose of maximizing electrical power while minimizing total volume. [Copyright &y& Elsevier]

This paper sets forth a sizing optimization methodology of a surface permanent magnet machine-converter system over a torque-speed operating profile. The two optimization objectives are to minimize the cost of the machine-converter system and to minimize (or maximize) electrical energy consumption (or generation). The optimization parameters serve to describe both the machine geometry and the electrical ratings of the electronic power converter. Each operating point of the profile is treated independently, and current control is optimized at every operating point to not only minimize machine drive losses but also satisfy several constraints and then implicitly considering flux-weakening possibility. This optimization methodology is generic and is applied to a particular case: a direct-drive conversion chain for a wave energy converter (WEC). We show that taking into account both the sizing parameters of the converter and the flux-weakening control, in addition to the classical sizing parameters of the machine, has a strong impact on the machine-converter system optimal results. Moreover, the strong coupling with the WEC through damping parameters plays also a crucial role on the sizing results. [ABSTRACT FROM PUBLISHER]

This paper will begin by presenting two power takeoff (PTO) technologies for the SEAREV wave energy converter (WEC) followed by the design methodology applied to electromagnetic generator cycles for the all-electric solution. The operating principle associated with the SEAREV WEC will be described before discussing the two conversion technologies intended to transform wave energy into electricity. The types of systems are twofold: hydroelectric and all-electric. The strong coupling between the hydrodynamic, mechanical, and electrical phenomena heavily influences the behavior of the recovery (PTO) system and leads to a complex system design that requires a full-scale modeling description. A unique design methodology for the all-electric conversion chain has been developed around several distinct control modes, including one featuring power leveling. [ABSTRACT FROM AUTHOR]

• Details of the development of a magnetic gear with transverse flux architecture. • Experimental validation of the magnetic behavior from comparison with 3D FEM. • Iron losses in pole pieces are a major disadvantage of the structure. This article focuses on the realization of a magnetic gear with transverse flux architecture. In order to analyze both the behavior and modeling of this magnetic gear architecture, an experimental test bench was developed, and 3D finite element computations were performed. The instrumentation of this test bench serves to measure torque, transverse flux in pole pieces, speeds and efficiency. A comparison between experimental findings and 3D finite element model output is proposed in order to validate system behavior. [ABSTRACT FROM AUTHOR]

A new axial-field synchronous machine designed for a flywheel accumulator is presented herein. The armature and field windings, fixed in the air gap, are made with double-face printed circuits. A specific armature layout provides a sine-distributed magnetomotive force and solves the problem of crossing the ends of the winding. A two-dimensional semi-analytical model at the mean radius, using surfacic permeances, is then developed. Then, inductances, torque, and eddy-current losses are calculated using this model and compared with experimental results. [ABSTRACT FROM AUTHOR]

Presents information on a multi-rod linear actuator for direct-drive, wide mechanical bandpass applications. Explanation of the multi-air-gap concept; Advantages of the multi-rod linear actuator; Discussion on a multi-rod prototype technology; Details of experimental measurements for prototype forces.

A sensitivity analysis is carried out on the parameters of a photovoltaic water pumping system (PVWPS) for domestic water supply in rural areas. The results show that the photovoltaic modules peak power, the motor-pump efficiency, and the water tank volume strongly influence the system performance. This highlights that these parameters constitute judicious optimization variables. Besides, the cost of the motor-pump, the cost of the water tank, and the lifetime of the PVWPS have the largest impact on the system cost. These six parameters are therefore of primary importance for the technoeconomic optimal sizing of the system. Finally, it is shown that the hydraulic losses play a minor role and that it is not necessary to consider the evolution of the ambient temperature when modeling PVWPS for domestic water supply. This study can be useful to nongovernmental organizations, companies, and governments which install PVWPS for domestic water access. It can help them to determine the accuracy at which a given parameter has to be known to correctly model or size these systems. Besides, it can allow them to evaluate the robustness of PVWPS sizing to parameters variation with time and may guide their choice of components. [ABSTRACT FROM AUTHOR]

Highlights • The energy conversion chain in a photovoltaic water pumping system was modelled. • Water collection by the inhabitants was included as a model input. • The model was validated by using data acquired on a system in rural Africa. • The accuracy of the model is higher than 95% when using local climatic data. • Accuracy drops of 1–3% when replacing local climatic data by satellite ones. Abstract The low electrification rate in rural sub-Saharan Africa prevents access to energy services which are essential to improve living conditions. One of these energy services is electrified water pumping, which is particularly relevant for these areas where water access continues being a significant challenge. Pumping systems powered by photovoltaic energy have emerged as an interesting solution in off-grid areas. This article presents a model of photovoltaic water pumping system (PVWPS) for providing domestic water to off-grid rural communities. The model simulates the pumped flow rate and the water level in the storage tank from the climatic data (irradiance, ambient temperature) and the profile of water collection by the users of the system. The modelling of the different stages of the energy conversion chain and a method for identifying the unknown parameters of PVWPS are presented in this article. The model is applied to a pilot PVWPS situated in a rural village of Burkina Faso. The comparison between the measurements performed on the system and the model outputs allows to validate the model experimentally. Results indicate that the model permits to accurately simulate the water height in the tank both when climatic data from local sensors and from satellite are inputted in the model. The model could therefore be applied to other off-grid areas to perform techno-economic optimization and size new PVWPS as well as to evaluate the performances of existing PVWPS. The originalities of this work include the consideration of the water collection profile as a model input and the monitoring of a PVWPS in a rural village of Sub-Saharan Africa, an area where no continuous measurements on these systems has been performed, to the best knowledge of the authors. Further, the comparison of the impact of inputting satellite climatic data instead of measured ones on the PVWPS model accuracy is also a novel contribution. [ABSTRACT FROM AUTHOR]

This paper focuses on a two-dimensional (2-D) analytical model for a fast computation of magnetic losses due to eddy currents in the permanent magnets as well as iron losses in the ferromagnetic parts within coaxial magnetic gears. The magnetic field distribution is computed in yokes and permanent magnets by solving both Maxwell's equations, whereas for pole pieces, the magnetic field is computed by coupling the previous analytical model with a reluctance network model. Both the eddy current losses and iron losses are determined from this hybrid analytical model. The iron loss model takes into account the temporal and spatial variations of flux density. The eddy current loss model takes into account the magnet splitting. Results of this magnetostatic eddy current loss model are then compared to the results obtained with a 2-D magnetodynamic finite element model. A verification of validity limits is also proposed. The final function of this analytical model is to ensure integration into a set of models in the aim of a global mechatronic optimization of magnetic gears, for their insertion into multimegawatt wind turbines. A preliminary bi-objective, mass-efficiency optimization protocol is subsequently proposed along with an analysis of the computation time reduction via the presented models. [ABSTRACT FROM AUTHOR]

A solar-powered switch reluctance motor drive using photovoltaic transistors (PVTs) is presented. The expression “PVT” is used to designate a conventional photovoltaic (PV) cell used as a light-controlled power transistor. To obtain a motor drive, a set of PVTs controls the current fed from an external dc power source to the motor phases. The control is achieved by modulating the sunlight hitting the PVTs using a shutter driven by the motor rotor. If the external dc source is a solar panel, the resulting system is able to convert light energy into mechanical energy, without the need of any brushes or other power electronics components. This system could be more affordable and reliable than conventional ones, and therefore, is well suited for off-grid applications like water pumping. This paper first discusses the operation of a PVT through the proposition and the validation of a model. Then, the operating principle of a PVT inverter is clarified. Finally, experimental and numerical results on the first PVT inverter-fed switched reluctance motor are reported. A prototype was built using a switched reluctance motor 6/4 and 12 PVTs. It was here connected to an external 12 V dc power source as a step before using a solar PV source. Results that the PVT inverter-fed switched reluctance motor was operating as expected and provided useful power. [ABSTRACT FROM AUTHOR]

This paper focuses on the computation time and precision of a linear 2-D magnetic gear analytical model. Two main models of magnetic gears are studied: 1) the first with an infinite relative permeability of yokes and 2) the second with a finite relative permeability of yokes. These models are based on the subdomain resolution of Laplace and Poisson equations. To accurately compute the magnetic field distribution, it is necessary to take into account certain harmonics of the various rings and other system harmonics due to modulation. Global system harmonics, which increase the value of computation time, must also be taken into account. If the magnetic gear has a high pole number, then computation time increases even more and no longer allows for system optimization. This paper proposes to compute magnetic field distribution using different harmonic selection methods in order to significantly reduce the computation time for the magnetic torque without any loss of accuracy. [ABSTRACT FROM AUTHOR]

This paper compares the sizing of distributed energy storage systems (ESS) with two control types in order to smooth a direct wave energy converter farm production, namely a centralized one that deals with the point of common coupling (PCC) power with aggregated information and a decentralized one that deals with each unit with only local information. The main objective is to compare the two controls on the basis of their life cycle cost. The ESS is necessary for grid integration in the case considered here due to the flicker constraint. The co-optimization strategies for both the sizing and the management of an ESS are based on a rule-based energy management and a sequential approach to deal with the power quality constraint. This management strategy has been optimized for each size in order to reduce aging speed while respecting the flicker criterion. The final design is expected to minimize total system cost. The centralized control clearly allowed smaller capacity. However, it may lead to an increase in cables losses compared with the decentralized case, although it is expected to be negligible under the conditions considered in this paper. The confirmation of this hypothesis will be the objective of future work. [ABSTRACT FROM PUBLISHER]

This paper proposes a flicker severity study for Wave Energy Converter farms. The flicker severity is introduced and the reason why it is an important constraint for a wave farm is explained. A new representation called intrinsic flicker severity is introduced which describes the flicker severity independently of the grid. The influence of device type, its control and the sea-state on average production, flicker severity and on the ratio between flicker and production are studied with three types of devices: an Oscillating Water Column and two Direct Wave Energy Converters (two point absorbers: a Heaving Buoy and the SEAREV). The influence of the size and the placement of each unit in the wave farm is presented with a farm-unit flicker ratio, compared with the square-root of unit hypothesis (noise behavior), as a function of wave direction by taking into account wave direction dispersion. Finally, solutions are presented to reduce the flicker produced to comply with grid code requirements in order to allow grid integration of wave farms. [ABSTRACT FROM AUTHOR]

We usually find applications of rotary induction generator, direct-drive tubular linear permanent-magnet generator, etc. for the mechanoelectrical conversion process within Stirling microcogenerator systems. This paper presents the design optimization investigation for a direct-drive tubular linear induction generator for a dual free-piston Stirling microcogenerator system. On the one hand, a high oscillating frequency and a relatively long piston's travel bring about a very high acceleration of the generator's moving part, up to 1018 m/s 2. On the other hand, the tubular linear induction generator offers many interesting assets in this application: low weight mover, appearance of levitation force, no mechanical spring, low mechanical losses, no cogging force, easy manufacture, very low investment and maintenance cost, and so on. However, the tubular linear induction generator is sparsely used, because of its a priori relatively low energetic efficiency. This paper presents a sizing optimization approach for maximizing the performance and demonstrates that, with an astute arrangement of electrical devices, the tubular linear induction generator can constitute a well adapted solution for free-piston Stirling microcogenerator systems. [ABSTRACT FROM PUBLISHER]

• Optimally scheduling the cleaning of remote photovoltaic systems is challenging. • Low cost detection of cleaning interventions helps to decide on further operations. • 4 machine learning algorithms are applied on data from a remote photovoltaic system. • Reliability of 95% is reached with 3.5 mHz voltage, current and temperature signals. • 3 implementation strategies are proposed to meet low cost and accuracy goals. Soiling losses are a major concern for remote power systems that rely on photovoltaic energy. Power loss analysis is efficient for the monitoring of large power plants and for developing an optimal cleaning schedule, but it is not adapted for remote monitoring of standalone photovoltaic systems that are used in rural and poor regions. Indeed, this technique relies on a costly and dirt sensitive irradiance sensor. This paper investigates the possibility of a low-cost monitoring of cleaning interventions on photovoltaic modules during daytime. We believe that it can be helpful to know whether the soiling is regularly removed or not, and to decide if it is necessary to carry out additional cleaning operations. The problem is formulated as a classification task to automatically identify the occurrence of a cleaning intervention using a time window of temperature, voltage and current measurements of a photovoltaic array. We investigate machine learning tools based on Logistic Regression, Support Vector Machines, Artificial Neural Networks and Random Forest to achieve such classification task. In addition, we study the influence of the temporal resolution of the signals and the feature extraction on the classification performance. The experiments are conducted on a real dataset and show promising results with classification accuracy of up to 95%. Based on the results, three implementation strategies addressing different practical needs are proposed. The results may be particularly useful for non-governmental organizations, governments and energy service companies to improve the maintenance level of their photovoltaic facilities. [ABSTRACT FROM AUTHOR]

• Design of stand-alone hybrid PV systems including a new real-time DSM strategy. • Simulation of 'real-time' domestic demand based on Bayesian network and Monte Carlo simulation. • Benefits of DSM in the enhancement of the system's performance, benefits for users, and user comfort. • Parametric study of the benefits of DSM with varying diesel prices and battery capacity. Demand-side management (DSM) represents a potential way to improve the profitability of renewable energy systems. In this paper, power management including a new DSM strategy in a stand-alone hybrid Photovoltaic (PV) Diesel/Battery system with multiple customers has been studied. A new probabilistic model of the consumer behavior based on Bayesian network and Monte Carlo simulation has been carried out so as to capture the real-time and stochastic aspect of the demand. The analysis has been made by means of a one-year period simulation of the whole system. Statistical data on consumers and meteorological observation data have been used to set the simulation's parameters. Numerical results showed that with the implementation of DSM, energy costs are reduced by 11.3% for equal total consumption, and the use of solar energy resources rose to 54%. This provides insight on the significant performance enhancement offered by a DSM scheme in such a system. [ABSTRACT FROM AUTHOR]