Battery sizing for a stand alone passive wind system using statistical techniques

In this paper, an original optimization method to jointly determine a reduced study term and an optimum battery sizing is investigated. This storage device is used to connect a passive wind turbine system with a stand alone network. A Weibull probability density function is used to generate different wind speed data. The passive wind system is composed of a wind turbine, a permanent magnet synchronous generator feeding a diode rectifier associated with a very low voltage DC battery bus. This study is essentially based on a similitude model applied on an 8 kW wind turbine system. Our reference model is taken from a 1.7 kW optimized system. The wind system generated power and the load demand are coupled through a battery sized using a statistical approach

Synthesis of a compact wind profile using evolutionary algorithms for wind turbine system with storage

In this paper, the authors investigate two methodologies for synthesizing compact wind speed profiles by means of evolutionary algorithms. Such profile can be considered as input parameter in a prospective design process by optimization of a passive wind system with storage. Compact profiles are obtained by aggregating elementary patterns in order to fulfil some target indicators. The main difference between both methods presented in the paper is related to the choice of these indicators. In the first method, they are related to the storage system features while they only depend on wind features in the second

Integrated optimal design and sensitivity analysis of a stand alone wind turbine system with storage for rural electrification

In this paper, the authors investigate a robust Integrated Optimal Design (IOD) devoted to a passive wind turbine system with electrochemical storage bank: this stand alone system is dedicated to rural electrification. The aim of the IOD is to find the optimal combination and sizing among a set of system components that fulfils system requirements with the lowest system Total Cost of Ownership (TCO). The passive wind system associated with the storage bank interacts with wind speed and load cycles. A set of passive wind turbines spread on a convenient power range (2 – 16 kW) are obtained through an IOD process at the device level detailed in previous papers. The system cost model is based on data sheets for the wind turbines and related to battery cycles for the storage bank. From the range of wind turbines, a “system level” optimization problem is stated and solved using an exhaustive search. The optimization results are finally exposed and discussed through a sensitivity analysis in order to extract the most robust solution versus environmental data variations among a set of good solutions

Finite element simulation of magnesium alloys laser beam welding

The authors are grateful to FONDERIE MESSIER (HONSEL group) that provided the as-cast magnesium alloy workpieces. The authors would like also to acknowledge the technical support of Dr. Morraru of the IMS Laboratory, ARTS ET MÉTIERS PARISTECH, Aix En Provence, France.In this paper, a three-dimensional finite element model is developed to simulate thermal history magnesium-based alloys during laser beam welding. Space–time temperature distributions in weldments are predicted from the beginning of welding to the final cooling. The finite element calculations were performed using Cast3M code with which the heat equation is solved considering a non-linear transient behaviour. The applied loading is a moving heat source that depends on process parameters such as power density, laser beam dimensions and welding speed, and it is associated to moving boundary conditions. Experiments were carried out to determine temperature evolution during welding and to measure the laser weld width. By comparing the thermal model answers with the measurements, it is found that numerical simulations results are in a good agreement with the experimental data

Impact of SOC variations on the battery bank sizing of a stand-alone system fed by a passive wind turbine

In this paper, the authors compare and analyse two passive wind turbine system models in order to show their equivalence through a storage bank sizing procedures. The main differences between both models reside in the design accuracy and the computational time needed for each model to simulate the wind turbine system behaviour. On the one hand, a first "mixed reduced model" neglects the electrical mode effect and assumes that the DC battery bus voltage is constant (i.e. invariable State Of Charge: SOC). On the other hand, the second "full analytic model" couples SOC fluctuations (i.e. bus voltage variations) in the whole system. When compared to the second model, the "mixed reduced model" allows reducing computational time, which is a major factor in the context of systemic design by optimization. The analysis is performed to put in evidence the correspondence between both sizing approaches with the two corresponding models. The results are finally discussed from the point of view of the compromise design accuracy and computational time reduction. In this paper, the authors compare and analyse two passive wind turbine system models in order to show their equivalence through a storage bank sizing procedures. The main differences between both models reside in the design accuracy and the computational time needed for each model to simulate the wind turbine system behaviour. On the one hand, a first "mixed reduced model" neglects the electrical mode effect and assumes that the DC battery bus voltage is constant (i.e. invariable State Of Charge: SOC). On the other hand, the second "full analytic model" couples SOC fluctuations (i.e. bus voltage variations) in the whole system. When compared to the second model, the "mixed reduced model" allows reducing computational time, which is a major factor in the context of systemic design by optimization. The analysis is performed to put in evidence the correspondence between both sizing approaches with the two corresponding models. The results are finally discussed from the point of view of the compromise design accuracy and computational time reduction. Do not use abbreviations in the title unless they are unavoidable

Liquid Film Evaporation: Review and Modeling

Liquid film evaporation is encountered in various applications including in air humidifiers, in multiple effect distillers in thermal desalination, and in absorption cooling evaporators. It is associated with a falling pure, binary or multicomponent liquid film with associated complex and coupled heat and mass transfer processes. This chapter presents important fundamental aspects inherent to falling film evaporation in several geometrical configurations such as on horizontal tubes and inside inclined or vertical tubes or channels. The first part of the chapter concerns a review of recent works on this topic with emphasis on modeling and simulation features related to falling liquid films with heat and mass transfers. This document aims also to establish a frame for the modeling of the fluid flow with heat and mass transfer in the presence of evaporation. The main governing equations and the appropriate boundary and interfacial conditions corresponding to the fluid flow and associated heat and mass transfer and phase change are systematically presented and discussed for the case of falling film in a vertical channel with the presence of flowing gas mixture. Various simplifications of the governing equations and boundary and interfacial conditions have been proposed and justified. In particular, the formulation with extremely thin liquid film approximation is discussed

From an integrated optimal design to a systemic optimization of a stand alone passive wind turbine system with storage

In this paper, the authors report the development of a Systemic Optimization Process (SOP) devoted to a passive wind turbine system with electrochemical storage bank. Aim of the SOP is to find the optimal combination and sizing among sets of system components, that meets the desired system requirements with the lowest system owning cost. The passive wind system associated to the storage bank interacts with wind and load cycles (deterministic data). Sets of passive wind turbines are obtained through an Integrated Optimal Design (IOD) process. The system cost model is inspired from constructor data for the wind turbines and related to the battery cycles for the storage bank. An optimization problem is developed and performed using an exhaustive search. The optimization results are finally exposed and discusse

Integrated optimal design of a photovoltaic/wind system for electricity and water production

This paper investigates the integrated optimal design of a hybrid PV/wind generator coupled with two kinds of storage i.e. electric (battery) and hydraulic (tanks) devices for the production of electricity and drinking water in remote areas. Taking account wind and PV potentials in such system for assessing its performance implies its simulation over long periods of time. This can drastically increase the CPU time cost related to the design step, especially if the system energy management and sizing are sequentially integrated into a two level optimization process. In order to solve this problem and accelerate the system simulation, two complementary approaches are suggested. On one hand, metamodels are used for representing the system constraints and objectives. On the other hand, PV and wind cycles are compacted with a synthesis procedure which preserves their influence on the system performance with regard to the reference data. Those approaches are applied to the grey energy optimization of the studied hybrid system

Smart power management of a hybrid photovoltaic/wind stand-alone system coupling battery storage and hydraulic network

An off-grid energy system based on renewable photovoltaics (PV) and wind turbines (WT) generators is coupled via converters to electric and hydraulic networks. The electric network is composed of consumers and of a battery bank for electrical storage,while the hydraulic part is made of motor-pumps and hydraulic tanks for water production and desalination. Both battery and water tanks are used to optimize the power management of both electric and hydraulic subsystems by ensuring electric load demand and by reducing at the same time water deficit following the operation of the renewable intermittent source. Thus, both electric and hydraulic subsystems are strongly coupled in terms of energy making necessary to manage the power flows provided by renewable sources to optimize the overall system performance. In this paper, two kinds of management strategies are then compared in the way they share the hybrid power sources between the storage devices (battery and tanks) and the electrical/hydraulic loads. The first approach deals with an “uncoupled power management” in which the operation of electrical and hydraulic loads does not depend on the state of the intermittent renewable sources: in particular, hydraulic pumps are operated only taking account of water demand and tank filling but without considering power sources. On the contrary, given the available power produced by the sources, the second class of strategy (i.e. the “coupled management strategy”) consists of a “smart” power sharing between the electrical and hydraulic networks with regard to the battery SOC and the tank L1 and L2. A dynamic simulator of the hybrid energy system has been developed and tested using a MATLAB environment. The system performance is shown under the two investigated approaches (uncoupled vs coupled). Several tests are carried out using real meteorological data of a remote area and a practical load demand profile. The simulation results show that the “coupled strategy” clearly outperforms the classical “uncoupled” management strategies

CO2 laser beam welding of AM60 magnesium-based alloy

The authors are grateful to FONDERIE MESSIER HONSEL group that provided the as-cast magnesium alloy workpieces. The authors would like also to acknowledge the technical support of Dr. Moraru of the LSIS Laboratory-Arts et Métiers ParisTech-Aix En Provence-France.Magnesium alloys have a 33% lower density than aluminum alloys, whereas they exhibit the same mechanical characteristics. Their application increases in many economic sectors, in particular, in aeronautic and automotive industries. Nevertheless, their assembly with welding techniques still remains to be developed. In this paper, we present a CO2 laser welding investigation of AM60 magnesium-based alloy. Welding parameters range is determinate for the joining of 3 mm thickness sheets. The effects of process parameters including beam power, welding speed, focusing position, and shielding gas flow are studied. Experimental results show that the main parameters that determine the weld quality are the laser beam power, the welding speed, and the shielding gas flow. The focal point position has a minor effect on weld quality, however, it has an influence on melting zone width. For optimized welding parameters, metallurgical observations show that after laser welding of AM60 alloy dendritic microstructure is observed on melting zone after high solidification rate. A small heat affected zone is also detected. Finally, hardness tests indicate that microhardness of the weld is higher than that of base metal