Critères de choix d'un système de stockage électrochimique hybride d'énergie photovoltaïque

International audienceThe design of battery systems is an important issue in many cases conditioned by several constraints and modeling challenges. This work proposes a design method for electrochemical hybrid energy storage system associated with photovoltaic modules. Based on this method, an optimization procedure is used to discuss the interest of creating a hybrid system combining two different types of batteries. The batteries are modeled as a constant voltage source in series with an internal resistance and the finite capacity of the batteries is considered independent from their use. The model uses the battery capacity, maximum charge rate, internal resistance and cost given at the beginning of the battery life.Une procédure d'optimisation et de dimensionnement d'un système de stockage électrochimique d'énergie associé à des panneaux solaires est décrite et discutée. Elle permet d'étudier l'intérêt ou non de réaliser un système hybride associant deux types de batteries différents. Cet outil utilise un modèle simplifié de batteries : elles sont considérées comme une source de tension constante en série avec une résistance interne avec une capacité finie indépendante du type d'utilisation. Le modèle prend ainsi en compte des caractéristiques de batteries à l'état neuf : capacité, régime maximal de charge, résistance interne et coût

Dimensionnement et gestion optimaux d’éléments de stockage pour le déploiement de sources renouvelables, réalisation d'un micro-réseau LVDC

National audienceBecause of our global high consumption of fossil fuels, these resources are becoming scarce and the environmental equilibrium of the Earth is endangered. Other energy sources are developed in order to build a new diversified and decarbonised energy mix. For example, in an urban context, the solar photovoltaic system has many assets such as the decentralized production of electricity, easy integration in buildings, transportation losses reduction, no sound during production, low environmental impact, etc. However, the production of this energy source is highly varying, difficult to predict (several timescales, from the cloud shadows to seasonal meteorological variations) and not correlated across time with our consumption needs.In order to enable a massive penetration of renewable energy sources in our conventional grid, the use of energy storage systems (e.g. electrochemical storage) seems a promising solution, taking into account the costs, supply security, technological maturity and ease of set up. Hence, new microgrids constituted by decentralized energy sources and energy storage systems have been developed in order to replace or complement the main centralized grid by ensuring some support functions (i.e. enhancement of the grid stability, black-start operation, replacement of diesel generators, etc.). The consumers become actors able to inject a part of all their surplus energy to the main grid, if the operation is accepted by the transmission system operator. A new business model is to define, especially in the case of putting a valuation on the functions that can help the main grid.During this thesis, several years of data from production and consumption of a photovoltaic building have been analysed in order to define the operating profile of an energy storage system that ensures the equilibrium of the microgrid. A behavioural model taking into account the ageing has been made for three storage technologies: lead-acid batteries, lithium-ion batteries, and supercapacitors. It enables the optimal sizing, the hybrid association of storage systems, and the optimal energy management of the microgrid. Several criteria assessing the operation of microgrids have been studied (e.g. annual cost of the storage system, self-consumption rate, loss of load probability, etc.). A multi-objective methodology, based on Pareto optimality, has been developed in order to optimize economic, environmental, and autonomy aspects. A low voltage DC prototype of some kilowatts has been developed for validating the different concepts presented in this thesis.La forte consommation des énergies fossiles au niveau mondial entraine une raréfaction de ces ressources et met en danger l’équilibre environnemental global du fait de la pollution qu’elle engendre. D’autres sources d’énergie dites renouvelables se développent afin de proposer un mix énergétique très diversifié et progressivement décarboné. Par exemple, dans un contexte urbain, le solaire photovoltaïque présente de nombreux atouts comme la possibilité de produire de l’électricité de façon décentralisée, l’intégration aisée dans les bâtiments et infrastructures publiques, la réduction des pertes liées au transport de l’électricité, pas de pollution sonore, pas ou peu d’impact sur l’écosystème environnant, etc. Cependant, cette source est très intermittente et difficilement prédictible (diverses échelles de temps liées au passage de nuages, cycle diurne ou cycle saisonnier) et doit être implantée dans des endroits sans ombrage d’infrastructure pour assurer la meilleure production et durée de vie. De plus, sa production n’est généralement pas temporellement en phase avec des profils de consommation de type résidentiel ou tertiaire.Afin de répondre à la problématique d’intégration des énergies renouvelables dans nos réseaux électriques conventionnels, l’usage de moyens de stockage, par exemple de type électrochimique, semble aujourd’hui la meilleure solution, en considérant le coût, la sécurité d’approvisionnement, la maturité technologique et la facilité de mise en œuvre. Ainsi, de nouveaux micro-réseaux constitués de sources décentralisées et d’éléments de stockage apparaissent en concurrence du réseau centralisé conventionnel ou en complément de ce dernier afin d’atteindre de nouveaux objectifs (stabilité accrue du réseau, mode isolé de secours en cas de panne avec possibilité d’aider le redémarrage du réseau principal, remplacement de générateurs diesel auxiliaires, etc.). Parmi les grandes transformations actuelles, les consommateurs de plus en plus acteurs et peuvent injecter tout ou partie du surplus d’énergie produit vers le réseau ou choisir de consommer de l’énergie du réseau selon leurs souhaits. Un nouveau modèle économique se dessine avec la possibilité de voir apparaître de nouvelles tarifications de l’électricité notamment liées aux prestations assurant une plus grande robustesse du réseau.Durant cette thèse, plusieurs années de données de production et de consommation d’un bâtiment photovoltaïque ont été analysées pour définir les contraintes imposées à l’unité de stockage assurant l’équilibre du micro-réseau électrique. Un modèle de performance et de vieillissement a été élaboré pour trois technologies de stockage: batteries plomb-acide, batteries lithium-ion et supercondensateurs. Celui-ci permet le dimensionnement, l’association d’éléments de stockage et la gestion optimale des flux énergétiques au sein du micro-réseau. Divers critères permettant d’évaluer le fonctionnement des micro-réseaux ont également été étudiés comme le coût annuel de l’unité de stockage, le taux d’autoconsommation de l’énergie photovoltaïque, la quantité d’énergie qui n’a pas été fournie au consommateur, etc. Une approche multi-objective, basée sur le concept d’optimum de Pareto, a été mise en œuvre afin d’optimiser les aspects économique, environnemental et d’autonomie de fonctionnement des futurs réseaux électriques distribués. Un démonstrateur basse tension continue de quelques kilowatts a été développé pour valider les différents points étudiés dans cette thèse

LVDC grid based on PV energy sources and multiple electrochemical storage technologies

International audienceIn the global context of the electric power grid modernization, storage of electricity is a crucial issue. Nowadays, energy storage systems (ESS) are used more and more in positive energy buildings in conjunction with new Low Voltage Direct Current (LVDC) grids. However, the impact of renewable energy sources (RES) on ESS is not well known. The main objective of this article is to determine a systematic methodology to study energy data from a positive energy building in order to determine the impact on ESS dedicated to be included in smart-grids. The aim is to obtain comparative results in normalized working conditions and determine charge/discharge cycles. Clustering methods were compared to choose the more adapted one to treat the stored data of energy production and consumption during more than three years in our experimental platform in LAAS-CNRS, Toulouse. Each type of cycle will help further study in order to estimate its impact on efficiency and lifetime of ESS and then choose the more adapted element for each application

Working towards greener golf carts – A study on the second life of lead-acid batteries

International audienceAs electric cars become more popular, the disposal of used batteries will become a greater problem across the world. E-mobility requires a high power capability from the batteries to supply the necessary torque to engines. If a battery can no longer supply this power, it is no longer fit to be used in e-mobility. However, some batteries can still supply enough power for other applications, such as renewable energy systems. Repurposing a battery in these conditions is considered by the literature as giving it a second-life. Second-life batteries pose an important problem of cost. While they are sold at cheaper prices, they still require expensive equipment and tests to evaluate if and for how long they can be re-used, making them less competitive. This work proposes a low-cost solution to this issue

Control and design of a hybrid energy storage system

International audienceThe increasing deployment of intermittent renewable energy sources (RESs) around the world has revealed concerns about the power grid stability. To solve this problem, a massive use of storage systems is needed. The main goal of this work is to develop a hybrid energy storage system (HESS) combining several storage devices with complementary performances. In this paper, lead-acid batteries and supercapacitors (SCs) are associated in order to deliver a pulsed current. An innovative cascade control with anti-windup tracking manages the power sharing between a buck and a boost converters connected to the same DC bus. Analog control circuits and power converters have been designed to evaluate the performances of the HESS in real conditions

Dimensionnement multi-objectif d'une association batterie – supercondensateur pour une application photovoltaïque

National audienceLes énergies renouvelables comme le solaire photovoltaïque (PV) et l'éolien présentent une production intermittente et difficile à prédire précisément. Le stockage de l'énergie permet, a priori, d'assurer à chaque instant l'équilibre entre production et demande, condition nécessaire au bon fonctionnement de tout réseau électrique. Cependant, bien que les éléments de stockage électrochimique (ESE) soient adaptés pour remplir ce rôle, leur coût étant important, il est nécessaire de trouver un compromis entre conditions d'utilisation, performances et capacité de stockage d'énergie. Ce papier présente une méthodologie d'association d'ESE qui peuvent être plutôt destinés à fournir de l'« énergie » (ESE ayant une grande énergie spécifique exprimée en Wh/kg) comme des batteries au plomb-acide, lithium-ion, Ni-MH avec d'autres ESE de type « puissance » comme des supercondensateurs (SC) ou des batteries lithium-ion dédiées. Une modélisation de type circuit électrique avec prise en compte du vieillissement des ESE est développée et validée par quelques résultats expérimentaux. Trois critères ont ensuite été retenus pour évaluer le caractère optimal du dimensionnement de l'unité de stockage hybride

Development of a photovoltaic low voltage DC microgrid for buildings with energy storage systems

International audienceIn order to develop a sustainable datacenter, which would help to validate energy management and task scheduling algorithms, a low voltage direct current (LVDC) microgrid (MG) has been deployed in the ADREAM Building-Integrated Photovoltaic (BIPV) of the LAAS-CNRS in Toulouse, France. This MG is composed of a 1 kWp PV source, 300 Ah – 36 V lead-acid batteries, 330 F – 48 V supercapacitor (SC) pack and DC loads (cloud servers, USB chargers, sensors monitoring an apartment…). A very simple and efficient energy flow management strategy, based on the " DC bus signaling " approach has been implemented. It takes advantage of the DC bus architecture and enables a scalable electrical structure constituted of several sources, loads and storage elements easy to connect/disconnect via their converters. The development of this MG put in evidence the need for future theoretical developments regarding the determination of optimal DC bus signaling thresholds

Optimal Design and Operation Management of Battery-Based Energy Storage Systems (BESS) in Microgrids

International audienceEnergy storage systems (ESSs) can enhance the performance of energy networks in multiple ways; they can compensate the stochastic nature of renewable energies and support their large-scale integration into the grid environment. Energy storage options can also be used for economic operation of energy systems to cut down system’s operating cost. By utilizing ESSs, it is very possible to store energy in off-peak hours with lower cost and energize the grid during peak load intervals avoiding high price spikes. Application of ESSs will also enable better utilization of distributed energy sources and provide higher controllability at supply/demand side which is helpful for load leveling or peak shaving purposes. Last but not least, ESSs can provide frequency regulation services in off-grid locations where there is a strong need to meet the power balance in different operating conditions. Each of the abovementioned applications of energy storage units requires certain performance measures and constraints, which has to be well considered in design phase and embedded in control and management strategies. This chapter mainly focuses on these aspects and provides a general framework for optimal design and operation management of battery-based ESSs in energy networks

Optimal scheduling of a battery-based energy storage system for a microgrid with high penetration of renewable sources

International audienceA new scheduling method is proposed to manage efficiently the integration of renewable sources in microgrids (MGs) with energy storage systems (ESSs). The purpose of this work is to take into account the main stress factors influencing the ageing mechanisms of a battery energy storage system (BESS) in order to make an optimal dispatch of resources in the microgrid and enhance the storage system lifetime while minimizing the cost of electric consumption. The load demand and generation profiles are derived from the analysis of consumption and renewable production (solar photovoltaic sources and wind turbines) of the Western Denmark electric grid. Thus, the proposed microgrid is mainly fed by renewable sources and few electricity is coming from the main grid (which helps operating costs minimization). In this respect, a cost analysis is performed to find the optimal hourly power output of the BESS as well as the purchased electricity from the utility

Optimal sizing of a lithium battery energy storage system for grid-connected photovoltaic systems

International audienceThis paper proposes a system analysis focused on finding the optimal operating conditions (nominal capacity, cycle depth, current rate, state of charge level) of a lithium battery energy storage system. The purpose of this work is to minimize the cost of the storage system in a renewable DC microgrid. Thus, main stress factors influencing both battery lifetime (calendar and cycling) and performances are described and modelled. Power and energy requirements are also discussed through a probabilistic analysis on some years of real data from the ADREAM photovoltaic building of the LAAS-CNRS in Toulouse, FRANCE