Power Management in a Utility Connected Micro-Grid with Multiple Renewable Energy Sources

As an efficient alternative to fossil fuels, renewable energy sources have attained great attention due to their sustainable, cost-effective, and environmentally friendly characteristic. However, as a deficiency, renewable energy sources have low reliability because of their non-deterministic and stochastic generation pattern. The use of hybrid renewable generation systems along with the storage units can mitigate the reliability problem. Hence, in this paper, a grid connected hybrid micro-grid is presented, which includes wind and photovoltaic resources as the primary power sources and a hydrogen storage system (including fuel cell and electrolyzer) as a backup. A new power management strategy is proposed to perform a proper load sharing among the micro-grid units. Hybrid (distributed/central) control method is applied for the realization of the control objectives such as DC bus voltage regulation, power factor control, synchronous grid connection, and power fluctuation suppression. Distributed controllers have the task of fulfilling local control objectives such as MPPT implementation and storage unit control. On the other hand, the central control unit is mainly responsible for power management in the micro-grid. Performance and effectiveness of the proposed power management strategy for the presented micro-grid are verified using a simulation study

Modélisation et optimisation de la gestion énergétique d’un nano-réseau multisource autonome

Les installations électriques en régions éloignées dépendent d’une source d’énergie indépendante du réseau principal pour s’alimenter. Une petite installation autonome alimentée par différentes sources, comme des panneaux solaires, une génératrice et des batteries, aussi appelée un nano-réseau, est une solution efficace pour répondre à ce besoin. Cependant, elle fonctionne avec une source d’énergie solaire intermittente, ce qui pose des défis de gestion énergétique. Un tel système multisource nécessite une gestion visant à maximiser l’utilisation de l’énergie solaire afin de réduire l’utilisation de la génératrice et les impacts environnementaux qui l’accompagnent. Ce projet de maîtrise vise à réduire l’utilisation de la génératrice des nano-réseaux. Il se base sur le cas d’étude d’une antenne de télécommunication alimentée par ce type de nano-réseau à Dorval-Lodge, Québec, Canada. Afin de développer des méthodes de réduction d’appel de la génératrice, un modèle numérique complet de la station a d’abord été développé et validé avec le cas d’étude. Ce modèle, basé sur sa représentation énergétique macroscopique, permet d’estimer la production des panneaux solaires, la production de la génératrice et l’état de charge des batteries avec respectivement 1,6 %, 2,1 % et 2,2 % d’erreur par rapport au comportement réel. À partir de ce modèle, une nouvelle proposition des paramètres de contrôle de la station ont été suggérés pour différentes saisons permettant d’atteindre des réductions de frais d’exploitation de la génératrice en hiver et au printemps de respectivement 10 % et 12 %. Le cadre de modélisation développé dans ces travaux peut être réutilisé pour des études de gestion de l’énergie, d’analyse économique et de projections pour les nano-réseaux existants et potentiels. Il permet aussi d’améliorer la proposition d’optimisation saisonnière avec des approches de contrôle en temps réel considérant d’autres capteurs ou des prévisions météorologiques reliées aux performances de production d’énergie solaire

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School of Energy and Chemical EngineeringThe interest in hydrogen energy is rapidly increasing worldwide for developing renewable and clean energy. Among various hydrogen production methods, green hydrogen source produced by solar energy is a promising way with zero emission. Photoelectrochemical (PEC) water splitting system is widely considered as one of most promising systems to generate green hydrogen since PEC system can produce green hydrogen by using water and solar energy, and when hydrogen energy is used, it can form the most ideal energy cycle. The categories of PEC system can be broadly divided into two parts: photoanode and photocathode. We have focused photoanode part by using ??-Fe2O3 called as hematite. Hematite is one of the cheapest materials used as a photoanode and has outstanding potential to theoretically achieve an efficiency of 15% solar-to-hydrogen (STH) conversion efficiency. In hematite-based photoanode, a variety of categories can be formed such as substrate, underlayer, overlayer, doping, oxygen evolution co-catalyst (OEC), and surface treatment. Herein, in the OEC part, we present an approach to minimize the light shielding effect by OEC in hematite surface. By successfully selectively adsorbing the developed Ti doped FeOOH (Ti-FeOOH) co-catalyst into the inner surface (inside pores) of hematite, Ti-FeOOH/Ti doped porous hematite (Ti-PH) shows a photocurrent density of 4.06 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) with good stability for 36 hours. In addition, we have focused on enhancing the performance of hematite itself and have been studying the synergy effect that can achieve structural evolution and doping through surface treatment at the same time as well as problems that may occur in the fabrication process. We cover two case of Si doping and Ge doping, respectively, and show the effects of dopants on hematite. Both cases utilize an overlayers of SiOx and GeO2, and Sn diffusion into hematite from the fluorine-doped tin oxide (FTO) coated glass can be suppressed when the overlayers are used. In the case of Si doping, we demonstrate the deep mechanism by which Si can be easily doped with Si and Ti interaction with efficient structural evolution. NiFeOx coated Si and Ti co-doped hematite shows 4.3 mA cm-2 at 1.23 V vs. RHE without any demanding fabrication process. In the case of Ge doping, we present that when Sn doping from FTO is suppressed, Ge is less affected by Sn and can make more efficient Ge doping effect. After decorating NiFeOx co-catalyst, NiFeOx/Ge doped porous hematite (Ge-PH) shows a photocurrent density of 4.6 mA cm-2 at 1.23 V vs. RHE and our tandem device with a perovskite solar cell (PSC) achieves 4.8% STH efficiency. Our works suggests a straightforward way to develop efficiently doped hematite, that can be easily expanded to other doping systems for green hydrogen production.ope

Stand-alone solar-pv hydrogen energy systems incorporating reverse osmosis

The world’s increasing energy demand means the rate at which fossil fuels are consumed has increased resulting in greater carbon dioxide emissions. For many small (marginalised) or coastal communities, access to potable water is limited alongside good availability of renewable energy sources (solar or wind). One solution is to utilise small-scale renewably powered stand-alone energy systems to help supply power for everyday utilities and to operate desalination systems serving potable water (drinking) needs reducing diesel generator dependence. In such systems, on-site water production is essential so as to service electrolysis for hydrogen generation for Proton Exchange Membrane (PEM) fuel cells. Whilst small Reverse Osmosis (RO) units may function as a (useful) dump load, it also directly impacts the power management of stand-alone energy systems and affects operational characteristics. However, renewable energy sources are intermittent in nature, thus power generation from renewables may not be adequate to satisfy load demands. Therefore, energy storage and an effective Power Management Strategy (PMS) are vital to ensure system reliability. This thesis utilises a combination of experiments and modelling to analyse the performance of renewably powered stand-alone energy systems consisting of photovoltaic panels, PEM electrolysers, PEM fuel cells, batteries, metal hydrides and Reverse Osmosis (RO) under various scenarios. Laboratory experiments have been done to resolve time-resolved characteristics for these system components and ascertain their impact on system performance. However, the main objective of the study is to ascertain the differences between applying (simplistic) predictive/optimisation techniques compared to intelligent tools in renewable energy systems. This is achieved through applying intelligent tools such as Neural Networks and Particle Swarm Optimisation for different aspects that govern system design and operation as well as solar irradiance prediction. Results indicate the importance of device level transients, temporal resolution of available solar irradiance and type of external load profile (static or time-varying) as system performance is affected differently. In this regard, minute resolved simulations are utilised to account for all component transients including predicting the key input to the system, namely available solar resource which can be affected by various climatic conditions such as rainfall. System behaviour is (generally) more accurately predicted utilising Neural Network solar irradiance prediction compared to the ASHRAE clear sky model when benchmarked against measured irradiance data. Allowing Particle Swarm Optimisation (PSO) to further adjust specific control set-points within the systems PMS results in improvements in system operational characteristics compared to using simplistic rule-based design methods. In such systems, increasing energy storage capacities generally allow for more renewable energy penetration yet only affect the operational characteristics up to a threshold capacity. Additionally, simultaneously optimising system size and PMS to satisfy a multi-objective function, consisting of total Net Present Cost and CO2 emissions, yielded lower costs and carbon emissions compared to HOMER, a widely adopted sizing software tool. Further development of this thesis will allow further improvements in the development of renewably powered energy systems providing clean, reliable, cost-effective energy. All simulations are performed on a desktop PC having an Intel i3 processor using either MATLAB/Simulink or HOMER

Alimentation électrique d'un site isolé à partir d'un générateur photovoltaïque associé à un tandem électrolyseur/pile à combustible (batterie H2/O2)

Les systèmes à énergies renouvelables couplés à un stockage hydrogène apportent des solutions nouvelles et innovantes à l'alimentation électrique des milieux peu ou non électrifiés. Le concept de batterie H2 qui équipe ce type de système est une forme de stockage originale qui apporte l'autonomie et l'indépendance électrique pour des longues durées (typiquement stockage saisonnier). Le fonctionnement de cette batterie H2 est le suivant : un électrolyseur produit des gaz (H2 et O2) avec les surplus d'énergie de la source renouvelable ; l'hydrogène, voire l'oxygène, est ensuite stocké dans des réservoirs pour être utilisé ultérieurement grâce à une pile à combustible lorsque la source renouvelable est insuffisante. Dans cette étude, nous nous intéresserons spécifiquement au couplage entre des générateurs photovoltaïques avec une batterie H2/O2 pour l'alimentation d'un site isolé sans interruption. Ces travaux de recherche s'inscrivent dans le projet ANR PEPITE (ANR-PanH 2007-2012) et ont été menés en partenariat avec HELION Hydrogen Power, le CEA Liten et l'Université de Corse. Le projet est également labellisé par les pôles de compétitivité CAPENERGIES et TENERRDIS. Tout d'abord, une réflexion générale s'appuyant sur les propriétés d'une batterie H2/O2 démontre la nécessité d'introduire une batterie (ici au plomb) pour garantir un fonctionnement instantané et sans interruption. Puis, une étude qualitative sur les architectures électriques possibles (bus de tension DC, AC…) a été menée pour s'achever sur une étude quantitative réalisée spécifiquement pour le projet PEPITE. Parallèlement à cela, différentes stratégies de gestions énergétiques ont été proposées afin d'utiliser les deux stockages dans les meilleures conditions, de limiter leur vieillissement ainsi que les pertes. Deux bancs d'essais à échelle réduite (un premier à bus DC et un second à bus AC) ont été réalisés au sein du laboratoire LAPLACE afin de valider les études et de préparer le prototype final qui sera testé sur le site de HELION Hydrogen Power au cours de l'été 2011. ABSTRACT : Renewable energy systems coupled to a hydrogen storage bring new and innovative solutions to supply power to environments with little or no electricity. The concept of H2 battery which is a part of such system is a form of storage that gives autonomy and electric independence for long periods (typically seasonal storage). The operation of this H2 battery is this: an electrolyser produces gases (H2 and O2) with the extra energy from the renewable source. Hydrogen or oxygen is then stored in tanks for later use with a fuel cell when the renewable source becomes insufficient. In this study, we focus specifically on the coupling between photovoltaic arrays with a H2/O2 battery to supply power to a remote site without interruption. This work is part of the PEPITE Project, partially funded by the french National Research Agency (ANR-Panh 2007-2011) and was conducted in partnership with HELION Hydrogen Power, CEA-Liten and the University of Corsica. The project is also accredited by the CAPENERGIES and TENERRDIS clusters. First, a general discussion based on the properties of a H2/O2 battery demonstrates the need to introduce a secondary battery (lead in our case) to ensure an instant and uninterrupted operation. Then, a qualitative study on the possible electrical architectures (DC bus or AC bus) was conducted and resulted in a quantitative study conducted specifically for the PEPITE project. At the same time, various energy management strategies have been proposed to use both storage in the best conditions, limiting their losses and aging. Two small scale bench tests (one with a DC bus and a second with an AC bus) were performed in the LAPLACE laboratory to validate our strategies and prepare the final prototype which will be tested on the site of HELION Hydrogen Power during the summer of 2011