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<p>Storage systems play a vital part in modern IT systems. As the volume of data grows explosively and greater requirement on storage performance and reliability is put forward, effective and efficient design and operation of storage systems become increasingly complicated. </p><p>Such efforts would benefit significantly from the availability of quantitative analysis techniques that facilitate comparison of different system designs and configurations and provide projection of system behavior under potential operational scenarios. The techniques should be able to capture the system details that are relevant to the system measures of interest with adequate accuracy, and they should allow efficient solution so that they can be employed for multiple scenarios and for dynamic system reconfiguration. </p><p>This dissertation develops a set of quantitative analysis methods for modern storage systems using stochastic modeling techniques. The presented models cover several of the most prevalent storage technologies, including RAID, cloud storage and replicated storage, and investigate some major issues in modern storage systems, such as storage capacity planning, provisioning and backup planning. Quantitative investigation on important system measures such as reliability, availability and performance is conducted, and for this purpose a variety of modeling formalisms and solution methods are employed based on the matching of the underlying model assumptions and nature of the system aspects being studied. One of the primary focuses of the model development is on solution efficiency and scalability of the models to large systems. The accuracy of the developed models are validated through extensive simulation.</p> / Dissertation

The hydrocarbon combustion process used to generate electricity releases harmful levels of Carbon, Sulfur and Nitrogen Oxides into the atmosphere. The alternative to environmentally toxic hydrocarbon based fuel, is electricity generated from solar powered microgrids. Solar photovoltaic microgrids represent a clean, renewable and economically viable energy alternative to hydrocarbon based fuel. The microgrid project outlined the specifications required to the charge the battery powered material handling vehicles at General Stamping & Metalworks. The project was designed to replace utility supplied electrical power with a solar microgrid to charge three lead acid type batteries. The solar microgrid project specifies the system requirements, equipment selection and installation methodology. Operational strategies for additional photovoltaic applications within the organization are discussed. Outlined in the report are the costs of installation and return on investment. The project was designed to demonstrate a practical application of microgrids within a manufacturing environment. The goal of the project was to design and build a small scale installation to provide a proof of concept. The overarching goal was to reduce the toxic emissions produced by utility supplied electrical power by installing a solar powered microgrid. The end result of the analysis was that photovoltaic powered microgrids represent a viable energy generating system for battery powered applications. However, based on the regional utility price of .092 $/kWh, the solar installation did not meet the organizations investment acceptance criteria.

The thesis investigates deployment of a Peer-to-Peer storage system in a cluster environment, in which machines have good and persist network connection, in order to provide the functionality of a data centre. For various reasons, the implementation is based on the Peer-to-Peer system known as Chord. Chord naturally provides storage load-balancing, especially if its virtual node scheme is used, but this needs to be improved if Chord is used to implement a storage system. A novel, threshold-based storage load-balancing scheme is proposed. Each machine in the system contributes a fixed amount of disk storage space to the Peer-to-Peer storage system. The system commences operation in the normal Chord manner except that two distinct sets of tables are initialised, one to maintain the usual Chord Ring, and one to maintain proximity information about the machines in the system. As files are inserted, the collective storage space gradually fills up. When any machine reaches the threshold for usage of its contributed space, the system behaviour is modified. Attempts are made, repeatedly if necessary, to migrate virtual nodes from heavily loaded machines to less-heavily loaded machines elsewhere in the system. The proximity information is used so as to minimise the costs of this migration. The nature of the proximity information is complex, and a Space-Filling Curve is utilised to reduce the complexity. For reasons of effectiveness, demonstrated by an evaluation against other kinds of Space-Filling Curve, the Hilbert curve is specifically chosen. The performance of the resulting implementation is evaluated in a practical experimental environment which consists of five teaching laboratories in the author’s school. Under the specific conditions of the experiments, the new system achieves significantly better distribution of storage utilisation across the participating machines and also defers the onset of unreliable behaviour in the system. In one experiment, the amount of the total storage space available that is actually utilised by the system increased from ∼ 43% to ∼ 62% using the proposed mechanism. The parameters used in the experiments have been chosen somewhat arbitrarily, so it is possible that even better results might be feasible.

Under 2011 började MacBat AB ta fram ett elenergilager kallat Macbat Energy Storage System (MESS), vilket är uppbyggt av 360 stycken tvåvolts bly-syrabatterier inhysta i ett 20 fots container. Då bly-syrabatterier är känsliga för värme är den här studien inriktad på att utreda hur stort kylbehovet blir under olika förutsättningar där kyldistribution, drifttemperatur på batterierna, klimat, isolering och termiska tröghet är varierande parameterar. Det ska även avgöras vilken konfiguration av kyldistribution och isolering som ger lägst kylbehov för de studerade klimaten, vilka är av varmtempererad, arid och tropisk karaktär. För att besvara studiens två mål togs fyra matematiska modeller fram i SIMULINK. Två luftkylda och två vattenkylda där en av varje var isolerad med 100 mm mineralull medan den andra var oisolerad. För samtliga modeller varierades drifttemperaturen mellan 25 – 35 °C och de studerade klimaten utgjordes av Phnom Phen, Kambodja, Djibouti, Djibouti, Bagdad, Irak samt London, England. För de vattenkylda modellerna varierades även MESS termiska tröghet i spannet 1,8058 – 9,0288 MJ/K genom att öka mängden kylvatten i systemet som användes för att kyla batterierna. Batteriernas drifttemperatur visade sig vara den parameter som i högst grad avgör kylbehovets storlek. Isoleringen gav en reducerande effekt på kylbehovet i de fall då omgivningstemperaturen under längre perioder överstiger batteriernas drifttemperatur. Varierande termisk tröghet, i de vattenkylda modellerna, hade liten eller ingen inverkan på kylbehovet. Det beror förmodligen på att den termiska massa som konstant finns i batterierna i form av elektrolyt var betydligt större. I fråga om vilken konfiguration av distributionssystem och isolering som ska användas för att erhålla ett lågt kylbehov visade sig detta bero på klimatet och drifttemperaturen på batterierna. Varmtemperade klimat som London behöver dock inget kylsystem överhuvudtaget. / In 2011 MacBat AB began to develop a electrical energy storage system called Macbat Energy Storage System (MESS), which is made up of 360 two volt lead acid batteries housed in a 20 foot container. However, while lead acid batteries are sensitive to heat this study is focused on investigating how great a cooling demand will be required under different conditions in which chilled distribution, operating temperature of the batteries, climate, insulation and thermal inertia are varied parameters. The study will also determine the configuration of chilled distribution and isolation that gives minimum cooling requirements for the studied climates, which is warm temperate, arid and tropical nature To answer the study's two goals four mathematical models were developed in SIMULINK. Two air-cooled and two water-cooled where one of each was insulated with 100 mm mineral wool while the other was bare. For all models the operating temperature varied between 25 - 35 ° C and the studied climates consisted of Phnom Penh, Cambodia, Djibouti, Djibouti, Baghdad, Iraq, and London, England. For the water cooled models thermal inertia was also varied in the range of 1.8058 to 9.0288 MJ/ K by increasing the amount of cooling water in the system used to cool the batteries. The battery operating temperature was proven to have the most significant impact on the cooling load. The isolation yielded a reducing effect on the cooling load in the case where the ambient temperature surpassed the battery operating temperature during longer periods. Varying thermal inertia of the water cooled models had little or no impact on the cooling load. It is probably due to the electrolyte in the batteries. It is a considerably larger source of thermal mass and is constant in all the models. Which configuration, regarding the distribution system and insulation, that obtains a low cooling requirement was found to depend on the ambient climate and the battery operating temperature. However, warm temperate climates such as London requires no cooling system at all.

The overall performance of a hydrogen storage system can be affected by various parameters, such as operation and design parameters, but also by the state of the hydrogen contained inside the storage tanks. In this work, a methodology is developed to evaluate the state of the hydrogen during the filling process and its impact on the overall system performance under variable operation conditions and design parameters. To approach as close as possible hydrogen as real gas, the thermodynamic properties of it are obtained from experimental thermodynamic tables. Based on those thermodynamic tables, a discrete database for each thermodynamic property is constructed. To minimize the error and achieve acceptable execution time, a searching method based on curve fitting techniques is developed to derive the thermodynamic properties from the discretized data. The evaluation of the hydrogen state is done based on a developed method that derives the pressure and temperature based on calculated thermodynamic properties during the filling process. The interaction between the contained hydrogen and tank during the filling process is taken into account during the methodology development. Furthermore, energy requirements for the compression system of the hydrogen storage system, including the cooling demand, are also included in the methodology. Based on the developed methodology, a transient model that can evaluate the hydrogen state condition, storage tank wall temperature condition, and energy requirement of the storage system is developed. Validation against experimental and simulation results for an actual filling event of a hydrogen storage tank is done, showing good agreement in the results. The model was used to simulate the performance of a hydrogen storage system, inspired in terms of layout by a real-world HRS storage system. The results showed that the total amount of filled hydrogen and the filling duration of the charging process are greatly affected by the compression and heat transfer phenomena occurring inside the tank. The storage tanks with lower volumes and higher operation pressure tend to be more affected by compression and heat transfer phenomena. Operation parameters such as inlet mass flow and inlet temperature, can have an impact on the system, both in terms of energy consumption and filling performance. Furthermore, based on the investigation of compression stages, the results showed that the number of stages can affect the compression ratio of each stage, resulting in lower or higher efficiency, which directly affects the energy consumption of the compression system. A parametric investigation of the upper operation pressures of the hydrogen tanks showed that the total amount of stored hydrogen is affected when the respective upper pressures vary. Last, it was shown that there is an optimal upper pressure level for each bank that can result in lower specific compression energy, indicating that the model could be used for optimization purposes.

A resilient power grid system is important to ensure the delivery of power to consumers while minimizing the cost of new technologies. Due to the increase of electricity consumption and CO2 emission, renewable energies and energy storage system are a compelling alternative. We started to identify decisions that need to be made, and parameters associated to model a power grid system expansion plan. Then, we investigated a utility company demand for the next 15 years. Also, we identified their current resources, and used that as a starting point. Then, we formulated an optimization model for a power grid expansion with different types of renewable energies, such as solar and wind, to meet the demand and minimize the cost of installation; as well as, a battery storage system (Lithium-ion) that is considered to come up with an optimal solution of a resilient power grid. Moreover, uncertainties of renewables are considered in the model, and robust optimization formulation is used to model them. Existing coal facilities are considered as a part of the model as well, and this part is designed on the optimization model in a way that would help decrease the use of such facilities and still manage them to meet demand. Numerical experiments are performed on several scenarios, and compared to what the utility company has forecasted in terms of cost, and renewable energies integration.A resilient power grid system is important to ensure the delivery of power to consumers while minimizing the cost of new technologies. Due to the increase of electricity consumption and CO2 emission, renewable energies and energy storage system are a compelling alternative. We started to identify decisions that need to be made, and parameters associated to model a power grid system expansion plan. Then, we investigated a utility company demand for the next 15 years. Also, we identified their current resources, and used that as a starting point. Then, we formulated an optimization model for a power grid expansion with different types of renewable energies, such as solar and wind, to meet the demand and minimize the cost of installation; as well as, a battery storage system (Lithium-ion) that is considered to come up with an optimal solution of a resilient power grid. Moreover, uncertainties of renewables are considered in the model, and robust optimization formulation is used to model them. Existing coal facilities are considered as a part of the model as well, and this part is designed on the optimization model in a way that would help decrease the use of such facilities and still manage them to meet demand. Numerical experiments are performed on several scenarios, and compared to what the utility company has forecasted in terms of cost, and renewable energies integration.

Magíster en Ciencias de la Ingeniería, Mención Eléctrica / Ingeniero Civil Eléctrico / Los sistemas de almacenamiento de energía (ESS) pueden ser utilizados para realizar mejoras sustanciales en los sistemas eléctricos de potencia. Esto se debe a la flexibilidad que entregan durante la carga y la descarga, permitiendo diversas aplicaciones, entre las que destacan el recorte de potencia punta; compra y venta de energía, disminución de pérdidas en líneas de transmisión y evitar congestión el líneas de transmisión. En particular para una distribuidora resulta de especial interés estas características del ESS, ya que le permiten aumentar su rentabilidad. El objetivo principal de esta tesis es dimensionar y localizar de manera óptima ESS con el objetivo de recortar la punta de demanda en redes de distribución (RD). Junto con lo anterior se busca relacionar la optimización con parámetros importantes de ESS, tales como los costos de inversión, eficiencia y vida útil. Para lograr esto se propone una metodología que considera el punto de vista de la distribuidora. Esta metodología evalúa el pago por potencia y compra de energía por parte de la distribuidora; los costos de inversión, y los costos de operación y mantenimiento del ESS. A partir de esta metodología se obtienen diferentes costos de inversión frontera al variar parámetros del BESS tales como la eficiencia y la vida útil. Estas fronteras de costos de inversión determinan el límite costo que hace aún rentable al proyecto de BESS para la distribuidora. Los resultados muestran que el dimensionamiento óptimo está fuertemente afectado por los costos de inversión del BESS. Por otro lado, el parámetro técnico que permite una mayor mejora desde el punto de vista de la reducción de costos de la distribuidora es la vida útil de ESS, donde, por sobre los 5000 ciclos es posible rentabilizar proyectos con los costos de inversión presentes en varias tecnologías actuales. Al utilizar una estrategia de localización óptima la reducción de costos aumenta en de un 4 al 7,5% con respecto al dimensionamiento óptimo y su importancia relativa en el proyecto de BESS depende del precio de la energía. La reducción de costos que se obtiene de la localización óptima de módulos de BESS alcanza una saturación a medida que la cantidad de módulos de BESS aumenta. Este efecto sugiere que existe una cantidad óptima de módulos a localizar.

Microgrids are local power systems of different sizes located inside the distribution systems. Each microgrid contains a group of interconnected loads and distributed energy resources that acts as a single controllable entity with respect to the grid. Their islanding operation capabilities during emergencies improve the resiliency and reliability of the electric energy supply. Due to its low kinetic energy storage capacity, maintaining microgrid stability is challenging under system contingencies and unpredictable power generation from renewable resources. This dissertation highlights the potential benefits of flexibly utilizing the battery energy storage systems to enhance the stability of microgrids. The main contribution of this research consists in the development of a storage converter controller with an additional stability margin that enables it to improve microgrid frequency and voltage regulation as well as its induction motor post-fault speed recovery. This new autonomous control technique is implemented by adaptively setting the converter controller parameters based on its estimated phase-locked loop frequency deviation and terminal voltage magnitude measurement. This work also assists in the microgrid design process by determining the normalized minimum storage converter sizing under a wide range of microgrid motor inertia, loading and fault clearing time with both symmetrical and asymmetrical fault types. This study evaluates the expandability of the proposed control methodologies under an unbalanced meshed microgrid with fault-induced feeder switching and multiple contingencies in addition to random power output from renewable generators. The favorable results demonstrate the robust storage converter controller performance under a dynamic changing microgrid environment.

The goal of this study was to determine the economic feasibility of battery energy storage system (BESS). Three major economic benefits derived from BESS using were studied: 1. Energy Purchase Shifting, 2. Distribution Feeder Deferral, 3. Outage Avoidance. The economic analysis was based on theoretical modeling of the BESS and distribution system. Three simulation models were developed to quantify the effects of different parameters, such as: BESS round-trip efficiency, life span, rated power, rated discharge time, marginal cost of electric energy, 24 h feeder load profile, annual load variation, feeder load growth rate and feeder length. An optimal battery charging/discharging method was presented to determine the differential cost of energy (DCE). The annual maximum DCE was calculated using stochastic probability analysis on seasonal load variation. The net present value was evaluated as the present value difference between two investments: first, the distribution feeder upgrade without BESS deferral, and second, with BESS deferral. Furthermore, the BESS’s contributions under different outage strategies were compared. It was determined that feeder length is the most significant parameter. The economics of the studied system becomes favorable when the feeder length exceeds a critical value.