Dissertations / Theses on the topic 'Sugar Renewable energy sources'

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The extraction of hemicelluloses prior to pulping that would have been dissolved in black liquor during pulping process, is an attractive alternative for pulp and paper mills as they, in addition to their core products, can increase their revenue by producing biofuels, biopolymers, paper additives and other chemicals. However, the amount of hemicelluloses extracted will be limited by the requirement to maintain pulp yield and pulp quality in comparison to existing pulping processes. In the present study, mild alkaline (NaOH) and dilute sulphuric acid conditions were used to extract hemicelluloses from Eucalyptus grandis, giant bamboo (Bambusa balcooa) and sugarcane (Saccharum officinarum) bagasse (SCB) prior to kraft or sodaAQ pulping processes. The effects of catalyst concentration, temperature and reaction time on hemicelluloses pre-extraction were studied, using a statistical experimental design to investigate conditions under which hemicelluloses could be extracted prior to alkaline pulping with minimal interference on cellulose (glucan) content. Subsequently, selected pre-extracted materials were subjected to kraft or sodaAQ pulping to evaluate the effect of the hemicelluloses pre-extraction on cooking chemicals, pulp yield and properties. This study also included evaluation of hot water hemicelluloses pre-extraction of SCB as it was part of a dilute sulphuric acid experimental design. The pulp yield, cooking chemicals and handsheet strength properties were compared with those obtained from kraft or sodaAQ pulping of non extracted raw materials. The results showed that alkaline pre-extraction options investigated preserves the pulp yield with minimal effect on handsheet strength properties depending on the choice of the subsequent pulping method while a fraction of xylan was extracted in polymeric form. In addition, less active alkali was required to delignify the xylan extracted materials. The integration of hemicelluloses pre-extraction by alkaline methods into a kraft pulping process was preferred for giant bamboo and E. grandis since it maintained pulp yields at desired industrial levels of 50%, and pulps within a bleachable kappa number range. Another advantage observed was the reduction in total cooking active alkali required to delignify alkaline extracted giant bamboo or E. grandis by 8or 3 percentage points respectively. However, the compromise to maintain the pulp yield was obtained when only 13.6% or 12.4% polymeric xylan was solubilised from giant bamboo or E. grandis respectively. Slight improvement in burst index of the handsheet was observed for extracted giant bamboo. On the other hand, pulp viscosity was increased by 13% due to the removal of low molecular weight hemicelluloses, while the breaking strength of the handsheet was also increased by 8.9% for pulps produced from extracted E. grandis. In the case of sugarcane bagasse, hemicelluloses pre-extraction by alkaline methods integrated well with the sodaAQ pulping process. It enabled a xylan recovery of 69.1%, while providing pulp with higher screened pulp yield (45.0%), with an advantageous decrease in kappa number (15.5). The handsheet tear index was superior without reduction in viscosity compared to pulp produced from non extracted SCB. On the contrary, results obtained from optimised dilute sulphuric acid pre-extraction of all the tested feedstocks were found to negatively impact subsequent kraft or sodaAQ pulping processes resulting in lower pulp yields and poorer strengths properties. Nonetheless, the differences were better when sodaAQ pulping was used compared to kraft pulping. SodaAQ protects the carbohydrates against the peeling reaction under alkaline medium. Conversely, pre-extraction of SCB with hot water resulted in low concentration of xylooligomers (5.7%), while the subsequent sodaAQ pulping resulted in no pulp yield reduction. The tear index and optical brightness of the handsheet papers produced from hot water extracted SCB were slightly improved while the breaking length, tensile and burst indexes were similar to those of pulps produced from non extracted SCB fibres. Of equal importance were the observed higher tear and burst indexes of handsheets produced from giant bamboo compared to E. grandis for both extracted and non extracted materials prepared under similar pulping processes. The advantage of bamboo was due to the larger fibre length and different morphological properties to those of hardwoods. However, the pulps produced from giant bamboo showed higher kappa numbers than those pulps produced from E. grandis due to the high condensation behaviour of bamboo lignins under alkaline conditions. Higher kappa numbers explained the higher demand for subsequent bleaching chemicals. In conclusion, the pulp mill biorefinery concept through hemicelluloses pre-extraction with NaOH can be achieved with modified kraft pulping or the sodaAQ pulping processes, but it depends on the type of raw material, extraction method and quality and performance requirements of a particular paper. The low pulping chemicals demand, comparable pulp yields and the improvement in some physico-chemical properties of the pulps from preextracted materials were observed. Furthermore, owing to xylan pre-extraction a larger amount of (extracted) material could be loaded into the digester as when non-extracted materials were used.
AFRIKAANSE OPSOMMING: Ekstraksie van hemiselluloses wat tydens verpulping in die swartloog opgelos word, bied ‘n aantreklike alternatief aan pulp- en papiermeulens om, addisioneel tot hul hoofprodukte, hul inkomste deur die vervaardiging van biobrandstowwe, biopolimere, papierbymiddels en ander chemikalië, daardeur te kan verhoog. Die hoeveelheid hemiselluloses wat ge-ekstraheer kan word, sal egter beperk word deur die vereiste dat pulpopbrengs en –kwaliteit tydens bestaande verpulpingsprosesse gehandhaaf moet word. In hierdie ondersoek is matige alkaliese (NaOH) en verdunde swawelsuurtoestande gebruik om hemiselluloses vóór kraft- of natriumantrakinoonverpulping uit Eucalyptus grandis, reuse bamboes (Bambusa balcooa) en suikerriet (Saccharum officinarum) bagasse, mee te ekstraheer. Die invloed van katalisatorkonsentrasie, temperatuur en reaksietyd is mbv ‘n statistiese, eksperimentele ontwerp ondersoek om die toestande te bepaal waaronder hemiselluloses, met minimale effek op die sellulose (glukaan) –inhoud, vóór alkaliese verpulping ge-ekstraheer kan word. Die pre-ge-ekstraheerde materiale, met hoë glukaan- en voldoende hemisellulosesinhoud, is vervolgens aan kraft- en natriumantrakinoonverpulping onderwerp om die invloed van pre-ekstraksie van hemiselluloses op die verpulpingsreagense, pulpopbrengs en - eienskappe vas te stel. Hierdie studie het ook die evualering van warmwater hemisellulosespre-ekstraksie van suikerrietbagasse, wat deel is van ‘n verdunde swawelsuur eksperimentele uitleg, ingesluit. Pulpopbrengs, die hoeveelheid verpulpingsreagense en handveleienskappe van dieselfde materiale wat nie vooraf ge-ekstraheer is nie, is vergelyk. Die resultate toon dat alkaliese pre-ekstraksie metodes wat ondersoek is die pulpopbrengs met minimale effek op handvel sterkte-eienskappe afhangende van die keuse van daaropvolgende pulpmetode kon handhaaf terwyl ‘n fraksie van xilaan in polimeriese vorm ge-ekstraheer is. Addisioneel, is minder aktiewe alkali benodig om die xilaan ge-ekstraheerde materiale te delignifiseer. Die integrasie van hemisellulosespre-ekstraksie dmv alkaliese metodes tydens ‘n kraft verpulpingsproses is vir reuse bamboes en E. grandis verkies omdat pulpopbrengste op ideale industriële vlakke van 50% gehandhaaf en is en pulp in ‘n bleikbare kappa nommergebied interval kon lewer. ‘n Verdere voordeel wat waargeneem is was die vermindering in die totale gekookte aktiewe alkali benodig vir reuse bamboes of E. grandis met 8 of 3 persentasiepunte onderskeidelik. Die kompromie om die pulpopbrengs te handhaaf is verkry toe slegs 13.6% of 12.4% polimeriese xilaan opgelos is vanuit reuse bamboes of E. grandis onderskeidelik. ‘n Effense verbetering in bars-indeks van die handvelle is waargeneem vir ge-ekstraheerde reuse bamboes. Pulpviskositeit het met 13% gestyg agv die verwydering van die lae molekulêre massa hemiselluloses, terwyl breeksterkte van handvelle ook met 8.9% toegeneem het vir pulp verkry uit pre-gekstraheerde E. grandis. NaOH pre-ekstraksie van 69.1% xilaan (droë massa) uit suikerriet bagasse (SCB) het ‘n hoër natriumantrakinoon, gesifte pulpopbrengs gelewer (45.0%) met ‘n verbeterde afname in kappa-getal (15.5) en uitstekende skeursterkte sonder verlaging in viskositeit, soos vergelyk met nie-ge-ekstraheerde suikkerrietbagasse. Daarteenoor het die resultate verkry met die geoptimeerde verdunde swawelsuur preekstraksie van al die getoetste rumateriale getoon om‘n negatiewe effek te gehad het op die daaropvolgende kraft- of natriumantrakinoonverpulping dws het laer pulpopbrengste en swakker sterkte-eienskappe opgelewer. Die verskille was nietemin kleiner toe natriumantrakinoonverpulping ipv kraftverpulping gebruik is. Antrakinoon beskerm die koolhidrate teen die afskilreaksie in alkaliese medium. Daarteenoor het pre-ekstraksie van suikerrierbagasse met warm water tot 'n lae hoeveelheid (5.7%) xilaanoligomere gelei, terwyl die daaropvolgende natriumantrakinoonverpulping geen verlaging in pulpopbrengs veroorsaak het nie. Skeursterkte en optiese helderheid van handvelle wat uit warm water ge-ekstraheerde suikerrietbagasse vervaardig is, het ietwat verbeter terwyl breek-, trek- en barssterkte dieselfde was as van suikerrietbagasse pulp wat nie ge-ekstraheer is nie. Net so belangrik was die waargenome hoër skeur- en barsindekse van handvelle vervaardig van reuse bamboes in vergelyking met E. grandis van beide geekstraheerde en nie ge-ekstraheerde materiale voorberei onder dieselfde verpulpings toestande. Bamboes se sterker eienskappe was as gevolg van die hoër vesellengte en ander morfologiese eienskappe as diévan loofhout. Pulp wat vervaardig is van reuse bamboes het ‘n hoër kappanommer getoon as pulp van E. grandis as gevolg van die hoë kondensasiegedrag van bamboeslignien onder alkaliese toestande. Hoër kappanommers kon die gepaardgaande hoër aanvraag vir bleikchemikalieë verklaar. Ten slotte, die pulpmeul bio-raffinaderykonsep nl. deur hemisellulosesekstraksie met NaOH gekombineer met óf ‘n gemodifiseerde kraft verpulping óf ‘n gemodifiseerde natriumantrakinoon verpulping, is wel uitvoerbaar. Dit word egter sterk beïnvloed deur die tipe ru-materiaal en die ekstraksie-metode gebruik, asook deur die kwaliteits- en gebruiksvereistes van verskillende tipes papier. ‘n Lae aanvraag vir verpulpingschemikalieë, vergelykbare pulpopbrengste en die verbetering in fisies-chemiese eienskappe van pulp vanaf pre-ge-ekstraheerde materiale is waargeneem. Verder kon, as gevolg van xilaan ekstraksie, meer ge-ekstraheerde materiaal in die verteerder gelaai word as wanneer nie-ge-ekstraheerde materiaal gebruik is.

A geração termelétrica a partir da biomassa proveniente do setor sucroenergético brasileiro, além de ser vista como opção para investimentos no setor de energias renováveis, pode contribuir com o suprimento de energia mantendo aspectos inerentes às vantagens sociais, estratégicas e ambientais que o favorecimento de um setor genuinamente desenvolvido no Brasil pode atribuir à matriz de energia elétrica. O objetivo principal deste trabalho é analisar o potencial adicional de energia elétrica que pode ser gerado a partir de recursos do setor sucroenergético. Os objetivos específicos estão em determinar e dimensionar os possíveis combustíveis para geração termelétrica no setor sucroenergético, em determinar quais rotas tecnológicas possibilitam o aumento da geração de energia e em quantificar a geração específica bruta de energia para cada tecnologia selecionada. O método consiste na realização de revisão bibliográfica para alocar o tema de estudo e pesquisa, com posterior elaboração de pesquisas documentais com o intuito de reunir dados e estimativas necessárias ao desenvolvimento do cálculo, coletando dados em publicações de institutos, entidades, empresas e consultores (dados de estimativas de produção de cana-de-açúcar para o período projetado e a definição dos recursos combustíveis e dos recursos tecnológicos). A seguir, para cada tecnologia de geração de energia elétrica, são apresentados arranjos com seus respectivos balanços de energia, índices de geração específica bruta de energia para as condições de cogeração e de geração de energia elétrica pura, vantagens, desvantagens e a inserção destas tecnologias ao longo do período estimado. Os resultados apontam que a expansão da produção de cana-de-açúcar, baseada na expansão agrícola e no aumento da produtividade, bem como o incremento tecnológico dos sistemas termelétricos de potência disponíveis comercialmente para o setor sucroenergético podem permitir a projeção de cenários com 26 GW de capacidade instalada com a utilização do bagaço e 33 GW com a inserção de palha. A importância deste trabalho está relacionada com a apresentação do estado da arte da tecnologia disponível para a geração termelétrica a partir do setor sucroenergético, pelo fato de apresentar os índices de geração específica para diferentes cenários de disponibilidade combustível e de tecnologias aplicáveis e por permitir análises entre os grupos tecnológicos e as biomassas disponíveis para a geração.
The biomass power generation in the Brazilian sugar & ethanol industry, besides being seen as an option for investments in the renewable energy sector, may contribute to the energy supply while maintaining aspects related to social, strategic and environmental advantages that the support of a sector genuinely developed in Brazil can attribute to the electricity matrix. The main purpose of this study is to analyze the surplus electricity that can be generated from resources of the sugar & ethanol industry. The specific aims are to determine and measure the potential fuels for power generation in the sugar & ethanol industry, to determine which technological routes enable an increase in the power generation and to quantify the specific gross power generation for each selected technology. The method consists of conducting a literature review in order to place the subject of study, with further development of documentary research in order to collect data necessary for developing the calculation, collecting data in publications from institutes, organizations, companies and consultants (sugarcane production data estimates for the foreseen period of study and the definition of fuel and technology resources for power generation). Afterwards, for each power generation technology, arrangements are presented with their respective energy balances, the specific gross power generation for the cases of process cogeneration and power generation stand-alone, the advantages, disadvantages and the inclusion of these technologies over the projected period. The results show that the expansion of production of sugarcane, based on agricultural expansion and increased productivity as well as the technological improvement of commercially available power generation systems for the sugarcane industry may allow scenarios with 26 GW of installed capacity using the sugarcane bagasse and 33 GW with the insertion of the sugarcane straw. The significance of this work is related to the presentation of the state of the art technology available for the thermoelectric generation from sugarcane industry. It is also connected to the fact of presenting an index of specific power generation for different scenarios of fuel availability and applicable technologies as well as enabling analysis of technological groups and available biomass for power generation.

Renewable energy sources support policy employs a great variety of economic tools in order to promote the use of green energy. Following thesis at first offers an overview and economic insight into the most applied ones. Since the majority of the European Union Member States nowadays prefer so-called feed-in tariffs schemes we proceed in-depth analysis of effectiveness of that instrument in electricity sector in four selected European countries Austria, Czech Republic, Germany and Spain. An effectiveness indicator which compares marginal electricity generation potential with additional realizable potential of particular renewable energy sources technology is used for that analysis. The results clearly show that the best practice of feed-in tariff design is pursued in Germany where the special set of tariff design and adjustment measures is applied.

This doctoral study discusses how to control fluctuating renewable energy sources at converter, unit, and system layers to deliver smoothed power output to the grid. This is particularly relevant to renewable power generation since the output power of many kinds of renewable energy sources have huge fluctuations (e.g. solar, wind and wave) that needs to be properly treated for grid integration. In this research, the energy quality is developed to describe the friendliness and compatibility of power flows/waveforms to the grid, by contrast with the well-known concept of power quality which is used to assess the voltage and current waveforms. In Chapter 1 & 2, a background introduction and a literature review of studied subjects are presented, respectively. In Chapter 3, the problem of determining the PI parameters in dq decoupling control of voltage source converter (VSC) is studied based on a state-space model. The problems of the conventional method when there is insufficient interface resistance are addressed. New methods are proposed to overcome these drawbacks. In Chapter 4 & 5, energy quality and the energy filters (EFs) are proposed as tools to assess and manage power fluctuations of renewable energy sources. The proposed EFs are energy storage control systems that could be implemented on a variety of energy storage hardware. EFs behave like low-pass filters to the power flows. Finally, in Chapter 6, as an application example of renewable power plant with energy filter control and smoothed power output, a master-slave wave farm system is proposed. The wave farm system uses enlarged rotor inertia of electric machines as self-energy storage devices.

Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, School of Engineering, System Design and Management Program, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 56).
Renewable energy is one of the most important technologies for decarbonizing the economy and fighting climate change. In recent years, wind energy has become cheaper and more widely adopted. However, the variable nature of wind production creates unique challenges that are not faced by conventional thermal technologies. Several studies to date have showed the decrease in economic value of wind energy as penetration increases due to this variable nature. Plus, they also show that high wind penetration favors intermediate energy sources such as natural gas. I claim however, that few of these studies have considered the dynamic behavior and feedbacks of these systems, including investment delays and learning curves. This thesis uses system dynamics models to simulate the long term changes in the electric grid for Texas. The goal is to test two hypothesis: that the economic value of wind energy decreases as penetration increases, and that variable wind production favors natural gas technologies. It does this by calculating how wind energy changes the shape of the net load duration curve for a given region. This affect changes the profitability of different technologies in unique ways, due to their different fix and variable costs. The conclusions of this thesis are consistent with the literature, with the caveat that they are highly dependent on assumptions regarding the learning curve for energy technologies. The economic value of wind decreases, but this effect can be compensated by lower costs, leading to a continuing adaptation. Faster Wind adoption also reduces the profitably of technologies with high fixed costs such as coal and nuclear, and favors intermediate and peaking sources such as natural gas.
by Leonardo Mendes Barlach.
S.M. in Engineering and Management

Master of Science
Department of Electrical and Computer Engineering
Balasubramaniam Natarajan
Anil Pahwa
Electric vehicles (EVs) are becoming increasingly popular because of their low operating costs and environmentally friendly operation. However, the anticipated increase of EV usage and increased use of renewable energy sources and smart storage devices for EV charging presents opportunities as well as challenges. Time-varying electricity pricing and day-ahead power commitment adds another dimension to this problem. This thesis, describes development of coordinated EV charging strategies for renewable energy-powered charging stations at homes and parking lots. We develop an optimal control theory-based charging strategy that minimizes power drawn from the electricity grid while utilizing maximum energy from renewable energy sources. Specifically, we derive a centralized iterative control approach in which charging rates of EVs are optimized one at a time. We also propose an algorithm that maximizes profits for parking lot operators by advantageously utilizing time-varying electricity pricing while satisfying system constraints. We propose a linear programming-based strategy for EV charging, and we specifically derive a centralized linear program that minimizes charging costs for parking lot operators while satisfying customer demand in available time. Then we model EV charging behavior of Active Consumers. We develop a real-time pricing scheme that results in favorable load profile for electric utility by influencing EV charging behavior of Active Consumers. We develop this pricing scheme as a game between electric utility and Active Consumers, in which the electric utilities decide optimal electricity prices that minimize peak-to-average load ratio and Active Consumers decide optimal charging strategy that minimizes EV charging costs for Active Consumers.

Thesis (Ph.D.)--RAND Graduate School, 2008.
Title from title screen (viewed on Oct. 24, 2008). "This document was submitted as a dissertation in September 2008 in partial fulfillment of the requirements of the doctoral degree in public policy analysis at the Pardee RAND Graduate School." --T.p. Includes bibliographical references: p. 168-178.

The increasing focus on large scale integration of new renewable energy sources like wind power and wave power introduces the need for energy storage. Superconducting Magnetic Energy Storage (SMES) is a promising alternative for active power compensation. Having high efficiency, very fast response time and high power capability it is ideal for levelling fast fluctuations. This thesis investigates the feasibility of a current source converter as a power conditioning system for SMES applications. The current source converter is compared with the voltage source converter solution from the project thesis. A control system is developed for the converter. The modulation technique is also investigated. The SMES is connected in shunt with an induction generator, and is facing a stiff network. The objective of the SMES is to compensate for power fluctuations from the induction generator due to variations in wind speed. The converter is controlled by a PI-regulator and a current compensation technique deduced from abc-theory. Simulations on the system are carried out using the software PSIM. The simulations have proved that the SMES works as both an active and reactive power compensator and smoothes power delivery to the grid. The converter does however not seem like an optimum solution at the moment. High harmonic distortion of the output currents is the main reason for this. However this system might be interesting for low power applications like wave power. I

Kiljanov G.M. Energy storage in autonomous power plants using renewable energy sources, 2017 - p.104, 11 tables, 40 pic. Head Bessel V.V., Professor, Ph.D. Department of Thermodynamics and Thermal Engines. An analysis of existing energy storage devices in the world is carried out. The scientific and technical basis of energy storage. The device and the operating principle of an autonomous combined power plant with an energy storage device are considered. On the basis of the technological calculation, an optimal combination of a wind generator, a system of solar panels and a reservoir, which can provide reliable and uninterrupted power generation, was chosen. The economic efficiency of the project on the use of combined medium power plants at gas production facilities in remote areas was estimated. Conclusions are drawn about the advisability of introducing energy systems based on renewable sources with energy storage devices at the country's enterprises.
Kilyanov G.M. Energilagring i autonoma kraftverk som använder förnybara energikällor, 2017 - s.105, 11 tabeller, 40 bild. Chef Bessel V.V., professor, Ph.D. Institutionen för termodynamik och termiska motorer. En analys av befintliga energilagringsenheter i världen utförs. Den vetenskapliga och tekniska grunden för energilagring. Enheten och driftsprincipen för ett autonomt kombinerat kraftverk med en energilagringsanordning beaktas. Baserat på den tekniska beräkningen valdes en optimal kombination av en vindgenerator, ett system av solpaneler och en reservoar, som kan ge pålitlig och oavbruten elproduktion. Projektets ekonomiska effektivitet på användningen av kombinerade medelkraftverk vid gasproduktionsanläggningar i avlägsna områden uppskattades. Slutsatser dras om att det är lämpligt att införa energisystem baserade på förnyelsebara källor med energilagringsenheter hos landets företag.

With the current climate crisis with the global temperature increasing due to fossil fuels being used there are big investments in green energy. Wind power is a good alternative to fossil fueled power and already has a widespread use. One of the problems with wind poweris control and keeping the grid frequency stable during peaks and lows of power generation. In this master thesis there is a goal to implement a system which can regulate wind mills while always trying to use as much wind power as possible. A model was built in Matlab to represent the final product which was translated into a SCADA system. A fully integrated communication from SCADA computer to PLC to IED to wind mill and back was built. The simulation in the SCADA system gave satisfactory result where the wind power wasutilized to the maximum, and other conditions met. The laboratory experiment with an Arduino represented as the wind mill lacked in communication and the model did not achieveperfect results in every case. There is future work to be done, improved communication, additional or alternative automatic control and creating a bigger system with several powerproducers integrated.

Weakness analysis based on grid strength assessment is useful for identifying potential weak grid issues. However, when taking into account the impact of the interactions among Renewable Energy Sources (RESs), the weakness analysis becomes computationally challenging. Different combinations of PointsofInterconnections (POIs) of RESs may have different impacts on grid strength at each POI. Due to the combination nature, such weakness analysis may be time-consuming when identifying the weakest combination of POIs from a large number of potential candidate locations in realistic power grids. This dissertation addresses the topic of determination of the weakest RESs combinations. Based on impedance ratios as a criterion, the dissertation shows that the impacts of impedance ratios magnitudes and angles are ?quasi-mutually exclusive?. Such a concept is then used to reduce the computational burden with a fast screening algorithm. To further understand the impact of network components on grid strength, vector-based interaction analysis is developed based on the concepts of operational transfer impedances and operational interaction operators. In particular, this dissertation shows how mathematical models of interaction of multiple RESs can be simplified by replacing them with equivalent impedances, allowing us to simplify the mathematical expressions that quantify interactions among RESs. The conclusions and concepts established based on simplified models are statistically tested for their applicability to the generalized interaction model. The result would be a more simplified mathematical representation of interaction among RESs. Finally, a new technique is presented to efficiently update the Bus Impedance Matrix (Zbus) following changes in the series impedance of a branch. Conventionally, such update requires redundant recalculations, which involve matrix inversion operations (i.e., inverting the Bus Admittance Matrix, Ybus) and thus cause high computational burden because of potential matrix ill-conditioning, especially for largescale power grids. This dissertation overcomes these shortcomings by deriving an analytical expression for changes in Zbus in terms of its old elements and the variation of the impedance of a given branch. Hence, the computation overhead is comparatively small, and no issues arise due to the new Ybus being ill-conditioned. Such contribution helps facilitate real-time applications of methods that rely on Zbus.

With the increasing demand for energy throughout the world, the environment around us is getting severely affected. The conventional energy sources (coal, oil and gas) are unfortunately the biggest polluters of the environment. The aforementioned energy sources emit greenhouse gases like carbon dioxide and methane, which are responsible for global warming and ozone layer depletion. The only feasible answer to this problem is to reduce the use of the conventional energy sources and focus more on other energy sources. The renewable energy sources (solar, wind and hydro) have been present in nature, but the technology to harvest these energies have always been relatively expensive until recently. The biggest advantage of using renewable energy sources is the fact that these energy sources will never run out and they also do not pollute the environment as their more conventional counterparts. With more research being conducted into better ways of storing the power trapped from the renewable energy sources and the relative difficulty of obtaining the ever-depleting conventional energy sources, the future for renewable energy sources definitely looks better than at any time in the past

The energy and power used at various areas like households and industries is increasing gradually due to many reasons and there is a need to sustain it. This project introduces a method to reduce the energy used in a household by considering the energy sources and the amount of energy used by the appliances concurrently. Modules are used to measure and check the energy utilized by the appliances using ZigBee. Energy is generated on a conventional basis using three sources: solar panel, wind mill and conventional power. An inverter and a battery are used to connect these sources to a grid. When a device is connected, the units of power consumed are computed and shown on the LCD using LPC2148 microcontroller. The output of the battery is connected to the controller, which shows the voltage of the battery and also selects the best source to be used. Modules use a 5V supply and the controller uses 3.3V power supply. Voltage is controlled with the help of a 7805 voltage regulator and the output of transformer is revised by a rectifier.

Cette thèse propose principalement, un algorithme État-Flow MPPT basé P&O, amélioré avec deux degrés de liberté, dans lequel le système événementiel (MPPT) de comportement est modélisé par le décrivant en terme de transition entre les états, sous certaines conditions. Secondairement, un algorithme étendu MPPT, base d'exploitation en parallèle de l'état-débit est en outre proposé d'être une solution difficile pour le contrôle indépendant du système hybride, où la caractéristique de contrôle continu peut se présenter au cours d'un certain état de travail tout en discrète, est indiquée le long des transitions d'état. Deux configurations possibles pour le système hybride sont proposées : deux convertisseurs DC/DC séparés, et un convertisseur de sortie unique à double entrée (DISO) de configurations. Enfin, il est proposé, un comportement du système DC modélisation utilisant État-Flow, menant à l'ensemble de la conception de la stratégie de commande qui concernent RES MPPT, RES et la coordination BESS, la stabilité du système d'alimentation et de régulation de la tension du bus DC. La simulation et les résultats expérimentaux valident l'efficacité et l'applicabilité de l'algorithme proposé. Les deux résultats montrent la supériorité du MPPT basé proposé État-Flow pour réduire les oscillations de puissance RESs à l'état d'équilibre dans diverses conditions d'exploitation, en plus de son démarrage plus rapide, et l’opération de transition sans divergence de la MPP, selon des conditions météorologiques variables
This thesis primarily proposes, an improved P&O based State-Flow MPPT algorithm featuring two degree of freedom, in which the event driven system (MPPT) behaviour is modelled by describing it in terms of transitions among states under certain conditions. Secondarily, an extended parallel operating State-Flowbased MPPT algorithm is further proposed to be a challenging solution for the independent control of the hybrid system, where continuous control characteristic can present during a certain working state while discrete one is indicated along state transitions. Two possible configurations for the hybrid system are proposed; two separate DC/DC converters and dual input single output converter (DISO) configurations. Finally it is proposed, DC system behaviour modelling using State-Flow leading to the whole control strategy design which concern RESs MPPT, RESs and BESS coordination, power system stability and DC bus voltage regulation.Simulation and experimental results validate the effectiveness and applicability of the proposed algorithm, both results show the superiority of the proposed State-Flow based MPPT in reducing the RESs power oscillations at steady-state in various operating conditions in addition to its faster start-up and transition operation without divergence from the MPP during sudden varying weather conditions

This thesis presents a study on the design method to optimise the performance for producing green power from multiple renewable energy generators. The design method is presented through PLC (Programmable Logic Controller) theory. All the digital and analogue inputs are connected to the input cards. According to different operations conditions for each generator, the PLC will image all the inputs and outputs, from these images; a software program has been built to create a control method for multiple renewable energy generators to optimise production of green power. A control voltage will supply the output contractor from each generator via an interface relay. Three renewable generators (wind, solar, battery bank) have been used in the model system and the fourth generator is the back up diesel generator. The priority is for the wind generator due to availability of wind 24 hours a day, then solar, battery bank, and LPG or Diesel generators. Interlocking between the operations of the four contractors has been built to prevent interface between them. Change over between contractors, according to the generator's change over has also been built, so that it will delay supplying the main bus bar to prevent sudden supply to the load. Further study for controlling multiple renewable energy generators for different conditions such as controlling the multi-renewable energy generators from remote, or supplying weather forecast data from bureau of meteorology to the PLC directly as recommended.
Master of Electrical Engineering (Hons)

Geothermal energy is an important emerging renewable technology that has the potential to provide power from a virtually unlimited reserve worldwide. The downside to exploiting geothermal energy is the capital intensive drilling of the borehole needed to access relatively hot resources located deep under the ground. However, abandoned petroleum wells present an interesting opportunity to circumvent the capital costs associated with drilling. This thesis proposes a sophisticated heat transfer model that is capable of realistically simulating the heat flow through a double pipe heat exchanger and the surrounding rock mass. The sophisticated model is compared with the analytical cylindrical source model, and two numerical models and reaches comparable results. The purpose of this model is to provide an accurate and realistic representation of heat flow and temperature distribution for a heat exchanger retrofitted to an abandoned well. The effects that inlet fluid temperature, insulation, thermal conductivity of the rock mass, mass flow rate of the working fluid, and vertical movement of groundwater have on the sustainability and performance of the double pipe heat exchanger are investigated. A constant power model is also proposed in order to assess the sustainable rate of heat extraction from a geothermal resource.
L'énergie géothermique est une technologie renouvelable émergente importante qui a le potentiel de fournir de l'énergie d'une source pratiquement illimitée. Le désavantage de l'énergie géothermique est l'ampleur du capital des forages qui sont requis pour accéder aux ressources plus chaudes. Utiliser les forages de pétrole abandonnés est une opportunité originale pour circonvenir ce désavantage. Cette thèse propose un modèle sophistiqué qui est capable de simuler le flux de chaleur à travers un échangeur de chaleur à tube double et le flux de chaleur à travers la masse rocheuse autour du forage. Le modèle sophistiqué est comparé avec le modèle analytique de source cylindrique, et deux autres modèles numériques et arrivent aux résultats comparables. Le but de cette modèle sophistiqué est de fournir une représentation précise et réaliste du flux de chaleur et la distribution de la température pour un échangeur de chaleur situé dans un forage de pétrole abandonné. Les effets de la température d'entrée de fluide, l'isolation, la conductivité thermique de la masse rocheuse, le taux de débit massique du fluide actif, et le mouvement vertical de l'eau souterraine sur la durabilité et performance de la conception sont enquêtés. Un modèle de puissance constante est aussi proposé pour l'extraction de l'énergie géothermique encore plus durable.

During the past decade, renewable energy sources have become an indispensable pillar in European electricity generation. This paper aims at examining if the increasing importance of renewables stimulates investment in European power transmission networks. The question of interest is addressed by an error correction investment model that builds on Neoclassical theory and is further augmented by recent literary findings. Under the proposed threefold estimation strategy, the share of renewables is not found to significantly influence investment spending when the full set of transmission system operators are considered. However, a slight and justified sample restriction leads to the conclusion that a rising share of renewable energy sources substantially increases investment in power transmission networks.
Series: Department of Economics Working Paper Series

Microgrid is an emerging technology in the eld of electrical engineering which employs the concept of Distributed Energy Resources (DERs) in order to generate electricity in a small sized power system. The main objectives of this dissertation are to: 1- design a new control for lower level control of DERs in microgrids, 2- implement distributed upper level control for DERs in microgrids and 3- apply analytical approaches in order to analyze DERs in microgrids. The control in each DER can be divided into two main categories: lower and upper level. Lower level control is the main objective of control in each DER. For example, the lower level control in Photovoltaic (PV) is in charge of transferring the maximum power from sun into the main grid. Unlike the lower level control, the upper level control is an additional control loop on top of the lower level controls. For example, Voltage/Frequency (VF) controllers are installed on top of Active/Reactive (PQ) power controller in energy storage devices as upper level control. In this dissertation, for the lower level control improvements, two widely used DERs are selected (PV, and oshore wind farm) and new control algorithms are developed in order to improve the performance of lower level controllers in these DERs. For the PV lower level improvement, a new control methodology is proposed in order to minimize the maximum power tracking error in PV lower level controller. Second contribution in lower level control is for the oshore wind farm applications based on Multi-Terminal High Voltage Direct Current (MTDC) transmission; a new control is designed in order to minimize the losses in transmission lines through lower level control of High Voltage Direct Current (HVDC) converters. For the upper level control, this dissertation considers the energy storage as another mostly used type of DER in microgrids. The lower level control for energy storage is in charge of controlling the PQ of the energy storage. The main contribution in the upper level control is to implement the distributed control algorithm based on consensus theory for battery energy storages in order to maximize the efficiency, energy management as well as synchronizing the performance of parallel energy storage devices in microgrids. In this case, the consensus based distributed control algorithm with limited information exchange between neighboring energy storage units is proposed and implemented to validate the claim. The third contribution of this research is to apply advanced analysis techniques to evaluate the performance of the DERs in microgrids. Two approaches are introduced for microgrid modeling in this research. Firstly, an impedance modeling technique is used to model the oshore wind farm connected to the main AC grid through HVDC transmission line. Multiple Input Multiple Output (MIMO) Nyquist analysis and singular value analysis are used to assess the interactions between HVDC converter and grid. Secondly, an unbalanced microgrid is considered and Dynamic Phasor (DP) analysis is applied in order to nd the stability limitations under different scenarios. This dissertation has led to seven journal papers (five published, one journal in revision process and one journal submitted recently) and four conference papers.

The growth of the industry and population of South Africa urges to seek new sources of electric power, hence the need to look at alternative power sources. Power output from some renewable energy sources is highly volatile. For instance power output from wind turbines or photovoltaic solar panels fluctuates between zero and the maximum rated power out. To optimize the overall power output a model was designed to determine the best trade-off between production from two or more renewable energy sources putting emphasis on wind and solar. Different measures of risk, such as coefficient of variation (CV) and value at risk (VAR), were used to determine the best hybrid renewable energy system (HRES) configuration. Depending on the investors’ expected returns (demand) and risk averseness, they will be able to use the model to choose the best configuration that suites their needs. In general it was found that investing in a diversified HRES is better than investing in individual power sources.

Thesis (D. Tech. (Electrical Engineering)) -- Central University of Technology, Free State, 2014
For a sustainable and clean electricity production in isolated rural areas, renewable energies appear to be the most suitable and usable supply options. Apart from all being renewable and sustainable, each of the renewable energy sources has its specific characteristics and advantages that make it well suited for specific applications and locations. Solar photovoltaic and wind turbines are well established and are currently the mostly used renewable energy sources for electricity generation in small-scale rural applications. However, for areas in which adequate water resources are available, micro-hydro is the best supply option compared to other renewable resources in terms of cost of energy produced. Apart from being capital-cost-intensive, the other main disadvantages of the renewable energy technologies are their resource-dependent output powers and their strong reliance on weather and climatic conditions. Therefore, they cannot continuously match the fluctuating load energy requirements each and every time. Standalone diesel generators, on the other hand, have low initial capital costs and can generate electricity on demand, but their operation and maintenance costs are very high, especially when they run at partial loads. In order for the renewable sources to respond reliably to the load energy requirements, they can be combined in a hybrid energy system with back-up diesel generator and energy storage systems. The most important feature of such a hybrid system is to generate energy at any time by optimally using all available energy sources. The fact that the renewable resources available at a given site are a function of the season of the year implies that the fraction of the energy provided to the load is not constant. This means that for hybrid systems comprising diesel generator, renewable sources and battery storage in their architecture, the renewable energy fraction and the energy storage capacity are projected to have a significant impact on the diesel generator fuel consumption, depending on the complex interaction between the daily variation of renewable resources and the non-linear load demand. V This was the context on which this research was based, aiming to develop a tool to minimize the daily operation costs of standalone hybrid systems. However, the complexity of this problem is of an extremely high mathematical degree due to the non-linearity of the load demand as well as the non-linearity of the renewable resources profiles. Unlike the algorithms already developed, the objective was to develop a tool that could minimize the diesel generator control variables while maximizing the hydro, wind, solar and battery control variables resulting in saving fuel and operation costs. An innovative and powerful optimization model was then developed capable of efficiently dealing with these types of problems. The hybrid system optimal operation control model has been simulated using fmincon interior-point in MATLAB. Using realistic and actual data for several case studies, the developed model has been successfully used to analyse the complex interaction between the daily non-linear load, the non-linear renewable resources as well as the battery dynamic, and their impact on the hybrid system’s daily operation cost minimization. The model developed, as well as the solver and algorithm used in this work, have low computational requirements for achieving results within a reasonable time, therefore this can be seen as a faster and more accurate optimization tool.

Pavements are one of the most important components of modern civil infrastructure systems. Being constantly exposed to weather conditions, pavements may be subject to heating and cooling cycles, which vary as a function of the location and are proven to reduce the lifespan and reliability of our transport infrastructure. The most extreme effects of weather are generally seen in the form of overheating of the paving materials or freezing of the pavement surface. In this Thesis, natural convection of air is considered as a means to harvest heat from pavements during hot periods and to provide heat to them when the weather is cold. In the research presented, a buoyancy-driven air flow is allowed through metal pipes installed under an asphalt wearing course. The analysis of the phenomena at work is performed from an experimental, computational, and theoretical point of view. The main contribution to research provided by this Thesis it that the experiments performed show that a convection-powered air flow can be effectively used for the reduction or increase of pavement temperatures up to about �5°C. Moreover, the effects of variations in the design of energy harvesting pavements are quantified and discussed, proving that the installation of all pipes in a single row under the wearing course of a pavement is the overall best solution for the implementation of this technology. Finally, CFD simulations suggest that the air pores that are naturally present in asphalt mixtures are not suitable to allow the air flow required for convection-powered energy harvesting, due to both fluid-dynamic and practical reasons.

Sustainable cities is an area that has grown in size over the last couple of years. The SESAC (Sustainable Energy Systems in Advanced Cities) is a EU-project looking at the potential to increase the share of Renewable Energy Sources (RES) and promote energy efficiency measures in different EU cities. This master thesis is a part of that project. Specifically, the thesis examines the cities of Grenoble, Delft and Växjö and looks at what measures regarding RES and energy efficiency have been taken historically, both under the SESAC project and otherwise, and assesses the possibility of further measures in the cities. The main RES evaluated are wind power (large scale and urban), solar (PV and thermal) and waste treatment (waste incineration and biogas production). The feasibility of these renewable technologies is evaluated both physically, technically and economically for each city. Further, the historical and current hinders and promoters in the form of different support schemes and other economic and institutional schemes are summarized for each country and city and the effects of which included in the feasibility calculations. Also, current CO2 emissions of Grenoble, Delft and Växjö are stated and the impact of implementing the measures examined is calculated. A comparison between the three cities is also made and suggestions are made to what they can learn from each other and what synergies there are.    Results show that the technical potential for RES is sizeable in the cities, as seen in Table 1. Important to note are the differences between the cities. Besides from their differences in population size, ranging from 83 000 (Växjö) and 96 000 (Delft) to 400 000 (Grenoble), available land area as well as climate are very different in the cities, therefore affecting the potential for the RES technologies.   RES potential [GWh] Grenoble Delft Växjö Wind 458 1,2 (Urban only) 297-2000 Solar PV 375 150 0,06-0,3 Waste treatment 41 11 10 Table 1. Technical potential of RES in Grenoble, Delft and Växjö Looking at the economic potential, however, the picture is not as optimistic. The only economically feasible investments of the options in Table 1 are investing in solar PV in Grenoble and Delft (IRR of 0-10%) and wind in Växjö (IRR of 4%). All other investments have negative NPV:s and IRR:s, meaning that either the cost of the technologies must be reduced or more favorable support scheme be introduced in order to make the them profitable.

El núcleo de la tesis consta de tres capítulos en los que se explora la naturaleza de los flujos de conocimiento que influyen en la innovación en energías renovables. En los tres capítulos se utiliza información de patentes europeas a nivel regional para poder capturar el concepto de innovación. En el segundo capítulo explora la naturaleza de la base del conocimiento subyacente en las energías renovables. Se plantea que esta tecnología tiene un mayor contenido de conocimiento científico y abstracto que el resto de campos tecnológicos en general. Esta característica haría que, por un lado, el flujo de conocimiento desde la academia y ciencia sea más importante para la innovación en energías renovables que para el resto de innovación en general, y que por otro lado, el flujo de conocimiento no estaría tan restringido geográficamente, hecho que es un hallazgo común en la literatura. Empleando información de las citas hechas por las patentes para medir los flujos de conocimiento, se estima una función de producción de conocimiento. Se distingue entre el flujo del conocimiento desde el sector científico del proveniente del sector técnico. Los resultados muestran que el conocimiento proveniente de la ciencia es más importante para para la innovación en energías renovables que para el resto de innovación en general. También se halla evidencia de que los flujos de conocimiento provenientes del sector técnico que influyen en la innovación en energías renovables estarían menos constreñidos geográficamente que los que influyen en el resto de innovación en general. Este hallazgo se debería al mayor contenido de conocimiento abstracto y científico, que es más fácil de codificar y por lo tanto más fácil de transportar en el espacio. El tercer capítulo estudia cómo diferentes fuentes de conocimiento pueden influir en que un inventor con experiencia previa en otros campos, patente en energías renovables. Se postula que un inventor puede adquirir conocimiento o ideas de tres fuentes: su red de coautores, la compañía en la que trabaja y de su ámbito local. Además, se plantea que en estas tres fuentes, un inventor podría ser influenciado por sus pares de forma directa, ya sea por un efecto ‘manada’ o porque ellos proporcionan conocimiento especializado sobre energías renovables que es necesario para producir tecnología en este campo. Se postula que las fuentes más cercanas de conocimiento, son las que influirían más en que un inventor se aventure en un campo en el que no tiene experiencia previa, pues las relaciones más cercanas facilitarían que fluya conocimiento más complejo. Por tal motivo, el conocimiento más importante provendría de la red de coautores. El análisis empírico se realza utilizando información de patentes, de la cual se identifica a los inventores, su centro de trabajo y la región donde radican, asi como su experiencia previa en innovación. Los resultados muestran que el factor más importante para que un inventor se aventure en innovar en energías renovables es tener en su red de coautores a algún inventor que haya patentado antes en energías renovables. Esto implicaría que para entrar en el campo de la innovación en energías renovables es importante contar con alguien con experiencia previa en dicho campo, pues podría ejercer influencia personal y también contribuir con conocimiento específico en este campo tecnológico. Por último, el cuarto capítulo de la tesis ahonda en la relación de los diferentes tipos de distancia que podrían existir: distancia cognitiva, las formas distintas de entender un mismo fenómeno, distancia social, la interacción directa entre individuos basada en la confianza, distancia organizacional, las distintas reglas y normas que enmarcan las relaciones de los individuos entre distintas organizaciones, y distancia geográfica, la distancia física entre individuos. Se plantea que debe haber un equilibrio entre el conocimiento próximo y el conocimiento distante en términos cognitivos, pues el conocimiento próximo facilitaría el flujo de información, pero quizás redundante, mientras el distante aportaría ideas nuevas, pero quizás difíciles de comprender para los interlocutores. Se busca explicar si es el conocimiento próximo o distante el que influye en que un inventor experimentado patente por primera vez en energías renovables y de donde provendría este conocimiento (la red de coautores, la firma o el ámbito regional/local). Utilizando la clasificación tecnológica de las patentes se establece lo que sería conocimiento próximo o distante por medio de la coocurrencia de clases tecnológicas en las patentes. Asi, se construye que tan próximo y distante el conocimiento de un inventor con el de su red de coautores, de la compañía donde trabaja y del conocimiento de su entorno. También se mide que tan próximo está el conocimiento de un inventor respecto al conocimiento en energías renovables. El principal hallazgo es que el factor más importante para que un inventor patente en energías renovables sería que su propio conocimiento previo esté próximo al de energías renovables. Luego, el conocimiento de los coautores sería importante en tanto sea conocimiento distante. De esta forma se alcanzaría ese equilibrio entre conocimiento próximo (el del inventor) y conocimiento distante (el de los coautores) para innovar en un campo nuevo. La razón de esto sería que el conocimiento distante, podría ser transmitido por los coautores, pues ellos son quienes más relación tienen con un inventor, por tanto podrían transmitir conocimiento más complejo de entender.

Les technologies de l'information et de la communication sont devenues, au cours des dernières années, un pôle majeur de consommation énergétique avec les conséquences environnementales associées. Dans le même temps, l'émergence du Cloud computing et des grandes plateformes en ligne a causé une augmentation en taille et en nombre des centres de données. Pour réduire leur impact écologique, alimenter ces centres avec des sources d'énergies renouvelables (EnR) apparaît comme une piste de solution. Cependant, certaines EnR telles que les énergies solaires et éoliennes sont liées aux conditions météorologiques, et sont par conséquent intermittentes et incertaines. L'utilisation de batteries ou d'autres dispositifs de stockage est souvent envisagée pour compenser ces variabilités de production. De par leur coût important, économique comme écologique, ainsi que les pertes énergétiques engendrées, l'utilisation de ces dispositifs sans intégration supplémentaire est insuffisante. La consommation électrique d'un centre de données dépend principalement de l'utilisation des ressources de calcul et de communication, qui est déterminée par la charge de travail et les algorithmes d'ordonnancement utilisés. Pour utiliser les EnR efficacement tout en préservant la qualité de service du centre, une gestion coordonnée des ressources informatiques, des sources électriques et du stockage est nécessaire. Il existe une grande diversité de centres de données, ayant différents types de matériel, de charge de travail et d'utilisation. De la même manière, suivant les EnR, les technologies de stockage et les objectifs en termes économiques ou environnementaux, chaque infrastructure électrique est modélisée et gérée différemment des autres. Des travaux existants proposent des méthodes de gestion d'EnR pour des couples bien spécifiques de modèles électriques et informatiques. Cependant, les multiples combinaisons de ces deux parties rendent difficile l'extrapolation de ces approches et de leurs résultats à des infrastructures différentes. Cette thèse explore de nouvelles méthodes pour résoudre ce problème de coordination. Une première contribution reprend un problème d'ordonnancement de tâches en introduisant une abstraction des sources électriques. Un algorithme d'ordonnancement est proposé, prenant les préférences des sources en compte, tout en étant conçu pour être indépendant de leur nature et des objectifs de l'infrastructure électrique. Une seconde contribution étudie le problème de planification de l'énergie d'une manière totalement agnostique des infrastructures considérées. Les ressources informatiques et la gestion de la charge de travail sont encapsulées dans une boîte noire implémentant un ordonnancement sous contrainte de puissance. La même chose s'applique pour le système de gestion des EnR et du stockage, qui agit comme un algorithme d'optimisation d'engagement de sources pour répondre à une demande. Une optimisation coopérative et multiobjectif, basée sur un algorithme évolutionnaire, utilise ces deux boîtes noires afin de trouver les meilleurs compromis entre les objectifs électriques et informatiques. Enfin, une troisième contribution vise les incertitudes de production des EnR pour une infrastructure plus spécifique. En utilisant une formulation en processus de décision markovien (MDP), la structure du problème de décision sous-jacent est étudiée. Pour plusieurs variantes du problème, des méthodes sont proposées afin de trouver les politiques optimales ou des approximations de celles-ci avec une complexité raisonnable
In recent years, information and communication technologies (ICT) became a major energy consumer, with the associated harmful ecological consequences. Indeed, the emergence of Cloud computing and massive Internet companies increased the importance and number of datacenters around the world. In order to mitigate economical and ecological cost, powering datacenters with renewable energy sources (RES) began to appear as a sustainable solution. Some of the commonly used RES, such as solar and wind energies, directly depends on weather conditions. Hence they are both intermittent and partly uncertain. Batteries or other energy storage devices (ESD) are often considered to relieve these issues, but they result in additional energy losses and are too costly to be used alone without more integration. The power consumption of a datacenter is closely tied to the computing resource usage, which in turn depends on its workload and on the algorithms that schedule it. To use RES as efficiently as possible while preserving the quality of service of a datacenter, a coordinated management of computing resources, electrical sources and storage is required. A wide variety of datacenters exists, each with different hardware, workload and purpose. Similarly, each electrical infrastructure is modeled and managed uniquely, depending on the kind of RES used, ESD technologies and operating objectives (cost or environmental impact). Some existing works successfully address this problem by considering a specific couple of electrical and computing models. However, because of this combined diversity, the existing approaches cannot be extrapolated to other infrastructures. This thesis explores novel ways to deal with this coordination problem. A first contribution revisits batch tasks scheduling problem by introducing an abstraction of the power sources. A scheduling algorithm is proposed, taking preferences of electrical sources into account, though designed to be independent from the type of sources and from the goal of the electrical infrastructure (cost, environmental impact, or a mix of both). A second contribution addresses the joint power planning coordination problem in a totally infrastructure-agnostic way. The datacenter computing resources and workload management is considered as a black-box implementing a scheduling under variable power constraint algorithm. The same goes for the electrical sources and storage management system, which acts as a source commitment optimization algorithm. A cooperative multiobjective power planning optimization, based on a multi-objective evolutionary algorithm (MOEA), dialogues with the two black-boxes to find the best trade-offs between electrical and computing internal objectives. Finally, a third contribution focuses on RES production uncertainties in a more specific infrastructure. Based on a Markov Decision Process (MDP) formulation, the structure of the underlying decision problem is studied. For several variants of the problem, tractable methods are proposed to find optimal policies or a bounded approximation

Les énergies renouvelables variables prennent une part croissante de la production raccordée aux réseaux électriques. Par conséquent, elles doivent s’intégrer aux mécanismes de services système qui assurent l’équilibre entre production et con-sommation de puissance sur les réseaux. Toutefois la forte incertitude de la production variable est un obstacle à la fourniture de ces services qui requièrent une fiabilité élevée. L’agrégation de centrales renouvelables dispersées et contrôlées par une centrale virtuelle permet de diminuer cette incertitude en profitant du foisonnement entre les centrales. Cette thèse propose plusieurs modèles de prévision probabiliste afin d’évaluer la capacité d’une centrale virtuelle renouvelable variable à offrir des services système avec une fiabilité maximale: ces modèles sont des adaptations d’arbres de décisions, de réseaux de neurones récurrents et convolutifs, ainsi que de distributions dédiées aux quantiles extrêmement faibles. Une attention particulière est portée à la combinaison de sources d’énergie (Photovoltaïque, éolien, hydraulique au fil de l’eau). Ensuite, des stratégies d’offre optimale d’énergie et de réserve par une agrégation renouvelable sont établies en utilisant les prévisions de production et en considérant les incertitudes associées aux différents marchés. Ces stratégies explorent plusieurs options de modélisation: dépendance entre production renouvelable et prix par une copule, taux de défaillance contrôlé par optimisation sous contraintes probabilistes, et enfin offre de services système multiples à l’aide d’une formulation Lagrangienne
As variable renewable energy plants penetrate significantly the electricity generation mix, they are expected to contribute to the supply of reserve power, albeit the high uncertainty levels on their production. A solution to reduce the uncertainty consists in aggregating renewable plants dispersed over several climates to obtain a smoother production profile and operate them within a Virtual Power Plant control system. In this thesis, a series of probabilistic forecasting models are proposed to assess the capacity of a variable renewable Virtual Power Plant to provide ancillary services with maximum reliability: these models are adapted decision-tree regression models, recurrent and convolutional neural networks, as well as distributions dedicated to extremely low quantiles. The combination of energy sources (Photovoltaics, Wind, Run-of-river Hydro) is considered in detail. Optimal strategies for the joint offer of energy and ancillary services by a variable renewable Virtual Power Plant are later defined, based on production forecasts and market uncertainties. Offer strategies explore several modelling options:dependence between renewable production and prices via a copula, controlled rate of reserve underfullfilment with a chance-constraint optimization, and finally offer of multiple ancillary services thanks to a Lagrangian formulation

Includes bibliographical references.
With the drive for cleaner energy, Independent power producers (IPP’s) have to find suitable potential land sites that meet their renewable project needs and that prove to be technically feasible to integrate into the nearest distribution electrical infrastructure. Project feasibility for utility grid connection can in certain instances be directed to a specific area due to resource availability and existing electrical plant capability. This invariability leads to multiple establishments of renewable energy plants in the same geographic location. Distribution substations and high voltage (HV) lines in the South African National utility, Eskom, are planned and constructed based on simulation models derived from power system models built in DIgSILENT Powerfactory analysis software. For a Network Planning Engineer, planning for this integration can be become quite complex in a multi-machine scenario as above. This dissertation provides network planning criteria that a planning engineer in the utility can successfully use to plan for this integration. Three sets of criteria are established. With the inclusion of widespread distributed generation in close proximity of each other, sharing the same grid electrical infrastructure, a critical path of HV electrical elements exists, which the effects of the combined generation control. The first set of planning criteria is derived from the analysis of locating this critical path. This is determined by means of using iterative programming and calculations. Grid voltage stability is one the most important factors in determining the feasibility of generator grid integration. The voltage stability effects of the Eskom Distribution network to which these generating plants connect to, are analysed and tabulated results established. This will enable the utility to determine the location of a specific size of renewable plant, just by knowing the grid strength and not going into detail voltage stability studies. For the second set of planning criteria three sets of network range strengths are identified with corresponding ratios of grid strengths to generator short circuit current contributions. Successfully integrating DG to the grid also has many technical and cost solutions of network configurations. The third set of planning criteria identifies four generic network configurations and the building blocks of physically costing the engineering integration. Solar density maps provide an indication of proposed MW output in a particular area. In this research, solar density maps are used to identify the maximum connecting generation to the electrical grid in feasible geographic areas. The results derived from this study enable the planning engineer and/or developer to better plan the optimal location of a PV project wrt the chosen geographic area of KZN. This study case may be extended to other technologies leading to a more concise framework of network planning for renewable project integration.

La plupart des infrastructures de cloud efficace en énergie proposées dans la littérature ne tiennent pas compte de la disponibilité électrique et des énergies renouvelables dans leurs modèles. L’intégration des énergies renouvelables dans les centres de données réduit considérablement leur consommation d’énergie et leur empreinte carbone. Étant donné que l’énergie renouvelable est intermittente et fluctue en fonction du temps, elle est habituellement sous-utilisée. Nous abordons le problème de l’amélioration de l’utilisation des énergies renouvelables dans un centre de données unique et étudions deux approches : la planification opportuniste et le stockage de l’énergie. Nos résultats démontrent que les deux approches permettent de réduire la consommation d’énergie non-renouvelable sous différentes configurations. Nous étendons ce travail au contexte des Edge Clouds et de l’Internet des Objets dans le cas de l’analyse de flux de données. Nous montrons comment rendre les Edge Clouds plus verts avec une production d’énergie renouvelable sur site combinée à un stockage d’énergie et à une dégradation de performance des applications des utilisateurs
Most of the energy-efficient Cloud frameworks proposed in literature do not consider electricity availability and renewable energy in their models. Integrating renewable energy into data centers significantly reduces the traditional energy consumption and carbon footprint of these energy-hungry infrastructures. As renewable energy is intermittent and fluctuates with time-varying, it is usually under-utilized. We address the problem of improving the utilization of renewable energy for a single data center and investigate two approaches: opportunistic scheduling and energy storage. Our results demonstrate that both approaches are able to reduce the brown energy consumption under different configurations. We extend this work to the context of Edge Clouds and Internet of Things on the use case of data stream analysis. We show how to make Edge Clouds greener with on-site renewable energy production combined with energy storage and performance degradation of the users’ applications

All across the world, attention is turning to renewable energies to serve at least as a partial substitute to fossil fuels in the global energy mix, braking the latter’s depletion and providing a greener solution for a more sustainable future. However, the intermittent nature of most renewable energy sources, wind and solar in particular, raises major concerns over the integration of these technologies, on a large scale, to grid systems. This thesis focuses on large-scale renewable energy storage systems, primarily compressed air energy storage (CAES) systems, which are particularly well suited for renewable energy applications. CAES can play a major role in shaping the future of renewable energy systems for not only can it bring load levelling to the system, but it can also add substantial value by providing ancillary services to the grid. The main focus of this research is adiabatic CAES which endeavours to minimize the use of natural gas by using recuperators and thermal energy storage systems, where the heat from the air during the compression stages is absorbed by a heat transfer fluid, stored, and then supplied back during the expansion process. This project aimed to explore the potential of CAES systems as an energy storage technology for large-scale grid integrated renewable energy system. A computer model was developed to size the different components in the CAES system and also to predict the operational performance of the CAES system for different conditions using MATLAB programming. The thermal energy storage of an adiabatic CAES system was optimized using CFD analysis and experimental testing of the thermal energy storage system was carried out to validate the models. Also, an economic study was performed to assess the feasibility of the CAES system based on a case study of the Egyptian grid. The dynamic simulation of a novel configuration of an adiabatic CAES system showed that the system can achieve improved performance compared to existing CAES plants, while the economic study showed that CAES can improve the economics of a wind farm, at least by the standards of our chosen case study location.

Thesis (M. S.)--Economics, Georgia Institute of Technology, 2010.
Committee Chair: Vivek Ghosal; Committee Member: Byung-Cheol Kim; Committee Member: Chun-Yu Ho; Committee Member: Tibor Besedes. Part of the SMARTech Electronic Thesis and Dissertation Collection.

xii, 91 p. :ill. (some col.), maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
The ability to provide an adequate supply ofrenewable energy necessary to offset the emissions of"zero emission" vehicles is of importance for Oregon's planners and policy makers. An increase in electricity generation caused by the electricity required for zero-emissions hydrogen fuel cell vehicles will result in an increase in greenhouse gas emissions ifrenewable energy is not installed to meet hydrogen fuel cell needs. What are the renewable energy implications for Oregon planners to consider for meeting future fuel cell zero emission vehicle (ZEV) needs? Work done in Iceland can serve as an example for Oregon's need for renewable energy to meet ZEV needs. Icelandic data about hydrogen generation and the renewable energy requirements necessary for ZEVs at the Gtj6thaIs hydrogen fueling station set a benchmark for Oregon planners to consider when figuring the impact of ZEVs.
Committee in Charge: Dr. Robert F. Young, Chair; Dr. Greg Bothun; Mr. Roger Ebbage

The reliable supply of hydrogen to a vehicle re-fuelling station has been tackled in this thesis. A currently operational system based on supplying energy from a bio-generator, fuelled from biogas generated by organic matter in an Anaerobic Digester, formed the basis of an expanded renewable energy system. The criterion for the new design was the supply of energy to an electrolyser/compressor/storage system at minimum cost and minimum interruption to supply. By separating hydrogen production from energy generation, the operating parameters of the electrolyser and compressor were optimized, leading to an energy load profile that guaranteed a reliable supply of hydrogen sufficient to fuel the daily needs of up to two hydrogen fuelled vehicles. Based on the energy load profile, a renewable energy system was designed around the existing bio-generator. A multi-objective optimization by Genetic Algorithm was employed to design a hybrid renewable energy system that minimized lifetime costs and unmet load. The resulting design consisted of a mixture of wind turbines, batteries, inverters/rectifiers, as well as the bio-generator. A control strategy that directed the interaction of all components was also produced. Multi-objective optimization by Genetic Algorithm was found to be a reliable, efficient method in designing a complex hybrid renewable energy system with non-linear characteristics. The results of modelling and simulation showed that an uninterrupted supply of energy could be produced, based on specific meteorological conditions, at a minimal cost. The research has shown that it is possible to develop a design that produces hydrogen reliably purely from renewable energy sources. The design is flexible enough to integrate other renewable energy sources and technologies as they develop.

Worldwide energy consumption is estimated to double between 2008 and 2035. Over-dependence on energy imports from a few, often politically unstable countries, and unpredictable oil and gas prices, pushes energy to a critical agenda. While there is an agreement that we need to change the production and consumption of energy, there is still disagreement about the specific changes that are needed and how they can be achieved. The conventional energy plans relying primarily on fossil fuels and nuclear technologies, which are in need of transformation due to limited resources and carbon dioxide emissions. Energy efficiency improvements and renewable energy should play a leading role in the America's energy future. Energy and environmental organizations believe that renewable energy and energy efficiency can meet half of the world's energy needs by 2050. This thesis describes a model that predicts renewable energy portfolios for the Southern portion of the United States, by evaluating multiple renewable energy sources such as solar, wind, hydropower, biomass, and geothermal. The Southern US is divided into three regions: Southwest, South Central, and Southeast, which are chosen given their location and the level of abundance of renewable resources, thereby minimizing inefficiencies and losses associated to the present generation system. A mathematical predictor takes into account variables such as supply/demand, non-renewable/renewable sources, and time. From the results, the Southwest and South Central regions confirm an surplus of renewable electricity by 2050, but the Southeast region does not have enough renewable resources to detach itself from the use of fossil fuels. The South Central region begins producing a surplus of renewable energy in 2014 and reaches an excess amount of 14,552 billion KWh by 2050. This means there will be no need to transfer electricity over long distances, which will increase the overall efficiency of electrical generation.

In a time of a fast growing renewable electricity generation sector, there are challenges regarding the integration of such generation with current transmission infrastructure. Such challenges include problems associated with the intermittent power output of renewable energy sources and the inability to control there output to meet varying electrical demand. Using part of this available energy for the provision of domestic heating loads may help bridge the gap between supply and demand. The use of intermittent electrical energy sources for charging water based thermal energy stores was identified as a research gap. This research project studies the use of intermittent electrical supplies from wind turbines for the provision of space heating and hot water in domestic buildings. It also addresses how solar water heating may be incorporated into the same thermal energy storage unit to create a hybrid system. This thesis outlines and analyses two charge strategies that may be used to promote stratification in water based thermal energy stores when adding intermittent electrical energy. The first makes use of multiple heating elements switched on in sequence (direct system) while the second uses buoyancy forces to take cool water from the bottom of the tank, pass it through the heating element and then place it back in at the top of the tank at a higher temperature (side-arm). The research method includes; 1) a simplified theoretical simulation of direct and side-arm configurations in the transient system simulation software (TRNSYS) to identify system performance when charged from wind and solar energy; 2) a detailed theoretical representation of the side-arm charge mechanism with a modulating valve for TRNSYS; 3) an empirical validation of the detailed theoretical model of the side-arm charge cycle. Outcomes from the simplified theoretical model indicate that the side-arm configuration may have benefits over the direct configuration due to reduced heat loss from the tank, reduced auxiliary energy consumption and increased solar collector performance. The detailed theoretical representation of the side-arm was calibrated using the empirical data gathered. From this, important parameters affecting the performance of the side-arm charge cycle are evaluated. These include the effects of tank height, operating temperature and the power range from the intermittent electrical supply. It is identified that the assumptions made in the simple model are not possible to reproduce in real life and that an analysis using the complex model must be made in order to evaluate any potential benefits of the side-arm over a direct configuration.

Thesis (MPhil)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The South African Government developed the REIPPPP to ensure the implementation of Green Economy and job creation policies, while mitigating the current power crises with the short lead times of RE technologies. Current South African literature is ambiguous when discussing the legitimacy of the REIPPPP and the overall understanding of the programme and its associated outcomes in terms of job creation, are therefore, vague. A need therefore exists to unpack the quantitative job creation submissions of the REIPPPP and to carry out an investigation into the opportunities and challenges associated with meaningful job creation. Through a non-linear iterative exploratory design, hinging on the researcher’s position within industry, this empirical research comprises of two components. Firstly, a literature study informs the development of a meaningful job creation framework which is used to analyse the programme’s bid documentation and publicly available data. Secondly, mixed-methods are utilised to collect quantitative data from the DoE and qualitative data from job creation stakeholders. The result is an enriched understanding of the REIPPPP in terms of meaningful job creation, identifying trends, similarities and unexpected outcomes across methods. The study concludes that the programme does create meaningful jobs yet data is misaligned and currently unavailable to the public. Secondly, since job creation is a feature of South African Government development policy, a more robust emphasis is required in the REIPPPP weighting and auditing process, which includes further research of intended benefits and suggested improvements to align job creation data.
AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse regering het die hernubare energie onafhanklike kragprodusent verkrygingsprogram ontwikkel om die voorsiening van die werksskeppingsbeleid en groen-ekonomiebelied te verseker. Huidige Suid-Afrikaanse letterkunde is dubbelsinnig wanneer die wettigheid van die program bespreek word. Die algehele begrip van die program en sy geassosieerde uitkoms is dus vaag. Daar is n behoefte om die kwantitatiewe werkskeppingvoorleggings te analiseer en om ondersoek in te stel in die geleenthede en uitdagings wat geassosieer word met betekenisvolle werkskepping. Deur n nie- lineêre iteratiewe ondersoekende ontwerp, wat gebaseer is op die navorser se posisie in die industrie, bestaan hieride empiriese navorsing, uit twee komponente. Eerstens, lig n literatuurstudie die ontwikkeling van n betekenisvolle werkskeppingsraamwerk in, en word gebruik om die program se boddokumentasie en publieke data te analiseer. Tweedens, word gemengde metodes gebruik om kwantitatiewe data van die departement van energie te versamel asook kwalitatiewe data van werkskeppingbelanghebbendes. Die resultaat is n meer verrykende verstandhouding van die hernubare energie onafhanklike kragprodusent verkrygingsprogram in terme van betekenisvolle werkskepping asook die identifisering van tendense en onverwagse uitkomste. Die studie kom tot die gevolgtrekking dat die program nie betekenisvolle werk skep nie en is tans onbeskikbaar vir die publiek. Tweedens, aangesien werkskepping 'n kenmerk is van die Suid-Afrikaanse regering se ontwikkelingsbeleid, word 'n meer robuuste klem vereis op die hernubare energie onafhanklike kragprodusent verkrygingsprogram se ouditeringsproses en verdere navorsing van die beoogde voordele word voorgestel.

This thesis considers the generation and demand challenges of a 100% renewable UK electricity grid and how this can be addressed with interconnection or energy storage. Hourly demand and electricity generation profiles for a year have been constructed: Business as Usual with a yearly demand of 540TWh and Green Plus (rapid uptake of energy efficiency and green measures) with a demand of 390TWh. In addition, two extra scenarios based on the above have been considered with electrification of heating (air source heat pumps) and transportation. The resultant hourly imbalances have been used to calculate the interconnection and energy storage requirements. The calculated interconnector capacity required was found to be 60GW at a cost of GBP 58 billion for the BAU scenario. Energy storage capacity requirements vary depending on the selected technology. Rated capacity was estimated to be 14GW with storage capacity of 3TWh for pumped storage, 11GW and 2.3TWh for liquid air, and 65GW and 13.6TWh for hydrogen storage, at a cost of GBP 65, GBP 76 and GBP 45 billion respectively. This thesis indicates that storing hydrogen in underground caverns would offer the cheapest solution. However, whilst these technological solutions can address generation and demand imbalance in a fully renewable electricity grid, there remain barriers to each technology. A further technological solution is to exploit the use of electric heat pumps for domestic heating and hot water, as well as the moderate uptake of electric vehicles. It is proposed that these technologies are used on a local scale to help integrate the additional renewable electricity generated within a pre-determined zone of the electricity network. Analysis has been carried out to determine the constraints in the UK network where renewable electricity generation is greater than local electricity demand. From this, consideration has been made to understand the real impact distributed energy storage in the form of heat pumps and electric vehicles could have. Results show that depending on the demand scenario and location on the network, there is the potential to accommodate up to 50% of the excess electricity generated. Lastly, analysis was conducted on a hybrid technological solution which combines interconnector and energy storage capacity in order to ensure that demand is met year round. This analysis indicates that an optimal combination of a 37GW interconnector plus 11GW of hydrogen (cavern) storage at a cost of GBP 42 billion for the BAU scenario is possible. Likewise, for the GP scenario a 24GW interconnector plus 8.5GW of hydrogen (cavern) storage at a cost of GBP 28 billion was found to be optimal. This analysis shows that a hybrid solution provides a lower cost option than installing either one of the solutions separately.