Today many computing resources distributed geographically are idle much of time. The aim of the grid computing is collecting these resources into a single system. It helps to solve problems that are too complex for a single PC. Scheduling plays a critical role in the efficient and effective management of resources to achieve high performance on grid computing environment. Due to the heterogeneity and highly dynamic nature of grid, developing scheduling algorithms for grid computing involves some challenges. In this work, we concentrate on efficient scheduling of distributed tasks on grid. We propose a novel scheduling heuristic for bag-of-tasks applications. The proposed algorithm primarily makes use of history based runtime estimation. The history stores information about the applications whose runtimes and other specific properties are recorded during the previous executions. Scheduling decisions are made according to similarity between the applications. Definition of similarity is an important aspect of this approach, apart from the best resource allocation. The aim of this scheduling algorithm (HISA-History Injected Scheduling Algorithm) is to define and find the similarity, and assign the job to the most suitable resource, making use of the similarity. In our evaluation, we use Grid simulation tool called GridSim. A number of intensive experiments with various simulation settings have been conducted. Based on the experimental results, the effectiveness of HISA scheduling heuristic is studied and compared to the other scheduling algorithms embedded in GridSim. The results show that history injection improves the performance of future job submissions on a grid.

The importance of access to modern energy has been well understood by governments and donor agencies in many developing countries, and significant effort has been made in recent years to address energy access challenges. However, despite these efforts, the International Energy Agency (IEA) has predicted that the energy access problem will remain unresolved by 2030. Therefore, adequate and appropriate action is needed to resolve this problem more quickly. This dissertation analyses policies and their impacts and will help researchers and policy makers in developing countries to (i) understand the impact of policies in the formation of a renewable energy (RE) market, (ii) consider the determinants of technological choices when promoting access to energy services and, (iii) better appreciate the sustainability performance of rural energy. For the purpose of analysis, several country cases from Asia and Sub-Saharan Africa region were carried out as these are the two main regions where the energy access problem are most acute. To understand the impact of policies in the formation of RE based rural electrification market, a case study was conducted in Nepal. The study has shown that rural electrification has been expanding as a consequence of market-oriented policies. When it comes to selection of electrification path-ways, different technological alternatives are analysed in Afghanistan and Nepal, taking levelized cost of electricity (LCOE) as the means to select cost effective options. The analysis has presented best-fit conditions for these various technological pathways in the two countries and verified whether they are following the appropriate and cost effective course in their efforts to expand rural electrification. For understanding the determinants of cooking fuel choices and to analyse policy implications in the transition of large populations from traditional to modern fuels, fuel choices are modelled in the case of China. Choices are modelled (using MESSAGE–ACCESS mod-el) with standard economic variables such as income, technology costs and fuel prices, along with some unique variable such as inconvenience costs. Future access scenarios are designed considering different policy options to accelerate the transition. Sustainability is one of the key concerns in terms of energy access. This dissertation introduces methods for evaluating (i) the sustainability performance of energy technologies and (ii) the status and progress of developing countries in providing sustainable energy access. Different sets of sustainability indicators are considered for the rural energy sector and aggregated to form a single composite index. The energy technology sustainability index (ETSI) is used for assessing the performance of different energy technological systems in the case of India. The analysis reveals that mature technologies such as biomass gasifiers, biogas and micro hydro have relatively better sustainability performance among the options considered, while solar and wind, though showing fairly good improvement in sustainability performance, still have difficulties competing with more mature and conventional technologies without policy support. The Energy Sustainability Index (ESI) has been applied to China, India, South Africa, Sri-Lanka, Bangladesh and Ghana between 1990 and 2010 to evaluate the status and progress made by these countries in rural energy sustainability. The analysis suggests that South Africa’s rural energy sustainability index is highest followed by China, Sri Lanka, India, Bangladesh and Ghana respectively. The rural energy sustainability has improved relatively over time in all countries except Ghana. The dissertation shows that policies are helping the rapid expansion of the RE market though with uneven penetration in rural Nepal. Access to credit and cumbersome subsidy delivery mechanism are perceived as the major factors affecting the expansion of rural electrification, requiring innovation. The electrification pathways taken by Nepal seem functional and moving in the right direction but some flaws in the delivery mechanisms require attention. Meanwhile in Afghanistan, pathways are not well defined and the country lacks a clear-cut national policy framework for the expansion of rural electrification. The analysis on fuel transition shows that even a fast developing country such as China will continue to have serious problems guaranteeing the access to solid fuels for cooking for one third of its rural population by 2030. The problem could be more severe in poorer nations. There-fore, further policy intervention addressing the high implicit discount rate of the poorer section of the population, reducing the upfront cost of more efficient technology (stoves) or the costs of cleaner fuels with subsidies must be considered to promote energy transition. Overall, this dissertation has analysed key issues in the global discussion about sustainable energy access. The methods for sustainability assessment suggested have been specially designed for rural settings in developing countries and are instrumental to assess the performance of rural energy technologies and track the progress of sustainable energy access efforts among rural households. / <p>QC 20140210</p>

Com o crescimento constante da infraestrutura do sistema de distribuição de baixa tensão, tem-se a necessidade de um monitoramento mais preciso das grandezas elétricas no ponto de conexão com os clientes. O impacto da implantação de sistemas smart grids são positivos, visto que para o lado do consumidor o acompanhamento do consumo de forma online permite realizar um melhor planejamento, e para o lado da concessionária, o levantamento de perfil dos clientes e planejamento de demanda, visto que os medidores podem fornecer os dados em tempo real de horários de maior consumo e acompanhamento dos níveis, de forma a adequar conforme os níveis de qualidade de energia definidos pelo módulo 8 PRODIST. Além do acompanhamento, das variáveis e limites, este projeto poderá atuar de forma a auxiliar as companhias elétricas a comparar os pontos de cargas estimadas com o fornecimento para detectar possíveis fraudes no ponto de distribuição. Outro aspecto importante é tornar possível a integração com uma rede de clientes que além de consumidores podem tornar-se pequenas unidades geradoras, alimentando o sistema maior. / With the constant growth of the infrastructure of the low voltage distribution system, there is a need for a more refined monitoring of the electrical quantities in the distribution network. The impact of the implementation of smart grids systems are positive, since for the consumer side the monitoring of consumption in an online way allows to carry out consumption planning, and for the side of the concessionaire, customer profile survey and demand planning, Since the meters can provide the real time data of schedules of greater consumption and monitoring of the levels, in order to adapt according to the levels of quality of energy defined by the module 8 PRODIST. In addition to the monitoring of variables and limits, this project may act in a way that helps utilities compare the estimated load points with the supply to detect possible fraud at the distribution point. Another important aspect is to make it possible to integrate with a network of customers that in addition to consumers can become small generating units, feeding the larger system.

Philosophiae Doctor - PhD / The high rate of grid computing adoption, both in academe and industry, has posed challenges regarding efficient access control, interoperability and scalability. Although several methods have been proposed to address these grid computing challenges, none has proven to be completely efficient and dependable. To tackle these challenges, a novel access control architecture framework, a triple-domain grid-based environment, modelled on role based access control, was developed. The architecture’s framework assumes three domains, each domain with an independent Local Security Monitoring Unit and a Central Security Monitoring Unit that monitors security for the entire grid.The architecture was evaluated and implemented using the G3S, grid security services simulator, meta-query language as “cross-domain” queries and Java Runtime Environment 1.7.0.5 for implementing the workflows that define the model’s task. The simulation results show that the developed architecture is reliable and efficient if measured against the observed parameters and entities. This proposed framework for access control also proved to be interoperable and scalable within the parameters tested.

published_or_final_version / Business / Doctoral / Doctor of Philosophy

published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

While solar photovoltaic (PV) panels can offset fuel, emissions, and water use at the power plant, high levels of installed rooftop PV capacity can have negative impacts on the stability and efficiency of the local grid because of power factor (PF) degradation. Specifically, electric utilities have noted voltage fluctuations from solar PV that occur more dynamically than legacy, electromechanical voltage regulation solutions like capacitor banks are designed to correct. At the same time, distributed power electronics devices like inverters can provide the type of dynamic voltage support that utilities seek to maintain reliability while juggling load growth and a greening grid. Using data from Pecan Street Inc. Smart Grid Demonstration Project in Austin, Texas and Austin Water Utility (AWU), this research examines the potential for a three-phase, four quadrant variable speed drive (VSD) in the water sector to provide PF correction to a load pocket of 63 homes experiencing varying levels of PV penetration. In the analysis, the VSD is not reserved for voltage support; instead it is predominantly used to drive a 30 kilowatt (kW) centrifugal sewage pump. The simulation determines the degree to which the VSD can restore PF to a threshold of 0.95, slightly below the targeted value for Austin's electric utility. Further, the economic viability of using the VSD as a grid device is explored by comparing the per unit cost of the PF correction it provides to a current utility solution for dynamic voltage regulation. / text

The understanding of the physics of the Coherent Structures and their interaction with the remaining fluid motions is of paramount interest in Turbulence Research. Indeed, recently had been suggested that separating and understanding the the different physical behavior of Coherent Structures and "uncoherent" background might very well be the key to understand and predict Turbulence. Available understanding of Coherent Structures shows that their size is considerably larger than the turbulent macro-scale, making permissible the application of Large Eddy Simulation to their simulation and study, with the advantage to be able to study their behavior at higher Re and more complex geometry than a Direct Numerical Simulation would normally allow. Original purpose of the present work was therefore the validation of the use of Large Eddy Simulation for the study of Coherent Structures in Shear-Layer and the its application to different flow cases to study the effect of the flow topology on the Coherent Structures nature. However, during the investigation of the presence of Coherent Structures in numerically generated LES flow fields, the aging in house Large Eddy Simulation (LES) code of the Environmental & Applied Fluid Dynamics Department has shown a series of limitations and shortcomings that led to the decision of relegating it to the status of Legacy Code (from now on indicated as VKI LES legacy code and of discontinuing its development. A new natively parallel LES solver has then been developed in the VKI Environmental & Applied Fluid Dynamics Department, where all the shortcomings of the legacy code have been addressed and modern software technologies have been adopted both for the solver and the surrounding infrastructure, delivering a complete framework based exclusively on Free and Open Source Software (FOSS ) to maximize portability and avoid any dependency from commercial products. The new parallel LES solver retains some basic characteristics of the old legacy code to provide continuity with the past (Finite Differences, Staggered Grid arrangement, Multi Domain technique, grid conformity across domains), but improve in almost all the remaining aspects: the flow can now have all the three directions of inhomogeneity, against the only two of the past, the pressure equation can be solved using a three point stencil for improved accuracy, and the viscous terms and convective terms can be computed using the Computer Algebra System Maxima, to derive discretized formulas in an automatic way. For the convective terms, High Resolution Central Schemes have been adapted to the three-dimensional Staggered Grid Arrangement from a collocated bi-dimensional one, and a system of Master-Slave simulations has been developed to run in parallel a Slave simulation (on 1 Processing Element) for generating the inlet data for the Master simulation (n - 1 Processing Elements). The code can perform Automatic Run-Time Load Balancing, Domain Auto-Partitioning, has embedded documentation (doxygen), has a CVS repository (version managing) for ease of use of new and old developers. As part of the new Frame Work, a set of Visual Programs have been provided for IBM Open Data eXplorer (OpenDX), a powerful FOSS Flow visualization and analysis tool, aimed as a replacement for the commercial TecplotTM, and a bug tracking mechanism via Bugzilla and cooperative forum resources (phpBB) for developers and users alike. The new M.i.O.m.a. (MiOma) Solver is ready to be used again for Coherent Structures analysis in the near future.

We consider the impact that various shocks and stresses have on the reliability of networks with radial topology, such as an electrical power grid. We incorporate the effects of aging, geographical risk, and local dependence between components into a model of overall system reliability. We also simulate how the system fares under extreme weather events, such as hurricanes. Our model gives a flexible and general understanding of how outside forces affect network reliability and can be adapted to a range of specific uses. We run a simulation using this model which yields realistic results.

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