Many scenarios try to describe a future of supply and demand for electricity in Sweden. All the studied scenarios contain an increased amount of variable renewable energy (VRE) power production. VRE power sources, such as solar and wind power, depend on weather conditions, like solar irradiance and wind speed. There are also scenarios predicting an increased amount of plug-in electrical vehicles (PEVs), which charge their batteries from the electricity grid and thereby changes the consumption patterns. In a future power system with less nuclear power and increased VRE power production it is of interest to investigate the scenarios impact on supply and demand. The scenarios were compiled into cases for the years 2030, 2050, and 2100. Simulations of each case VRE shares resulted in hourly power production data. Aggregating the data and comparing it with the consumption gives an understanding of the power and regulation need.  For Case 2030, a VRE share of 10.3% was calculated. The hydropower in Sweden could cover the power need for the whole year and even peaks in demand. For the larger shares of Case 2050 and 2100, hydropower was not able to cover peaks in power demand solemnly. The consumption of PEVs was small for all cases, reaching shares of 1.5% to 7.1%, compared to the consumption of all other sectors. Considering short-term statistics for wind power and the latest news that some of Sweden’s nuclear reactors might shut down in advance, it is possible that Case 2030 might occur sooner than predicted. If larger shares of VRE power have to be produced to meet consumer needs in the near future, grid-stabilizing measures has to be investigated.

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (p. 459-469). Also available via the World Wide Web.

The use of electricity in 21st century living has been firmly established throughout most of the world, correspondingly the infrastructure for production and delivery of electricity to consumers has matured and stabilised. However, due to recent technical and environmental–political developments, the electricity infrastructure worldwide is undergoing major restructuring. The forces driving this reorganisation are a complex interplay of technical, environmental, economic and political factors. The general trend of the reorganisation is a dis–aggregation of the previously integrated functions of generation, transmission and distribution, together with the establishment of competitive markets, primarily in generation, to replace previous regulated monopolistic utilities. To ensure reliable and cost effective electricity supply to consumers it is necessary to have an accurate picture of the expected generation in terms of the spatial and temporal distribution of prices and volumes. Previously this information was obtained by the regulated utility using technical studies such as centrally planned unit–commitment and economic–dispatch. However, in the new deregulated market environment such studies have diminished applicability and limited accuracy since generation assets are generally autonomous and subject to market forces. With generation outcomes governed by market mechanisms, to have an accurate picture of expected generation in the new electricity supply industry, it is necessary to complement traditional studies with new studies of market equilibrium and stability. Models and solution methods have been developed and refined for many markets, however they cannot be directly applied to the generation market due to the unique nature of electricity, having high inelastic demand, low storage capability and distinct transportation requirements. Intensive effort is underway to formulate solutions and models that specifically reflect the unique characteristics of the generation market. Various models have been proposed including game theory, stochastic and agent–based systems. Similarly there is a diverse range of solution methods including, Monte–Carlo simulations, linear–complimentary and quadratic programming. These approaches have varying degrees of generality, robustness and accuracy, some being better in certain aspects but weaker in others. This thesis formulates a new general model for the generation market based on the Cournot game, it makes no conjectures about producers’ behaviour and assumes that all electricity produced is immediately consumed. The new formulation characterises producers purely by their cost curves, which is only required to be piece–wise differentiable, and allows consumers’ characteristics to remain unspecified. The formulation can determine dynamic equilibrium and multiple equilibria of markets with single and multiple consumers and producers. Additionally stability concepts for the new market equilibrium is also developed to provide discrimination for dynamic equilibrium and to enable the structural stability of the market to be assessed. Solutions of the new formulation are evaluated by the use of evolutionary computation, which is a guided stochastic search paradigm that mimics the operation of biological evolution to iteratively produce a population of solutions. Evolutionary computation is employed as it is adept at finding multiple solutions for underconstrained systems, such as that of the new market formulation. Various enhancements to significantly improve the performance of the algorithms and simplify its application are developed. The concept of convergence potential of a population is introduced together with a system for the controlled extraction of such potential to accelerate the algorithm’s convergence and improve its accuracy and robustness. A new constraint handling technique for linear constraints that preserves the solution’s diversity is also presented together with a coevolutionary solution method for the multiple consumers and producers market. To illustrate the new electricity market formulation and its evolutionary computation solution methods, the equilibrium and stability of a test market with one consumer and thirteen thermal generators with valve point losses is examined. The case of a multiple consumer market is not simulated, though the formulation and solution methods for this case is included. The market solutions obtained not only confirms previous findings thus validating the new approach, but also includes new results yet to be verified by future studies. Techniques for market designers, regulators and other system planners in utilising the new market solutions are also given. In summary, the market formulation and solution method developed shows great promise in determining expected generation in a deregulated environment.

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Eskom, the South Africa and trans-Africa electrical power utility, has a capacity expansion project that is estimated to cost roughly R340 billion. The programme is anticipated to continue through 2018. Eskom will be contracting with a multitude of suppliers and it is imperative that the projects delivered under the capacity expansion programme meet Eskom’s required quality standards. The question then arises whether the set quality standards are sufficiently comprehensive to provide confidence that suppliers will achieve high quality standards. This aim of this research was to examine supplier assessment programmes to determine the criteria that will best provide supplier assurance. The researcher consulted a vast range of literature available on supplier quality assessment programmes. From the literature consulted, there appeared to be some recurring themes from the range of assessment tools. It also becomes apparent that the assessment tool cannot only focus on a quality system, but a balance of strategic and operational focus was needed to fully understand suppliers’ ability to deliver. One of the key considerations was establishing longer-term collaborative relationships with key suppliers. Long-term relations encourage trust, transparency and innovation. It was equally important to ensure that operational assessments provided insight on suppliers’ capability. Based on the literature reviewed, a proposed framework was tested against the current methodology for supplier evaluation. From these comparisons, some gaps were identified and recommendations were suggested to improve the supplier evaluation programme.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

The aim of this thesis is to apply and evaluate potential forecasting models for solar power production, based on data from a photovoltaic facility in Sala, Sweden. The thesis evaluates single step forecasting models as well as multiple step forecasting models, where the three compared models for single step forecasting are persistence, autoregressive integrated moving average (ARIMA) and ARIMAX. ARIMAX is an ARIMA model that also takes exogenous predictors in consideration. In this thesis the evaluated exogenous predictor is wind speed. The two compared multiple step models are multiple step persistence and the Gaussian process (GP). Root mean squared error (RMSE) is used as the measurement of evaluation and thus determining the accuracy of the models. Results show that the ARIMAX models performed most accurate in every simulation of the single step models implementation, which implies that adding the exogenous predictor wind speed increases the accuracy. However, the accuracy only increased by 0.04% at most, which is determined as a minimal amount. Moreover, the results show that the GP model was 3% more accurate than the multiple step persistence; however, the GP model could be further developed by adding more training data or exogenous variables to the model.

Tu, Jinlong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 92-95). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Orientador: Marcor Julio Rider Flores / Banca: Sergio Azevedo de Oliveira / Banca: Roberto Cayetano Lotero / Resumo: Esta dissertação de mestrado discute sobre o investimento em capacidade de transmissão em mercados elétricos competitivos e sua relação com o investimento em capacidade de geração. O principal problema que surge ao descentralizar os investimentos são as externalidades, devido à dependência entre os custos de oportunidade da capacidade transmissão e geração. As externalidades são distorções nomercado que se apresentam quando as decisões de um agente afetam o bem-estar de outro agente, porém não vice-versa. Em presença de externalidades não é válido afirmar que a solução descentralizada seja igual ao resultado centralizado (ótimo de Pareto). Para solucionar este problema deve-se implementar um processo descentralizado através de esquemas regulatórios. Logo, é proposto um modelo binível que procura o ótimo de Pareto e serve como referência para implementação de esquemas regulatórios que permitam avaliar os investimentos em capacidade de transmissão e geração em um mercado competitivo. O modelo binível proposto é transformado em um problema de programação linear inteira mista, usando a teoria de dualidade e técnicas de linearização. O modelo proposto foi implementado em AMPL e solucionado usando o solver comercial CPLEX. Finalmente, são apresentados os resultados obtidos para dois sistemas testes e um sistema real / Abstract: This dissertation discusses about the investing in transmission capacity in competitive electricity markets and its relation with the investing in generation capacity. Since opportunity costs of transmission and generation capacity are dependent, externalities arise when the investments decisions are decentralized. Externalities are present whenever a decision of a certain agent affects another agent's welfare but not vice versa. In presence of externalities, the decentralized outcome does not lead to a Pareto optimal solution. In order to overcome this problem, the Pareto optimal solution should be found, and set in the market by means of regulation. Moreover, a bi-level multistage model is proposed, which finds the Pareto optimal solution. This solution can be used as reference for the implementation of regulatory mechanisms that asses the investments in transmission and generation capacity. The proposed bi-level model is transformed into a mixed integer linear problem using duality theory and linearization techniques. Finally, the proposed model is implemented in AMPL and solved using CPLEX; results for several study cases are presented / Mestre

Thesis (Master of Engineering in Electrical Engineering))--Cape Peninsula University of Technology, 2018. / Industry, which forms the lifeblood of South Africa’s economy, is under threat as a result of increased electricity pricing and unstable supply. Wheeling of energy, which is a method to transport electricity generated from an Independent Power Producer (IPP) to an industrial consumer via the utility’s network, could potentially address this problem. Unlike South Africa’s electricity landscape, which is highly regulated and monopolized by Eskom, most developed countries have deregulated their electricity market, which has led to greater competition for electricity supply. This thesis, presents an evaluation of the economic viability and technical concerns arising from third party transportation of energy between an IPP and an industrial consumer. IPP’s are able to generate electricity from various renewable distributed generation (DG) sources, which are often physically removed from the load. In practice, electricity could be generated by an IPP and connected to a nearby Main Transmission Substation (MTS) in a region with high solar, wind or hydropower resources and sold to off-takers a few hundred kilometres away. Using two software simulation packages, technical and economic analysis have been conducted based on load data from two industrial sites, to determine the viability of wheeling energy between an IPP and off-taker. The viability will be evaluated based on levelized cost of electricity (LCOE); net present cost (NPC); DG technology; distance from the load; available renewable resources; impact on voltage profile, fault contribution, thermal loading of the equipment and power loss. The results from both case studies show that the impact of DG on the voltage profile is negligible. The greatest impact on voltage profile was found to be at the site closest to the load. Asynchronous and synchronous generators have a greater fault contribution than inverter-based DG. The fault contribution is proportional to the distance from the load. Overall, thermal loading of lines increased marginally, but decreased based on distances from the load. Power loss on short lines is negligible but there is a significant loss on the line between the load and DG based on the distance from the load. Electricity generated from wind power is the most viable based on LCOE and NPC. For larger wind systems, as illustrated by the second case study, grid parity has already been reached. Wheeling of wind energy has already proven to be an economically viable option. According to future cost projection, large scale solar energy will become viable by 2019. The concept of wheeling energy between an IPP and off-taker has technical and economic merit. Wheeling charges are perceived to be high, but this is not the case as wheeling tariffs consist of standard network charges. In the future, renewable energy will continue to mature based on technology and cost. Solar energy, including lithium-ion battery back-up technology, looks promising based on future cost projections. Deregulation of the electricity market holds the key to the successful implementation of energy wheeling as it will open the market up for greater competition.

Ce travail a été réalisé dans le cadre du projet Systèmes Mécaniques Adaptatifs (SMA)du laboratoire mécatronique M3M de l’UTBM impliqué dans l’institut FCLAB de recherche sur les systèmes pile à combustible et du projet de l’équipe de recherche «Modélisation Multiphysique », en cours de constitution, du département Sciences et Technologies de l’USEK. Les PEMFC font l’objet de nombreuses recherches pour augmenter leurs performances et diminuer leur coût mais la plupart des études se concentrent sur leurs aspects physicochimiques.Cette thèse par contre se propose de mettre en évidence l’influence, sur la production d’énergie, des sollicitations mécaniques statiques, dynamiques voire thermiques (serrages, vibrations, frottements, …) comme phénomènes couplés relevant du domaine multiphysique (interactions fluide-structure, électrique …). En premier, une analyse des différents paramètres de modèles dépendant des aspects mécaniques a été effectuée et les principaux paramètres à étudier dans le cadre de cette thèse ont été sélectionnés : porosité, perméabilité et coefficients de diffusion de la GDL, conductivité électrique du contact GDL/PB et volume des canaux après compression de la cellule. Ensuite, un modèle partiel de représentation mécanique de la GDL d’une PEMFC du côté cathode a été mis en oeuvre afin de déterminer la déformation de la GDL comprimée par une force répartie sur la PB. Sur la base des contraintes mécaniques calculées dans la GDL, les champs locaux de porosité, de perméabilité et de résistance électrique de contact GDL/PB sont obtenus. D’autre part, une modélisation 3D de type volumes finis pour l’étude de la pression du fluide à l’interface GDL/PB a été élaborée. L’analyse a permis de déterminer le champ local de pression d’oxygène sur l’interface GDL/PB du côté cathode. Les champs locaux de porosité et de perméabilité de la GDL, de résistance électrique de contact GDL/PB et de pression d’interface GDL/PB sont alors introduits dans le modèle multiphysique 2D d’une cellule de pile PEMFC. Une étude détaillée du comportement de la pile et de la modification de sa performance a pu être réalisée. Les résultats ont été présentés sous forme de courbes de polarisation et de densité de puissance. Finalement tous les résultats ont été rassemblés pour une analyse d’influence et de sensibilité afin d’identifier les paramètres qui auront le plus d'influence sur les variables simulées. Cette étude peut s'avérer un outil fort utile à la prise de décision concernant la géométrie de la dent des PB, la nature des PB, … / Most of the studies related to PEMFC emphasize on their physico-chemical aspects. The present study is concerned by the modeling for which a multiphysical coupling is primary for the balance of the energetic performance of the fuel cell. An analysis for the different parameters that depend on mechanical aspects is done and the major parameters for study are selected : prosity, permeability, diffusion coefficients of the GDL, electrical conductivity of the contact GDL / BP and volume of the channels after compression of the cell. The rectangular sections of graphite BP and trapezoid sections with or without a radius of curvature for steel BP are chosen. A partial model for the mechanical representation of the GDL of a PEMFC from the cathode side is first implemented in order to determine the deformation of the GDL induced by a uniformly distribued force. On the base of the mechanical constraints that are calculated in the GDL, the local fields of porosity abd contact resistance GDL / BP are obtained.The local field of the oxygen pressure on the GDL from the cathode side is determined by a 3D modeling. The local fields of GDL porosity, electrical contact resistance GDL / BP and pressure at the interface GDL / BP are then introduced in the 2D multiphysical model of the fuel cell. The results are presented as polarization and power density curves.Finally, all the results are gathered for an analysis of influence and sensibility in order to identify the parameters that wil have the bigger influence on the simulated variables.