983 resultados para Electricity in dentistry.


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Ancillary service plays a key role in maintaining operation security of the power system in a competitive electricity market. The spinning reserve is one of the most important ancillary services that should be provided effectively. This paper presents the design of an integrated market for energy and spinning reserve service with particular emphasis on coordinated dispatch of bulk power and spinning reserve services. A new market dispatching mechanism has been developed to minimize the cost of service while maintaining system security. Genetic algorithms (GA) are used for finding the global optimal solutions for this dispatch problem. Case studies and corresponding analyses have been carried out to demonstrate and discuss the efficiency and usefulness of the proposed method.

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This paper is located within the corporate social reporting and stakeholder management literature. It is concerned with the use of the Internet as a way of communicating with stakeholders and the extent to which this communication is or is not two-way. The evidence from the electricity industry in the UK is that the Internet is used but this use is selective and there is little true dialogue. It appears that the Internet provides an opportunity for greater corporate accountability in the future but whether this potential will be fulfilled is as yet unclear. Further research of a longitudinal nature is required to see how the Internet and more specifically corporate social or stakeholder reporting develops over time.

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This thesis proposes to explore the potential for stakeholder based accounting as a means to explain the social performance of organisations. It argues that organisations have a contract with society and as a consequence they must be accountable to that society for their actions. Further, it is suggested that as part of this accountability there is a broader need in the public interest for social accounting. Due to the pluralistic nature of modern societies it is argued that a stakeholder framework is one way in which this accountability can be achieved. In order to consider the nature of such social accounting a case study of the electricity industry in England and Wales is undertaken. This industry is very important to modern society, has significant environment implications and has a recent history of remarkable change. These factors make it an interesting and unique case within which to consider accountability. From the performance measurement and accounting literature and a series of interviews with both stakeholders and privatised companies a model of stakeholder performance is developed. This is then used to analyse the electricity industry in England and Wales since privatisation. The objective is to demonstrate how certain stakeholders have fared, whether they have won or lost. Further, institutional and resource dependency theories are used to consider what factors determine the relative success or failure of the different stakeholder groups. Finally the possible implications of recent developments in Social Accounting Standards, such as the Global Reporting Initiative (GRI), AccountAbility 1000 (AA1000) and Social Accountability 8000 (SA8000), and the potential for Internet reporting are considered.

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This thesis analyses the impact of deregulation on the theory and practice of investment decision making in the electricity sector and appraises the likely effects on its long term future inefficiency. Part I describes the market and its shortcomings in promoting an optimal generation margin and plant mix and in reducing prices through competition. A full size operational model is developed to simulate hour by hour operation of the market and analyse its features. A relationship is established between the SMP and plant mix and between the LOLP and plant margin and it is shown bow a theoretical optimum can be derived when the combined LOLP payments and the capital costs of additional generation reach a minimum. A comparison of prices against an idealised bulk supply tariff is used to show how energy prices have risen some 12% in excess of what might have occurred under the CEGB regime. This part concludes with proposals to improve the marlin particular advocates a new approach to encourage optimal capacity planning using lagrangian techniques to indicate needs without loss of data confidentiality. Part 2 demonstrates that the classical approach to generation investment appraisal is no longer valid and develops a new approach. It is shown how an individual generator can predict his utilisation and income to establish the worth of investment and demonstrates the validity of the operational model proposed. An empirical relationship is developed between profit and capacity and this is used to develop the theory to illustrate how companies interact. 1bree different economic models are developed to represent different market conditions and these are tested against the actual investment decisions since deregulation to demonstrate their appropriateness. It is shown that the current market mechanisms could lead to suboptimal investment. Part 3 discusses the essential role of transmission in enabling competition and reviews worldwide practices illustrating little consensus on charging for its use. Basic costing principles are described and a new model is developed to demonstrate bow a generator may strike supply agreements either side of an interconnector to influence prices so as to maximise his income. The optimal pricing strategy for the transmitter is also derived and consumer response is simulated .The concept of transmission uplift is developed and the operational model is extended to include transmission constraints and then used to establish monthly incremental transmission constraint cost functions. It is shown how these can be used to appraise investment options and optimally plan outages. Part 4 concludes by discussing the regulatory framework and its limitations in improving efficiency or encouraging the optimum levels of investment. The principal findings of the thesis are reviewed and potential market improvement are described. This part concludes with a discussion of alternative market structures and likely future developments.

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This thesis investigates the cost of electricity generation using bio-oil produced by the fast pyrolysis of UK energy crops. The study covers cost from the farm to the generator’s terminals. The use of short rotation coppice willow and miscanthus as feedstocks was investigated. All costs and performance data have been taken from published papers, reports or web sites. Generation technologies are compared at scales where they have proved economic burning other fuels, rather than at a given size. A pyrolysis yield model was developed for a bubbling fluidised bed fast pyrolysis reactor from published data to predict bio-oil yields and pyrolysis plant energy demands. Generation using diesel engines, gas turbines in open and combined cycle (CCGT) operation and steam cycle plants was considered. The use of bio-oil storage to allow the pyrolysis and generation plants to operate independently of each other was investigated. The option of using diesel generators and open cycle gas turbines for combined heat and power was examined. The possible cost reductions that could be expected through learning if the technology is widely implemented were considered. It was found that none of the systems analysed would be viable without subsidy, but with the current Renewable Obligation Scheme CCGT plants in the 200 to 350 MWe range, super-critical coal fired boilers co-fired with bio-oil, and groups of diesel engine based CHP schemes supplied by a central pyrolysis plant would be viable. It was found that the cost would reduce with implementation and the planting of more energy crops but some subsidy would still be needed to make the plants viable.

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This study of concentrating solar thermal power generation sets out to evaluate the main existing collection technologies using the framework of the Analytical Hierarchy Process (AHP). It encompasses parabolic troughs, heliostat fields, linear Fresnel reflectors, parabolic dishes, compound parabolic concentrators and linear Fresnel lenses. These technologies are compared based on technical, economic and environmental criteria. Within these three categories, numerous sub-criteria are identified; similarly sub-alternatives are considered for each technology. A literature review, thermodynamic calculations and an expert workshop have been used to arrive at quantitative and qualitative assessments. The methodology is applied principally to a case study in Gujarat in north-west India, though case studies based on the Sahara Desert, Southern Spain and California are included for comparison. A sensitivity analysis is carried out for Gujarat. The study concludes that the linear Fresnel lens with a secondary compound parabolic collector, or the parabolic dish reflector, is the preferred technology for north-west India.

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Use of agricultural residues, like wheat or rice straw for energy generation, is the most effective measure in terms of costs and availability. The present paper focuses the need of such measure, its impact on the environment as practiced today (open burning). The application of intermediate pyrolysis technology for straw conversion in India is discussed herein. A 20 kg/h Pyroformer has been coupled to a direct quenching system without filtration. The process temperature was around 360 ?C and the yields for the product fractions, char pyrolysis oil, and non-condensable gas fractions were, 32%, 35%, and 33% respectively. The pyrolysis oil was condensed in a quenching unit using bio-diesel or diesel. The blend produced was 30 % pyrolysis liquid and 70 % bio-diesel. The engine has been tested with the pyro-oil/biooil mixture over a long term (75 hours). An overall economic analysis of the process has been carried out.

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This paper investigates vertical economies between generation and distribution of electric power, and horizontal economies between different types of power generation in the U.S. electric utility industry. Our quadratic cost function model includes three generation output measures (hydro, nuclear and fossil fuels), which allows us to analyze the effect that generation mix has on vertical economies. Our results provide (sample mean) estimates of vertical economies of 8.1% and horizontal economies of 5.4%. An extensive sensitivity analysis is used to show how the scope measures vary across alternative model specifications and firm types. © 2012 Blackwell Publishing Ltd and the Editorial Board of The Journal of Industrial Economics.

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Five principles for accommodating cultural nuances

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This paper presents research from part of a larger project focusing on the potential development of commercial opportunities for the reuse of batteries on the electricity grid system, subsequent to their primary use in low and ultra-low carbon vehicles, and investigating the life cycle issues surrounding the batteries. The work has three main areas; examination of electric vehicle fleet data in detail to investigate usage in first life. Batteries that have passed through a battery recycler at the end of their first life have been tested within the laboratory to confirm the general assumption that remaining capacity of 80% after use in transportation is a reasonable assumption as a basis for second-life applications. The third aspect of the paper is an investigation of the equivalent usage for three different second-life applications based on connection to the electricity grid. Additionally, the paper estimates the time to cell failure of the batteries within their second-life application to estimate lifespan for use within commercial investigations. © 2014 IEEE.

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Az Európai Unión belül az elmúlt időszakban megerősödött a vita arról, vajon a Közösség versenyképességének javításához milyen módon és mértékben járulhat hozzá az ipari és lakossági fogyasztók számára kedvező áron elérhető villamos energia. Az uniós testületek elsődlegesen a verseny feltételeinek további javításában látják a versenyképesség javításának fő eszközét, ám egyesek az aktívabb központi szabályozás mellett érvelnek. A jelenleg alkalmazott európai szabályozási gyakorlat áttekintése, a szabályozási modellek és a piaci árak alakulásának vizsgálata hozzásegíthet, hogy következtetéseket vonjunk le a tagállami gyakorlatok tekintetében, vajon sikeresebb-e a központi ármegállapításon alapuló szabályozói mechanizmus, mint a liberalizált piacmodell. ______ There is a strengthening debate within the European Union in recent years about the impact of the affordable industrial and household electricity prices on the general competitiveness of European economies. While the European Institutions argues for the further liberalization of the energy retail sector, there are others who believe in centralization and price control to achieve lower energy prices. Current paper reviews the regulatory models of the European countries and examines the connection between the regulatory regime and consumer price trends. The analysis can help to answer, whether the bureaucratic central regulation or the liberalized market model seems more successful in supporting the competitiveness goals. Although the current regulatory practice is heterogeneous within the EU member states, there is a clear trend to decrease the role of regulated tariffs in the end-user prices. Our study did not find a general causal relationship between the regulatory regime and the level of consumer electricity prices in a country concerned. However, the quantitative analysis of the industrial and household energy prices by various segments detected significant differences between the regulated and free-market countries. The first group of member states tends to decrease the prices in the low-consuming household segments through cross-financing technics, including increased network tariffs and/or taxes for the high-consuming segments and for industrial consumers. One of the major challenges of the regulatory authorities is to find the proper way of sharing these burdens proportionally with minimizing the market-distorting effects of the cross-subsidization between the different stakeholder groups.