Incidencia de la cooperación internacional para el desarrollo de las organizaciones internacionales en las políticas públicas de Nigeria. ¿Cooperación o injerencia política? una aproximación de la comisión para la energía de la ECOWAS. 2005 – 2011

La cooperación Internacional para el desarrollo ha jugado un papel determinante en las dinámicas de desarrollo de los países de África, sin embargo, las organizaciones internacionales que la promocionan tienen el riesgo de ser sesgadas por influencias de Estados que patrocinan la Cooperación Internacional, hecho que genera, irremediablemente, injerencia política; esto se puede ver reflejado en la ECOWAS y sus programas energéticos.

A Bayesian approach for multi-model downscaling: Seasonal forecasting of regional rainfall and river flows in South America

This study addresses three issues: spatial downscaling, calibration, and combination of seasonal predictions produced by different coupled ocean-atmosphere climate models. It examines the feasibility Of using a Bayesian procedure for producing combined, well-calibrated downscaled seasonal rainfall forecasts for two regions in South America and river flow forecasts for the Parana river in the south of Brazil and the Tocantins river in the north of Brazil. These forecasts are important for national electricity generation management and planning. A Bayesian procedure, referred to here as forecast assimilation, is used to combine and calibrate the rainfall predictions produced by three climate models. Forecast assimilation is able to improve the skill of 3-month lead November-December-January multi-model rainfall predictions over the two South American regions. Improvements are noted in forecast seasonal mean values and uncertainty estimates. River flow forecasts are less skilful than rainfall forecasts. This is partially because natural river flow is a derived quantity that is sensitive to hydrological as well as meteorological processes, and to human intervention in the form of reservoir management.

Life cycle analysis of UK coal fired power plants

This paper examines the life cycle GHG emissions from existing UK pulverized coal power plants. The life cycle of the electricity Generation plant includes construction, operation and decommissioning. The operation phase is extended to upstream and downstream processes. Upstream processes include the mining and transport of coal including methane leakage and the production and transport of limestone and ammonia, which are necessary for flue gas clean up. Downstream processes, on the other hand, include waste disposal and the recovery of land used for surface mining. The methodology used is material based process analysis that allows calculation of the total emissions for each process involved. A simple model for predicting the energy and material requirements of the power plant is developed. Preliminary calculations reveal that for a typical UK coal fired plant, the life cycle emissions amount to 990 g CO2-e/kWh of electricity generated, which compares well with previous UK studies. The majority of these emissions result from direct fuel combustion (882 g/kWh 89%) with methane leakage from mining operations accounting for 60% of indirect emissions. In total, mining operations (including methane leakage) account for 67.4% of indirect emissions, while limestone and other material production and transport account for 31.5%. The methodology developed is also applied to a typical IGCC power plant. It is found that IGCC life cycle emissions are 15% less than those from PC power plants. Furthermore, upon investigating the influence of power plant parameters on life cycle emissions, it is determined that, while the effect of changing the load factor is negligible, increasing efficiency from 35% to 38% can reduce emissions by 7.6%. The current study is funded by the UK National Environment Research Council (NERC) and is undertaken as part of the UK Carbon Capture and Storage Consortium (UKCCSC). Future work will investigate the life cycle emissions from other power generation technologies with and without carbon capture and storage. The current paper reveals that it might be possible that, when CCS is employed. the emissions during generation decrease to a level where the emissions from upstream processes (i.e. coal production and transport) become dominant, and so, the life cycle efficiency of the CCS system can be significantly reduced. The location of coal, coal composition and mining method are important in determining the overall impacts. In addition to studying the net emissions from CCS systems, future work will also investigate the feasibility and technoeconomics of these systems as a means of carbon abatement.

An overview of the current status of research into adopting high levels of renewables in Ireland

This paper provides an overview of the reduction targets that Ireland has set in the context of decarbonising their electricity generation through the use of renewables. The main challenges associated with integrating high levels (>20% of installed capacity) of non-dispatchable renewable generation are identified. The rising complexity of the challenge as renewable penetration levels increase is highlighted. A list of relevant research questions is then proposed, and an overview is given into the previous work that has gone into answering some of them. In particular, studies into the Irish energy market are identified, the current knowledge gap is described, and areas of necessary future research are suggested

Can microgrids make a major contribution to UK energy supply?

Almost all the electricity currently produced in the UK is generated as part of a centralised power system designed around large fossil fuel or nuclear power stations. This power system is robust and reliable but the efficiency of power generation is low, resulting in large quantities of waste heat. The principal aim of this paper is to investigate an alternative concept: the energy production by small scale generators in close proximity to the energy users, integrated into microgrids. Microgrids—de-centralised electricity generation combined with on-site production of heat—bear the promise of substantial environmental benefits, brought about by a higher energy efficiency and by facilitating the integration of renewable sources such as photovoltaic arrays or wind turbines. By virtue of good match between generation and load, microgrids have a low impact on the electricity network, despite a potentially significant level of generation by intermittent energy sources. The paper discusses the technical and economic issues associated with this novel concept, giving an overview of the generator technologies, the current regulatory framework in the UK, and the barriers that have to be overcome if microgrids are to make a major contribution to the UK energy supply. The focus of this study is a microgrid of domestic users powered by small Combined Heat and Power generators and photovoltaics. Focusing on the energy balance between the generation and load, it is found that the optimum combination of the generators in the microgrid- consisting of around 1.4 kWp PV array per household and 45% household ownership of micro-CHP generators- will maintain energy balance on a yearly basis if supplemented by energy storage of 2.7 kWh per household. We find that there is no fundamental technological reason why microgrids cannot contribute an appreciable part of the UK energy demand. Indeed, an estimate of cost indicates that the microgrids considered in this study would supply electricity at a cost comparable with the present electricity supply if the current support mechanisms for photovoltaics were maintained. Combining photovoltaics and micro-CHP and a small battery requirement gives a microgrid that is independent of the national electricity network. In the short term, this has particular benefits for remote communities but more wide-ranging possibilities open up in the medium to long term. Microgrids could meet the need to replace current generation nuclear and coal fired power stations, greatly reducing the demand on the transmission and distribution network.

Modelling the economics of farm-based anaerobic digestion in a UK whole-farm context

Anaerobic digestion (AD) technologies convert organic wastes and crops into methane-rich biogas for heating, electricity generation and vehicle fuel. Farm-based AD has proliferated in some EU countries, driven by favourable policies promoting sustainable energy generation and GHG mitigation. Despite increased state support there are still few AD plants on UK farms leading to a lack of normative data on viability of AD in the whole-farm context. Farmers and lenders are therefore reluctant to fund AD projects and policy makers are hampered in their attempts to design policies that adequately support the industry. Existing AD studies and modelling tools do not adequately capture the farm context within which AD interacts. This paper demonstrates a whole-farm, optimisation modelling approach to assess the viability of AD in a more holistic way, accounting for such issues as: AD scale, synergies and conflicts with other farm enterprises, choice of feedstocks, digestate use and impact on farm Net Margin. This modelling approach demonstrates, for example, that: AD is complementary to dairy enterprises, but competes with arable enterprises for farm resources. Reduced nutrient purchases significantly improve Net Margin on arable farms, but AD scale is constrained by the capacity of farmland to absorb nutrients in AD digestate.

Energy supply, consumption and access dynamics in Botswana

The growing dependence on electricity for economic growth in all countries prompts the need to manage current resources for future sustainability. In today’s world, greater emphasis is placed on energy conservation for energy security and for the development of every economy. However, for some countries understanding the basic drivers to such achievements is farfetched. The research presented in this paper investigates the electricity generation and access potential for Botswana. In addition detailed documentation and 13 years energy consumption and generation trends are investigated. Using questionnaires and empirical studies the energy demand for the entire nation was estimated. From the research it was established that current energy generation trends account for 38- 39% of the country’s population with access to electricity. Considering the percentage rate of sector energy demand, the proposed total installed capacity of 1332 MW, would not meet the country's energy demand at 100% access. The likely consequence of the lack of adequate supply would cumulate to significant increase of imports and/or load shedding to meet demand.

Emergy-based sustainability assessment of different energy options for green buildings

It is necessary to minimize the environmental impact and utilize natural resources in a sustainable and efficient manner in the early design stage of developing an environmentally-conscious design for a heating, ventilating and air-conditioning system. Energy supply options play a significant role in the total environmental load of heating, ventilating and air-conditioning systems. To assess the environmental impact of different energy options, a new method based on Emergy Analysis is proposed. Emergy Accounting, was first developed and widely used in the area of ecological engineering, but this is the first time it has been used in building service engineering. The environmental impacts due to the energy options are divided into four categories under the Emergy Framework: the depletion of natural resources, the greenhouse effect (carbon dioxide equivalents), the chemical rain effect (sulphur dioxide equivalents), and anthropogenic heat release. The depletion of non-renewable natural resources is indicated by the Environmental Load Ratio, and the environmental carrying capacity is developed to represent the environmental service to dilute the pollutants and anthropogenic heat released. This Emergy evaluation method provides a new way to integrate different environmental impacts under the same framework and thus facilitates better system choices. A case study of six different kinds of energy options consisting of renewable and non-renewable energy was performed by using Emergy Theory, and thus their relative environmental impacts were compared. The results show that the method of electricity generation in energy sources, especially for electricity-powered systems, is the most important factor to determine their overall environmental performance. The direct-fired lithium-bromide absorption type consumes more non-renewable energy, and contributes more to the urban heat island effect compared with other options having the same electricity supply. Using Emergy Analysis, designers and clients can make better-informed, environmentally-conscious selections of heating, ventilating and air-conditioning systems.

Greenhouse gas emission scenario modeling for cities using the PURGE model

Cities globally are in the midst of taking action to reduce greenhouse gas (GHG) emissions. After the vital step of emissions quantification, strategies must be developed to detail how emissions reductions targets will be achieved. The Pathways to Urban Reductions in Greenhouse Gas Emissions (PURGE) model allows the estimation of emissions from four pertinent urban sectors: electricity generation, buildings, private transportation, and waste. Additionally, the carbon storage from urban and regional forests is modeled. An emissions scenario is examined for a case study of the greater Toronto, Ontario, Canada, area using data on current technology stocks and government projections for stock change. The scenario presented suggests that even with some aggressive targets for technological adoption (especially in the transportation sector), it will be difficult to achieve the less ambitious 2050 emissions reduction goals of the Intergovernmental Panel on Climate Change. This is largely attributable to the long life of the building stock and limitations of current retrofit practices. Additionally, demand reduction (through transportation mode shifting and building occupant behavior) will be an important component of future emissions cuts.

The decline of the world`s energy intensity

Energy intensity of the total primary energy supply (TPES), total final energy consumption (TFC) and LOSSES in the conversion from TPES to TFC were analyzed for the World, OECD and Rest of the World (ROW) countries. LOSSES increased significantly for all groups of countries due to the increase of electricity production from coal in the period studied (1971-2008). Electricity share final consumption almost doubled, increasing from 8.8% to 17.2% in the period studied. However the energy intensity of LOSSES remained practically constant, which reflects the fact that the efficiency of electricity generation from coal (the main source of electricity) remained practically constant in that period. Despite the attractiveness of end-use devices running on electricity such as computers, which is typical of modern societies, the CO(2) emissions are bound to increase unless coal is replaced by less carbon emitting sources such as natural gas, renewables and nuclear energy. (C) 2011 Elsevier Ltd. All rights reserved.

Use of Photovoltaic on an E-bike? : A Feasibility Study

In recent years the number of bicycles with e-motors has been increased steadily. Within the pedelec – bikes where an e-motor supports the pedaling – a special group of transportation bikes has developed. These bikes have storage boxes in addition to the basic parts of a bike. Due to the space available on top of those boxes it is possible to install a PV system to generate electricity which could be used to recharge the battery of the pedelec. Such a system would lead to grid independent charging of the battery and to the possibility of an increased range of motor support. The feasibility of such a PV system is investigated for a three wheeled pedelec delivered by the company BABBOE NORDIC.The measured data of the electricity generation of this mobile system is compared to the possible electricity generation of a stationary system.To measure the consumption of the pedelec different tracks are covered, and the energy which is necessary to recharge the bike battery is measured using an energy logger. This recharge energy is used as an indirect measure of the electricity consumption. A PV prototype system is installed on the bike. It is a simple PV stand alone system consisting of PV panel, charge controller with MPP tracker and a solar battery. This system has the task to generate as much electricity as possible. The produced PV current and voltage aremeasured and documented using a data logger. Afterwards the average PV power is calculated. To compare the produced electricity of the on-bike system to that of a stationary system, the irradiance on the latter is measured simultaneously. Due to partial shadings on the on-bike PV panel, which are caused by the driver and some other bike parts, the average power output during riding the bike is very low. It is too low to support the motor directly. In case of a similar installation as the PV prototype system and the intention always to park the bike on a sunny spot an on-bike system could generate electricity to at least partly recharge a bike battery during one day. The stationary PV system using the same PV panel could have produced between 1.25 and 8.1 times as much as the on-bike PV system. Even though the investigation is done for a very specific case it can be concluded that anon-bike PV system, using similar components as in the investigation, is not feasible to recharge the battery of a pedelec in an appropriate manner. The biggest barrier is that partial shadings on the PV panel, which can be hardly avoided during operation and parking, result in a significant reduction of generated electricity. Also the installation of the on-bike PV system would lead to increased weight of the whole bike and the need for space which is reducing the storage capacity. To use solar energy for recharging a bike battery an indirect way is giving better results. In this case a stationary PV stand alone system is used which is located in a sunny spot without shadings and adjusted to use the maximum available solar energy. The battery of the bike is charged using the corresponding charger and an inverter which provides AC power using the captured solar energy.

Solcellsdrivet FTX-system för miljonprogramshus : Tjärna Ängar, Borlänge

Projektet omfattade undersökning och framtagande av ett solcellssystem med förmåga att försörja ett FTX-system i ett flerbostadshus från miljonprogrammet med el. För att kunna bedöma storlek och utformning av komponenter har information tagits genom: Informationssökning via databaser, kurslitteratur och intervjuer Simuleringar av solceller i datorprogrammet PVSYST Modulering av ventilationskanaler i datorprogrammet MagiCAD Syftet var främst att undersöka om det gick att få fram ett teoretiskt fungerande system med avseende på både solceller och ventilation. Beroende på vad resultatet blev skulle även ekonomin i projektet undersökas. Undersökningen visade att det teoretiskt ska gå att installera solceller för elframställning som klarar av att täcka FTX-systemets elbehov på årsbasis. Solcellerna bedöms även producera tillräckligt med el för viss övrig elkrävande utrustning under stora delar av året. Det visade sig även att det skulle gå att få solcellerna ekonomiskt lönsamma om en kalkyltid på 14 år används. Metoden som använts för dessa resultat är noga beskriven och är med små förändringar tillämpbar för ett stort antal byggnader i det svenska byggnadsbeståndet. En viktig slutsats är att om fastighetsägarna kan se 15 år fram i tiden för en investering i solenergi, skulle det innebära inte bara miljömässiga utan även ekonomiska vinster. Det finns redan idag kunnande, teknik och produkter för att utvinna en stor del av fastigheternas elbehov genom solens energi.

Valorização dos gases da carbonização da madeira via rota de combustão

A produção de carvão vegetal a partir de florestas plantadas mudou de forma determinante a logística desta atividade dotando-a de escala e fixando a estrutura de produção composta por fornos e periféricos. A lógica de se ter os fornos construídos ao lado das frentes de exploração florestal, e se deslocando junto com ela à medida em que a colheita é realizada foi abandonada. A partir de então, tem-se buscado uma forma de aproveitar a disponibilidade energética contida nos gases da carbonização, que segue sem uso, tendo quando muito um aproveitamento incipiente e marginal. Esta dissertação apresenta uma proposta de lay out para a Unidade de Produção de Carvão (UPC) de fornos retangulares tradicionais em alvenaria projetados e posicionados de forma a possibilitar seu acoplamento a um sistema de coleta e queima dos gases da carbonização. Após exaustiva pesquisa bibliográfica e visitas técnicas para conhecimento de diferentes tecnologias de carbonização, elaborou-se o projeto, com objetivo de eliminar as limitações identificadas nas tecnologias tradicionais em uso atualmente pelas empresas com produção em escala industrial, reduzindo as perdas e dificuldades operacionais para aproveitamento dos gases. É caracterizado pela saída dos gases somente por uma chaminé instalada no fundo do forno, possui entradas de ar do processo em minicâmaras, que atuam evitando excesso de ar, queima excessiva de madeira e consequente geração excessiva de CO2 e metano – dois gases causadores de efeito estufa. Preconiza-se a queima dos gases da carbonização para uso posterior em geração de energia elétrica e/ou secagem da madeira antes da carbonização. Os resultados dos indicadores técnicos (ciclos dos fornos e produtividade, etc.) e de produção obtidos até o momento na planta em operação vêm confirmando a operacionalidade do conjunto de fornos na nova disposição concebida. Não houve perda de produtividade dos fornos causada pela nova disposição, e as modificações no projeto do forno não impactaram negativamente em seu desempenho operacional. A capacidade produtiva da Unidade vem se confirmando até o momento. Tivemos frustradas nossas expectativas de já apresentar nesta dissertação os resultados operacionais dos fornos juntamente com os do sistema de queima dos gases dado que houve considerável atraso na construção do mesmo impedindo-nos de tê-los antes da data limite de entrega da dissertação. Apresentamos os conceitos que nos levaram à tomada de decisão para o novo lay out e propomos a continuidade dos estudos comprobatórios da viabilidade econômica operacional do sistema, tão logo ele entre em operação.

Comparação entre modelos equivalentes de aerogeradores síncronos utilizando o programa ATP

At present, the electricity generation through wind energy has an importance growing in the world, with the existence of very large plans for future wind power installation worldwide. Thus, the increasing the electricity generation through wind power requires, more and more, analysis of studies of interaction between wind parks and electric power systems. This paper has as purposes to implement equivalent models for synchronous wind generators to represent a wind park in ATP program and to check behavior of the models through simulations. Simulations with applications of faults were achieved to evaluate the behavior of voltages of system for each equivalent model, through comparisons between the results of models proposed, to verify if the differences obtained allows the adoption of the simplest model

Desenvolvimento de um rastreador solar do tipo polar com ajuste do ângulo de inclinação

The use of solar energy for electricity generation has shown a growing interest in recent years. Generally, the conversion of solar energy into electricity is made by PV modules installed on fixed structures, with slope determined by the latitude of the installation site. In this sense, the use of mobile structures with solar tracking, has enabled increased production of the generated energy. However, the performance of these structures depends on the type of tracker and the position control used. In this work, it is proposed position control a strategy applied for a solar tracker, which will be installed in Laboratory of Power Electronics and Renewable Energy (LEPER), located in the Federal University of Rio Grande do Norte (UFRN). The tracker system is of polar type with daily positioning east-west and tilt angle manual adjustment in the seasonal periods, from north to south