Orientador: Gilberto De Martino Jannuzzi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T21:42:51Z (GMT). No. of bitstreams: 1 Nogueira_LarissaGoncalves_M.pdf: 2506781 bytes, checksum: 2b63fc90bfa86344fd1d43917510b57c (MD5) Previous issue date: 2011 / Resumo: Apesar da geração de energia elétrica no mundo ainda ser majoritariamente oriunda de combustíveis fósseis e não renováveis, várias políticas de incentivo ao uso de fontes renováveis alternativas de energia têm sido desenvolvidas. Dentre estas fontes, a geração de energia elétrica a partir de sistemas fotovoltaicos conectados à rede se destaca devido à elevada taxa de crescimento dos últimos anos; pelas expressivas reduções de preço e por ser uma das tecnologias chave para a geração descentralizada de energia elétrica em áreas remotas. Alguns dos benefícios da geração distribuída a partir de sistemas fotovoltaicos conectados à rede são: postergação de investimentos em expansão nos sistemas de distribuição e de transmissão; baixo impacto ambiental e tempo reduzido de implantação; redução no carregamento das redes e de perdas; e diversificação da matriz energética. No entanto, observa-se que a fonte tem sido mais bem aproveitada em países com baixos índices de irradiação solar. Chile e Brasil, por exemplo, possuem excelente potencial solar e oportunidades semelhantes de investimento na tecnologia, mas restringiram a utilização da fonte basicamente a sistemas isolados. Neste contexto, algumas iniciativas no Brasil e Chile têm visado o desenvolvimento da energia solar fotovoltaica. Esta dissertação tratou de analisar comparativamente as principais barreiras enfrentadas pela geração distribuída a partir de sistemas fotovoltaicos conectados à rede e, em seguida, sugeriu, através de cenários, quais mecanismos de incentivo seriam mais adequados para a promoção desta tecnologia / Abstract: Despite the generation of electricity in the world is still mainly coming from non-renewable fossil fuels, various policies to encourage the use of alternative renewable energy sources have been developed. Among these sources, electricity generation from photovoltaic systems connected to the grid has shown high rate of growth in recent years, due to the significant price reductions and also for being one of the preferred technologies for decentralized electricity generation in remote areas. Some of the benefits of distributed generation from photovoltaic systems connected to the grid are: postponement of investments needed for expanding distribution and transmission systems, low environmental impact and reduced time to deployment, reduction in network load and losses, improvement of voltage levels during heavy load and electric matrix diversification. Nevertheless, it is observed that the source has been utilized better in countries with low levels of solar radiation. Chile and Brazil, for example, have excellent solar potential and similar opportunities to investment in the technology, but the source use has been basically restricted to isolated systems. However, many initiatives in Brazil and Chile have targeted the development of solar photovoltaic systems in these countries. This thesis has the objective to analyze the major barriers faced by distributed generation from photovoltaic systems connected to the grid and then suggest, through scenarios, which mechanisms would be more appropriate for the promotion of this technology / Mestrado / Planejamento de Sistemas Energeticos / Mestre em Planejamento de Sistemas Energéticos

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EU har, genom antagandet av paketet för ren energi 2019, erkänt värdet och potentialen hos lokala energisamhällen inom Europeiska unionen. Det har observerats vara ett lönsamt verktyg för de europeiska medborgarna att direkt kunna delta i energiomställningen. Betydelsen av medborgarnas deltagande i kampen mot klimatförändringar har fastställts som avgörande och som en andra pelare bredvid uppifrån-och-ner-strategin genom Parisavtalet 2015. Denna uppsats fastställer definitionen och funktionen av lokala energigemenskapersom en del av den europeiska klimatstrategin. Svenska energimarknadsinspektionen har nyligen släppt en rapport och ett förslag om genomförandet av lokala energigemenskaper i Sverige. Jag tycker att förslaget är otillräckligt och otillfredsställande mot bakgrund av målet och syftet bakom EU-direktiven. Värdet av detta verktyg har inte erkänts i förslaget. Genom att granska deras förslag har jag hittat ett par viktiga aspekter som bör beaktas, särskilt för gemenskaper för förnybar energi, när de implementeras i Sverige. Bland annat bör Sverige göra en vidare utredning kring de ekonomiska incitamenten, möjligheten att förvalta och äga eget nät samt lokala energigemenskaper i relation till de nationella klimatmålen och Sveriges behov. Avslutningsvis kunde konstateras att det finns en hel del att reflektera över innan implementeringen kan färdigställas i Sverige. Anförda aspekter i denna uppsats är långt ifrån uttömmande och avser enbart de aspekter jag funnit särskilt viktiga. För att lokala energigemenskaper ska nå framgång, särskilt gemenskaper för förnybar energi, förutsätter det att Sverige är beredd på att ändra sin nuvarande strategi, men också inse att det finns ett behov av förändring. / EU have, through the adoption of the Clean energy package 2019, recognized the value and potential of local energy communities within the European union. They have been observed to be a profitable tool for the European citizens to be able to directly participate in the energy transition. The importance of the citizens participation in the fight against climate changes have been established as crucial and a second pillar beside the top-down approach through the Paris Agreement. This essay aims to determine the definition and function of local energy communities as a part of the European climate strategy. The Swedish Energy Markets Inspectorate has recently released a report and proposal on the implementation of local energy communities in Sweden. I have found the proposal inadequate and unsatisfactory in the light of the goal and purpose behind the EU directives. The value of this tool has not been recognised in the proposal. By reviewing their proposal, I have found a couple of key aspects that should be heeded, especially concerning Renewable energy communities, when implemented in Sweden. For example, it is deemed necessary that Sweden needs to further investigate the economic incentivesfor these communities. Further investigation is also needed regarding the possibility for Renewable energy communities to own and govern their own grid. Local energy communities as a tool to achieve the national climate goals and to solve other energy-related issues in Sweden should be explored. Finally, we can ascertain that there are several aspects to reflect further upon before the finalization of the implementation of local energy communities. Aspects touched upon in this essay is far from exhaustive and reflect those that I have deemed to be of utmost importance. To unlock the potential of local energy communities and ensure their success, especially concerning renewable energy communities, Sweden must be prepared to change their current strategy as well as realize the need for said change.

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.

Renewable energy use is a growing topic worldwide due to climate change mitigation. Countries worldwide are trying to increase renewable energy use because it has many benefits, such as decreased air pollution, improved health conditions, and improved Human Development Index. The objective of the study is to compare the country-specific trajectories of renewable energy as a percentage of total energy production and electricity production from renewable sources, evaluate the link between renewable energy use and outdoor air pollution worldwide, and also understand whether the use of renewable energy is linked to population health and the human development index. The data was collected from the University of Oxford’s Our World in Data. The source has global temporal data on the use of renewable energy, energy access, indoor and ambient pollution, human development index, and several health indicators. The study was done by statistical analysis. My trend analyses suggest that renewable energy production as the percentage of total energy production increased for most countries in Eastern Europe, Western Europe, Northern Europe, and North America (except for Mexico). The same scenario was also observed for the share of renewable energy for electricity production. Many countries in other regions of the world, including many low-income countries, didn’t have the same trend. For many counties and regions globally, renewable energy reduces PM2.5 concentrations in the ambient air. Also found in many countries, renewable energy use is associated with increased life expectancy, decreased cancer deaths, reduced deaths due to ambient PM2.5 concentration, and a high human development index.

Renewable power systems are becoming more affordable and provide better options than fossil-fuel generation, for not only the environment, but a benefit of a reduced cost of operation. Methods to optimize charging batteries from renewable technologies is an important subject for off-grid and micro-grids, and is becoming more relevant for larger installations. Overcharging or undercharging the battery can result in failure and reduction of battery life. The Arduino hybrid MPPT controller takes the advantage of solar and wind energy sources by controlling two systems simultaneously. The ability to manage two systems with one controller is better for an overall production of energy, cost, and manageability, at a minor expense of efficiency. The hybrid MPPT uses two synchronous buck DC-DC converters to control both wind and solar. The hybrid MPPT performed at a maximum of 93.6% efficiency, while the individual controller operated at a maximum 97.1% efficiency when working on the bench test. When designing the controller to manage power production from a larger generator, the inductor size was too large due to the frequency provided by the Arduino. A larger inductor means less allowable current to flow before the inductor becomes over saturated, reducing the efficiency of the controller. Utilizing a different microcontroller like the PIC16C63A produces a much faster frequency, which will reduce the inductor size needed and allow more current before over saturation.

Previous studies have shown that provision of sustainable electricity supply to rural households is essential to bring development to off-grid populations. For this reason, most developing countries put large efforts into rural electrification programs to stimulate development and reduce poverty. However, to be sustainable these programs need to recover costs, which poses a challenge to remote low income populations.  This often forces governments and other institutions involved in rural electrification to subsidize the electricity production. It also affects the choice of technology and places a barrier on the level of energy provided in line with the ability to pay for services. As a result of this, most programs have failed to achieve the desired objectives, as the technologies used often do not support income generating activities that could increase the payment capabilities of the beneficiaries and contribute to development. This thesis is focused on the rural electrification program of South Africa, the country in sub-Saharan Africa that has the highest access to electricity. It investigates the success elements that influence the sustainability of rural electrification programs and their contributions to socio-economic development. This was achieved by evaluating the South African program that provides solar home systems to off-grid communities, and a hybrid solar-wind mini-grid project in South Africa. The study also draw lessons from other rural electrification programs in neighbouring countries, i.e. an evaluation of a hybrid solar-diesel mini-grid system in Namibia, and a review of two systems, a hybrid solar-biomass mini-grid project in Botswana and a hydro mini-grid program in Lesotho. The study revealed that hydro based hybrid mini-grid systems provide the most cost effective way of bringing energy services to rural settlements. Regardless of technology, successful programs depend on adequate support from the government, implementation of a progressive tariff system that allows the high consuming high income earners and businesses, to cross subsidize the low consuming , low income users. It shows that it is more likely for rural electrification programs to survive if the design considers the existing businesses, population growth and the corresponding load increase. The thesis further shows that provision of sufficient energy to induce income generating activities is essential to decrease the need for subsidies and to ensure the sustainability of programs. In addition, availability of spare parts and a capable management team is essential for the successful operations and maintenance of these systems.

The synthesis and characterization of novel complexes of silver supported by sterically demanding, highly electrophilic N-heterocyclic carbene (NHC) ancillary ligands, is described. Stable hydride, fluoride, alkoxide, alkyl, aryl, and alkynyl complexes are characterized by NMR spectroscopy and X-ray diffraction crystallography, and their reactivity is investigated. The interaction of silver centers in dinuclear complexes is probed by 109Ag NMR spectroscopy. Relevance to renewable fuel technology is demonstrated through the mediation of fundamental chemical transformations, including the heterolysis of hydrogen, the transfer of hydride to carbon dioxide, and the formation of carbon-carbon bonds. Kinetic studies shed light on the mechanism of hydrogen activation by hard-soft mismatched complexes of silver, and a formal catalytic cycle for the hydrogenation of carbon dioxide to formate derivatives is reported.

Nowadays, electricity markets are becoming more deregulated, especially development of smart grid and introduction of renewable energy promote regulations of energy markets. On the other hand, the uncertainties of new energy sources and market participants’ bidding bring more challenges to power system operation and transmission system planning. These problems motivate us to study spot price (also called locational marginal pricing) of electricity markets, the strategic bidding of wind power producer as an independent power producer into power market, transmission expansion planning considering wind power investment, and analysis of the maximum loadability of a power grid. The work on probabilistic spot pricing for a utility grid includes renewable wind power generation in a deregulated environment, taking into account both the uncertainty of load forecasting and the randomness of wind speed. Based on the forecasted normal-distributed load and Weibull-distributed wind speed, probabilistic optimal power flow is formulated by including spinning reserve cost associated with wind power plants and emission cost in addition to conventional thermal power plant cost model. Simulations show that the integration of wind power can effectively decrease spot price, also increase the risk of overvoltage. Based on the concept of loacational marginal pricing which is determined by a marketclearing algorithm, further research is conducted on optimal offering strategies for wind power producers participating in a day-ahead market employing a stochastic market-clearing algoivrithm. The proposed procedure to drive strategic offers relies on a stochastic bilevel model: the upper level problem represents the profit maximization of the strategic wind power producer, while the lower level one represents the marketing clearing and the corresponding price formulation aiming to co-optimize both energy and reserve. Thirdly, to improve wind power integration, we propose a bilevel problem incorporating two-stage stochastic programming for transmission expansion planning to accommodate large-scale wind power investments in electricity markets. The model integrates cooptimizations of energy and reserve to deal with uncertainties of wind power production. In the upper level problem, the objective of independent system operator (ISO) modelling transmission investments under uncertain environments is to minimize the transmission and wind power investment cost, and the expected load shedding cost. The lower level problem is composed of a two stage stochastic programming problem for energy schedule and reserve dispatch simultaneously. Case studies are carried out for illustrating the effectiveness of the proposed model. The above market-clearing or power system operation is based on direct current optimal power flow (DC-OPF) model which is a linear problem without reactive power constraints. Power system maximum loadability is a crucial index to determine voltage stability. The fourth work in this thesis proposes a Lagrange semi-definite programming (SDP) method to solve the non-linear and non-convex optimization alternating current (AC) problem of the maximum loadability of security constrained power system. Simulation results from the IEEE three-bus system and IEEE 24-bus Reliability Test System (RTS) show that the proposed method is able to obtain the global optimal solution for the maximum loadability problem. Lastly, we summarize the conclusions from studies on the above mentioned optimization problems of electric power market under modern grid, as well as the influence of wind power integration on power system reliability, and transmission expansion planning, as well as the operations of electricity markets. Meanwhile, we also present some open questions on the related research, such as non-convex constraints in the lower-level problem of a bilevel problem, and integrating N-1 security criterion of transmission planning. / Graduate / lei.ming296@gmail.com

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2011. / Due to greenhouse gas emissions from fossil fuel usage, the impending threat of global climate change has increased. The need for an alternative energy feedstock that is not in direct competition to food production has drawn the focus to microalgae. Research suggests that future advances in microalgal mass culture will require closed systems as most microalgal species of interest thrive in highly selective environments. A high lipid producing microalga, identified as Chlorella vulgaris was isolated from a freshwater pond. To appraise the biofuel potential of the isolated strain, the growth kinetics, pyroletic characteristics and photosynthetic efficiency of the Chlorella sp was evaluated in vitro. The optimised preliminary conditions for higher biomass yield of the selected strain were at 4% CO2, 0.5 g l-1 NaNO3 and 0.04 g l-1 PO4, respectively. Pulse amplitude modulation results indicated that C. vulgaris could withstand a light intensity ranging from 150-350 μmol photons m-2s-1. The pyrolitic studies under inert atmosphere at different heating rates of 15, 30, 40 and 50 ºC min-1 from ambient temperature to 800 oC showed that the overall final weight loss recorded for the four different heating rates was in the range of 78.9 to 81%. A tubular photobioreactor was then designed and utilised for biomass and lipid optimisation. The suspension of microalgae was circulated by a pump and propelled to give a sufficiently turbulent flow periodically through the illuminated part and the dark part of the photobioreactor. Microalgal density was determined daily using a Spectrophotometer. Spectrophotometric determinations of biomass were periodically verified by dry cell weight measurements. Results suggest that the optimal NaNO3 concentration for cell growth in the reactor was around 7.5 g l-1, yielding maximum biomass of 2.09 g l-1 on day 16. This was a significant 2.2 fold increase in biomass (p < 0.005) when compared to results achieved at the lowest NaNO3 cycle (of 3.8 g l-1), which yielded a biomass value of 0.95 g l-1 at an OD of 1.178. Lipid accumulation experiments revealed that the microalga did not accumulate significant amounts of lipids when NaNO3 concentrations in the reactor were beyond 1.5 g l-1 (p > 0.005). The largest lipid fraction occurred when the NaNO3 concentration in the medium was 0.5 g l-1. Results suggest that the optimal trade-off between maximising biomass and lipid content occurs at 0.9 g l-1 NaNO3 among the tested conditions within the photobioreactor. Gas chromatograms showed that even though a greater number of known lipids were produced in Run 8, the total lipid percentage was much lower when compared to Runs 9-13. For maximal biomass and lipid from C. vulgaris, it is therefore crucial to optimise nutritional parameters such as NaNO3. However, suitable growth conditions for C. vulgaris in a tubular photobioreactor calls for innovative technological breakthroughs and therefore work is ongoing globally to address this.