The research described in this dissertation was motivated by the global demand for energy that is not dependent on coal, oil, natural gas and other non-renewable fossil fuels. The technology used in this project is related to the use of biomass to produce a viable alternative to conventional sources of fuel. A bench scale biomass to liquid (BTL) facility was built and tested. This produced results confirming the feasibility of the BTL process. The findings of the pilot study outlined in this dissertation justified the conclusion that the next step will be to expand the capacity and productivity of the BTL pilot plant to an industrial scale. Biomass comes from a variety of renewable sources that are readily available. In this case, the material used in the fixed bed biomass gasification facility to generate wood gas was agricultural and forestry waste, such as straw and wood chips. The gasifier had the capacity to produce up to 10 cubic metres/hr of gas with a carbon monoxide and hydrogen content of between 20–40% by volume, when it was operated at ambient pressure and with air as the oxidizer. The gas, produced at a temperature above 700º C, was cooled in a quench/water scrubber in order to remove most of the mechanical impurities (tars and water-soluble inorganic particles), condensed and dried with corn cobs before being compressed in cylinders at over 100 bar (g) for use in the Fischer-Tropsch Synthesis (FTS). The syngas was subjected further to a series of refining processes which included removal of sulphur and oxygen. The sulphur removal technology chosen entailed applying modified activated carbon to adsorb H2S with the help of hydrolysis in order to convert organic sulphur impurities into H2S which reduced the sulphur content of the gas to less than 5 ppbv. Supported cobalt catalyst (100 grams), were loaded into a single-tube fixed bed FT reactor with an inner diameter of 50 mm. The reactor was fitted with a heating jacket through which, heated oil ran to cool the reactor during a normal reaction occurring at < 250 ºC, while nitrogen was used in the heating jacket during reduction, which occurred at temperatures up ~ 350 ºC. The FTS reaction was carried out at different pressures and temperatures. Liquid and wax products were produced from the facility. The properties of the liquid and solid hydrocarbons produced were found to be the same as FT products from other feed stocks, such as natural gas and coal.

Given increasing problems in the availability, affordability and deliverability of commercial primary and secondary energy resources, coupled with growing macroeconomic uncertainties, the use of renewable, non-commercial energy resources has been actively promoted in rural areas of developing countries. This, in addition to the fact that conventional, 'state-of-the-art' energy facilities present technical problems, are inequitable and pose potential environmental hazards, has led to proposals for instituting alternative, intermediate or 'appropriate' technologies in rural settlements. This thesis identifies technical, economic, social, cultural and institutional barriers to the introduction of intermediate or 'appropriate' technologies in rural areas. The cases of solar and biogas technologies in Korea, Malaysia, Papua New Guinea the Philippines and Thailand are considered. Policy and planning process recommendations are made on the roles of government, voluntary aid-agencies and the rural user, to overcome the obstacles to implementing these technologies. These recommendations cover the micro (village) and macro (regional and national) levels over two time horizons, and stress the need for a comprehensive approach to discerning rural needs, followed by integrated technology diffusion through effective program and project implementation. In addition, this thesis identifies the need for a continuous collection of information on rural socio-economic conditions and potential for rural interfuel substitution and finally, recommends research into improving technical efficiencies of alternative energy technologies such as solar and biogas. Alternative or intermediate energy technologies such as solar and biogas can play an important role in augmenting rural energy supply. Unless steps are taken to remove the identified barriers to implementation in future technology diffusion efforts, this potential will not be realized. Policy and planning process recommendations made in this thesis present means through which these barriers could be removed. / Applied Science, Faculty of / Community and Regional Planning (SCARP), School of / Graduate

M.Phil. ( Energy Studies) / In contrast to conventional energy sources, the advantage of renewable energy lies in the fact that it is virtually inexhaustible and that its utilisation is accompanied by minima environmental pollution. I t is, furthermore, very appropriate especially seen in the light of the large Third World component of the South African energy economy. It therefore becomes necessary to evaluate the adequacy of Government strategy as far as the optimal development and utilisation of the renewable energy sources with the best potential in South Africa are concerned, against present and future needs for and the utilisation possibilities of these sources...

Sustainable energy has taken center stage in materials research and global markets, which has encouraged an explosion in related materials development. Practical implementations of sustainable energy solutions rely upon high-performance and cost-effective materials for energy harvesting and storage. Organic electronics, a class of materials composed principally of carbon, are regarded as promising candidates in this respect. Carbon, when arranged with atomic precision and warped carefully into desirable conformations, can generate exceptionally inexpensive and high-performance materials. These materials can then be readily integrated into solar cells, capacitors, and transistors. This dissertation explores our progress in the field of high-performance organic electronics in the context of these practical devices, and aims to establish simple design principles for the future development of contorted organic electronics. Of principal importance to this thesis is the conclusion that localized molecular contortion seems to bestow unique and somewhat unexpected properties upon extended systems. Therefore, a key theme underlying our work herein is the idea that for specific applications, contorted or extended graphene nanoribbons can be shown to be superior to planar organics. This advantage has allowed us to report exceptionally high performance metrics in the fields of energy harvesting and storage. Chapter 1 comprises an overview of the entire body of work contained within this dissertation, in a highly condensed format. This includes in-depth specific background on the innovations of prior researchers who have enabled our present work. Chapter 2 details the elongation of the small graphene fragment perylene into long, electronically active, and ambient-stable nanoribbons. This chapter is assembled from three research manuscripts investigating the employment of these nanoribbons as electron transporting materials in photovoltaics and one set of preliminary results on their incorporation as potential surface arrays for chip technologies. Chapter 3 examines the expansion of our perylene-based nanoribbons into large single-molecule three-dimensional nanostructures up to 5 nm in wingspan. These structures, by consequence of their three-dimensional geometry and contorted nature, exhibit curious enhancements over their one-dimensional counterparts. Such enhancements, namely in photovoltaic efficiency and electron transport behavior, are investigated over the course of two research manuscripts. Chapter 4 explores the idea of organic energy storage through the lens of pseudocapacitance, and further expands the perylene toolbox by developing high-capacitance and highly stable polymer structures. These ideas ultimately culminate in the final subchapter, wherein our most recent work on contorted, semi-two-dimensional capacitive polymers is disclosed. The exceptionally strong and potentially economically viable results of our most recent energy storage architecture are enabled entirely by our understanding of molecular contortion. Namely, contortion’s unique ability to manifest long-range electronic conjugation concomitant with the prevention of aggregation, thus improving surface area for ion diffusion and bulk processability. In consideration of the impact these nanoscale ideas could have on the global scale, it is our belief that ideas concerning contortion within the context of organic electronics will continue to generate high-performance energy storing and harvesting materials. Our explorations towards such solutions have garnered substantial interest in the materials community thus far, and this dissertation seeks to add to that growing body of literature by inspiring numerous new twisted architectures.

Multimodular designs of electron donor-acceptor systems are the ultimate strategy in fabricating antenna-reaction center mimics for artificial photosynthetic applications. The studied photosystems clearly demonstrated efficient energy transfer from the antenna system to the primary electron donor, and charge stabilization of the radical ion pair achieved with the utilization of secondary electron donors that permits either electron migration or hole transfer. Moreover, the molecular arrangement of the photoactive components also influences the route of energy and electron transfer as observed from the aluminum(III) porphyrin-based photosystems. Furthermore, modulation of the photophysical and electronic properties of these photoactive units were illustrated from the thio-aryl substitution of subphthalocyanines yielding red-shifted Q bands of the said chromophore; hence, regulating the rate of charge separation and recombination in the subphthalocyanine-fullerene conjugates. These multicomponent photosystems has the potential to absorb the entire UV-visible-NIR spectrum of the light energy allowing maximum light-harvesting capability. Furthermore, it permits charge stabilization of the radical ion pair enabling the utilization of the transferred electron/s to be used by water oxidizing and proton reducing catalysts in full-scale artificial photosynthetic apparatuses.

Yes / The penetration of renewable energies in the energy market has increased significantly over the last two decades due to environmental concerns and clean energy requirements. The principal advantage of renewable energy resources (RESs) over non-RESs is that it has no direct carbonisation impact on the environment and that it has none of the global warming effects which are caused by carbon emissions. Furthermore, the liberalisation of the energy market has led to the realisation of the virtual power plant (VPP) concept. A VPP is a unified platform for distributed energy resources that integrates the capacities of various renewable energies together for the purpose of improving power generation and management as well as catering for the buying and selling of energy in wholesale energy markets. This review study presents a comprehensive review of existing approaches to planning, operation and scheduling of the VPP system. The methodologies that were adopted, their advantages and disadvantages are assessed in detail in order to benefit new entrants in the power system and provide them with comprehensive knowledge, techniques and understanding of the VPP concept.

The objective of this PhD thesis is to create a Unit Commitment and Economic Dispatch (UCED) modelling tool that can used to simulate the deterministic performance of a power system with thermal and renewable generators and energy storage technologies. The model was formulated using mixed integer programing (MIP) on GAMS interface. A robust commercial solver by IBM (CPLEX) is used as solver. Emphasis on the development of the tool has been given on the following aspects. a) Technical impacts of Variable Renewable Energy (VRE) integration. The UCED model developed in this thesis is a high resolution short-term dispatch model. It captures the variability of VRE power on the intra-hour level. In addition the model considers a large number of important real world, system, unit and policy constraints. Detailed representation of a power system allows for a realistic estimation of maximum penetration levels of VRE and the related technical impacts like cycling of generators (part-loading and number of start-ups). b) CO2 emissions. High levels of VRE penetration can potentially increase consumption of fuel in thermal units per unit of electricity produced due to increased thermal cycling. The dispatch of units in the UCED model is based on minimizing system wide operational costs the most important of those being fuel, start-up costs and the cost of carbon. Fuel consumption is calculated using technical data from Input/Output curves of individual generators. The start-up cost is calculated based on times the generator units have been off and the energy requirement to bring the unit back to hot state. Thus dynamic changes on fuel consumption can be captured and reported. c) Technical solutions to facilitate VRE integration. VRE penetration can be facilitated if appropriate solutions are implemented. Energy storage is an effective way to reduce the impact of RE variability. The UCED model includes an integrated Mixed Integer Linear (MILP) compressed air energy storage (CAES) simulation sub-model. Unlike existing CAES models, the new “Thermo-Economic” (TE) CAES model developed in this thesis uses technical data from major CAES manufacturers to model the dynamic effect of cavern pressure on both the compression and expansion sides during CAES operation. More specifically the TE model takes into account that a) a compressor discharges at a pressure equal to the back-pressure developed in the cavern at each moment, b) the speed of charging can be regulated through inlet guide vanes; higher charging speed can take place at the expense of additional power consumption, c) the maximum power output during expansion can be limited by the levels of cavern pressure; there is a threshold pressure level below which the maximum output decreases linearly with pressure. Since it uses actual power curves to simulate CAES operation, the TE model can be assumed to be more accurate than conventional Fixed Parameter (FP) models that don’t model dynamic effects of cavern pressure on CAES operation. The TE model in this thesis is compared with conventional FP models using historical market prices from the Irish electricity market. The comparison was based on the ability of a CAES unit to arbitrage energy for making profit in the Irish electricity market. More specifically a “Base” scenario was created that included the operation of a 270MW CAES unit with technical characteristics obtained from a major CAES manufacturer and assumed discharge time of 13hr. Various sensitivities on discharge time, natural gas prices and system marginal prices (SMPs) were modeled. An additional scenario was created to show the benefit on CAES profitability if the unit participated in both the energy and ancillary services markets. All scenarios were modeled using both the TE and FP CAES models. The results showed that the most realistic TE model returns around 15% less profitability across more scenarios. The reduction in profitability grows to around 30% when the cavern volume (discharge time) is reduced to half (6 hours). The latter is related to the sensitivity of the TE model on cavern pressure that is being built faster when the volume is reduced. A CAES unit won’t get a positive net present value (NPV) in Ireland under any scenario unless SMPs are greatly increased. Thus, it was shown that that existing FP CAES models overestimate CAES profitability. More accurate models need to be used to estimate CAES profitability in deregulated markets. Additionally, it might deem necessary to create additional markets for energy storage units and increase the possible revenue sources and magnitude to facilitate an increase of storage capacity worldwide. The second step of analysis involved the integration of the CAES and UCED models. The UCED model developed in this thesis was validated and applied using data from the Irish grid, a power system with more than 50 thermal generators. A vast of existent data was used to create a mathematical model of the Irish system. Such data include technical specifications and variables of thermal generators, maintenance schedules and historical solar, wind and demand data. The validation exercise was deemed successful since the UCED model simulated utilization factors of 45 out of 52 generators with an absolute difference between modeled and actual results on utilization factors of less than 6% (the absolute differences are called Delta in this thesis). In addition the results of validation exercise were compared with the results of a similar exercise where PLEXOS was the modelling tool and it was found that the results of the two models were similar for the vast majority of generators. More specifically, the PLEXOS model results showed higher deltas for the coal-fired generators compared to the UCED model. On the other hand the UCED model, reported higher delta values for peat-fired generators. The results of the PLEXOS model were slightly better for the gas-fired generators while both models reported deltas nearly zero for all oil and distillate-fired generators. Finally the model was applied to study the benefits of energy storage in Ireland in 2020 when wind penetration is expected to reach 37% of total demand. The analysis involved the development of two groups of 3 scenarios each. In the first group the main scenario also called the “Reference” was used to simulate the short-term unit (30 min step) commitment within the Irish system without storage. The results of the reference scenario were compared with two additional scenarios that assumed the existence of one 270MW CAES unit in Northern Ireland by 2020 (again the first scenario involved the TE and the second the FP CAES model). The results showed –when using the TE model- that the inclusion of one 270MW CAES unit in AI can help reduce wind curtailment by 88GWh, CO2 emissions by 150,000 tonnes and system costs by € 6 million per year. If an FP model had been used instead the reductions would be: wind curtailment by 108GWh, CO2 emissions by 270,000 tonnes and annual system costs by €13 million. Two main conclusions can be obtained from the specific set of results. The first conclusion is that storage units have a financial benefit over the whole system. Thus, when a CAES unit operates to minimize the costs of the whole system can incur substantially more benefits compared to if the CAES unit operated to maximize the individual unit’s profits as in the case presented earlier. The benefits of storage over the whole system should be accounted to make policy decisions and create incentives for investors to increase energy storage capacity in national grids. The second important conclusion is that existing CAES FP models overestimate the ability of a CAES unit to facilitate VRE penetration. More accurate TE models should be used to assess a unit’s capability to increase system flexibility. A second group of scenarios was created to simulate the benefit of CAES at even higher VRE penetration levels. In the second group the “Reference” scenario again, assumed no storage however, wind production was increased by 25%. Again the “Reference” was compared with two additional scenarios that assumed integration of 3x270MW=810MW of storage capacity in AI (one scenario used the TE model and the other the FP). The results for the TE model show that each of the 3 CAES units reduces wind curtailment by 188,000MWh, total system costs by €29 million and CO2 emissions by 180,000 tonnes. The same reductions for the FP model are 217,000MWh of wind curtailment, €25.6 million on total system costs and 180,000 tonnes of CO2. Thus, the results of the second group of scenarios show that as the installed capacity of both CAES and wind increases in Ireland a) the system-wide benefits of CAES increase and b) the differences on results between the TE and FP models become much smaller.

Thesis (MPA.) --University of Limpopo, 2016 / Refer to the document

Thesis (Ph.D.)--University of Melbourne, Melbourne School of Land and Environment, 2009. / Typescript. Includes bibliographical references (p. 361-386)

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