No description available.

Before tidal stream energy is exploited, tidal power resource and environmental assessments must be undertaken. This thesis explores limits to power extraction for tidal sites defined by a strait between an island and landmass. Numerical simulations provided by Fluidity are used to analyse power extraction from locations in the strait and around the island for an idealised island-landmass domain and an actual coastal site. The numerical model is verified by comparing predictions with analytical solutions for inviscid flow past a circular cylinder located in the centre of a channel and in the vicinity of a wall. The model is then validated against laboratory measurements of flow patterns for impulsively-started flow past a submerged circular cylinder, and for flow past a surface-piercing circular cylinder in oscillatory laminar shallow flow. It is demonstrated that the numerical method captures satisfactorily the mechanisms of early wake formation, which indicates the model can be applied to assess tidal stream resource within the coastal geometries considered herein. Finally, the methodology to account for power extraction is satisfactorily verified for bounded and unbounded flows. Contrary to current practices, results from a parameter study for different idealised coastal sites reveal that the maximum power extracted in the strait is not well approximated by either the power extracted naturally at the seabed or the undisturbed kinetic power. Moreover, an analytical channel model underpredicts the maximum power extracted in the strait due to its inability to account for changes in the driving head resulting from power extraction and flow diversion offshore of the island. An exception is found for islands with large aspect ratios, with the larger dimension extending parallel to the landmass; i.e. the island-landmass geometry approaching that of a channel. In this case, the extracted power is satisfactorily approximated by the power naturally dissipated at the seabed and there is good agreement with the analytical model. The maximum power extracted in the strait is shown to decrease when water depths offshore are greater than in the strait, underlining the importance of fully understanding the wider bathymetry of a given site. A similar conclusion is reached when strait blockage is reduced. The power extraction in the strait is found to be sensitive to both viscosity and seabed friction, and these parameters need to be properly estimated during the setup and calibration of models in order to reduce uncertainty. Power extraction increases when turbines are sited simultaneously both in the strait and offshore. Tidal power assessment is performed for Rathlin Sound, off the coast of Northern Ireland. Again, no clear relationship is found between maximum power extracted in the strait and either the power dissipated naturally at the seabed or the undisturbed kinetic power. A similar ratio of power extracted to undisturbed kinetic power is obtained as for the equivalent idealised model. The analytical channel model underpredicts the maximum power extracted. The actual and idealised coastal site models indicate similar responses to changes in seabed friction, and similar reduction in power extraction with decreasing strait blockage.

This dissertation proposes a power management and control strategy for islanded microgrids, which consist of multiple electronically-interfaced distributed energy resource (DER) units, to achieve a prescribed load sharing scheme. This strategy provides i) a power management system to specify voltage set points based on a classical power flow analysis; 2) DER local controllers, designed based on a robust, decentralized, servomechanism approach, to track the set points; and 3) a frequency control and synchronization scheme. This strategy is then generalized to incorporate both power-controlled and voltage-controlled DER units. Since the voltage-controlled DER units do not use inner current control loops, they are vulnerable to overcurrent/overload transients subsequent to system severe disturbances, e.g., faults and overloading conditions. To prevent DER unit trip-out or damage under these conditions, an overcurrent/overload protection scheme is proposed that detects microgrid abnormal conditions, modifies the terminal voltage of the corresponding VSC to limit DER unit output current/power within the permissible range, and restores voltage controllers subsequently. Under certain circumstances, e.g., microgrid islanding and communication failure, there is a need to switch from an active to a latent microgrid controller. To minimize the resultant transients, control transition should be performed smoothly. For the aforementioned two circumstances, two smooth control transition techniques, based on 1) an observer and 2) an auxiliary tracking controller, are proposed to achieve a smooth control transition. A typical microgrid system that adopts the proposed strategy is investigated. The microgrid dynamics are investigated based on eigenvalue sensitivity and robust analysis studies to evaluate the performance of the closed-loop linearized microgrid. Extensive case studies, based on time-domain simulations in the PSCAD/EMTDC platform, are performed to evaluate performance of the proposed controllers when the microgrid is subject to various disturbances, e.g., load change, DER abrupt outage, configuration change, faults, and overloading conditions. Real-time hardware-in-the-loop case studies, using an RTDS system and NI-cRIO industrial controllers, are also conducted to demonstrate ease of hardware implementation, validate controller performance, and demonstrate its insensitivity to hardware implementation issues, e.g., noise, PWM nonidealities, A/D and D/A conversion errors and delays.

This dissertation proposes a power management and control strategy for islanded microgrids, which consist of multiple electronically-interfaced distributed energy resource (DER) units, to achieve a prescribed load sharing scheme. This strategy provides i) a power management system to specify voltage set points based on a classical power flow analysis; 2) DER local controllers, designed based on a robust, decentralized, servomechanism approach, to track the set points; and 3) a frequency control and synchronization scheme. This strategy is then generalized to incorporate both power-controlled and voltage-controlled DER units. Since the voltage-controlled DER units do not use inner current control loops, they are vulnerable to overcurrent/overload transients subsequent to system severe disturbances, e.g., faults and overloading conditions. To prevent DER unit trip-out or damage under these conditions, an overcurrent/overload protection scheme is proposed that detects microgrid abnormal conditions, modifies the terminal voltage of the corresponding VSC to limit DER unit output current/power within the permissible range, and restores voltage controllers subsequently. Under certain circumstances, e.g., microgrid islanding and communication failure, there is a need to switch from an active to a latent microgrid controller. To minimize the resultant transients, control transition should be performed smoothly. For the aforementioned two circumstances, two smooth control transition techniques, based on 1) an observer and 2) an auxiliary tracking controller, are proposed to achieve a smooth control transition. A typical microgrid system that adopts the proposed strategy is investigated. The microgrid dynamics are investigated based on eigenvalue sensitivity and robust analysis studies to evaluate the performance of the closed-loop linearized microgrid. Extensive case studies, based on time-domain simulations in the PSCAD/EMTDC platform, are performed to evaluate performance of the proposed controllers when the microgrid is subject to various disturbances, e.g., load change, DER abrupt outage, configuration change, faults, and overloading conditions. Real-time hardware-in-the-loop case studies, using an RTDS system and NI-cRIO industrial controllers, are also conducted to demonstrate ease of hardware implementation, validate controller performance, and demonstrate its insensitivity to hardware implementation issues, e.g., noise, PWM nonidealities, A/D and D/A conversion errors and delays.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24924号 / エネ博第466号 / 新制||エネ||87(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 MCLELLAN Benjamin, 教授 宇根﨑 博信, 教授 河本 晴雄 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

In the last two decades, energy is becoming one of the main issues in the manufacturing industry as it contributes substantially to production cost, CO2 emissions, and other destructive environmental impact. Due to rising energy costs, environmental concerns and stringent regulations, manufacturing is increasingly driven towards sustainable manufacturing which needs to address the associated environmental, social and economic aspects simultaneously. One common approach is to achieve sustainability and to implement energy-resource efficient production management systems that enable optimisation of energy consumption and resource utilisation in the production system. However, by reducing energy consumption, the product quality and production cost may be compromised. To remain competitive in the dynamic environment, the energy-efficient management system should not only concern energy consumption but also maintain product quality and production efficiency. This thesis presents a development of the Energy-smart Production Management (e-ProMan) system which provides a systematic, virtual simulation that integrates manufacturing data relating to thermal effect and correlation analysis between energy flow, work flow and data flow for the heating, ventilation and air conditioning (HVAC) system and production process. First, the e-ProMan system comprises of the multidimensional analysis between energy flow, work flow and data flow. The results showed that the product quality is significantly affected by ambient temperature in CNC precision machining. Product quality appears to be improved at lower temperatures. This research highlights the significance of ambient temperature in sustainable precision machining. Second, the simulation experiment was modelled at the production process due to it being the main source of energy consumption in manufacturing. An up-hill workload scenario was found to be the most energy and cost-efficient production processes. In other words, energy consumption, CO2 emission and total manufacturing cost could be reduced when workload capacity and operating machine increase incrementally. Moreover, the e-ProMan system was modelled and simulated using the weather forecast and real-time ambient temperature to reduce energy consumption of the HVAC system. The e-ProMan system results in less energy consumption compared to the fuzzy control system. To conclude, the e-ProMan demonstrates energy efficiency at all relevant levels in the manufacturing: machine, process and plant. For the future research, the e-ProMan system needs to be applied and validated in actual manufacturing environments.

Power converters are used in many distributed energy resources (DER) applications. With proper controls, DER systems can reduce losses and achieve higher energy efficiency if various power sources and loads are integrated through DC bus. High voltage electric vehicle (EV) DC charging station is becoming popular in order to reduce charging time and improve energy efficiency. A DC EV charging station model involving photovoltaic, energy storage system (ESS), fuel cell and DC loads is studied in this work. A dynamic programming technique that considers various uncertainties involved in the system is adopted to obtain optimal dispatch of ESS and fuel cell system. The effects of different tariffs, demand response programs and contract capacities of demand in the power scheduling are investigated and the results are presented.

The concern over depleting fossil fuel resources and increasing greenhouse gas emissions has prompted the research into alternative and renewable energy resources. Bioethanol is seen as a potential alternative to petroleum fuels and is mainly produced from sugar and starch containing crops such as sugar cane and maize. In South Africa the use of maize for ethanol production has been prohibited due to food security concerns; therefore, alternative feedstocks need to be investigated. Tropical sugar beet, a new variety of sugar beet, is a potential alternative as it is able to grow in tropical and subtropical climates using much less water than sugar cane. The main objective of this study was to determine the potential of using tropical sugar beet for ethanol production. The study focused on the effects of dilution ratio, pH, yeast concentration and the addition of a nitrogen supplement on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% and a glycerol yield of 0.08 g.g–1 was obtained when no additional water was added to the juice. The best dilution ratio was found to be 1:4 which gave a maximum ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% and a glycerol yield of 0.07 g.g–1. An ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% was achieved at a yeast concentration of 5 g.L–1 after four hours of fermentation. Nitrogen supplements such as urea, peptone, yeast extract and ammonium sulphate were added during fermentation. The addition of a nitrogen supplement to fermentation had a positive effect on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% was achieved when urea was added to the fermentation. The addition of a nitrogen supplement also decreased the amount of glycerol formed from 0.15 g.g –1 to 0.08 g.g–1. Ammonium sulphate was chosen as the preferred nitrogen source as it is a simple component that can enter the cell directly. A maximum ethanol yield of 0.45 g.g–1 which is a conversion efficiency of 88%, was achieved when 750 mg N.L–1 ammonium sulphate was added. Adjusting the pH prior to fermentation had no real effect on the ethanol yield. The maximum ethanol yield of 0.45 g.g–1 was achieved at all the pH values investigated. Therefore the natural pH of the juice, or pH values between 4 and 5.5, could be used. Adjusting the pH was done to merely reduce the risk of contamination. The optimal fermentation parameters were found to be pH 4, yeast concentration 5 g.L–1 and a ammonium sulphate concentration of 750 mg N.L–1. At these conditions, a maximum ethanol of 0.45 g.g–1 was achieved. These results show that tropical sugar beet with a sugar content of approximately 21.8% (w.w–1) is a good feedstock for ethanol production in South Africa. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

The concern over depleting fossil fuel resources and increasing greenhouse gas emissions has prompted the research into alternative and renewable energy resources. Bioethanol is seen as a potential alternative to petroleum fuels and is mainly produced from sugar and starch containing crops such as sugar cane and maize. In South Africa the use of maize for ethanol production has been prohibited due to food security concerns; therefore, alternative feedstocks need to be investigated. Tropical sugar beet, a new variety of sugar beet, is a potential alternative as it is able to grow in tropical and subtropical climates using much less water than sugar cane. The main objective of this study was to determine the potential of using tropical sugar beet for ethanol production. The study focused on the effects of dilution ratio, pH, yeast concentration and the addition of a nitrogen supplement on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% and a glycerol yield of 0.08 g.g–1 was obtained when no additional water was added to the juice. The best dilution ratio was found to be 1:4 which gave a maximum ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% and a glycerol yield of 0.07 g.g–1. An ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% was achieved at a yeast concentration of 5 g.L–1 after four hours of fermentation. Nitrogen supplements such as urea, peptone, yeast extract and ammonium sulphate were added during fermentation. The addition of a nitrogen supplement to fermentation had a positive effect on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% was achieved when urea was added to the fermentation. The addition of a nitrogen supplement also decreased the amount of glycerol formed from 0.15 g.g –1 to 0.08 g.g–1. Ammonium sulphate was chosen as the preferred nitrogen source as it is a simple component that can enter the cell directly. A maximum ethanol yield of 0.45 g.g–1 which is a conversion efficiency of 88%, was achieved when 750 mg N.L–1 ammonium sulphate was added. Adjusting the pH prior to fermentation had no real effect on the ethanol yield. The maximum ethanol yield of 0.45 g.g–1 was achieved at all the pH values investigated. Therefore the natural pH of the juice, or pH values between 4 and 5.5, could be used. Adjusting the pH was done to merely reduce the risk of contamination. The optimal fermentation parameters were found to be pH 4, yeast concentration 5 g.L–1 and a ammonium sulphate concentration of 750 mg N.L–1. At these conditions, a maximum ethanol of 0.45 g.g–1 was achieved. These results show that tropical sugar beet with a sugar content of approximately 21.8% (w.w–1) is a good feedstock for ethanol production in South Africa. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

This master's thesis is aimed at analyzing the integration processes between the European Union and Azerbaijan. Azerbaijan is a major oil and gas supplier, while the European Union actively seeks diversification of energy resource supplies for the purpose of reaching higher energy security. The aim of the research is to investigate the relations between Azerbaijan and the European Union. The nature of relations between the two stated subjects are being analyzed, and the main preconditions favoring such relations. In order to provide comprehensive analysis, the situation of Azerbaijan's relations with the European Union with the same bilateral relations with the EU of Turkey, Ukraine and China are being analyzed within this thesis.