Indiana University-Purdue University Indianapolis (IUPUI) / In this research, a Split-Shaft Wind Energy Conversion System (SS-WECS) is investigated to improve the performance and cost of the system and reduce the wind power uncertainty influences on the power grid. This system utilizes a lightweight Hydraulic Transmission System (HTS) instead of the traditional gearbox and uses a Doubly-Fed Induction Generator (DFIG) instead of a synchronous generator. This type of wind turbine provides several benefits, including decoupling the shaft speed controls at the turbine and the generator. Hence, maintaining the generator’s frequency and seeking maximum power point can be accomplished independently. The frequency control relies on the mechanical torque adjustment on the hydraulic motor that is coupled with the generator. This research provides modeling of an SS-WECS to show its dependence on mechanical torque and a control technique to realize the mechanical torque adjustments utilizing a Doubly-Fed Induction Generator (DFIG). To this end, a vector control technique is employed, and the generator electrical torque is controlled to adjust the frequency while the wind turbine dynamics influence the system operation. The results demonstrate that the generator’s frequency is maintained under any wind speed experienced at the turbine. Next, to reduce the size of power converters required for controlling DFIG, this research introduces a control technique that allows achieving MPPT in a narrow window of generator speed in an SS-WECS. Consequently, the size of the power converters is reduced significantly. The proposed configuration is investigated by analytical calculations and simulations to demonstrate the reduced size of the converter and dynamic performance of the power generation. Furthermore, a new configuration is proposed to eliminate the Grid- Side Converter (GSC). This configuration employs only a reduced-size Rotor-Side Converter (RSC) in tandem with a supercapacitor. This is accomplished by employing the hydraulic transmission system (HTS) as a continuously variable and shaft decoupling transmission unit. In this configuration, the speed of the DFIG is controlled by the RSC to regulate the supercapacitor voltage without GSC. The proposed system is investigated and simulated in MATLAB Simulink at various wind speeds to validate the results. Next, to reduce the wind power uncertainty, this research introduces an SS-WECS where the system’s inertia is adjusted to store the energy. Accordingly, a flywheel is mechanically coupled with the rotor of the DFIG. Employing the HTS in such a configuration allows the turbine controller to track the point of maximum power (MPPT) while the generator controller can adjust the generator speed. As a result, the flywheel, which is directly connected to the shaft of the generator, can be charged and discharged by controlling the generator speed. In this process, the flywheel energy can be used to modify the electric power generation of the generator on-demand. This improves the quality of injected power to the grid. Furthermore, the structure of the flywheel energy storage is simplified by removing its dedicated motor/generator and the power electronics driver. Two separate supervisory controllers are developed using fuzzy logic regulators to generate a real-time output power reference. Furthermore, small-signal models are developed to analyze and improve the MPPT controller. Extensive simulation results demonstrate the feasibility of such a system and its improved quality of power generation. Next, an integrated Hybrid Energy Storage System (HESS) is developed to support the new DFIG excitation system in the SS-WECS. The goal is to improve the power quality while significantly reducing the generator excitation power rating and component counts. Therefore, the rotor excitation circuit is modified to add the storage to its DC link directly. In this configuration, the output power fluctuation is attenuated solely by utilizing the RSC, making it self-sufficient from the grid connection. The storage characteristics are identified based on several system design parameters, including the system inertia, inverter capacity, and energy storage capacity. The obtained power generation characteristics suggest an energy storage system as a mix of fast-acting types and a high energy capacity with moderate acting time. Then, a feedback controller is designed to maintain the charge in the storage within the required limits. Additionally, an adaptive model-predictive controller is developed to reduce power generation fluctuations. The proposed system is investigated and simulated in MATLAB Simulink at various wind speeds to validate the results and demonstrate the system’s dynamic performance. It is shown that the system’s inertia is critical to damping the high-frequency oscillations of the wind power fluctuations. Then, an optimization approach using the Response Surface Method (RSM) is conducted to minimize the annualized cost of the Hybrid Energy Storage System (HESS); consisting of a flywheel, supercapacitor, and battery. The goal is to smooth out the output power fluctuations by the optimal size of the HESS. Thus, a 1.5 MW hydraulic wind turbine is simulated, and the HESS is configured and optimized. The direct connection of the flywheel allows reaching a suitable level of smoothness at a reasonable cost. The proposed configuration is compared with the conventional storage, and the results demonstrate that the proposed integrated HESS can decrease the annualized storage cost by 71 %. Finally, this research investigates the effects of the reduced-size RSC on the Low Voltage Ride Through (LVRT) capabilities required from all wind turbines. One of the significant achievements of an SS-WECS is the reduced size excitation circuit. The grid side converter is eliminated, and the size of the rotor side converter (RSC) can be safely reduced to a fraction of a full-size excitation. Therefore, this low-power-rated converter operates at low voltage and handles the regular operation well. However, the fault conditions may expose conditions on the converter and push it to its limits. Therefore, four different protection circuits are employed, and their effects are investigated and compared to evaluate their performance. These four protection circuits include the active crowbar, active crowbar along a resistorinductor circuit (C-RL), series dynamic resistor (SDR), and new-bridge fault current limiter (NBFCL). The wind turbine controllers are also adapted to reduce the impact of the fault on the power electronic converters. One of the effective methods is to store the excess energy in the generator’s rotor. Finally, the proposed LVRT strategies are simulated in MATLAB Simulink to validate the results and demonstrate their effectiveness and functionality.

This thesis describes the study of a series of multimetallic supramolecules containing varied metals and ligands, synthesized by a building block method and characterized by mass spectrometry, electronic absorption spectroscopy, and electrochemistry. Incorporating different functional units into complex systems allowed these multimetallic supramolecules to perform various light activated tasks including DNA cleavage and hydrogen generation from water. The complex [({(bpy)₂Os(dpp)}₂Ru)₂(dpq)](PF₆)₁₂ and [{(bpy)₂M(dpp)}₂Ru(BL)PtCl₂](PF₆)₆ were synthesized (M = Os^II or Ru^II; BL = dpp or dpq; bpy = 2,2^'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline). The building blocks displayed varied electrochemical properties upon complexation. The bridging ligands dpp and dpq display their reduction potentials shifted to less negative values when they changed from monochelating to bischelating. The electronic absorption spectra of the multimetallic systems displayed transitions of each contributing chromophore, with overlapping metal to ligand charge transfer (MLCT) transitions in visible region of spectrum. Spectroelectrochemistry revealed the nature of MLCTs and helped to identify fingerprint features of complex supramolecules. Photophysical measurements include emission spectroscopy with quantum yield measurements and emission lifetime measurements. Photophysical data provided detailed information to aid in developing an understanding of excited state properties of these complexes. Supported by the electrochemical data and spectroelectrochemistry, the hexametallic complex was suggested to have a HOMO localizing in the peripheral Os and a LUMO localizing in the central dpq, separating by a Ru energy barrier. This research systematically investigated photophysical properties of some building blocks and the mixed-metal, mixed-ligand supramolecules constructed by a variety of building blocks coupling light absorbing subunits to a reactive Pt metal center. Preliminary studies suggested [{(bpy)₂Ru(dpp)}₂Ru(dpq)PtCl₂](PF₆)₆ was a photocatalyst for H2 production from water in the presence of a sacrificial electron donor. The complex [{(bpy)₂Ru(dpp)}₂Ru(dpq)PtCl₂](PF₆)₆ had been studied for its catalytic ability in generating hydrogen and was found to have 34 product turnovers after 3 h photolysis. Photolysis and gel electrophoresis revealed that the tetrametallic complexes were able to bind to and then photocleave DNA through an oxygen mediated mechanism. The independence of ionic strength variation when [{(bpy)₂Ru(dpp)}₂Ru(dpp)PtCl₂](PF₆)₆ interacted with DNA, suggested the covalent interaction nature of the complex. These results suggest future work on understanding the excited state properties of supramolecular complexes is suggested. The designs of future photocatalysts for hydrogen production from water and anticancer photodynamic therapy drugs are also proposed. / Ph. D.

The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout's visible impact in the graph of the yearly gross domestic product of the Unites States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected. Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful. However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation. In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models. Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited. More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid. / Doctor of Philosophy / The electric power system is designed to economically and reliably transmit electricity to homes, industry, and businesses. The economic impact of the electric grid was demonstrated by the 2003 blackout’s visible impact in the graph of the yearly gross domestic product of the United States. However, because the number of customers is so large and economies of scale are leveraged to keep electricity prices low, utilities are strongly interconnected. Performing comprehensive engineering analyses to ensure reliable operation is still impossible. Instead, heuristics and safety factors are incorporated into planning processes to continually meet demand in a way that complies with Federal regulations. As evidenced by the infrequency of blackouts in the United States, the sophisticated planning processes have up to date been relatively successful. However, the power system is constantly changing. Electrical generators based on renewable energies are a beneficial addition to the grid, but these and other technological changes like high-voltage power electronic converters also come with their own challenges. These systems as currently employed tend to have a different impact on the reliability of operation than traditional fossil fuel based generators. As the system changes, so do the engineering analyses required to ensure reliable operation. In particular, the wind energy conversion systems (WECS) negatively impact the response of the grid to disturbances in certain ways due to inherent challenges harnessing the wind as an energy sources. These negative impacts (and the advent of powerful personal computing) require an increase in the sophistication of power system models. Thus, there are competing challenges: the scale of the power system necessitates computationally efficient modeling, but the complexity of analysis required to maintain reliable operation is also increasing. The primary aim of this study is to develop models and methods for more detailed yet computationally manageable simulation. To this aim, higher order linearizations and the properties of linear systems (graph theory and linear algebra) are exploited. More specifically, this document contains three studies. In the short term planning and situational awareness context, a method is proposed to quickly check credible outages of important grid equipment. This methodology enables the inspection of a wider breadth of system conditions to ameliorate the negative impacts of the unpredictability of the wind. A linear model in the traditional sense is also developed to model any arbitrary number of wind turbines in a wind farm. This enables industry players to study the impacts wind turbine interaction on the dynamic stability of the grid in response to small disturbances. Finally, a wind farm is modeled as a large matrix to model even nonlinear behavior of wind farms. This helps industry players analyze the impact of large disturbances on the grid.

Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an ‘antenna' system causing an electron transfer into the ‘reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy. In this dissertation, we report on the design and synthesis of donor–acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the greatest amount of energy but must be fast to out compete intersystem crossing. To address this limitation, we have designed novel donor –acceptor conjugates that use high-energy triplet sensitizers in which electron transfer is initiated from the long lived triplet state of the donor. The triplet photosensitizers used were palladium(II) porphyrin and platinum(II) porphyrin. Heavy metal effect in these porphyrins promoted intersystem crossing and the energies of their excited state was quite high. For the case of palladium (II) porphyrin the energy stored was found to 1.89 eV and that of platinum(II) porphyrin 1.84 eV. In addition to using triplet photosensitizers as donors, we have used donors that are difficult to oxidize and hence producing long lived charge separated states with adequate amount of stored energy. The system that was used for this study is zinc porphyrin with meso-aryl pentafluorophenyl substituents and fullerene, C60 as the acceptor. The presence of fluorine substituents on zinc porphyrin makes it harder to undergo oxidation. When this high potential donor-acceptor system undergoes a photoinduced charge-separation, the estimated energy stored was found to be 1.70 eV, one of the highest reported in literature so far. To further extend the lifetime of the charge separated states generated in this high-potential zinc porphyrin-fullerene dyad a pyridine functionalized tetrathiafulvalene was axially coordinated to the Zn metal producing a supramolecular triad capable of producing long-lived charge separated state. In a subsequent study, a multi-modular donor-acceptor system composed of a porphyrin, fullerene (C60) and a BF2-chelated dipyrromethene (BODIPY) with a supramolecular arrangement in the form of porphyrin-BODIPY-C60, one of the few reported in literature. By selectively exciting BODIPY and ZnP moieties, efficient singlet-singlet energy transfer from 1BODIPY * to ZnP in toluene was observed in the case of the dyad ZnP-BODIPY. However, when ZnP is excited, electron transfer occurred with the formation ZnP.+-BODIPY-C60.- charge separated state persisting for microseconds.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008. / The sustainability and economy of the current South African National Antarctic Expedition IV (SANAE IV) base diesel-electric power system are threatened by the current high fuel prices and the environmental pollution reduction obligations. This thesis presents the potential technical, environmental and economical challenges associated with the integration of small wind energy conversion system (WECS) with the current SANAE IV diesel fuelled power system. Criteria derived from technical, environmental and economic assessments are applied in the evaluation of eight commercially available wind turbines as to determine the most technically and economically feasible candidates. Results of the coastal Dronning Maud Land and the local Vesleskarvet cold climate assessments based on long term meteorological data and field data are presented. Field experiments were performed during the 2007-2008 austral summer. These results are applied in the generation of a wind energy resource map and in the derivation of technical wind turbine evaluation criteria. The SANAE IV energy system and the electrical grid assessments performed are based on long term fuel consumption records and 2008 logged data. Assessment results led to the identification of SANAE IV specific avoidable wind turbine grid integration issues. Furthermore, electro-technical criteria derived from these results are applied in the evaluation of the eight selected wind turbines. Conceptual wind turbine integration options and operation modes are also suggested. Wind turbine micro-siting incorporating Vesleskarvet specific climatological, environmental and technical related issues are performed. Issues focusing on wind turbine visual impact, air traffic interference and the spatial Vesleskarvet wind distribution are analysed. Three potential sites suited for the deployment of a single or, in the near future, a cluster of small wind turbines are specified. Economics of the current SANAE IV power system based on the South African economy (May 2008) are analysed. The life cycle economic impact associated with the integration of a small wind turbine with the current SANAE IV power system is quantified. Results of an economic sensitivity analysis are used to predict the performance of the proposed wind-diesel power systems. All wind turbines initially considered will recover their investment costs within 20 years and will yield desirable saving as a result of diesel fuel savings, once integrated with the SANAE IV diesel fuelled power system. Finally, results of the technical and economical evaluation of the selected commercially available wind turbines indicated that the Proven 6 kWrated, Bergey 10 kWrated and Fortis 10 kWrated wind turbines are the most robust and will yield feasible savings.

Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: With the introduction of Section 17 of the EnWG (German Energy Economy Act), the legislator created a new situation for the complex relationships in the German offshore wind industry. The transmission system operators are now obliged not only to provide the connection for offshore wind farms, but also to reimburse the developers of such plants for the costs they incurred in the course of planning the cable connection between the wind farm and the onshore grid. Forecasts had predicted that by 2007 numerous offshore wind farms would be operational. But no development company in the entire sector had moved beyond the planning phase. However, the rapid development of the offshore wind industry is important in order to achieve the German goal to generate 20% of all energy from renewable energy sources by 2020 and thus contribute to the prevention of grave climate changes. It is also important for the domestic labour market and the initiation of further exports of energy technologies. Early domestic growth will eventually payoff as offshore wind energy is implemented by more countries, which will then rely on the experience of German companies. Under these circumstances, Section 17 (2a) S.3 of the EnWG induces a positive impulse for offshore development. Under the financial constraints that dampened the expectations of developers of offshore wind farms, the suggested reimbursement will offer welcome relief. However a broad interpretation of Section 17 (2a) S.3 of the EnWG must be applied in order to reach the goal of actually enhancing offshore development, as is the legislator's intent. Such a broad interpretation of the reimbursement claim will lead to rapid implementation of the new law, as this will be in the interest of the developers and transmission system operators. The developers will have a large interest in beginning with the actual construction of the wind farm, and the transmission system operators will need to proceed with the planning of the cable connection. Even though improvements remain necessary the introduction of Section 17 (2a) S.3 EnWG can be considered a success. / AFRIKAANSE OPSOMMING: Met die inwerkingstelling van afdeling 17 van die EnGW (Duitse Energie Ekonomie Wet), het die regering 'n nuwe situasie geskep vir die komplekse verhouding in die Duitse see-gebonde wind-energie industrie. Die transmissie stelsel operateurs word nou verplig om nie net die verbinding met die wind-plaas te verskaf nie, maar moet ook die ontwikkelaar van die aanleg vergoed vir enige kostes wat hulle aangegaan het met die beplanning van die verbinding tussen die windplaas en die elektrisiteits-netwerk. Vooruitskattings het voorspel dat verskeie see-gebonde windplase operasioneel sou wees teen 2007. Geen ontwikkelingsmaatskappy het egter al tot dusver verder as die beplanningstadium gevorder nie. Desnieteenstaande, die spoedige ontwikkeling van die see-gebonde wind industrie is onontbeerlik in die Duitse mikpunt om 20% van energiebehoeftes op te wek vanuit hernubare bronne teen 2020 en om dus klimaatsverandering teen te werk. Dit is ook belangrik vir werkskepping in Duitsland en vir die uitvoer van energie tegnologie. Spoedige groei in die industrie sal uiteindelik dividende lewer soos seegebonde wind-energie deur ander lande ontwikkel word en gevolglik op Duitse ervaring moet staatmaak. Onder hierdie omstandighede het afdeling 17 (2a) 5.3 van die EnGW 'n positiewe effek op seegebonde ontwikkeling. As gevolg van die dempende effek wat finansiele beperkinge het op die verwagtinge van ontwikkelaars sal die terugbetalings welkome verligting bied. Dit is egter nodig om 'n bree interpretasie van afdeling 17 (2a) 5.3 van die EnGW te gebruik om die mikpunt van werklike bevordering van seegebonde ontwikkeling te bewerkstellig soos die wetgewer beoog. So 'n bree interpretasie sal lei tot spoedige implimentasie van die nuwe wet omdat dit in die belang van ontwikkelaars en transmissie-netwerk eienaars sal wees. Die ontwikkelaars sal baat daarby om spoedig met ontwikkeling te begin, terwyl die netwerk operateurs vordering sal moet maak met die beplanning van die kabel-verbinding. Ten spyte daarvan dat verdere verbeteringe nodig is kan die inwerkingstelling van afdeling 17 (2a) 5.3 van die EnGW as 'n sukses gereken word.

Rapporten avhandlar en konceptstudie för omvandling av termisk energi till elektrisk samt mekanisk energi, i den autonoma undervattensfarkosten SAPPHIRES. Inledningsvis utreds vilka förväntningar och krav som finns på konceptet för energiomvandling samt om där finns någon publicerad litteratur som redan gjort ansträngningar för att lösa det aktuella problemet. Allmän teori kring värmemotorer och en bred, systematisk litteratursökning inkluderas även i det arbetet. Energiomvandlingen antas kunna ske enligt två fall kallade ”hög-prestanda” och ”låg/medel-prestanda”, vilka innebär att mekanisk samt elektrisk effekt, respektive endast elektrisk effekt ska kunna levereras av konceptet. De mekaniska samt elektriska effekterna ska, vidare, kunna levereras om maximalt 600, respektive 6 kW, och konceptet ska åtminstone kunna uppfylla ett av energiomvandlingsfallen. Den faktiska konceptstudien utgörs av två iterationer av konceptgenereringar, -utvärderingar och -val och de visar att ett koncept kallat ”Öppet system inspirerat av nukleär värmeframdrivning” förefaller vara det bästa sättet att omvandla termisk energi i SAPPHIRES. Därtill indikerar en mer detaljerad analys, bestående av bland annat matematisk modellering och konceptuell konstruktion, att konceptet möjligen skulle kunna uppfylla så kallad ”hög-prestanda” och sedermera leverera både mekanisk och elektrisk effekt om 600, respektive 6 kW. Mer specifikt visar en matematisk analys, med hjälp av vissa antaganden rörande konceptets funktion, att ett ”Öppet system inspirerat av nukleär värmeframdrivning” skulle kunna leverera en mekanisk effekt om 1025 kW samt en elektrisk effekt om 141 kW. En grov, konceptuell konstruktion bekräftar också att konceptets vitala, ingående komponenter faktiskt kan rymmas inom de specificerade dimensionskraven (en cylinderformad volym med en längd och diameter om 1,7, respektive 0,5 m.). Det står dock klart att de möjliga koncepten för energiomvandling kraftigt begränsas av deras möjligheter att leverera tillräcklig mekanisk effekt, för att uppnå ”hög-prestanda”. Om endast ”låg/medel-prestanda” ska uppfyllas tillåts fler av de möjliga koncepten och i ett sådant fall skulle faktorer som underhåll, miljöpåverkan och SAPPHIRES signatur kunna prioriteras i högre utsträckning. / The report discusses a concept study regarding the conversion of thermal energy into electrical and mechanical energy, in the autonomous underwater vehicle SAPPHIRES. First, the requirements and expectations regarding the concept of energy conversion are investigated and efforts are made to identify any published literature, which has already made attempts of solving the issue. General theory regarding heat engines and an extensive literature study are also included in this work. The energy conversion is assumed to perform according to two cases called "high-performance" and "low/medium-performance", meaning mechanical and electrical energy or electrical power should be delivered by the concept, respectively. More specifically, the mechanical and electrical powers should be delivered of a maximum of 600 and 6 kW, respectively and the concept should at least fulfill one of the performance settings. The actual concept study comprises of two iterations of concept generations, evaluations and selections and shows that a concept called "Open system inspired by nuclear thermal propulsion" seems to be the best way of converting thermal energy on-board SAPPHIRES. Moreover, a more detailed analysis, comprising of, inter alia, mathematical modelling and conceptual design, indicates that the concept possibly can meet the so-called "high-performance" and thus, deliver both mechanical and electrical powers of 600 and 6 kW, respectively. More specifically, a mathematical analysis, based on some assumptions regarding the concept's functionality, shows that an "Open system inspired by nuclear thermal propulsion" could deliver a mechanical power of 1025 kW and an electrical power of 141 kW. Rough conceptual design also shows that the vital parts of the concept could fit within the specified maximal dimensions (a cylinder-shaped volume with a length and diameter of 1.7 and 0.5 m, respectively). However, it is clear the possible concepts of energy conversion are severely limited by their capacities of delivering enough mechanical energy, to meet the "high-performance" demands. Assuming only the "low/medium-performance" has to be met, more possible concepts becomes available and in that case, factors such as maintenance, environmental impact and signature of SAPPHIRES could be considered to a greater extent.

Thesis (MScEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: South Africa has a signi cant potential resource for electrical power generation in the Agulhas Current on the southeast coast. The Ocean Current Energy Convertor studied in this project was designed to generate power from this current. The feasibility of this device was investigated by analysing the dynamic stability and controllability of the convertor, when acted upon by hydrodynamic forces while harvesting energy from the current. A simulation model was developed to predict the dynamic behaviour using the Simulink software suite. A scale model of the prototype was built and tested in the Towing Tank at Stellenbosch University, and the experimental results were compared against the simulation results. A control algorithm was designed, using the mathematical model, to control the roll angle and deployment depth. The control algorithm was tested in simulation. The results indicated that the simulation model accurately predicted the behaviour of the prototype in testing, and results showed that the device is both stable and controllable. It was concluded that this OCEC design concept warrants further investigation. The recommendations are that the experimental model be improved to ensure reliable experimental results, that further complexity be added to the simulation model, and that the control algorithm be tested on the improved prototype in the towing tank. / AFRIKAANSE OPSOMMING: Die Agulhas-seestroom aan die suidooskus van Suid-Afrika bied 'n aansienlike potensiële hulpbron vir elektriese kragopwekking. Die seestroomenergieomsetter (SEO) wat in hierdie projek bestudeer is was ontwikkel om krag uit hierdie seestroom te genereer. Die doenlikheid van hierdie toestel is ondersoek deur die dinamiese stabiliteit en beheerbaarheid van die omsetter onder die invloed van hidrodinamiese kragte te analiseer terwyl dit energie van die stroom inwin. 'n Simulasiemodel is met behulp van Simulink-sagteware ontwikkel om die dinamiese gedrag te voorspel. 'n Skaalmodel van die prototipe was gebou en in die sleeptenk by Universiteit Stellenbosch getoets en die eksperimentele resultate met die simulasie se resultate vergelyk. 'n Beheer-algoritme is daarna ontwerp, deur middel van die wiskundige model, om die rolhoek en diepte van ontplooiing te beheer.Hierdie algoritme is tydens simulasie getoets. Die resultate het aangedui dat die simulasiemodel akkuraat die gedrag van die prototipe tydens toetse voorspel het, en die resultate het gewys dat die toestel beide stabiel en beheerbaar is. Die gevolgtrekking is gemaak dat die SEO se ontwerpkonsep verdere studie regverdig. Die aanbevelings is dat die eksperimentele model verbeter word om betroubare eksperimentele resultate te verseker, dat verdere kompleksiteit by die simulasiemodel gevoeg word, en dat die beheer-algoritme op die verbeterde model in die sleeptenk getoets word.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2008. / This thesis is an investigation of the wave power resource on the South African coast, focusing on the spatial distribution of wave power of the coastal region exposed to the highest wave power. The study’s main objective is to provide a detailed description of the spatial distribution of wave power to assist in the selection of locations for deployment of Wave Energy Converter (WEC) units in this zone. The study methodology employed to achieve this main objective entails an analysis of measured wave data recorded at wave recording stations distributed along the South African coast. The analysis provided a general description of wave power at locations for which wave data exist. From this analysis it was found that the South West Coast is exposed to the highest wave power, with an average wave power of approximately 40 kW per meter wave crest. The rest of the South African coast is exposed to average wave power between approximately 18 kW/m to 23 kW/m. The wave power characteristics on the South West Coast region (from Cape Point to Elands Bay) were therefore the focus of this thesis. The study objective was achieved by transferring deep sea wave data into the nearshore South West Coast study area with the Simulating WAves Nearshore (SWAN) wave model. The deep sea wave data was obtained from a 10 year period of available hindcast data. A simplified simulation procedure was required in order to make the study practically feasible. A sensitivity analysis was carried out to determine the validity of the simplified simulation procedure and it was found that the procedure slightly overestimate wave power in the shallower water regions due to the underestimation of energy dissipation processes. This overestimation was deemed acceptable for the dominant wave conditions and the simplified model was therefore applied in the study. An appropriate programming system was developed and used to transfer the available 10 year deep sea wave data into the selected South West Coast region. From this exercise spatial distribution of wave power and related statistical parameters were obtained for the study area. The accuracy of the modelled output was investigated by directly comparing it to wave data recorded during the overlapping recording period. It was found that the model slightly overestimates the monthly wave power resource compared to the measured data with a maximum overestimation of 9%; which is sufficiently accurate for the purpose of the study. The results of this investigation can be used for the identification of areas of high wave power concentration within the study area for the location of WEC units. Further numerical modelling is required for the detailed design of wave farms, especially if potential sites are located in shallow water (shallower than approximately 50 m). / Centre for Renewable and Sustainable Energy Studies