The rise in popularity of renewable energy solutions, in particular wind energy systems, has resulted in a greater demand for low-speed direct-drive machines. The Vernier machine has inherent properties such as high torque density, sinusoidal induced voltages and low torque ripple which makes it suitable for low-speed direct-drive wind applications. Additionally, its mechanical structure is as simple as a conventional permanent magnet (PM) machine, whilst eliminating the need for a mechanical gearbox. The research problem addressed by this dissertation relates to the assessment of the Vernier permanent magnet (VPM) machine topology for direct-drive wind applications. It aims to outline a sizing, detailed design and analysis approach for a three-phase VPM wind generator. Furthermore, a comparative study is conducted using two different rotor types and two different stator types, namely; spoke-type and surface-mounted and fractional slot and integral slot respectively. Vernier theory is used to size the designs after which 2D Finite Element Analysis (FEA) simulations are used to analyse and validate the designs. The main outcome of the comparative study is an assessment of the suitability of four topologies for the direct-drive wind application. The design is assessed on parameters which are critical for wind turbine functionality; namely efficiency, torque ripple, torque density and material consumption. The most suitable of the topologies is selected for prototyping. The rotor is made more robust by adding structural features which mechanically secure laminations and PMs to the shaft. The FEA analysis of the prototype showed favourable performance characteristics, albeit with a small cost in power density. The prototype was -thus manufactured with further mechanical reinforcements made to the bearing system. Experimental results reveal the presence of a defect in the windings. Parameters which are dependent on the winding design are much lower than the analytical and FEA values. These parameters include resistance, inductance, and back-EMF. Further work should look into determining the root cause of the prototype defects.

Growing concerns about greenhouse gas emissions as well as electricity prices have led to more serious efforts by the state and federal government to provide promote renewable energy at affordable costs. I examine the effect of policies and incentives on added commercial solar PV capacity while controlling for pro-environmental preferences, energy prices, geographic controls, and demographic controls. I use county-level data that spans twelve northeastern states and the District of Columbia from 2005 through 2013. I utilize the Tobit estimator to account for a mass point of solar PV capacity at zero kilowatts. The results suggest that loans, performance-based incentives, rebates, sales tax waivers, and net metering standards increase the amount of added solar PV capacity. Solar Renewable Energy credits have a small impact on PV capacity growth, while interconnection standard and renewable portfolio standards are not statistically significant. If policy administrators aim to increase the amount of commercial solar PV, then they should consider loans, rebates, and performance-based incentives as the most effective policies.

This study aims to synthesize nanostructured hematite films using spray pyrolysis at different deposition temperatures. L-arginine was used to transform the irregular shaped nanoparticles to uniform nanospheres by chemical bath deposition at 90°C for 48 h. We also investigated the variation of L-arginine: iron precursor concentrations from 1:1 to 3:1, respectively. Likewise, hematite films doped with zinc (Zn), silver (Ag), and Zn/Ag were synthesized using spray pyrolysis. All the films were annealed at temperatures ranging from 450 to 500°C for complete hematite phase transformation. The films were used as photoanodes in photoelectrochemical (PEC) water splitting experiments. X-ray diffraction confirmed the formation of the corundum hexagonal structure of hematite with space group. Raman spectroscopy further confirmed the polycrystalline hematite symmetry with two Eg and five A1g vibrational phonon modes. UV-Vis absorption showed a variation of absorbance with bandgaps that ranged from 2.10 to 1.90 eV. Scanning electron microscopy reported the shape transformation of nanoparticles to nanospheres that ranged in size from 6 to 100 nm. The study showed that the nanostructured films synthesized at temperatures of 430 and 400°C have the highest photocurrent densities of 6 and 1.52 µAcm-2, respectively. There was an improvement of the photocurrent density from 6.4 to 10 µAcm-2 after the transformation of pristine irregularly shaped hematite nanoparticles to spherical hematite. However, on the variation of L-arginine: iron precursor concentrations, a photocurrent of 9.8 µAcm-2 was obtained for 3:1 sample. Also, an improvement of photocurrent from 17 to 89 µAcm-2 was observed for films prepared at 30 and 50 mM iron precursor concentration, respectively. In addition, there was a significant increase in the photocurrent density from 40 to 813 µAcm-2 for pristine and Zn/Ag hematite films, respectively. Ultrafast transient absorption spectroscopy was used to study the electron-hole recombination rates and lifetimes. The results indicated four lifetimes obtained from global analysis with a reduction in the electron-hole recombination rate in the femtosecond and nanosecond range, both for L-arginine/hematite and doped samples. From this study, we were able to prove that the nanostructured and doped hematite films had a longer charge carrier lifetime compared to bulk hematite. / Thesis (PhD)--University of Pretoria, 2021. / African Laser Center (ALC) National Research Foundation (NRF) Grant no. N0115/115463 (SARChI, M.D.) University of Pretoria / Physics / PhD / Restricted

Decarbonizing the electricity system (i.e. eliminating generation from fossil fuels and replacing it with non-emitting sources) is widely considered a necessary step to limiting anthropogenic emissions and minimizing the impacts of climate change. Selecting which non-emitting generators should replace existing fossil fuel sources, and when to build them, is critical to the success of this transition. The optimal pathway to decarbonisation is highly region-specific. It is impacted by both factors such as availability of renewable resources, existing generation resources, and government policy. This dissertation presents a techno-economic model that is used to assess the decarbonisation of the combined British Columbia and Alberta electricity system. It is found that high levels of decarbonisation are possible through a combination of new wind generation, particularly in Alberta, and increased trade between Alberta, British Columbia, and the United States. Following on this finding, the variability related to high penetrations of renewable generation is introduced to the model and its impact is assessed. These results indicate that variability will be an important constraint in planning decarbonized energy systems. Finally, the representation of British Columbia’s existing hydroelectric resources is expanded to determine the ability to buffer variable renewable generation with these resources. This study finds that, while existing hydroelectric resources can support much of the variability in a highly renewable energy system, additional technologies and/or policies are needed to reach a fully zero-carbon system. The findings in this thesis show that British Columbia and Alberta, with an expanded interconnection between the provinces, can reach high penetrations of variable renewable energy. The majority of this generation consists of wind energy in Alberta, which is abundant and low-cost compared to other generation options. While comparatively little generation is added in British Columbia, the existing hydroelectric resources in the province provide significant flexibility to support the variability of this wind generation. / Graduate

Stakeholder engagement-dialogue is proposed as a method of responding to the sustainable energy challenges facing South Africa. Establishing the renewable energy sector requires constructive engagement including consumers, energy suppliers, regulators and government. The purpose of this research is an attempt to gain a deeper understanding of the stakeholder engagement process - specifically dialogue - being used by government to establish the renewable energy sector. It evaluates the effectiveness of the current dialogue and the role this dialogue can play in establishing the renewable energy sector. Initially, the study analyses the dialogue contained in fifty public domain internet articles on renewable energy. This data is validated by face-to-face interviews with nine stakeholders. The analysis focuses on comparing the dialogue against an acceptable dialogue framework. Evidence from both sets of data suggests that the dialogue, although inclusive and open, lacks tolerance, empowerment and transparency. The study further found that effective dialogue should contain clarity, policies and trust. Moreover, findings from the research indicate that stakeholder dialogue can play a vital role in establishing the renewable energy sector but this dialogue needs to be with relevant stakeholders. This research adds to the existing literature in dialogue in that it proposes three additional dimensions for effective dialogue. Copyright / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

Many countries are advancing down the road of electricity privatization, deregulation, and competition as a solution to their growing electricity demand and other challenges posed by the monopolistic nature of the existing structure. Presently, Nigeria has a supply deficit of electricity as a result of the growing demand. This imbalance has negatively affected the economy of the country and the social-economic well-being of the population. Hence, there is an urgent need to reform the power sector for greater efficiency and better performance. The objectives of the reform are to meet the growing power demand by increasing the electric power generation and also by increasing competitiveness through the participation of more private sector entities. The renewable energy integration is one way of increasing the electricity generation in the country in order to cater for the growing demand adequately. Examples of the renewable energy that is available in the country include wind, geothermal, solar and hydro. They are considered to be environmentally friendly, replenishable and do not contribute to the climate change phenomena. The country presently generates the bulk of its electricity from both thermal (85%) and hydroelectric (15%) power plants. While electricity generation from the thermal power stations constitutes the largest share of greenhouse emission, this is mostly from burning coal and natural gas. The effect of this high proportion of greenhouse emission causes climate change which is referred to as a variation in the climate system statistical properties over a long period of time. It has been observed that many of the activities of human beings are contributory factors to the release of these greenhouse gases (GHG). But, as the traditional sources of energy continue to threaten the present and future existence on the planet earth, it is, therefore, imperative to increase the integration of the variable renewable energy sources in a sustainable and eco-friendly manner over a long period of time. The variability and the uncertainties of the renewable energy source's output, present a major challenge in the design of an efficient electricity market in a deregulated environment. The system deregulation and the use of renewable sources for the generation of electricity are major changes presently being experienced in power system. In a deregulated power system, the integration of renewable generation and its penetration affects both the physical and the economic operations. The main focus of this research is on the integration of wind energy into Nigerian power systems. Up till now, research on the availability of the wind energy and its economic impacts has been limited in Nigeria. Generally, the previous study of wind energy availability in Nigeria has been limited in scope. The wind energy assessment study has not been detailed enough to be able to ascertain the wind energy potential of the country. To cope with this shortcoming, a detailed statistical wind modeling and forecasting methodology have been used in this thesis to determine the amount of extractable wind energy in six selected locations in Nigeria using historical wind speed data for 30 years. The accuracy test of the statistical models was also carried using the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Chi-Square methods to determine the inherent error margin in the modeling and analysis. It is found that the error margin of the evaluations falls within the expected permissible tolerance range. For a more detailed wind assessment study of the Nigeria weather, the seasonal variation of the weather conditions as it affects the wind speed and availability during the two major seasons of dry and rainy was considered. A Self-Adaptive Differential Evolution (SADE) was used to solve the economic load dispatch problem that considers the valve-point effects and the transmission losses subject to many constraints. The results obtained were compared with those obtained using the "standard" Differential Evolution (DE), Genetic Algorithm (GA), and traditional Gradient Descent method. The results of the SADE obtained when compared with the GA, DE, and Gradient descent show the superiority of SADE over all the other methods. The research work shows that the wind energy is available in commercial quantity for generation of electricity in Nigeria. And, if tapped would help reduce the gap between the demand and supply of electricity in the country. It was also demonstrated that the wind energy integration into the power systems affects the generators total production cost.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In Latin America, the lack of electricity has been a serious problem for over several years. To overcome this lack of supply in electricity supply, hydraulic energy is now being used in a greater proportion to fulfill the electricity needs in the rural areas. Investigations have been conducted to assess the environmental conditions of these rural areas to optimize the functionality of turbines used for hydraulic energy generation. However, there are very few focused on turbines of less than 0.5 kW generation. The proposed study aims to analyze the positioning of the blades of the cross-flow turbines and designing an electric generation system for rural dwellings. A simulation of each evaluated design was performed, and the power generated from these turbines was calculated. The results show that the power outputs initially were high and stabilized at a value of approximately 180 W, hence satisfying the minimum demands of a rural house.

Recent years have seen a dramatic increase in first generation bio-fuel production, mainly driven by concerns of climate change and rising prices of transportation fossil fuels. Due to significant pressure on the few available food sources, second generation bio-fuels have entered the fray, as a sustainable alternative. This research‟s aim was to search for cellulolytic micro-organisms and enzymes from the gut of the dung beetle, Euoniticellus intermedius, (Coleoptera: Scarabaeida) that can be used in the production of second generation bio-fuels. Dung beetle larvae were dissected and the gut micro-flora cultured in cellulose medium. Bacterial growth and cellulase activity was monitored on a daily basis. DNA isolation was then done on the cellulose medium-cultured microbes and the isolated DNA cloned in E. coli. The clones were screened for cellulase activity using plate assays. A total of 7 colonies out of 160 screened colonies showed positive CMC (endo-β-1,4-glucanase) and MUC (cellobiohydrolase) activities. Sequencing of these positive colonies yielded mostly bacteria belonging to the Enterobacteriaceae family, most of which have not been previously reported to have cellulase activity. This study‟s findings prove that in addition to this dung beetle‟s gut being a fruitful source of microbial biodiversity, it is also a potential source of cellulolytic micro-organisms and enzyme activities that will aid the function and design of future bioreactors for the bio-fuel industry.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science in Engineering, Johannesburg 2018 / This research aims to assess the factors surrounding the emergence of markets with the greatest potential for rechargeable lithium battery adoption. The implications of the rise of electric vehicles and electrical energy storage are measured against lithium supply and market pricing. This was resolved by reviewing all available information and comparing it with the intricacies of resources, production and recycling. An analysis of price formation is also undertaken before making assumptions to enable a forecast of future market dynamics until 2030. Electric vehicles will require almost threefold the lithium produced in 2015 by the end of the period considered, with grid storage predicted to follow suit. No geological supply constraints were found, but economic scarcity is a strong possibility. Production is highly vulnerable to disruption due to concentration and the situation is exacerbated by inelastic demand. Recycling may be the most critical means of diversifying and improving supplies. / XL2019

Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical structure limits one of the electrode to be a transparent electrode as well as introducing inseparable relation between the electrodes separation and the active material thickness. In addition, it is also well known that the charge transport in OSC is anisotropic and the charge mobility is better in lateral direction rather than vertical direction. In order to address some of these issues, we fabricated OPV devices in a planar device structure where cathode and anode of dissimilar metals are in-plane with each other and their photovoltaic behaviors were studied. We used poly(3-hexylthiophene) and [6,6]- pheny1 C61-butyric acid methy1 ester (P3HT:PCBM) blend as an active material. In particular, we present a detailed study about the effects of the structural parameters such as the channel length, the active layer thickness, and the work function of the electrodes on the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and the power conversion efficiency (PCE). In order to determine the suitable anode and cathode for the planar organic photovoltaic (P-OPV) structure, we first fabricated and measured organic field effect transistor (OFET) devices with different contacts and studied the effect of barrier height at the iv P3HT:PCBM/electrode interface on the device output and transport properties. The study showed a clear effect of varying the contact material on the charge injection mechanism and on the carriers mobilities. The results have also shown that Au with high hole mobility and on current in the p-channel can be used as an anode (holes extractor) in the P-OPV device while In, Cr, and Ti that showed a reasonable value of electron mobility can be good candidates for cathode (electron extractor). We also found that, Ag, Al, and Mg showed large barrier which resulted in large threshold voltage in the I-V curve making them undesired cathode materials in the P-OPV device. We then fabricated P-OPV devices with Au as an anode material and varied the cathode material to study the effect of the interface between the P3HT:PCBM layer and the cathode material. When Al, Mg, or Ag used as a cathode material no PV behavior was observed, while PV behavior was observed for In, Cr, and Ti cathode materials. The PV behavior and the characteristic parameters including Voc, Isc, FF and PCE were affected by varying the cathode material. The results have shown that the P-OPV device performance can be affected by the cathode material depending on the properties and the work function of the metal. We have also studied the effect of varying the P3HT:PCBM layer thickness at a fixed channel length for Cr and Ti cathode materials and Au as anode. While Voc and FF values do not change, Isc and PCE increase with increasing the layer thickness due to the increase of the light absorption and charges generation. Moreover, we studied the effect of varying the channel length at a fixed film thickness; and showed that the values of Isc and PCE increase with decreasing channel length while Voc and FF maintain the same value. In this thesis we will also present the results on experimentally defining and testing the illuminated area in the P-OPV device by using different measurement set-ups and different v electrodes patterns. The results prove that the illuminated area in the P-OPV device is the area enclosed between the two electrodes. Lastly, we will present the effect of the P3HT:PCBM ratio on the P-OPV device performance. We show that 1:2 ratio is the optimized ratio for the P-OPV device. The detailed results in this thesis show a potential opportunity to help improving and understanding the design of OPV device by understanding the effects of the device structural parameters.