Wind is now established in Europe as a major 'renewable energy' resource, but its large scale exploitation is increasingly limited by environmental issues. Hence, on the way to a more sustainable development, it is desirable to seek ways to incorporate it into small scale embedded generation. As a first step, a prototype of a small scale Ducted Wind Turbine has been developed and tested, which seems to be feasible for integration into a conventional building. The wind flow around the building generates differential pressures which may cause an enhanced massflow through the turbine. This thesis is concerned with the investigation of the flow through building integrated duct configurations. Hence, pressure and wind speed measurements have been carried out on a wind tunnel model at different angles of incident wind. Different duct geometries with attached spoilers have been tested, and it was confirmed that wind speeds up to 30 % higher than in the approaching free stream are induced in the duct, in some cases tolerating an angle of incident wind up to 60°. The experimental work proceeded in parallel with Computational Fluid Dynamics modelling. Adaptive gridding of the complex full model geometry required a two dimensional approach, which was used to compare the predicted flow behaviour qualitatively. Three dimensional simulation of the flow field in the building integrated duct could be compared with experimental results. A new flow field mapping approach was initialised to form a two stage process in which conditions in the large-scale flow domain, modelled in a coarse three dimensional simulation, are used as boundary conditions for a localised simulation of the duct flow. Based on performance measurements of a free standing prototype in field trials and the experimentally determined wind speed in the duct, a power prediction model was developed. For the Scottish climate, the proposed device compares favorably with conventional small wind turbines and photovoltaics. The presented work evaluates the concept of harvesting wind energy in the built environment and provides outlines for the future design of a building integrated Ducted Wind Turbine module.

South Africa relies heavily on fossil fuels, particularly coal, to generate electricity and it is a well known fact that the use of fossil fuels contributes to climate change, as it produces greenhouse gases (GHGs). In fact, internationally South Africa is the 17th highest emitter of GHGs (Congressional Research Service (CRS), 2008). Coupled with the environmental consequences of fossil fuel use, South Africa has a further responsibility of addressing the inherited backlog of electricity provision to the rural, and previously disadvantaged communities. In an attempt to address these two problems, the government issued the White Paper on Renewable Energy. In this paper, renewable energy alternatives are proposed to replace a portion of traditional electricity generating methods. Concentrator photovoltaic (CPV) energy generation is one such renewable option available to government. CPV uses optic elements (such as lenses) to concentrate sunlight onto solar cells. Owing to the light being concentrated, the cells in CPV use less semiconductor material, which makes them more efficient in comparison to conventional photovoltaic (PV) cells. CPV is a technology that operates well in regions with high solar radiation. As such, South Africa is particularly well suited for this technology, with average solar radiation levels ranging from 4.5 to 6.5 05 ℎ/. CPV is also well suited for off-grid application, which addresses electricity demand in remote rural areas. This study is an economic project analysis of the installation, operation, maintenance, and decommissioning of CPV technology in a rural area in the Eastern Cape, South Africa. The study area chosen for this purpose is the Tyefu settlement in the Eastern Cape. Tyefu was deemed ideal for this type of analysis due to four characteristics. Firstly, Tyefu is a remote rural settlement at the end of the national grid. Secondly, the community is very poor and previously disadvantaged. Thirdly, many households are without Eskom generated electricity. Lastly, the study area is located in an area with ideal irradiance levels for CPV. Two methods of economic project analysis are applied to this case study, namely a costbenefit analysis (CBA) and a cost-effectiveness analysis (CEA). Additionally, two types of CBA are performed, namely a private CBA and a social CBA. The private CBA evaluates the Tyefu electrification project from a private investor's perspective and the social CBA evaluates the project from society's point of view. The CEAs carried out compare the costeffectiveness of the traditional PV technology to that of CPV in terms of private and social costs. The private costs and benefits of the CPV project were identified and valued in terms of market prices. Then, this cost benefit profile was used to calculate net benefits which in turn were discounted to present values using a private discount rate of 6.42 percent. Three decision making criteria were generated, namely the net present value (NPV), the internal rate of return (IRR) and the benefit cost ratio (BCR). Sensitivity analysis was carried out by varying the private discount rate and the bidding price. The social costs and benefits of the CPV project were identified and valued in terms of shadow prices. This cost benefit profile was used to calculate net benefits. The net benefits were discounted to present values using a composite social discount rate equal to 5.97 percent. The same decision making criteria used in the private CBA were used in the social CBA and a sensitivity analysis was completed by varying the social discount rate. In terms of the private CEA, the costs were identified and valued in terms of market prices. All costs were brought to present values using the private discount rate of 6.42 percent. In terms of the social CEA, the costs were identified and valued in terms of shadow prices. All costs were brought to present values using the social discount rate of 5.97 percent. The cost-effectiveness (CE) ratios calculated have identical denominators since the annual output for both technologies are identical - both CPV and PV systems deliver 30 300 kWh per annum. This output is based on the demand of the given case study. The private CBA showed unfavourable results. The private CBA has a NPV of R2 046 629.01, the IRR is undefined (this is due to no sign change being present in the cost benefit profile), and has a BCR of 0.365. However, the social CBA yielded positive results, with a NPV of R125 616.64, an IRR of 8 percent (which exceeds the social discount rate of 5.97 percent), and a BCR of 1.045. The CEA showed that the CPV is more cost-effective than the traditional PV both in terms of private and social costs. The private CE ratio of CPV is R4.23/kWh compared to PV's CE ratio of R4.39/kWh. Similarly, the social CE ratio of CPV is R3.51/kWh compared to PV's CE ratio of R3.69/kWh. CPV rollout appears to be socially efficient on a small scale according to the social CBA. Consequently, the CPV project is not seen as desirable in terms of the private CBA as the benefit (income received per kWh) in the private analysis is too small to outweigh the costs of implementing and running a CPV plant in Tyefu. On the other hand, a redeeming factor is that CPV may be feasible privately, for large scale applications. A major reason for the CPV project not being appealing to private investors is that the maximum bidding price of R2.85/kWh (as at August 2011) is not high enough for private investors to undertake the CPV project. The sensitivity analysis of the bidding price showed that the bidding price of R2.85/kWh needs to be increased in the range of 250 percent (R7.13/kWh) and 300 percent (R8.55/kWh) for a great enough incentive to exist for private investors. It is thus recommended that policymakers take this into consideration when formulating policy. In terms of the social CBA, it is recommended that government undertake CPV projects of this kind, as it will be a socially desirable allocation of resources. If government were to pursue these types of projects, it is recommended that CPV be implemented as it is more cost effective than PV.

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Joseph Seymour. Includes bibliographical references (leaves 69-70).

With the adoption of the Act on Promotion of Use of Renewable Energy Resources in 2005, the Czech Republic took a significant step forward to examine the economic field of energy in general in light of environmental and climate protection. With this act, the Czech Republic followed the example of other European Union member states in asserting the goal of reducing greenhouse gas emissions and seeking alternative energy resources in the spirit of the Kyoto Protocol obligations. The goal of this Master's thesis is to present and logically analyze the relevant legal legislation concerning renewable resources passed in the Czech law. The emphasis of this analysis of the Act No. 180/2005 Sb. on the Promotion of the Use of Renewable Energy Resources in the context of energy law, whereby the attention is placed on promotion of energy production, those in the Czech Republic represent two alternative schemes: "feed-in tariff" and "green bonus certificates." With the broad definition of renewable energy resources in the introduction, this thesis comprises a basic overview of this comprehensive legal problem. This thesis consists of five separate chapters, which are closely related.

M. Tech. (Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology, / “If we think oil is a problem now, just wait 20 years. It’ll be a nightmare.” — Jeremy Rifkin, Foundation of Economic Trends, Washington, D.C., August 2003. This statement harmonises with the reality that human civilisation faces today. As a result, humankind has been forced to look for alternatives to fossil fuels. Among possible solutions, fuel cell (FC) technology has received a lot of attention because of its potential to generate clean energy. Fuel cells have the advantage that they can be used in remote telecommunication sites with no grid connectivity as the majority of telecommunication equipment operates from a DC voltage supply. Power plants based on phosphoric acid fuel cell (PAFC) have been installed worldwide supplying urban areas, shopping centres and medical facilities with electricity, heat and hot water. Although these are facts regarding large scale power plants for on-site use, portable units have been explored as well. Like any other fuel cell, the PAFC output power is highly unregulated leading to a drastic drop in the output voltage with changing load value. Therefore, various DC–DC converter topologies with a wide range of input voltages can be used to regulate the fuel cell voltage to a required DC load. An interleaved synchronous buck converter intended for efficiently stepping down the energy generated by a PAFC was designed and developed. The design is based on the National Semiconductor LM5119 IC. A LM5119 evaluation board was redesigned to meet the requirements for the application. The measurements were performed and it was found that the converter achieved the expectations. The results showed that the converter efficiently stepped down a wide range of input voltages (22 to 46 V) to a regulated 13.8 V while achieving a 93 percent efficiency. The conclusions reached and recommendations for future research are presented. / Telkom Centre of Excellence, TFMC, M-Tech, THRIP.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Behrooz Mirafzal / Voltage source inverters (VSIs) are an essential interface for grid integration of renewable energy resources. Grid-tied VSIs are employed in power grids to integrate distributed generation units, e.g. photovoltaic arrays, wind turbines and energy storage units, to the utility and extract the maximum energy from the DG units in an efficient manner. However, the stability of VSIs and by extension the entire DG system can be degraded under abnormal grid conditions. In this dissertation, new control and switching techniques for stability and power quality improvement of grid-tied VSIs under abnormal grid conditions are presented. For grids with a low inertia and a low short-circuit ratio, commonly referred to as weak grids, grid connection may make VSIs susceptible to voltage distortion and instability. In this dissertation, through root locus analysis of a detailed state-space model, the design of several circuit and control parameters of the grid-tied VSI are evaluated for improving stability in weak grids. It is shown that grid-side filter inductances can be increased for stable operation of VSIs in weak grids. Accordingly, a virtual inductance emulating the effect of an increased inductance in the grid-side filter is developed in this dissertation, which enables stable operation of VSIs in weak grids without the tradeoffs, i.e. additional voltage drop, increased cost and larger size, associated with a larger inductor. The virtual inductance scheme is realized through the injection of a feedforward current element in the VSI controller through a gain component. The measured grid currents, which are sensed for regular VSI controller operation, are employed as the feedforward component eliminating the need for any additional sensors for the utilization of this control scheme. Furthermore, a direct model reference adaptive control (MRAC) scheme is employed in this dissertation to tune the virtual inductance gain block according to a stable reference model for varying grid conditions. The use of direct MRAC scheme allows tuning of the virtual inductance block without the need for a plant parameter estimation stage. The virtual inductance scheme enables stable operation of VSIs in weak grids without system parameter redesign, thereby maintaining the steady-state performance of the system. The efficacy of the virtual inductance feedforward scheme is verified through hardware tests carried out on a three-phase grid-tied experimental setup. Along with extracting energy from the DG sources, grid-tied VSIs are capable of providing various ancillary services to the utility under abnormal conditions. However, providing ancillary services could drive the inverter voltages beyond the linear modulation region resulting in grid current distortions, which could violate the requirements for grid integration of DGs. An atypical pulse width modulation (PWM) technique is proposed in this dissertation, which maximizes the dc-bus utilization of VSIs, which in turn enables the VSIs to supply the maximum extracted power from the DG units to the grid when providing ancillary services while operating in the linear modulation region. The switching scheme is realized by injecting common mode components in the PWM references, computed based on instantaneous reference magnitudes. The proposed scheme is suitable when providing both symmetrical and asymmetrical ancillary services. In this dissertation, negative-sequence compensation and harmonic compensation are employed as instances of symmetrical and asymmetrical ancillary services. The proposed scheme can be integrated with any control scheme and carrier-based PWM combinations. The efficacy of the proposed atypical PWM scheme is verified through both simulation and hardware tests.

abstract: Nowadays, the widespread introduction of distributed generators (DGs) brings great challenges to the design, planning, and reliable operation of the power system. Therefore, assessing the capability of a distribution network to accommodate renewable power generations is urgent and necessary. In this respect, the concept of hosting capacity (HC) is generally accepted by engineers to evaluate the reliability and sustainability of the system with high penetration of DGs. For HC calculation, existing research provides simulation-based methods which are not able to find global optimal. Others use OPF (optimal power flow) based methods where too many constraints prevent them from obtaining the solution exactly. They also can not get global optimal solution. Due to this situation, I proposed a new methodology to overcome the shortcomings. First, I start with an optimization problem formulation and provide a flexible objective function to satisfy different requirements. Power flow equations are the basic rule and I transfer them from the commonly used polar coordinate to the rectangular coordinate. Due to the operation criteria, several constraints are incrementally added. I aim to preserve convexity as much as possible so that I can obtain optimal solution. Second, I provide the geometric view of the convex problem model. The process to find global optimal can be visualized clearly. Then, I implement segmental optimization tool to speed up the computation. A large network is able to be divided into segments and calculated in parallel computing where the results stay the same. Finally, the robustness of my methodology is demonstrated by doing extensive simulations regarding IEEE distribution networks (e.g. 8-bus, 16-bus, 32-bus, 64-bus, 128-bus). Thus, it shows that the proposed method is verified to calculate accurate hosting capacity and ensure to get global optimal solution. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

One of the biggest threats to the power systems as critical infrastructures is large-scale blackouts resulting from cascading failures (CF) in the grid. The ongoing shift in energy portfolio due to ever-increasing penetration of renewable energy sources (RES) may drive the electric grid closer to its operational limits and introduce a large amount of uncertainty coming from their stochastic nature. One worrisome change is the increase in CFs. The CF simulation models in the literature do not allow consideration of RES penetration in studying the grid vulnerability. In this dissertation, we have developed tools and models to evaluate the impact of RE penetration on grid vulnerability to CF. We modeled uncertainty injected from different sources by analyzing actual high-resolution data from North American utilities. Next, we proposed two CF simulation models based on simplified DC power flow and full AC power flow to investigate system behavior under different operating conditions. Simulations show a dramatic improvement in the line flow uncertainty estimation based on the proposed model compared to the simplified DC OPF model. Furthermore, realistic assumptions on the integration of RE resources have been made to enhance our simulation technique. The proposed model is benchmarked against the historical blackout data and widely used models in the literature showing similar statistical patterns of blackout size.

Distributed generation (DG) with a converter interface to the power grid is found in many of the green power resources applications. This dissertation describes a multi-objective control technique of voltage source converter (VSC) based on multilevel converter topologies, for integration of DG resources based on renewable energy (and non-renewable energy)to the power grid. The aims have been set to maintain a stable operation of the power grid, in case of di erent types of grid-connected loads. The proposed method provides compensation for active, reactive, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently non-linear DG system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the DG output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that signi cantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the DG reference currents, is proposed. The rst step is to extract the DG reference currents from the sensed load currents by applying the stationary reference frame and then transferred into synchronous reference frame method, and then, the reference currents are modi ed, so that the delay will be compensated. The transformed variables are used in control of the multilevel voltage source converter as the heart of the interfacing system between DG resources and power grid. By setting appropriate compensation current references from the sensed load currents in control circuit loop of DG link, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages while required power of loads is more than the maximum injected power of the DG resources. The converter, which is controlled by the described control strategy, guarantees maximum injection of active power to the grid continuously, unity displacement power factor of power grid, and reduced harmonic load currents in the common coupling point. In addition, high current overshoot does not exist during connection of DG link to the power grid, and the proposed integration strategy is insensitive to grid overload. / La Generació Distribuïda (DG) injectada a la xarxa amb un convertidor estàtic és una solució molt freqüent en l'ús de molts dels recursos renovables. Aquesta tesis descriu una técnica de control multi-objectiu del convertidor en font de tensió (VSC), basat en les topologies de convertidor multinivell, per a la integració de les fonts distribuïdes basades en energies renovables i també de no renovables.Els objectius fixats van encaminats a mantenir un funcionament estable de la xarxa elèctrica en el cas de la connexió de diferents tipus de càrregues. El mètode de control proposat ofereix la possibilitat de compensació de les components actives i reactives de la potencia, i les components harmòniques del corrent consumit per les càrregues.La llei de control proporcional-Integral (PI) s’obté de la linearització del model inherentment no lineal del sistema, de forma que el problema de control del corrent injectat i de la tensió d’entrada del convertidor queden desacoblats. Aquest desacoblament permet el control dels corrents de sortida i la tensió del bus de forma independent, però amb un d’ells amb una dinàmica inferior.Per superar els inconvenients del mètode convencional, s’usa un retard computacional, que genera les senyals de referència de forma acurada i sense retard. El primer pas es calcular els corrents de referència a partir de les mesures de corrent. Aquest càlcul es fa primer transformant les mesures a la referència estacionaria per després transformar aquests valors a la referència síncrona. En aquest punt es on es poden compensar els retards.Les variables transformades son usades en els llaços de control del convertidor multinivell. Mitjançant aquests llaços de control i les referències adequades, el convertidor és capaç de compensar la potencia activa, reactiva i els corrents harmònics de la càrrega amb una elevada resposta dinàmica, obtenint uns corrents de la xarxa de forma completament sinusoïdal, i en fase amb les tensions.El convertidor, controlat amb el mètode descrit, garanteix la màxima injecció de la potencia activa, la injecció de la potencia reactiva per compensar el factor de potencia de la càrrega, i la reducció de les components harmòniques dels corrents consumits per la càrrega. A més, garanteix una connexió suau entre la font d’energia i la xarxa. El sistema proposat es insensible en front de la sobrecarrega de la xarxa

Electrification of low-income rural areas that have a limited connection or no access to electrical grids is one of the most demanding challenges in developing countries such as Peru. The international commitment to stop global warming and the reduction in the cost of renewable sources of energy have reduced the prices of fossil fuels in some cases. This has opened the way to the current research which proposes a hybrid energy system (HES) based on the use of renewable sources of energy. Therefore, a renewable electricity system (HRES) was set up at the village of Monte-Catache in the Cajamarca region, which is one of the poorest areas of Peru. Surveys and field studies were used to evaluate the socioeconomic characteristics, availability of renewable energy resources, and energy demand of this region. Potential energy sources were evaluated, and isolated photovoltaic systems with a battery bank were found to be the most appropriate according to the results obtained in the simulation with HOMER. This proposal constitutes an interesting contribution for future energy solutions in isolated and low-income rural areas. / Revisión por pares