This Masters project has involved detailed thermal analysis of a unique renewable energies building. A TRNSYS model of this building has been developed and validated by real measurements and has shown to be capable of accurately predicting room temperatures and total heat gain from a solar-thermal roofing system. Supporting experiments were conducted experimentally and numerically. An experimental solar thermal testing unit constructed for the purpose of validating the solar-thermal roof concept. This experimental apparatus has been used to evaluate the effect of various operating procedures on the total heat gain from the system under a range of meteorological conditions. The validated thermal building model is used to conduct long-term simulations to provide a measure of year-round thermal performance of the building and estimated gains from renewable energy systems. Similar techniques are used to assist in the design and optimisation of a new transportable sustainable building concept in association with StoneWood Homes. It was found that a 4.5kW BIVP/T system could supply the small building with 100% of the yearly electrical energy and space heating requirements.

Important considerations of a photovoltaic (PV) source are achieving a high voltage and drawing currents with very little ripple component from it. Furthermore, the output from such a source is variable depending on irradiation and temperature. In this research, literature review of prior methods employed to boost the output voltage of a PV source is examined and their limitations identified. This research then proposes a multi-phase tapped-coupled inductor boost DC-DC converter that can achieve high voltage boost ratios, without adversely compromising performance, to be used as an interface to a PV source. The proposed converter achieves minimal current and voltage ripple both at the input and output. The suitability of the proposed converter topology for variable input voltage and variable power operation is demonstrated in this dissertation. The proposed converter is also shown to have good performance at high power levels, making it very suitable for high power applications. Detailed analysis of the proposed converter is done. Advantages of the proposed converter are explained analytically and confirmed through simulations and experimentally. Regulation of the converter output voltage is also explained and implemented using a digital controller. The simulation and experimental results confirm that the proposed converter is suitable for high power as well as variable power, variable voltage applications where high voltage boost ratios are required. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] Indium nitride is an important III-V nitride semiconductor with many potential applications such as in high frequency transistors, laser diodes and photo voltaic cells. The mobility and peak drift velocity of this material are predicted to be extremely high and superior to that of gallium nitride. However, many material properties such as the origin of the n-type conductivity and the electronic band gap are not well understood. Moreover, there is limited information on the stoichiometry and the level of impurity contaminations in the films from different growth techniques. The n-type conductivity observed for as-grown indium nitride films has long been attributed to nitrogen vacancies, implying that the material is nitrogen deficient. A band gap value around 2 eV, as measured by the optical absorption method, is suggested by some authors to be a result of the formation of an InNIn2O3 alloy. Alternatively, the observation of a lower absorption edge, suggesting a band gap around 0.7 eV, may be caused by Mie scattering at indium clusters that may form during film growth. Secondary ion mass spectroscopy and x-ray techniques provide only qualitative composition information. The quantitative interpretation of the results relies on calibration samples which are not available for indium nitride. In Rutherford backscattering spectroscopy, while quantitative, the carbon, nitrogen and oxygen signals cannot be separated unless the film is very thin ([tilde]150 nm). However, with heavy ion Elastic Recoil Detection (ERD) analysis all the elements in indium nitride films can be fully separated even for a film thickness of [tilde] 800 nm. In this work, indium nitride films from different growth techniques have been analysed with ERD using 200 MeV 197Au projectiles. The observed nitrogen depletion during the ERD analysis was monitored as a function of projectile fluence using a gas ionisation detector with a large solid angle. Different models have been tested and it has been shown that the bulk molecular recombination model accurately describes the nitrogen depletion so that the original nitrogen-to- indium ratio can be measured with an accuracy of [plus or minus]3 [percent]. The correlation of nitrogen depletion rate and stopping power of the projectile ion has been investigated. The study has shown that the rate of depletion is slower for low-Z projectiles. It has been shown that for a film with good structural properties, no loss of nitrogen occurs during the ERD analysis with low-Z projectiles such as 42 MeV 32S. Thus, the original nitrogen-to-indium ratio can be obtained without any theoretical modelling, and with a precision of better than [plus or minus]1 [percent]. All the indium nitride films studied in this work, for which X-ray diffraction shows no metallic indium, are nitrogen-rich which is contradictory to expectation. Therefore, the common assertion that nitrogen vacancies are the cause of n-type conductivity in as-grown films is diffcult to explain. Instead, the existence of In vacancies, N antisites and interstitial N2 may be speculated. The carbon and oxygen contamination is an issue for films grown by all common growth techniques. However, the suggested correlation of oxygen content in the film with the apparent band gap is not supported by the ERD results. Instead, a correlation between nitrogen-to-indium ratio and the measured band gap has been observed for films grown by RF-sputtering. This work reports the implantation of radioisotope probes using negative ions. The 111In/Cd probe was selected for this work as it is a common Perturbed Angular Correlation (PAC) probe and ideally suited for the study of indium nitride. For the synthesis of the probe 111In/Cd, several possibilities, such as the production of 111In/Cd via nuclear fusion evaporation reactions and from commercially available 111InCl3 solutions, were explored. Different materials, including powders of Al2O3 and In2O3, were investigated as a carrier for the probe in the ion source of the radioisotope implanter. It has been established that combining the 111InCl3 solution as the source and In2O3 powder as the carrier material gives optimum implantation efficiency. The radioisotope implanter facility has been developed to a stage that the radioisotope probe 111In/Cd can be routinely implanted into materials as molecular 111InO?? ions. An implantation rate of 3x10 4[th] Becquerel per hour has been demonstrated. Measurements on different materials (Ag, In, Ni, Si, InP) have shown that condensed matter spectroscopies such as Low Temperature Nuclear Orientation, Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) and Perturbed Angular Correlation can be reliably performed. NMRON measurements on silver indicate a new resonance frequency of 75.08 MHz for 111InAg at 8.0 T. The local lattice environment of indium nitride thin films has been investigated with PAC spectroscopy. Several methods of introducing a radioisotope probe into a host material have been investigated for indium nitride. The thermal diffusion of the radioisotope probe 111In/Cd into indium nitride at a temperature below the dissociation temperature (about 550 [degrees] C) was not possible. The probe was, however, successfully introduced into indium nitride films with ion implantation techniques. Recoil implantation at MeV energies following fusion evaporation reactions and ion implantation at keV energies, both have been investigated for indium nitride films. An interaction frequency of v = 28 MHz has been measured for the 111In/Cd probe in indium nitride. This result is consistent with that obtained for indium nitride bulk grains. The PAC results suggest that all types of indium nitride films have a highly disordered lattice which could only be partially improved by annealing. Furnace annealing in nitrogen atmosphere above 400 [degrees] C resulted in the dissociation of the film. However, such dissociation could be avoided with rapid thermal annealing up to 600 [degrees] C. More detailed defect studies with PAC require the availability of better material. This study has also shown that indium nitride is highly sensitive to ion beam irradiation. Severe depletion of nitrogen during exposure to ions with MeV and KeV energies is an issue for the ion beam characterisation and processing of indium nitride.

[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] Indium nitride is an important III-V nitride semiconductor with many potential applications such as in high frequency transistors, laser diodes and photo voltaic cells. The mobility and peak drift velocity of this material are predicted to be extremely high and superior to that of gallium nitride. However, many material properties such as the origin of the n-type conductivity and the electronic band gap are not well understood. Moreover, there is limited information on the stoichiometry and the level of impurity contaminations in the films from different growth techniques. The n-type conductivity observed for as-grown indium nitride films has long been attributed to nitrogen vacancies, implying that the material is nitrogen deficient. A band gap value around 2 eV, as measured by the optical absorption method, is suggested by some authors to be a result of the formation of an InNIn2O3 alloy. Alternatively, the observation of a lower absorption edge, suggesting a band gap around 0.7 eV, may be caused by Mie scattering at indium clusters that may form during film growth. Secondary ion mass spectroscopy and x-ray techniques provide only qualitative composition information. The quantitative interpretation of the results relies on calibration samples which are not available for indium nitride. In Rutherford backscattering spectroscopy, while quantitative, the carbon, nitrogen and oxygen signals cannot be separated unless the film is very thin ([tilde]150 nm). However, with heavy ion Elastic Recoil Detection (ERD) analysis all the elements in indium nitride films can be fully separated even for a film thickness of [tilde] 800 nm. In this work, indium nitride films from different growth techniques have been analysed with ERD using 200 MeV 197Au projectiles. The observed nitrogen depletion during the ERD analysis was monitored as a function of projectile fluence using a gas ionisation detector with a large solid angle. Different models have been tested and it has been shown that the bulk molecular recombination model accurately describes the nitrogen depletion so that the original nitrogen-to- indium ratio can be measured with an accuracy of [plus or minus]3 [percent]. The correlation of nitrogen depletion rate and stopping power of the projectile ion has been investigated. The study has shown that the rate of depletion is slower for low-Z projectiles. It has been shown that for a film with good structural properties, no loss of nitrogen occurs during the ERD analysis with low-Z projectiles such as 42 MeV 32S. Thus, the original nitrogen-to-indium ratio can be obtained without any theoretical modelling, and with a precision of better than [plus or minus]1 [percent]. All the indium nitride films studied in this work, for which X-ray diffraction shows no metallic indium, are nitrogen-rich which is contradictory to expectation. Therefore, the common assertion that nitrogen vacancies are the cause of n-type conductivity in as-grown films is diffcult to explain. Instead, the existence of In vacancies, N antisites and interstitial N2 may be speculated. The carbon and oxygen contamination is an issue for films grown by all common growth techniques. However, the suggested correlation of oxygen content in the film with the apparent band gap is not supported by the ERD results. Instead, a correlation between nitrogen-to-indium ratio and the measured band gap has been observed for films grown by RF-sputtering. This work reports the implantation of radioisotope probes using negative ions. The 111In/Cd probe was selected for this work as it is a common Perturbed Angular Correlation (PAC) probe and ideally suited for the study of indium nitride. For the synthesis of the probe 111In/Cd, several possibilities, such as the production of 111In/Cd via nuclear fusion evaporation reactions and from commercially available 111InCl3 solutions, were explored. Different materials, including powders of Al2O3 and In2O3, were investigated as a carrier for the probe in the ion source of the radioisotope implanter. It has been established that combining the 111InCl3 solution as the source and In2O3 powder as the carrier material gives optimum implantation efficiency. The radioisotope implanter facility has been developed to a stage that the radioisotope probe 111In/Cd can be routinely implanted into materials as molecular 111InO?? ions. An implantation rate of 3x10 4[th] Becquerel per hour has been demonstrated. Measurements on different materials (Ag, In, Ni, Si, InP) have shown that condensed matter spectroscopies such as Low Temperature Nuclear Orientation, Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) and Perturbed Angular Correlation can be reliably performed. NMRON measurements on silver indicate a new resonance frequency of 75.08 MHz for 111InAg at 8.0 T. The local lattice environment of indium nitride thin films has been investigated with PAC spectroscopy. Several methods of introducing a radioisotope probe into a host material have been investigated for indium nitride. The thermal diffusion of the radioisotope probe 111In/Cd into indium nitride at a temperature below the dissociation temperature (about 550 [degrees] C) was not possible. The probe was, however, successfully introduced into indium nitride films with ion implantation techniques. Recoil implantation at MeV energies following fusion evaporation reactions and ion implantation at keV energies, both have been investigated for indium nitride films. An interaction frequency of v = 28 MHz has been measured for the 111In/Cd probe in indium nitride. This result is consistent with that obtained for indium nitride bulk grains. The PAC results suggest that all types of indium nitride films have a highly disordered lattice which could only be partially improved by annealing. Furnace annealing in nitrogen atmosphere above 400 [degrees] C resulted in the dissociation of the film. However, such dissociation could be avoided with rapid thermal annealing up to 600 [degrees] C. More detailed defect studies with PAC require the availability of better material. This study has also shown that indium nitride is highly sensitive to ion beam irradiation. Severe depletion of nitrogen during exposure to ions with MeV and KeV energies is an issue for the ion beam characterisation and processing of indium nitride.

Made available in DSpace on 2014-12-17T14:57:47Z (GMT). No. of bitstreams: 1 EdvaldoGS.pdf: 1519752 bytes, checksum: ed321ceae5e05555d63b38c5361fd548 (MD5) Previous issue date: 2007-05-31 / The conversion of solar energy in electric with photo-voltaic cells has been carried through exclusively with devices of semiconducting junction. To put this situation comes moving for better in them last years, thanks to a new technology of production of known solar cells as Dye Solar Cell. This proposal aims at to develop a DSC having as dye lavonoides of the Capsicum frutescens (malagueta pepper). Front is considered to evaluate the photo-voltaic parameters varies it regions of the visible specter, as well as a good efficiency of conversion / A convers?o de energia solar em energia el?trica com c?lulas fotovoltaicas tem sido realizada exclusivamente com dispositivos de jun??o semicondutora. Por?m, esta situa??o vem mudando para melhor nos ?ltimos anos gra?as a uma nova tecnologia de produ??o de c?lulas solares conhecidas como Dye Solar Cell, ou C?lulas Solares de Corantes Fotoexcit?veis (CSCF). Neste trabalho desenvolveu-se o ?xido de tit?nio pelo processo dos precursores polim?ricos para montagem de uma CSCF tendo-se como corante os flavon?ides da Capsicum frutescens, (pimenta malagueta). Foram avaliados os par?metros de pot?ncia, resposta corrente em fun??o da tens?o, corrente de pot?ncia m?xima e tens?o de pot?ncia m?xima frente ao espectro vis?vel

- Einführung in das Projekt Solar Impulse (Entstehung, Herausforderung, Errungenschaften) - Beschreibung der eingesetzten Software Tools zur Entwicklung des Flugzeuges - Fallbeispiele für den Einsatz von Mathcad

A TPV-system consists of a hot surface emitting heat radiation on a solar cell with a narrow bandgap.  A unit consisting of a boiler and a TPV-system has been constructed for testing of the performance of TPV cells. The emitter is heated by a fuel consisting of RME-oil. The radiation is collected and concentrated through two reflecting cones formed like a Faberge-egg, with an edge-type optical filter between the cones. The Faberge-egg is treated with electro-polishing in order to obtain a high reflectance of radiation. The edge filter transmits radiation of short wavelengths towards the solar cells and reflects long wavelengths back to the emitter. This increase the temperature of the emitter to prevent the TPV-cells to be overheated. The construction made was working as expected and can be used for further experiments. The performance of the TPV-cells were however very poor because of a low emitter temperature. The main problem was to obtain a good heat transport from the flame to the emitter. It is required that the emitter temperature is considerably increased for justifying a continued work on TPV-systems in combination with boilers.