Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-20T15:19:24Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ANÁLISE OPERACIONAL DE UM SISTEMA FOTOVOLTAICO COM ALTA CONCENTRAÇÃO DE 10 kWp INTERLIGADO À REDE.pdf: 7127801 bytes, checksum: 39d3f0fe3404be063b56673557bb9d3d (MD5) / Made available in DSpace on 2016-07-20T15:19:24Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ANÁLISE OPERACIONAL DE UM SISTEMA FOTOVOLTAICO COM ALTA CONCENTRAÇÃO DE 10 kWp INTERLIGADO À REDE.pdf: 7127801 bytes, checksum: 39d3f0fe3404be063b56673557bb9d3d (MD5) Previous issue date: 2015-08-13 / CNPq / No presente estudo foi avaliado o comportamento da eficiência na geração de energia, desempenho e influência sobre os parâmetros de operação da rede elétrica de um Sistema Fotovoltaico de Alta Concentração (HCPV- High Concentrating Photovoltaics) interligado à rede em condições reais de operação. O sistema foi instalado no Departamento de Energia Nuclear (DEN) da UFPE. Os ensaios experimentais, realizados com medições do recurso solar incidente no local de instalação, permitiram estabelecer o comportamento da energia gerada em condições instantâneas, médias diárias e mensais. O sistema HCPV foi comparado com um sistema convencional de Silício policristalino (Si-P), de capacidade similar, operando nas mesmas condições meteorológicas durante o mesmo período. Ao longo do período de análise verificou-se que devido ao alto índice de nebulosidade, o recurso solar em Recife não promove condições vantajosas para o aproveitamento da elevada eficiência de conversão do sistema HCPV, em média 22%, chegando a níveis de 26%. Quando comparado com o sistema Si-P, embora o sistema HCPV apresente uma eficiência maior, o mesmo gerou, em Recife, 22% a menos de energia que o sistema Si-P, devido à capacidade do Si-P de aproveitar a irradiância global, em média 40% maior que a direta normal vista pelo sistema HCPV. Para realizar uma comparação entre o desempenho e a energia gerada pelos dois sistemas foi utilizado o índice de desempenho (PR - Performance Ratio) e o fator de capacidade. Uma simulação com base nos resultados experimentais, comparando os dois sistemas, foi realizada para as cidades de Petrolina (PE), São Martinho (RS) e Barra (BA). Verificou-se que o sistema HCPV é capaz de gerar 9% a mais de energia em Petrolina que o Si-P. Os valores obtidos para São Martinho e Barra foram 22% e 32% superiores, respectivamente. Os resultados mostram que o sistema HCPV pode vir a ser viável para as localidades, com elevados níveis de irradiância direta. Foi possível verificar que devido à pequena potência instalada do sistema HCPV (10 kWp) - comparada ao nível de consumo de energia do DEN - não houve influência apreciável sobre os parâmetros de operação da rede elétrica. / This work presents an analysis of the power generation, efficiency’s behavior, performance and influence on the electrical grid of a High Concentrating Photovoltaic system (HCPV) connected to the grid operating under real conditions. The system was installed at Nuclear Energy Department (DEN) - UFPE. The experimental tests, with measurements of the solar radiation resources at the installation site, allowed establishing the behavior of generated energy in instantaneous conditions, daily and monthly averages. The HCPV system was compared with a conventional polysilicon (Si-P) system, similarly capacity, operating under the same weather conditions over the same period. Along the analysis period, it was found that due to the high amount of cloud cover, the solar resource in Recife does not promote favorable conditions to take advantage of the high conversion efficiency of the HCPV system, with average of 22%, reaching levels of 26%. When compared with the Si-P system, although the HCPV presents higher efficiency, it has generated, in Recife, 22% less energy than the Si-P system due to the ability of the Si-P to take advantage of the global irradiance, in average 40% higher than the direct normal irradiance “view” by the HCPV system. Making a comparison of the performance and of the energy generated by the two systems we used the performance ratio (PR - Performance Ratio) and capacity factor. A simulation based on the experimental results, comparing the systems, was held for the cities of Petrolina (PE), St. Martin (RS) and Barra (BA). It was found that the HCPV system is capable to generate 9% more energy in Petrolina than the Si-P. The values obtained for St. Martin and Barra were 22% and 32% larger, respectively. The results show that the HCPV system could be viable for locations with high levels of direct irradiance. The analysis of the behavior of the HCPV system connected to electrical grid shows that due to the small installed capacity of HCPV system (10kWp) - compared to the level of the Nuclear Energy Department power consumption - no appreciable influence on the operating parameters of the electric grid could be detected.

Dieser Beitrag untersucht die Verluste elektrischer Maschinen in Abhängigkeit von der verwendeten Stromrichtertopologie und bei verschiedenen Pulsfrequenz. Beispielhaft wird eine permanentmagneterregte Synchronmaschine (PMSM) mit einer Bemessungsleistung von 18 kW behandelt. Zum Betrieb der Maschine wird der Prototyp des 3-Level-Stromrichters LT300-ML von M&P Motion Control and Power Electronics GmbH (M&P) verwendet. Beim 3-Level-Stromrichter werden mehr Spannungsebenen geschaltet als beim 2-Level-Stromrichter. Dies führt zu einer geringeren Stromwelligkeit und u. a. zu geringeren Verlusten in der Maschine. Die Messergebnisse zeigen, dass die Maschinenverluste im Vergleich zum Einsatz eines 2-Level-Stromrichters um 20 ... 30 % reduziert werden können. Für die Untersuchung wird der M&P-Maschinen-Prüfstand verwendet. / This paper deals with the losses of electrical machines depending on the converter topology used and with different switching frequency’s. A permanent magnet synchronous machine (PMSM) with a rated output power of 18 kW is investigated. As power converter the LT300-ML (3-level converter) from M&P Motion Control and Power Electronics GmbH (M&P) is used. By using a 3-level topology, more voltage levels are switched than with a 2-level topology. This, among other things, results in a lower current ripple and lower losses in the machine. The measurement results show that the machine losses can be reduced by 20 ... 30 % compared to the use of a 2-level converter. The M&P machine test bench is used for the investigation.

Laser high-order harmonic generation in the presence of relatively weak interfering light is investigated. The interfering pulses intersect the primary harmonic-generating laser pulse at the laser focus. The interfering light creates a standing intensity and phase modulation on the field, which disrupts microscopic phase matching and shuts down local high harmonic production. Suppression of the 23rd harmonic (by two orders of magnitude) is observed when a counter-propagating interfering pulse of light is introduced. A sequence of counter-propagating pulses can be used to shut down harmonic production in out-of-phase zones of the generating volume to achieve quasi phase matching. Harmonic emission is enhanced in this case. A new high-power laser system with higher pulse energy has been constructed to further investigate quasi phase matching of high-order harmonics generated in difficult-to-ionize atomic gases (e.g., neon as opposed to argon). The new system can also be used to study harmonic generation in ions. A new counter-propagating beam produces a train of 5 pulses with regulated timing. In preliminary tests, the new system has produced high harmonics up to the 65th order in neon. This should increase with additional adjustments to the laser system. The high-order harmonics have also demonstrated to be useful for polarized reflectometry measurements of optical surfaces in the extreme ultraviolet (EUV) wavelength range.

We investigate the spatial evolution of an intense laser pulse as it generates high-order harmonics in a long gas cell, filled with 80 torr of helium. A thin foil separates the gas-filled region of the cell from a subsequent evacuated region. The exit plane of the gas cell can be scanned along the laser axis so that the evolution of the laser throughout the focus can be observed (full scanning range of 9 cm). We constructed an apparatus that images the laser radial energy profile as it exits the cell. The high harmonics, odd orders ranging from 45 to 91, are observed at the same time that the laser spot is characterized. Re-absorption of the harmonics within the gas cell restricts the region of harmonic emission to the final centimeter (or less) of the cell. We present the first direct evidence (to our knowledge) of laser filamentation under conditions ideal for high-order harmonic generation. The 30 fs, 4 mJ, laser pulses were observed to undergo double focusing within the gas cell, with about 4 cm separating the two foci. The region with best harmonic emission occurs midway between the two foci. The radial profile of the laser focus, 150-200 microns in diameter, evolves from a Gaussian-like profile to a more square-top profile as it propagates over several centimeters. The filamentation phenomenon as well as the brightness of the harmonics improves when an aperture is partially closed on the laser beam before reaching the focusing mirror. A spectral sampling of the imaged laser focus revealed a 4 nm blue-shift associated with the generation of plasma in the gas cell. The blue-shifting occurs primarily in the center of the laser beam and less at the wider radii. The initial laser pulse had a spectrum centered at 800 nm with a 35 nm bandwidth. The energy associated with each of the observed 26 harmonic beams was found to be approximately 1 nJ, yielding a conversion efficiency of approximately 2e−7.

This dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design, growth and fabrication processes of the laser chip are discussed, and its experimental data is presented. In order to further increase the TEP laser efficiency the development of QDs as the active region for TEP edge emitting laser (EEL) is studied. The usage of QD as TEP laser's active region is significant in terms of its low threshold current density, low internal optical loss and high reliability, which are mainly due to low transparency in QD laser. The crystal growth of self-organized QDs in molecular beam epitaxial (MBE) system and characterization of QDs are mentioned. The design, growth, processing and fabrication of a QD laser structure are detailed. The characteristics of laser devices with different cavity length are reported. QD active regions with different amount of material are grown to improve the active region performance. Theoretical calculations based on material parameters and semiconductor physics indicate that with proper design, the combination of high efficiency LED in TEP regime with a QD laser can result in the integrated laser chip power conversion efficiency exceeding unity.

Extreme Ultraviolet (EUV) sources rely on droplet laser plasmas for EUV generation. These sources consist of a small (30 µm diameter) droplet which is excited into plasma emitting EUV around 13.5 nm, the industry’s chosen wavelength for EUV lithography (EUVL). These sources are the best candidates for the commercialization of EUVL allowing mass production of computer chips with 32 nm or even smaller feature size. However, the biggest challenges which EUV source developers encounter today are the issues of conversion efficiency (CE) and debris. In order to satisfy the technology requirements, the source will need to meet high levels of stability, performance, and lifetime. Our tin-doped droplet plasma has demonstrated high CE and low debris resulting in long lifetime. Long term stability is obtained through the use of novel tracking techniques and active feedback. The laser plasma targeting system combines optical illumination and imaging, droplet technology innovation, advanced electronics, and custom software which act in harmony to provide complete stabilization of the droplets. Thus, a stable, debris-free light source combined with suitable collection optics can provide useful EUV radiation power. Detailed description of the targeting system and the evaluation of the system will be presented.

No description available.

In this thesis the development of a high efficiency harmonic re-radiator, consisting of a diode doubler and conjugate-matched receive and transmit antennas, is described. Diode-based frequency multipliers and rectifiers, coupled with antennas, are of interest for quasi-optical applications, for energy-scavenging and for sensing applications. The device studied operates by receiving an interrogating signal at a frequency of 1.3 GHz and re-radiating a signal at 2.6 GHz. The primary goal of this research was to develop a passive, miniature and effective frequency doubler integrated with planar antennas. The system is referred to as a frequency doubling reflectenna, (FDR). Prediction of accurate performance was achieved by employing precise modeling and measurement methods. The FDR can be utilized in data collection applications. The footprint of the FDR is occupied primarily by the receive and transmit antennas. Therefore, a significant portion of the research focused on the development of compact and efficient planar antennas, which would provide for a miniature FDR. A first-generation FDR design was designed, which utilized quarter-wavelength shorted microstrip patch antennas. The choice of antennas provided a small prototype with dimensions equal to 44 mm by 17 mm. In order to further reduce the size of the harmonic re-radiator, meandered planar antennas were investigated and optimized for efficient operation. A second-generation FDR design, which utilized meandered microstrip patch antennas, was produced and a size reduction of 75% was achieved. Both first- and second-generation harmonic re-radiator designs were designed for low input power operation and provided maximum measured conversion efficiencies of approximately 4.5% and 1.8%, with the input to the diode doubler at -14.5 and -17.5 dBm, respectively. Re-configurable microwave devices, which dynamically operate at different frequencies, are often desirable for sensing applications. Therefore, to conclude this research, a tunable FDR was realized using a semiconductor varactor that provided the dynamic capacitance required for the tunability.

Because of its excellent and unique physical properties, ZnO nanowires have been widely used in numerous scientific fields such as sensors, solar cells, nanogenerators, etc. Although it is believed that single crystal ZnO has a much higher electron transfer rate than TiO₂, it was found that ZnO nanowire-based dye-sensitized solar cells (DSSCs) have lower efficiencies than TiO₂ nanoparticle-based DSSCs because the density and surface area of ZnO nanowires are usually lower than that of TiO₂ nanoparticles, limiting the cell's light absorption, and because the open-root structure of ZnO nanowires results in electron back transfer that causes charge shortage of the cell. Here, experimental studies were performed that utilize strategic manipulations of the design of the ZnO nanowire based DSSCs in efforts to address and solve its key challenges. It was shown that by incorporating various blocking layers into the design of the cell, the performance of the DSSC can be improved. Specifically, by placing a hybrid blocking layer of TiO₂-P4VP polymer between the substrate and the ZnO nanowires, the conversion efficiency of the cell was 43 times higher than that of a cell without this blocking layer due to the reduction of electron back transfer. Furthermore, in efforts to improve the surface area of the ZnO nanowire array, unique three dimensional structures of ZnO nanowires were fabricated. It was found that by significantly improving the overall density and surface area of the ZnO nanowire array through distinctive hierarchal nanowire structures, the light harvesting efficiency and electron transport were enhanced allowing the DSSC to reach 5.20%, the highest reported value for 3D ZnO NW based DSSCs. Additionally, the development of a theoretical model was explored in efforts to investigate how the geometry of ZnO nanowires affects the incident photon-to-current conversion efficiency of 1D ZnO nanowire-based N719-sensitized solar cells at the maximum absorption wavelength of 543 nm.

This thesis presented the research, design and fabrication associated with a unique application of rectenna technology combined with lock-in amplification. An extremely low-power harmonic transponder is conjoined with an interrogator base-station, and utilizing coherent demodulation the Remote Lock-In Amplifier (RLIA) concept is realized. Utilizing harmonic re-radiation with very low-power input, the 1st generation transponder detects a transmitted interrogation signal and responds by retransmitting the second harmonic of the signal. The 1st generation transponder performs this task while using no additional power besides that which accompanies the wireless signal. Demonstration of the first complete configuration provided proof of concept for the RLIA and feasibility of processing relevant information under "zero" power operating conditions with a remote transponder. Design and fabrication of a new transponder where the existing zero-bias transponder was modified to include a DC bias to the diode-based frequency doubler is presented. Applied bias voltage directly changed the impedance match between the receiving 1.3 GHz antenna and the diode causing a change in conversion loss. Testing demonstrated that a change in conversion loss induces an amplitude modulation on the retransmission of the signal from the transponder. A test of bias sweep at the optimal operating frequency was performed on the 2nd generation transponder and it was seen that a change of ~ 0.1 V in either a positive or negative bias configuration induced an approximate 15 dB change in transponder output power. A diode-integrated radar detector is designed to sense microwaves occurring at a certain frequency within its local environment and transform the microwave energy to a DC voltage proportional the strength of the signal impinging on its receiving antenna. The output of the radar detector could then be redirected to the bias input of the 2nd generation transponder, where this DC voltage input would cause a change in conversion loss and modulate the retransmitted interrogation signal from the transponder to the base station. When the base station receives the modulated interrogation signal the information sensed by the radar detector is extracted. Simulations and testing results of the fabricated radar detector demonstrate capability of sensing a signal of approximately -53.3 dBm, and accordingly producing a rectified DC voltage output of 0.05 mV. A comparison is made between these findings and the transponder measurements to demonstrate feasibility of pairing the radar detector and the 2nd generation transponder together at the remote sensor node to perform modulation of interrogation signals.