Enhancing Electrical and Heat Transfer Performance of High-Concentrating Photovoltaic Receivers

In a world that is constantly in need of a continuous, reliable and sustainable energy supply, concentrating photovoltaic technologies have the potential to become a cost effective solution for large scale power generation. In this light, important progresses have been made in terms of cell’s design and efficiency, but the concentrating photovoltaic industry sector still struggles to gain market share and to achieve adequate economic returns. The work presented in this thesis is focused on the development of innovative solutions for high concentrating photovoltaics receivers. The design, the fabrication and the characterization of a large cell assembly for high concentrations are described. The assembly is designed to accommodate 144 multijunction cells and is rated to supply energy up to 2.6kWe at 500 suns. The original outline of the conductive copper layer limits the Joule losses to the 0.7% of the global power output, by reducing the number of interconnections. All the challenges and the issues faced in the manufacturing stage are accounted for and the reliability of the fabrication has been proven by quality tests and experimental investigations conducted on the prototype. An indoor characterization shows the receiver’s potential to supply a short-circuit current of 5.77A and an open circuit voltage per cell of 3.08V at 500×, under standard test conditions, only 4.80% and 2.06% respectively lower than those obtained by a commercial single-cell assembly. An electrical efficiency of 29.4% is expected at 500 suns, under standard conditions. A prototype’s cost of $0.91/Wp, in line with the actual price of CPV systems, has been recorded: a cost breakdown is reported and the way to further reduce the cost have been identified and is accounted. In a second approach, the design of a natural convective micro-finned array to be integrated in a single cell receiver has been successfully attempted. Passive cooling systems are usually cheaper, simpler and considered more reliable than active ones. After a detailed review of micro-cooling solutions, an experimental investigation on the thermal behaviour of micro-fins has been conducted and has been combined with a multiphysics software model. A micro-finned heat sink shows the potential to keep the CPV temperature below 100°C under standard conditions and the ability to handle the heat flux when the cell’s efficiency drops to zero. Moreover, a micro-finned heat sink demonstrates the potential to introduce significant benefits in terms of material usage and weight reduction: compared to those commercially available, a micro-finned heat sink has a power-to-weight ratio between 6 and 8 times higher, which results in lower costs and reduced loads for the CPV tracker.EPSRC-funded BioCPV projec

Blockchain, criptoativos e os títulos circulatórios do direito comercial

- Divulgação dos SUMÁRIOS das obras recentemente incorporadas ao acervo da Biblioteca Ministro Oscar Saraiva do STJ. Em respeito à Lei de Direitos Autorais, não disponibilizamos a obra na íntegra.- Localização na estante: 336.74:004 M623

Design, development, and analysis of a densely packed 500x concentrating photovoltaic cell assembly on insulated metal substrate

The paper presents a novel densely packed assembly for high concentrating photovoltaic applications, designed to fit 125x primary and 4x secondary reflective optics. This assembly can accommodate 144 multijunction cells and is one of the most populated modules presented so far. Based on the thermal simulation results, an aluminum-based insulated metal substrate has been used as baseplate; this technology is commonly exploited for Light Emitting Diode applications, due to its optimal thermal management. The original outline of the conductive copper layer has been developed to minimize Joule losses by reducing the number of interconnections among the cells in series. Oversized Schottky diodes have been employed for bypassing purposes. The whole design fits the IPC-2221 requirements. The plate has been manufactured using standard electronic processes and then characterized through an indoor test and the results are here presented and commented on. The assembly achieves a fill factor above 80% and an efficiency of 29.4% at 500x, less than 2% lower than that of a single cell commercial receiver. The novel design of the conductive pattern is conceived to decrease the power losses and the deployment of an insulated metal substrate represents an improvement towards the awaited cost-cutting for high concentrating photovoltaic technologies

General correlations among geometry, orientation and thermal performance of natural convective micro-finned heat sinks

ArticleOpen Access funded by Engineering and Physical Sciences Research Council.The version of record is available from Elsevier at: doi:10.1016/j.ijheatmasstransfer.2015.08.015The interest in micro-technologies has increased in the last decades, because of the low volumes and high performance granted by their application. Micro-fins can find application in several fields, such as power electronics, concentrating photovoltaics and LED. Although micro-technologies have been widely applied in cooling, there is still a lack of knowledge on the thermal behavior of micro-finned heat sinks under natural convective conditions. In the present study, the correspondences between fin geometries and heat transfer coefficients, as well as the effects of the orientation, are experimentally investigated using silicon micro-finned heat sinks with different geometries. The heat sinks are made of 5cm × 5cm squared silicon wafer and the fin height ranges between 0.6mm and 0.8mm, the spacing between 0.2mm and 0.8mm and the thickness between 0.2 and 0.8mm. Power loads higher than those considered in previous works are studied. The experimental setup is validated using a software simulation and the Nusselt number correlation available in literature. The influence of the fin thickness on this parameter is analyzed and a modified correlation is proposed. Also, the effect of the radiative heat exchange on the overall heat transfer is considered and commented. An analysis of the uncertainty is conducted and reported too.Engineering and Physical Sciences Research Council (EPSRC)EPSRC-DST BioCPV projec

A penetration efficiency model for the optimization of solid conical microneedles’ geometry

Microneedles (MNs) are promising alternatives to pills and traditional needles as drug delivery systems due to their fast, localized, and relatively less painful administration. Filling a knowledge gap, this study investigated and optimized the most influential geometrical factors determining the penetration efficiency of MNs. The effects of height, base diameter, and tip diameter were analyzed using the finite element method, with results showing that the most influencing factor was base diameter, followed by height. Moreover, the taper angle, which is dependent on all the geometrical factors, was found to directly affect the penetration efficiency at a fixed height. An additional model was developed to relate the height and taper angle to penetration efficiency, and the results were experimentally validated by compression testing of MN array prototypes printed using two-photon photolithography. The numerical model closely predicted the experimental results, with a root mean square error of 9.35. The results of our study have the potential to aid the design of high-penetration efficiency MNs for better functionality and applicability