Design and Validation of an LED-Based Solar Simulator for Solar Cell and Thermal Testing

An LED-based solar simulator has been designed, constructed, and qualified under ASTM standards for use in the Cal Poly Space Environments Laboratory. The availability of this simulator will enhance the capability of undergraduate students to evaluate solar cell and thermal coating performance, and offers further research opportunities. The requirements of ASTM E927-19 for solar simulators intended for photovoltaic cell testing were used primarily, supplemented by information from ASTM E491-73 for solar simulators intended for spacecraft thermal vacuum testing. Three main criteria were identified as design goals - spectral match ratio, spatial non-uniformity, and temporal instability. An electrical design for an LED-based simulator to satisfy these criteria was developed and implemented, making use of existing lab equipment where possible to minimize cost. The resulting simulator meets the desired spatial non-uniformity and temporal instability requirements of ASTM E927-19, but falls short of the spectral match ratio needed. This is shown to be due to a calibration issue that is easily amended via software. The simulator is overall Class UCB under ASTM E927, and Class CCC under ASTM E491. The simulator was used to conduct the same laboratory procedure for solar cell I-V curve testing as performed by undergraduate students, showing excellent promise as a course enhancement

Solar spectral irradiance - measurement and application in photovoltaics

This thesis presents the outcome of investigations undertaken in the field of terrestrial spectral solar irradiance characterisation and its impact on photovoltaics. Spectral irradiance has not previously been widely researched in the context of photovoltaic applications. Long-term, natural environment spectral irradiance observations are practically non-existent with availability very limited in terms of covered period, temporal resolution and site location. The work presented concentrates on four major aspects of spectral irradiance: spectroradiometer calibration spectral irradiance calibration transfer standards natural spectral irradiance variability and its impact on photovoltaic device efficiency impact of reference sensor spectral mismatch on accuracy of reference irradiance measurement

Light-emitting diodes and photodiodes in the deep ultra-violet range for absorption photometry in liquid chromatography, capillary electrophoresis and gas sensing

Absorbance measurement in the deep ultra-violet range (below 300 nm) has been one of the most widely used detection methods for analytical techniques as a large number of organic compounds have strong absorption bands in the deep UV region. The use of incandescent or discharge lamps coupled to a monochromator for the wavelength selection in a conventional UV detector makes it complex and costly. Light-emitting diodes (LEDs) for the deep UV range commercially available in recent years have become potential alternatives to thermal light sources. LEDs with their relatively narrow emission bandwidths (typically 20 nm) are well suited for absorption photometry in which a monochromator is not required. This dissertation, therefore, concerns the utilization LEDs and photodiodes (PDs) in the deep UV range as radiation sources and light detectors, respectively for absorption photometry in high-performance liquid chromatography (HPLC), capillary electrophoresis (CE) and gas sensing. LEDs were known to perform as light detectors. In measuring systems based on LEDs as light sources, PDs have been normally employed for detection devices. The practical reasons for the use of LEDs as alternatives to PDs, however, have not been demonstrated. Only an advantage of cost-saving was pointed out. In the first project, the performance of LEDs in the light intensity measurement was investigated and compared to that of standard silicon PDs in three different measuring configurations: current follower mode to measure to photocurrents, photovoltaic mode to determine the voltage developed across the diode on irradiation without load and discharge time mode to measure the rate to discharge the junction capacitance of diodes. LEDs as detectors were generally found to be adequate for the analytical work but PDs offered higher sensitivity and linearity as well as provided stable readings with faster settling times. Absorbance detectors for narrow-column HPLC (250 μm inner diameter) and CE (50 μm inner diameter) based on deep UV-LEDs and PDs selective for emission wavelengths were developed and evaluated in the quantification of model compounds at 255 and 280 nm. Absorbance measurements were directly obtained by the use of a beam splitter and PDs for reference signals and a logarithmic ratio amplifier-based circuitry to emulate the Lambert-Beer’s law. Narrow-column HPLC is useful for the applications in which the reduction in eluent consumption is desired or only limited amount of samples is available when utmost sensitivity is not required. In CE, the use of a capillary as the separation channel to minimize the peak broadening downscales the detection window to micrometer range which is even much narrower than that of a narrow-bore HPLC. This makes the design and construction of these LED-based detectors for narrow detection channels more challenging than for a standard HPLC as the higher efficiency for light coupling and stray light avoidance is essentially required. Additionally, high mechanical stability is needed to minimize the noise resulted from mechanical fluctuations. The performance of these optical devices at two measured wavelengths was excellent in terms of the baseline noise (low μAU range), linearity between absorbance values and concentrations (correlation coefficients > 0.999) and reproducibility of peak areas (about 1%). Not only was the potential of a deep UV-LED as a radiation source for absorption spectroscopy investigated for separation techniques but also for the detection of benzene, toluene, ethylbenzene and the xylenes compounds in the gas phase at 260 nm. In the first part of this work, its performance in the acoustic waves excitation was preliminarily investigated with some different measuring systems for the detection of the toluene vapor. It was found that the intensity of a deep UV-LED was insufficient to produce detectable acoustic signals. This was followed by the construction of an absorbance detector for the determination of these target compounds based on the combination of a deep UV-LED and PDs. This optical device was designed to use optical fibers for the light coupling from the LED to a measuring cell and a reference PD, that allows removing a beam splitter previously required for detectors of a narrow column HPLC and CE. Its performance with regard to linearity and reproducibility was satisfactory. Detection limits of about 1 ppm were determined. It could be concluded that viable absorbance detectors for narrow-column HPLC, CE and gas sensing based on deep UV-LEDs and PDs as light sources and light detectors, respectively can be constructed. The performance of these inexpensive LED-based optical devices with regard to linearity, reproducibility and baseline noise was satisfactory and found to be comparable to that of more complex and expensive commercial detectors. These detectors with features of low power consumption and small size are useful for portable battery-powered devices

Characterization Equipment of Aerospace Photovoltaic Panels

The main purpose of this project is the development of a system able to characterize solar panels in order to obtain higher TRL levels. This system consist of a photovoltaic measurement system and a low cost home-made Thermal and Vacuum Chamber. Furthermore, the system is managed by a graphical user interface where the obtained curves and data can also be visualized. From the beginning of the project, the methodology sought a product and market oriented philosophy. Each decision concerning the project’s development, without exception, is taken considering all the criteria involves, that is, engineering criteria as well as the pricing and the market availability. In this manner, the project arises from requirements which might be given by an assumed and imaginary client. Technical requirements emerge then from those previous requirements. Afterwards, a complete process involving analysis, design and implementation is carried out. This project is presented as a Master Thesis within the Master in Telecommunication Engineering of the University of Granada. Therefore, it is captivating to not merely focus on a specialised but also a multidisciplinary approach in which the student uses the competences acquired during the academic period as well as the concepts learn by the realization of this work. In order to enhance the significance of the project, several and distinct technologies are used. Some of the technologies used during the project are instrumentation and control, CAD/CAM design and software design. Moreover, the management system is presented via GUI which focus on the user experience and the ease of use. This system is intended to be a crucial tool for the new projects and challenges the GranaSAT Team will face. The result of this work concludes obtaining a comprehensive measurement system which meets the Functional and the Client’s Technical Requirements previously specified.El propósito principal de este trabajo es desarollar un sistema de caracterización de paneles solares aerospaciales que permita obtener un mayor TRL y afrontar con mayores garantías las certificaciones necesarias para poner en orbita un componente electrónico. Estas certificaciones se realizan para asegurar que dicho componente soportará las adversas condiciones de vacío y temperatura que tienen lugar en el espacio. El sistema desarollado esta compuesto por un subsistema de medida de paneles fotovoltaicos y una cámara TVAC de bajo coste diseñada y manufacturada de forma casera. Además, el sistema es controlado por medio de una interfaz de usuario encargada tanto de la configuración de los equipos como de la representación y el almacenamiento de los datos obtenidos por medio de las pruebas realizadas. Desde el comienzo del proyecto se sigue una metodología orientada tanto al producto como también a la situación del mercado, lo cual implica que cada decisión es tomada tras analizar todos los factores influyentes. Esos factores pueden ser tanto técnicos o ingenieriles como económicos o disponibilidad comercial. De esta forma, el proyecto se desarrolla a partir de los requrimientos técnicos facilitados por un cliente hipotético, a partir de los cuales, se obtienen los requerimientos funcionales de ingeniería. Posteriormente, se realiza un exhaustivo proceso de análisis, diseño e implementación del producto. Este proyecto se presenta como Trabajo Fin de Máster de la titulación de Máster de Ingeniería de Telecomunicación de la Universidad de Granada. Una idea interesante es afrontar el proyecto con un enfoque multidisciplinar en el cual el alumno es capaz de demostrar no solo los conceptos aprendidos durante esta etapa académica, sino también, los aprendidos en su especialidad, durante el Grado de Telecomunicación, y los desarrollados durante la realización de este mismo proyecto. Varias y distintas tecnologías han sido empleadas durante este proyecto con el fin de aportar un valor añadido al mismo. Algunas de estas tecnologías son el control y configuracion de equipos electónicos, el uso de software de diseño CAD/CAM y otras herramientas de software y programación. Además, el sistema de control se presenta por medio de una GUI la cual se centra en la funcionalidad, su facilidad de uso y la experienca final del usuario. El objetivo es que este sistema se consolide como una herramienta crucial para los futuros y exitosos retos que aguardan al equipo GranaSAT. Este proyecto culmina con la obtención de un sistema de caracterización completo, el cual garantiza su cumplimiento de los requerimientos técnicos del cliente y los requisitos funcionales de ingeniería derivados de estos.GranaSA

The global energy landscape and materials innovation

Availability of affordable energy has enabled spectacular growth of industrialization and human development in all parts of the world. With growth now accelerating in developing countries, demands on energy sources and infrastructure are being stretched to new limits. Additional energy issues include the push for renewable resources with reduced greenhouse gas emissions and energy security affected by the uneven distribution of energy resources around the globe. Together, these issues present a field of opportunity for innovations to address energy challenges throughout the world and all along the energy flow. These energy challenges form the backdrop for this special expanded issue of MRS Bulletin on Harnessing Materials for Energy. This article introduces the global landscape of materials issues associated with energy. It examines the complex web of energy availability, production, storage, transmission, distribution, use, and efficiency. It focuses on the materials challenges that lie at the core of these areas and discusses how revolutionary concepts can address them. Cross-cutting topics are introduced and interrelationships between topics explored. Article topics are set in the context of the grand energy challenges that face the world into the middle of this century

Phase Change Materials as thermal energy storage and management in solar energy-based systems

Le risorse energetiche rinnovabili hanno una natura intermittente e i sistemi di accumulo dell'energia sono fondamentali per aumentare la loro affidabilità. Tra le alternative, i materiali a cambiamento di fase (PCM) sfruttano il passaggio di fase solido-liquido (a temperatura quasi costante) per accumulare energia. I PCM mantengono più bassa la temperatura dei sistemi dove applicati, riducendo le dispersioni di calore verso l'esterno e per auto scarica. Questo lavoro si concentra su applicazioni basate su energia solare, in particolare pannelli fotovoltaici e laghi solari a gradienti salini.Renewable energy sources suffer from an intermittent nature and energy storage systems are a crucial step to increase their reliability. Among the alternatives, Phase Change Materials (PCM) belong to the latent thermal storage group, and exploit the solid-liquid phase change (at nearly constant temperature) to store energy. PCMs allows to reduce the heat loss outwards and the auto-discharge thermal losses, storing energy at lower the temperatures. This work investigates their applications in solar-based system to improve the energy performance, focusing on photovoltaic panels and solar ponds

SUSTAINABLE ENERGY FOR El YUNQUE NATIONAL FOREST

Puerto Rico\u27s El Yunque National Forest faces problems with excessive energy use and high electricity prices, which reduce resources available for important land management projects. This project outlines and investigates alternative energy production and energy conservation techniques as both environmentally responsible and sustainable solutions to these problems. The project team investigated possible solutions by performing site analysis, estimating energy production, evaluating environmental impacts, and performing cost analysis. These investigations culminated in recommendations to the United States Forest Service that solar power, hydropower, and multiple conservation techniques be implemented in El Yunque National Forest to reduce annual electricity expenditures

Manufacture and Investigation of Organic Composite Polymer Based Films for Advanced Flexible Solar Cells

Modern society has created big challenges in the area of sustainable supply of energy to satisfy the needs of growing population and to account for depleting fossil fuel resources. The Irish Government has set targets for the energy sector by 2020, with 33% of electricity to be generated from renewable sources. Organic photovoltaic devices offer several advantages over expensive silicon solar cells, including deposition of ultra-thin films by spin-coating, printing and spray-coating. This in turn provides for the exciting possibility to make lightweight, flexible solar cells for a broad range of existing and emerging applications for security, military and medicine. This research project was inspired by the current drive into finding alternative technologies and materials for the design and manufacture of advanced solar cells. The primary objective was to tailor the properties of Poly3Hexylthiophene: PhenylC60 Buturic Acid Methyl Esther composite (P3HT:PCBM) thin films for flexible organic solar cells performance. The extensive experimental work was conducted to reveal the effect of the solar irradiation and thermal annealing on the dielectric, optical and electrical properties of P3HT:PCBM thin films. A common degradation pattern was demonstrated in the films after UV exposure whereby the optical absorbance and the resistivity were shown to be inversely proportionate. These two correlating techniques showed similar patterns after exposure. It was also shown that annealing the structure after deposition increased the absorbance in the thin film and the quantum efficiency of the final prototype device was related to film morphology. The dielectric properties of these films were studied using a novel microwave spectroscopy technique and it is believed to be the first report on the application of this novel technique to photovoltaic materials characterisation. To examine the dielectric properties of the P3HT:PCBM films using microwave spectroscopy, two types of Electro Magnetic (EM) wave sensors were fabricated, one on a Rogers substrate with Cu patterns and a second on a flexible substrate with Ag patterns. Both types of EM sensors exhibited shifts in resonant peak frequencies and amplitude during exposure to solar irradiation. All other experimental parameters and environmental conditions were kept constant. Therefore it is reasonable to conclude that the proposed method of microwave spectroscopy is a reliable tool to trace the changes in the properties of the materials caused by solar irradiation. The optical properties of the P3HT:PCBM films displayed a decrease in absorbance after 40mins solar simulator irradiation and then an increase in absorbance from 40 min to 20hrs. The electrical properties of P3HT:PCBM films showed a resistance decrease as the films were illuminated by a solar simulator from 0 to 40 min, and a subsequent increase in resistance up to 20hrs. In addition, a bespoke solar cell on flexible Polyethylene terephthalate (PET) was constructed and tested. It exhibited a fill factor and an efficiency of 0.3238 and 0.49% respectively. Although the performance is poor compared to reported state of the art for organic solar cells, the work demonstrates that operational devices can be manufactured under non-optimised laboratory conditions

Accurate performance measurement of silicon solar cells

erformance measurement is an important part of the solar cell manufacturing process. Two classes of measurement can be considered: accurate calibration – for the creation of reference cells and the setting of records; and routine measurement – for cell sorting and process improvement. This work describes techniques that address both issues – an accurate calibration technique using natural sunlight, and a routine measurement technique using a xenon flashlamp. Both techniques are low-cost, yet in combination they achieve very good accuracy. The light source is very important when calibrating solar cells. Commonly used light sources – good quality solar simulators – are expensive and frequently inaccurate. This work shows that testing of solar cells under natural sunlight is simpler, cheaper, more accurate, and more reliable than all but the most careful simulator measurements. Periodic outdoor calibrations under natural sunlight can therefore eliminate the need for an expensive solar simulator and greatly reduce the need for calibration at standards labs. Solar spectra generated with the model SMARTS2 show that the direct solar spectrum, under clear sky and low air-mass conditions, is an excellent match to the AM1.5G standard spectrum – dramatically better than simulators costing US$20,000 or more. Millions of simulations of a broad range of silicon cells (efficiencies 6-25under the modelled direct spectra show that measurement errors of less than 5achievable. This is comparable to the reproducibility of results achieved by national standards laboratories. Climate data shows that the required atmospheric conditions occur commonly in summer for all but polar latitudes. Experimental verification of the modelling is encouraging but not yet conclusive. The outcome of the research is a testing ‘recipe’ that uses low-cost equipment and gives an estimate of measurement uncertainty. For routine measurement of large numbers of solar cells, an indoor solar simulator is essential. While simulators can introduce large measurement errors, most of these errors can be eliminated by using a reference cell that is well matched to the test cells. The use of a simpler, lower-cost simulator is possible since reference cells can easily be calibrated under natural sunlight. The second half of this work describes the design of a low cost flash-lamp solar simulator. Most conventional flash testing systems maintain constant light intensity while rapidly sweeping out the I-V curve of the cell. This method has two disadvantages – it requires a flash that is specially engineered to produce constant light output, and the rapid change in cell bias-voltage causes transient errors. The new approach developed in this work essentially does the reverse – it maintains a constant bias voltage on the cell while allowing the light level to vary. This allows the use of a commercial xenon flash, and reduces sensitivity to transient errors. In addition, it extracts a family of I-V curves at different light intensities, whereas the conventional approach only extracts a single I-V curve. The new design has been implemented, using commercial-off-theshelf equipment costing less than US$10,000, and it works well. One of these systems is in use at the Centre for Sustainable Energy Systems, ANU, where it has tested tens of thousands of concentrator cells. A second system has been sold to BP Solar, UK