Photovoltaic Sensors Research Articles

Novel Fully Automated Microcontroller Controlled Cloth Drying System under Direct Sun

Objectives: This paper outlines a completely automated system for drying the clothes under direct sun by eliminating the manual supervision. Methods: Such an automated system is constructed using smart sensors for monitoring humidity in the environment, a set of photo voltaic sensors and a drive system. Based on the output from the sensor a microcontroller instructs the drive system to move the cloth towards the optimal section. Findings: The simple design exhibits a reliable, fast-response in a continuous manner without manual supervision. Applications/Improvements: System can be put into operation throughout the duration of drying especially during inconsistent weather condition.

Photovoltaic Sensor for the Solar Battery Guidance on the Sun Based on GeS:Sb Layered Crystals

Photovoltaic tracking sensor monitoring the position of the sun in the sky was developed on the basis of GeS:Sb layered crystals. The operating principle of this sensor is based on the phenomenon of photovoltaic effect in GeS:Sb crystals; the magnitude and sign of generated photo-emf depend on the position of the light probe relative to the ohmic contacts, deposited on (001) surface of the crystal.

Nanoparticles in dielectric matrix for electronics and optics: from the fabrication to the devices

AbstractThe discovery of the nanosize‐related effects has led to tremendous efforts, numerous publications, international symposia and patents on the development and study of nanometer scale based structures. The achievements are specific and novel optical, electronic, and magnetic properties are reported that have never been obtained on a macroscopic scale. Among these nanostructured systems, nanoparticles embedded in a dielectric host matrix offer a wide range of applications in electronics and optics from non‐volatile memories to non‐linear optics, from light emitting diodes to enhanced photovoltaic sensors, and from optical amplifiers to plasmonic substrates. This requires a large range of skills in different fields such as chemistry, physics, and material science.This symposium aimed at gathering scientists and industrial partners from the above fields and involved in the fabrication and the study of such nanostructured systems and related applications. The goal was to share and discuss recent advances in fabrication, doping, optical and/or electrical properties, biosensing, photovoltaics, plasmonics, fundamental mechanisms of growth or excitation, devices that incorporate those properties, and applications of such materials systems. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures.

Recent developments in the technology of van der Waals heterostructures made from two-dimensional atomic crystals have already led to the observation of new physical phenomena, such as the metal-insulator transition and Coulomb drag, and to the realization of functional devices, such as tunnel diodes, tunnel transistors and photovoltaic sensors. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology.

Automatic Feedback Control System of Detection and Treatment of Infantile Jaundice

With the progress of photovoltaic technology and sensor, this paper propose a new automatic feedback control system which based on the color sensor TCS230 and LED flexible lighting equipment to detect and treat infantile jaundice. By testing the severity of the yellowing baby skin, the system makes any response, such as the lights’ intensity and working time. And the final aim is to realize the detection and treatment synchronously for infantile jaundice, promoting the development of intelligent medical treatment.

Microstructures of ZnO Electrospun Nanofibers on AZO Glass

ZnO electrospun nanofibers were considered to be potential novel materials in applications of photovoltaic devices and sensors. AZO glass was usually used in those devices as transparent electrodes. ZnO nanofibers on AZO glass were synthesized by electrospinning and calcination process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) spectrum was employed to investigate the morphology, structure and optical performance of ZnO nanofibers. Network structure composed of sheet ZnO was observed. Raman spectra and PL spectrum indicated the existence of defect states in the ZnO nanofibers.

AUTOMATIC ANTI-GLARE SYSTEM FOR NIGHT TIME DRIVING USING LIQUID CRYSTAL SCREENS

This paper proposes a prototype model for an automatic anti-glare system to reduce the risk of accidents during night time driving. The architecture consists of an aperture assembly and sensors. The aperture assembly is a two dimensional array of aperture elements, and their transmittances can be independently controllable. According to the transmittance, each aperture element will act either as opaque or transparent. The intensity of light ray is modulated by the transmittance of aperture elements, which causes the reduction of intensity of light passing through it. The prototype is implemented using liquid crystal display (LCD) and photovoltaic sensors. This system provides an automated mechanism to control the illumination according to the direction of incoming light. The fundamental idea is to measure the incoming light and using measured values to generate patterns on the LCD to reduce the illumination. The proposed prototype can be implemented in two ways: i) as spectacles with liquid crystal sheets placed in front of the glasses, which can be used while driving, ii) by placing large liquid crystal sheets in front of the windshields of vehicles. This method provides a flexible low cost implementation to build simple, reliable device to reduce the intensity of the light on-the-fly.

Low‐cost flexible thin‐film detector for medical dosimetry applications

The purpose of this study is to characterize dosimetric properties of thin film photovoltaic sensors as a platform for development of prototype dose verification equipment in radiotherapy. Towards this goal, flexible thin‐film sensors of dose with embedded data acquisition electronics and wireless data transmission are prototyped and tested in kV and MV photon beams. Fundamental dosimetric properties are determined in view of a specific application to dose verification in multiple planes or curved surfaces inside a phantom. Uniqueness of the new thin‐film sensors consists in their mechanical properties, low‐power operation, and low‐cost. They are thinner and more flexible than dosimetric films. In principle, each thin‐film sensor can be fabricated in any size (mm2 – cm2 areas) and shape. Individual sensors can be put together in an array of sensors spreading over large areas and yet being light. Photovoltaic mode of charge collection (of electrons and holes) does not require external electric field applied to the sensor, and this implies simplicity of data acquisition electronics and low power operation. The prototype device use for testing consists of several thin film dose sensors, each of about 1.5 cm×5 cm area, connected to simple readout electronics. Sensitivity of the sensors is determined per unit area and compared to EPID sensitivity, as well as other standard photodiodes. Each sensor independently measures dose and is based on commercially available flexible thin‐film aSi photodiodes. Readout electronics consists of an ultra low‐power microcontroller, radio frequency transmitter, and a low‐noise amplification circuit implemented on a flexible printed circuit board. Detector output is digitized and transmitted wirelessly to an external host computer where it is integrated and processed. A megavoltage medical linear accelerator (Varian Tx) equipped with kilovoltage online imaging system and a Cobalt source are use to irradiate different thin‐film detector sensors in a Solid Water phantom under various irradiation conditions. Different factors are considered in characterization of the device attributes: energies (80 kVp, 130 kVp, 6 MV, 15 MV), dose rates (different ms × mA, 100–600 MU/min), total doses (0.1 cGy‐500 cGy), depths (0.5 cm–20 cm), irradiation angles with respect to the detector surface (0°‐180°), and IMRT tests (closed MLC, sweeping gap). The detector response to MV radiation is both linear with total dose (~1‐400 cGy) and independent of dose rate (100‐600 Mu/min). The sensitivity per unit area of thin‐film sensors is lower than for aSi flat‐panel detectors, but sufficient to acquire stable and accurate signals during irradiations. The proposed thin‐film photodiode system has properties which make it promising for clinical dosimetry. Due to the mechanical flexibility of each sensor and readout electronics, low‐cost, and wireless data acquisition, it could be considered for quality assurance (e.g., IMRT, mechanical linac QA), as well as real‐time dose monitoring in challenging setup configurations, including large area and 3D detection (multiple planes or curved surfaces).PACS number: 87.56.Fc

Triphenylene-based discotic liquid crystals: recent advances

Since the early work of Chandrasekhar and his co-workers on hexaesters of benzene published in 1977, discotic liquid crystals (DLCs), in particular, triphenylene-based DLC materials have been investigated intensively, especially over the last decade. The first successful commercialisation of triphenylene-based DLCs has been accomplished in Fuji ‘Wide-View’ optical compensation films. DLCs represent a broad well understood class of soft matter which possess the ability to self-organise into highly anisotropic and ordered structures such as columns that function not only as organic anisotropic semiconductors, but also contribute to the development of new smart materials in the field of organic electronics for many device applications such as photovoltaic devices, light-emitting diodes, field-effect transistors, memory elements, and sensors. Over the last 35 years, more than 1000 triphenylene derivatives have been synthesised and investigated starting from structure-properties to structure-device performance relationships. The very first review by Cammidge and Bushby followed by Kumar summarised the chemistry and physical properties of triphenylene-based discotics up to 2003. In this review, progress in the research of triphenylene DLC materials since 2004 is comprehensively outlined.

Morphology-dependent optical properties of one-dimensional nanostructure-arrayed silicon

The optical properties of one-dimensional nanostructure-arrayed silicon (1DNSASi), which was fabricated by the metal assisted electroless chemical etching method under different conditions, were characterized in the wavelength range of 220 — 1000 nm. Whether the optical absorption of the 1DNSASi was enhanced relative to that of the polished Si was determined from the detailed morphology of the 1D nanostructures. For the yellow 1DNSASi prepared at a high etchant concentration and high temperatures, its optical absorption was relatively nice in the ultraviolet light region, while a gradual attenuation was shown in the visible and the near-infrared regions, and the optical absorption was lower than that of the polished Si at wavelengths above 800 nm. When the effects of zeroth-order reflectance and zero transmission were combined, the optical absorption of the black 1DNSASi prepared at a low etchant concentration and room temperature was very high (> 99%) in the wavelength range of 220–1030 nm and displayed a slight decrease at wavelengths above 1030 nm. Our results demonstrate that the optical absorption of the black 1DNSASi could be further improved by increasing the etching depth and exhibited its measurable maximum value when the etching depth was large enough. These results indicate that the 1DNSASi may be a promising candidate for high-efficiency photovoltaic devices, high-sensitivity sensors and detectors.

Clean water photovoltaic sensor for solar disinfection in developing countries

One of the limitations for the widespread use of solar water disinfection technologies in developing regions is the lack of low-cost clean water sensors. A new type of low-cost sensors using photovoltaic solar cells that provide information about received irradiance, temperature, UV irradiance and sunshine duration is presented. A key aspect of the design is the UV irradiance measurement. Two identical cells are used, one of them with a low-cost UV-blocking filter on top, so the total UV irradiance can be calculated as the difference between the two solar cells outputs. The first cell would be measuring UV–vis–NIR and the second only vis–NIR. The UV filter material was explored and a low-cost architectural film was selected. Materials costs for the first prototype were of approximately 4€ excluding labour. Initial testing also included experiments with real polluted water and Escherichia coli, showing the feasibility of the new design.

Experimental Study of Natural Gas Temperature Effects on the Flame Luminosity and No Emission

The flame radiation enhancement in gas-fired furnaces significantly improves the thermal efficiency without significantly affecting the NOx emissions. In this paper, the effects of inlet natural gas preheating on the flame luminosity, overall boiler efficiency, and NO emission in a 120 kW boiler have been investigated experimentally. Flame radiation is measured by use of laboratory pyranometer with photovoltaic sensor. A Testo350XL gas analyzer is also used for measuring the temperature and combustion species. The fuel is preheated from the room temperature to 350°C. The experimental measurements show that the preheating of natural gas up to about 240°C has no considerable effect on the flame luminosity. The results show that increasing the inlet gas temperature from 240°C, abruptly increases the flame luminosity. This luminosity increase enhances the boiler efficiency and also causes significant reduction in flame temperature and NO emission. The results show that increasing the inlet gas temperature from 240°C to 300°C increases the flame luminous radiation by 60% and boiler efficiency by 20%; while the maximum flame temperature and the boiler NO emission show a 10% and 8% decrease respectively.

Solar cells for the blind

Electronic implants have been used to restore visual function lost as a result of retinal degeneration. Combining subretinal high-pixel-density arrays with optically powered serial photovoltaic sensors may alleviate some of the difficulties associated with today's devices, which rely on implanted arrays and inductive coils.

SELECTIVE SYNTHESIS OF ZnO ARRAYS

ZnO nanosheet and nanorod arrays were selectively synthesized on zinc substrate through the reaction of zinc foil with dilute alkaline solution at 120–180°C for 12–24 h. The microscopic morphology and crystal phase of these products were characterized by scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). The growth mechanism and morphology evolution of the nanostructured ZnO arrays were investigated. Due to their uniform morphologies and large surface areas, the as-prepared ZnO nanosheet and nanorod arrays may be used as photovoltaic films and gas sensors for future applications.

Connecting the quantum dots

In this paper, paints, an optoelectronic materials were used to make better photovoltaic cells, imaging sensors, and optical communication equipment by considering the nanomaterial design understanding at a molecular level. Infrared solar cells from semiconductor quantum dots were developed and the paint-on technology for other device applications were also discussed.

Nano-structure fabrication for HgCdTe ultra-fast infrared sensors

High-speed infrared sensors are necessary for broad applications in optic fibre communications with high data capacity and high security and distance sensing by laser. In this paper, an ultra-fast infrared sensor with 100 nm ballistic channels has been proposed and successfully fabricated by electron beam lithography. The area of photosensitive surface is as large as 100 μm × 100 μm to ensure its high sensitivity. The principle is based on the ballistic transport of electrons in the nano-scale channels. The frequency is expected to be in the range of 10 GHz, one or two orders higher than conventional photovoltaic sensors.

Enhancing the Output Characteristics of a Photovoltaic Position Sensor Using a Feed-Forward Neural Network

Tracking solar-power devices often employ photovoltaic position sensors to detect the angle of misalignment between the axis of mounted solar panels and that of sunlight. The nonlinear input-output characteristics of this type of sensors tend to complicate controller design in such systems. This paper presents a nonlinear mathematical model of the photovoltaic position sensor. A three-layer feedforward neural network was trained to linearise the characteristics of the sensor. The MATLAB neural network tool (nntool) was used for neural network training. A final error of was obtained after training. Simulation of the neural network showed that linear sensor characteristics could be reproduced throughout the domain of sensor operation.

Estudo de simulações de microclimas em casas de vegetação visando à aclimatação de mudas micropropagadas de bananeira cv Grande Naine

Em processos de aclimatação, o controle ambiental assume papel de vital importância, pois, ainda na condição in vitro, as plantas não operam eficientemente a absorção de luz, água e nutrientes. Devem, portanto, ser submetidas a ambientes controlados sob condições favoráveis de luminosidade, temperatura (ao redor de 28ºC, com mínimas a 18ºC e máximas a 34ºC) e umidade relativa (acima de 75%). Para tanto, foram construídos 5 mini-túneis com temperatura e umidade relativa controladas. No controle da temperatura, usaram-se resfriadores evaporativos do tipo ventilador-meio poroso, 28/25ºC. No controle da umidade relativa, usou-se nebulização durante o dia a 75% sob intermitência de 6s a cada 40s. Para o monitoramento da temperatura e umidade relativa, foram instalados 3 psicrômetros aspirados em cada casa de vegetação, ligados a sistema programado para leituras diárias com partição de 60s. Os resultados indicam controle satisfatório nos ambientes, oferecendo condições favoráveis para as plantas de bananeira sob o 2º estágio de aclimatação, embora tenham sido observadas diferenças significativas entre eles. Para o estudo da luminosidade, sob filme plástico transparente PEBD de 100µm, foram utilizadas telas com média de sombreamento na faixa RFA (400 a 700nm) de 69,92%, 50,73%, 29,73% e 57,77%, sendo as 3 primeiras de cor vermelha (com picos na faixa de 580nm e redução abrupta a partir daí), e a última de cor preta (comportamento linear), respectivamente. O 5º ambiente contou apenas com o filme, apresentando 12,74% de interceptação da radiação solar. Esses valores foram obtidos a partir de amostras pareadas, tela e filme para os 4 primeiros ambientes e apenas o filme para o último, utilizando-se de espectro-radiômetro programado para a faixa de 400 a 1.100nm, com resolução espectral de 2nm. Dentro e fora de cada ambiente, obtiveram-se dados de irradiâncias RFA e global, por meio de sensores fotovoltaicos de silício, por volta das 9h, 12h e 15h, sob condições de céu claro e encoberto, durante o verão de 2004/05 e inverno de 2005. As malhas vermelhas apresentam transmitâncias diferenciadas ao longo do espectro da radiação fotossinteticamente ativa, constituindo-se assim em interessantes materiais para os pretendidos estudos sobre aclimatação. Resultados mostram maiores reduções na faixa RFA para as telas vermelhas, independentes do horário, insolação e estação do ano, concordantes com aqueles obtidos por espectro-radiômetro.

Applications of ferrofluids in Micro Electro Mechanical Systems (MEMS) and micropumps

The micro-pump is one of the most promising micro-flow devices. At micro-level electronically controlled pumping of any fluid by a mechanical pump is not so easy and reliable. In the realm of nano-tech materials, ferrofluids have unique properties in both liquids and solids and have potential applications for MEMS/NEMS devices. This paper presents two new types of concepts, a micro-flowmeter based on a micro-turbine made using MEMS technology and the other is a micro-pump based on ferrofluidic. actuation. In our first device an optical photovoltaic sensor has also been integrated with this device. and the, micro-turbine rotates with a Speed of 50000 rpm. We have fabricated a ferrofluid-based glass micro-pump of size 20 x 20 x 10 mm(3). in which micro actuation is electrically, controlled by NdFeB (N50) permanent magnets (diameter 5 x 3mm, B(r) = 1400 mT, coercive field H(c) = 840 kA/m) with a ferrofluid bearing. The device is able to pump the fluid at the rate of 10 mu L/actuation.

Concentrating PV: An Alternative to Calorimeters for Measuring High Solar Flux Densities

Gardon calorimetric transducers are widely used to measure concentrated solar radiation flux on solar thermal areas. These measurements need some correction to adapt their response from thermal to solar irradiance measurement. The authors propose the use of concentrating photovoltaic PV-cells to measure concentrated solar radiation flux. This paper shows the results obtained from a comparative test carried out in a solar furnace measuring concentrated solar irradiance with calorimetric and photovoltaic sensors, Gardon, and PV-Cells, respectively.