Transparent Back Research Articles

Modelling and Characterization of Transparent Building Integrated PV/T Collector

This paper is intended to develop a detailed thermal and electrical model of a transparent backing Building Integrated Photovoltaic/Thermal (TBIPV/T) collector integrated to the roof. This model was used to assess the energy performance of a typical transparent PVT air collector. The energy balance equations were derived for glazing glass, the PV cells, glass back surface of the PV module, air flowing in the duct of TBIPV/T collector and back insulation surface. The energy equations were solved using FORTRAN. A new TRNSYS type was created for the transparent backing PVT system. This type is intended to function with multi-zone building model in TRNSYS, that means thermal interaction between the PV/T collector and the building was taken into account. The effect of different PVT system parameters such as PV cell packing factor, panel cover optical properties on thermal energy production and electricity generation were examined and discussed.

Structural design of photonic crystal thin film silicon solar cells by sensitivity analysis: Inclusion of electrode absorption.

We carry out the structural design of photonic crystals (PCs) using sensitivity analysis for enhancing optical absorption of thin film microcrystalline silicon (μc-Si) solar cells. In this paper, we employ a model which includes absorption of not only the thin film μc-Si, but also the transparent conductive oxide and metal back reflector for design accuracy. We carry out structural design for this model using sensitivity analysis which maximizes optical absorption in μc-Si layer. As a result, we succeed in obtaining the maximum short circuit current density of 25.2 mA/cm2 for thin film (600-nm thick) μc-Si solar cells (1.4-fold increase compared to the case without a PC).

Introducing the 2013 JALA Ten.

Introducing the 2013 JALA Ten.

Use of digital image correlation technique to determine thermomechanical deformations in photovoltaic laminates: Measurements and accuracy

An experimental technique to measure the deformation of solar cells in transparent PV modules is presented. This method uses the digital image correlation technique with a stereo camera system. Deformations resulting from thermal loading, where rather small deformations occur compared to tensile or bending experiments, are measured by viewing through the window of a climate chamber. We apply this method to measure the thermomechanical deformation of the gap between two crystalline silicon solar cells by viewing through the transparent back sheet of the laminate. Two PV laminates are prepared, each with three crystalline silicon solar cells that are embedded in transparent polymer sheets on a glass substrate. The first laminate (A) contains non-interconnected cells while the second laminate consists of a standard-interconnected cell string (B). We find the gap between two solar cells to deform 66.3±2 μm between 79.6 and −17.3 °C (laminate A) and 66.4±2 μm (laminate B) between 84.4 and −39.1 °C. We determine an accuracy of 1 μm in displacement for the gap experiment by measuring free expansion of a copper strip and averaging displacement values over regions with homogeneous deformation. Furthermore, the relative error contribution in strain due to the optical influence of the layers on top of the object surface is less than 1×10 −6 for one camera. This is proven by a geometrical consideration.

Fiber Optic Sensor for Simultaneous Determination of Atmospheric Nitrogen Dioxide, Ozone, and Relative Humidity

We describe a novel optical sensor for the simultaneous measurement of atmospheric nitrogen dioxide (NO(2)), ozone (O(3)), and relative humidity (RH). A transparent backing thin layer silica gel chromatographic plate impregnated with 8-amino-1-naphthol-5-sulfonic acid (ANS) is used as the collection/sensor element. The plate transmittance is probed by three discrete light emitting diodes (LEDs) centered, respectively, at 442, 525, and 850 nm. The transmission of the plate changes reversibly across visible to NIR wavelengths as the RH around the plate changes; this is the basis for a limited-resolution RH sensor. The ANS on the plate reacts to form brown and pink colored products, respectively, when it reacts with NO(2) and O(3). The sample air impinges on the plate via an entrance nozzle. The LEDs are alternately turned on in a preprogrammed manner and the light is brought to the impregnated face of the plate by a three-legged fiber optic. The transmitted light is detected on the obverse side of the plate. The 850 nm signal provides the RH value and optionally serves as the reference measurement for the other two wavelengths; the NO(2) and O(3) reaction products do not absorb at this wavelength. The absorbance at 442 and 525 nm, thus referenced against 850 nm, are used to obtain NO(2) and O(3) concentrations from a pair of simultaneous equations. For a sampling period of 5 min, the limits of detection (LOD) based on 3 times the standard deviation of blank responses were 0.64 and 0.42 ppbv for NO(2) and O(3), respectively. Data obtained with collocated commercial instruments (O(3) induced chemiluminescence analyzer for NO(2) and UV-absorption for O(3)) show good agreement. Overall, this provides a viable affordable approach for inexpensive measurement of atmospheric NO(2) and O(3).

Photographic study of pool boiling CHF from a downward-facing convex surface

Heat transfer measurements and photographic studies are performed to capture the detailed evolution of the liquid–vapor interface near critical heat flux (CHF) for a 90-degree downward-facing convex surface. The test surface, with a width of 3.2 mm and a 102.6-mm radius, consists of a series of nine heaters that dissipate equal power. Instrumentation within each heater facilitates localized heat flux and temperature measurements along the convex surface, and transparent front and back windows enable optical access to a fairly two-dimensional liquid–vapor interface. Near CHF, vapor behavior along the convex surface is cyclical, repeatedly forming a stratified vapor layer at the bottom of the convex surface, which stretches as more vapor is generated, and then flows upwards along from the surface. Subsequently, heaters at the bottom of the convex surface, followed by the other heaters, are wetted with liquid before the nucleation/coalescence/stratification/release process is repeated. This study proves that despite the pronounced thickening of the vapor layer as it propagates upwards along the convex surface, CHF always commences on the bottom of the surface.

Transparent Back Contacts in CdTe/CdS: Evaluation for Tandem Cells

AbstractCdS/CdTe solar cells with 2.3 μm CdTe were prepared with four different types of p+/n+ transparent back contacts (TBCs) - ZnTe:Cu/ZnO:Al, ZnTe:N/ZnO:Al, ZnTe:Cu/ITO, and ZnTe:N/ITO. ZnTe:N/ITO was found to give the best results. This back contact was then used to make cells of lesser (1.8 μm and 0.7 μm) CdTe thickness, in those cases giving good performance up to 9.1% efficiency. Bifacial J-V was performed on all cells with the optimum ZnTe:N/ITO back contact.

Tunable liquid microlens with three-dimensional adjustment of the position of the focal spot

A tunable liquid microlens that can be varied from a concave to a convex configuration and which provides three-dimensional adjustment of the position of the focal spot is demonstrated. The tuning is carried out with no reduction of the effective diameter and no surface distortion of the microlens. The focal length is varied by changing the volume of liquid in a microtube. As the focal length is adjusted, three-dimensional adjustment of the focal spot can be obtained by suitably tilting the removable transparent backing. The operating quality of such a microlens is brought out in the results of an experiment: It can be used in such applications as optical switching, optical memory devices with multiple high-density recording, etc. © 2005 Optical Society of America

Influence of Light Scattering in Colorant Layers on Tertiary Color Reflectance

Xerographic color prints, soon expected to be introduced into the photofinishing market, are usually designed to have a maximum density close to 2.0. This value empirically proved insufficient for photofinishing applications. Factors to be analyzed include light scattering in the pigment-based colorant layers. In this report, the intensity of scattered light was measured under a 0/45 geometry with samples consisting of a primary colorant layer on a transparent backing sandwiched between a pair of glass plates. The results indicate that the scattered component acts to suppress the maximum density of pigment-based secondary or tertiary color images, but that, by choosing an appropriate order of color superimposition, the maximum density can be brought closer to that of photographic prints. The spectral reflectance of tertiary color images is also calculated based on the scattered and reflected light of primary colors, and shows a satisfactory agreement with the measured spectra.

An Integrated Tool for Rapid Prototyping of Electronic Circuits Using a Laser Direct Write Technique

ABSTRACTA laser-based tool has been developed for the fabrication of electronic circuits. The tool integrates three separate functions on a single platform. These functions are deposition, laser processing, and laser micromachining. Deposition is accomplished by dispersing a target material in a thin layer over a transparent backing layer, holding the target material in close proximity to a receiving substrate, and irradiating the target material from behind with a short pulse UV laser. The UV pulse vaporizes a small amount of the material at the material/backing interface, thereby propelling the remainder of the target material toward the receiving substrate. Patterning is achieved either by translating the receiving substrate, scanning the laser beam, or a combination of the two. After transfer, most materials require some thermal processing: either oven baking or laser sintering. Fabricated circuits have included conductors (Ag, AgPd, AgPt, Cu), resistors (cermet and polymer thick film), and dielectrics (ceramic and polymer thick film). These materials have been patterned with feature sizes as small as 10 m and linear write speeds as high as 1 meter per second. The tool includes an integrated, near IR laser which can be operated both CW and pulsed for thermal processing. Laser sintering of metals, cermet resistors, and ceramic dielectrics has been demonstrated on low temperature, polymer substrates. The localized heating achievable with the laser allows the sintering or annealing of high temperature materials without damaging the underlying substrate. The tool includes a complete, state-of-the-art laser micromachining system, capable of milling recesses, drilling vias, trimming components, and excising circuits. No masks or phototools are required. No photoresists or wet chemistries are needed. The tool does not require a clean room environment. The combined functionality and speed result in a flexible and powerful tool for the rapid prototyping of circuits, and potentially, small scale production.

A High-Resolution Laser Thermal Lenticular Printer

Lenticular printing is a method of generating 3-D, or moving, images by placing multiple image frames behind a series of cylindrical lenses. Lenticular images have been around for decades as exemplified by the kids give-away cards, which typically contain two still images.In this paper, we present a novel method for generating lenticular images based on the laser thermal process. A highpower infrared multimode laser is used to thermally transfer dyes from three donor sheets (cyan, magenta, and yellow) to a lenticular card. The beam is oriented and aligned to the cylindrical lenses to allow a minimum spot size in the cross lens direction. The printing resolution is asymmetric at approximately 2500 by 300 dpi. This method allows the printing of 10 micron continuous tone lines, which yields 34 images behind a 75 lenses per inch substrate. Printing occurs in alignment with the lenticules by premeasurement, rotational alignment, and adjustment of relevant parameters.The printed card is then thermally laminated with either a transparent or reflective backing, which acts as a receiver and protection. The current printer allows individual cards to be printed in less than 5 minutes. Samples will be presented, which show the high-quality motion and stills possible by this process.

Alumer: A “rigid,” acoustically transparent, composite material

The elastic properties of foamed aluminum have been reported in an earlier presentation [J. Acoust. Soc. Am. Suppl. 1 88, S22 (1990)]. When the open-cell structure of this material is impregnated with a light elastomer, a composite material results that has a density and dilatational wave speed close to that of water. The Young's modulus and bulk modulus of this “Alumer” material have been measured, as a function of frequency, for various combinations of foamed aluminum, characterized by relative density and pore size, and polyurethane. The aluminum matrix imparts stiffness to the material, for use as an acoustically transparent backing plate or other structure. The elastomer may be chosen to give more or less absorptive properties to the material. [Work supported by the Office of Naval Research.]

Dissipative Processes in Interfacial Failure

Abstract An investigation of the failure behavior of pressure sensitive adhesive tape was performed utilizing the constrained blister test. The constrained blister test was designed to measure the energy of interfacial adhesion of thin polymeric coatings. A constant energy of interfacial adhesion of 1.8J/m2 was determined for a rubber based pressure sensitive adhesive on a copper substrate. An active zone was visualized through the transparent backing. The deformation within the active zone was found to consist of cavitation and deformation of ligaments. Fracture of the ligaments causes the detachment front to advance. It was proposed that the rate of energy dissipation, D, reflects the resistance of the bond to time dependent deformation, and therefore dictates the lifetime for this particular specimen geometry. A direct relationship was established between lifetime and the inverse of the rate of energy dissipation in the active zone, D.

Streaming motions in a bed of vibrationally fluidized dry granular material

Experimental and theoretical studies of vibration-induced flow and mixing of dry granular materials are described. Tests were performed on rounded polystyrene beads contained in a rectangular box having transparent front and back walls and a flexible, nominally horizontal bottom which could be driven at various frequencies and amplitudes. The amplitude of the bottom vibrations was a maximum at the centre and decreased towards the vertical sidewalls. Slow recirculating flows were observed; they had the form of two vortices in which the velocity was upwards at the vertical centreline and downwards along the vertical sidewalls. The streaming velocities were measured as a function of bed vibration frequency and displacement amplitude. An explanation proposed for the recirculating flows is that the vibrating base sends ‘acoustic’ waves upwards through the bed. These waves ‘fluidize’ the granular material but are in turn attenuated because of the dissipative nature of the collisions between the ‘fluidized’ particles. Thus the slow recirculating flows in the granular material are analogous to the more familiar ‘acoustic streaming’ in air. An approximate analysis of these streaming motions is developed by making use of a modification of the constitutive theory of Jenkins & Savage (1983). A number of simplifying assumptions are introduced to make the analysis tractable. The general flow patterns of the streaming motions are predicted, but the velocities are overestimated as a result of the simplifying assumptions. The analysis is restricted to a rather narrow range of conditions.

Piston‐diaphragm speaker

A planar diaphragm type magnetic transducer with an acoustically transparent magnetic backing, and a diaphragm overlying and spaced from the magnetic backing, the magnetic backing having magnetized strips lying parallel to each other and adjacent magnetized strips having opposite polarities at their faces confronting the diaphragm, the diaphragm being stiff and resisting flexing and connected by a flexible surround at its periphery.

A Large Cloud Chamber Using Rear Illumination

A large cloud chamber is described that makes use of rear illumination by means of a transparent piston and back plate. This system of illumination is particularly advantageous for a large cloud chamber since the increase in the amount of scattered light for small angles of scattering from droplets reduces the total light required.