In-field Characterization Research Articles

Comparison of Commercial Reflectometers for Solar Mirrors

The important in-field characterization of solar mirror reflectance can be performed by a variety of commercial portable reflectometers. In this study the most common commercially available reflectometers are evaluated in a campaign comparing different reflector materials, covering a wide range of realistic reflectance and specularity values. Where possible, measurements are compared to reference values measured with laboratory equipment. In general, good agreement between measurements is detected for highly specular mirrors (average deviation 0.005±0.004) and methods for improvement are proposed when deviations are detected. Important differences between measurements are found for less specular reflectors, which are caused by the disparity of the measurement parameters of the devices. These differences confirm that detailed knowledge about the device characteristics is important, to be able to correctly interpret and utilize gained results, especially for soiled and degraded mirrors.

Tracer gas techniques for airflow characterization in double skin facades

Monitoring airflow rates and fluid dynamics phenomena in the ventilated cavity is a challenging aspect of the experimental assessment of the performance of double-skin facades (DSF). There are various methods to characterize the fluid-dynamics behavior of DSF, but each of these has its advantages and drawbacks. This paper presents the airflow characterization in the cavity of a double-skin façade installed in a full-scale outdoor facility through various methods, and, more specifically, it compares two tracer gas methods with the velocity traverse method. In the paper, we highlight how different characterization results can be explained by considering the features of each method, and how these differences are linked to velocity ranges and airflows in the cavity. By discussing (i) the challenges of these methods and their applicability, (ii) the requirements in terms of experimental set-up and (iii) the limitations linked to instrumentation, we aim to enhance the discussion on experimental methods for advanced building envelope characterization and contribute to a more grounded understanding of the suitability of tracer gas methods for in-field characterization of airflows in facades.

Monitoring of Photovoltaic System Performance Using Outdoor Suns-VOC

Summary In-field characterization of photovoltaics is crucial to understand performance and degradation mechanisms, subsequently improving overall reliability and lifespans. Current outdoor characterization is limited by logistical difficulties, variable weather, and requirements to measure during peak production hours. We capitalize on Suns-VOC, which is widely used for laboratory measurements of single solar cells and discuss the barriers in extending the technique to outdoor systems. We demonstrate the normalization of measurements using both backsheet temperature sensors and on-site weather stations. Despite weather variation, VOC, ideality factor, and pseudo fill factor all fall within 1% of the laboratory measurements. It is also demonstrated that monitoring the system VOC at 0.05 to 0.1 suns, during minimal power production, provides a figure of merit that can indicate early degradation of the system. Extensive simulations show that shading portions of a system has minimal effect on measurements, allowing the technique to be used in all weather conditions.

In-field characterization of key performance parameters for bifacial photovoltaic installation in a desert climate

Abstract To address the main challenges inhibiting the adoption of bifacial PV technology in hot desert environment, continuous performance monitoring and comprehensive analyses are timely required. Therefore, for strengthening its bankability, this techno-economic study presents an in-field bifacial parametric analysis for the environment of Middle-East. Impacts of ground coverage ratio (GCR), stand-alone/in-array mounted losses, albedo, module temperature, mounting height, tilt, and azimuth angle were quantified. To highlight the bifacial potential, economic analysis as a function of energy gain and investment premium was carried out for demarcating profitable operating zones. Moreover, multi-variable analysis for rear irradiance was performed using ground coverage ratio, height, albedo and array size, specifically:1 × 1 (free-standing module), 3 × 3 and 5 × 5. It was found that for systems where the land costs are significant, high GCR coupled with increased mounting height would result in a better energy yield per area. Module with a bifacial gain of 8.6% was found to be profitable provided that the bifacial premium investment doesn’t exceed 10% of monofacial. Thermally, bifacial power gain was found to determine the cell temperature under different irradiation conditions. The study reveals vital insights that will allow engineers and researchers to optimize bifacial PV performance in hot and sunny desert climates.

On-Site Identification of the Material Composition of PV Modules with Mobile Spectroscopic Devices

With the increased development of portable and handheld molecular spectrometers within recent years, new fields of applications have opened up, such as their use (i) for material identification of samples contained in large and non-portable components and (ii) the detection of material degradation effects and failures directly in the plant. The usability and transferability of well-established analytical characterization techniques, such as attenuated total reflection (ATR) Infrared (IR)-, Raman, and Near-Infrared (NIR)-spectroscopy as mobile devices for the in-field characterization of Photovoltaic (PV) modules, are described and discussed. Material identification of the polymeric compounds incorporated in the PV modules (encapsulants, backsheets) is often an important task, especially when degradation and failures occur. Whereas the knowledge of the bill of materials is one challenge, the detection of material degradation effects is another important issue. Both tasks can be solved nondestructively by the application of mobile spectrometers. Raman spectroscopy is the best-suited method for the identification of the encapsulant within the module (measurement through 3-mm glass), while NIR measurements allowed for the nondestructive determination of the composition of the multilayer backsheet. Surface degradation effects (e.g., oxidation, hydrolysis) are best detectable with IR-spectroscopy. The application of mobile devices allows for direct material analysis in the field without dismantling PV modules, transporting them to the lab, cutting them in smaller pieces, and analyzing them in conventional bench-top spectrometers.

The POLARBEAR Fourier transform spectrometer calibrator and spectroscopic characterization of the POLARBEAR instrument.

We describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio >20 for ∼69% of the focal plane detectors due to three features: a high throughput of 15.1 sr cm2, optimized optical coupling to the POLARBEAR optics using a custom designed output parabolic mirror, and a continuously modulated output polarizer. The PB-FTS parabolic mirror is designed to mimic the shape of the 2.5 m-diameter HTT primary reflector, which allows for optimum optical coupling to the POLARBEAR receiver, reducing aberrations and systematics. One polarizing grid is placed at the output of the PB-FTS and modulated via continuous rotation. This modulation allows for decomposition of the signal into different harmonics that can be used to probe potentially pernicious sources of systematic error in a polarization-sensitive instrument. The high throughput and continuous output polarizer modulation features are unique compared to other FTS calibrators used in the CMB field. In-field characterization of the POLARBEAR receiver was accomplished using the PB-FTS in April 2014. We discuss the design, construction, and operation of the PB-FTS and present the spectral characterization of the POLARBEAR receiver. We introduce future applications for the PB-FTS in the next-generation CMB experiment, the Simons Array.

New cool concrete for building envelopes and urban paving: Optics-energy and thermal assessment in dynamic conditions

Urban Heat Island (UHI) is an acknowledged effect that causes higher temperatures in urban areas compared to the surrounding rural areas. Such urban overheating directly increases buildings’ energy demand for cooling, to reach thermal comfort conditions in the indoor areas. This phenomenon increases energy consumption and, consequently, greenhouse gas emissions in the cooling season. Moreover, it seriously threatens citizens’ environmental comfort in urban areas. In this context, the use of cool (high solar reflectance and thermal emittance) materials has been widely acknowledged as a promising passive UHI mitigation solution. However, the application of such cool materials does not comply with the environmental preservation of cultural heritage sites, for architectural reasons. In fact, historical districts, which constitute a large part of European building stock, are often characterized by non-cool, dark colored materials. Therefore, the most common, light-colored cool solutions cannot be applied, since regulations on such protected areas are strict. Indeed, the above-mentioned regulations do not allow the modification of visible parts of the building. In this paper, innovative concrete elements with infrared-reflective (IR) pigments are presented to be used as i) urban paving, ii) building façade elements, and iii) retrofit strategies for walls and pavements in historical buildings. Both in-lab and in-field characterization of the samples are carried out with dynamically varying thermal and radiative forcing. Results indicate that prototypes with IR pigments have higher solar reflectance, up to +15.8% compared to standard concrete prototypes and +12.5% with respect to same color prototypes without high infrared reflective pigments. Moreover, they are able to maintain surface temperatures that are up to −10.6°C lower with respect to non-IR samples. These results confirm that the presented composite material represents a good solution for passive cooling at building and inter-building scale.

Obp4 and Act5C gene expression is related to Hygienic behavior in honeybee families

Honeybees (Apis mellifera) evolved social immunity mechanisms based on coordinated behavioral mechanisms for reducing the spread of pathogens and parasites. In particular, Hygienic Behavior (HB) is an actively participation of family defense by uncapping and removal of dead, diseased or parasitized brood. Currently, HB evaluation is performed only by in-field empirical assays, and suitable molecular markers that could allow the discrimination between families with High and Non-High HB score are not yet available. The research activity was characterized by a transversal approach: from in-field phenotypic characterization, to expression profiling of selected coding genes in honeybee brains. The expression analysis was performed on pools of 15 days-old honeybees collected in spring 2017 from 10 different colonies (5 with high HB and 5 with low HB scores). The brains were dissected and total RNA was purified. After quantitation and quality evaluation, the extracted RNAs were reverse transcribed to cDNAs and Real Time PCR was performed on different target genes (Act5C, Mblk-1, Obp3, Obp4, Obp16 and Obp18) previously showed by transcriptomic and proteomic studies to be involved in HB. The comparative analysis of RT-PCR threshold cycles (Ct) showed that Mblk-1 was the least expressed gene among the analyzed targets. Most importantly, statistical analysis of expression data validated (p<0.05) the delta-Ct between Obp4 and Act5C as a predictive index of high vs low HB score. These results confirmed the findings obtained through a preliminary experiment performed in spring 2016.

Candidate molecular markers of hygienic behavior in honeybees (Apis mellifera): an expression study.

Honeybees (Apis mellifera) evolved social immunity mechanisms based on coordinated behavioral mechanisms for reducing the disease risk in the hive. Among these, Hygienic Behavior (HB) leads to the uncapping and removal of dead, diseased or parasitized brood (Cremer, 2007). The characterization of expression markers of HB could greatly assist in-field selection still incomplete. This work was characterized by a transversal approach: from in-field phenotypic characterization, to expression profiling of selected honeybee brain non-coding (microRNAs) and coding (RNAm) genes to assess differential expression of selected gene targets between selected honeybee families with high and low HB, respectively. After a preliminary work performed in 2015, during spring 2016 honeybee nurses were sampled from 28 hives simultaneously with the evaluation of HB score through freeze-killed brood assay performed with the cooperation of professional honeybee breeders (E. Bonfanti, L. Sesso). The nurses from 16 families (8 with the highest and 8 with the lowest HB scores, respectively) underwent expression analysis of the following target genes potentially linked to HB and/or learning processes: ame-miR-219, ame-miR-276, let-7a (Behura, 2010) ame-miR-932 (Cristino, 2014), and Act5C, Mblk-1 (Takeuchi, 2001) and Obp4 (Chandrasekaran, 2011). The experimental workflow was as follows: 1) dissection and pooling of brains, 2) total RNA extraction, quantification and retrotranscription, 3) RT-quantitative Real Time PCR. The differential expression analysis of the candidate markers, performed after selection of the normalizing gene through geNorm and NormFinder algorithms, highlighted a correlation of OBP4 and ACT5C expression level with HB score.

Thermal and Optical Properties of a Thermotropic Glass Pane: Laboratory and In-Field Characterization

Switchable windows are glazing technologies that exhibit dynamic optical properties and may thus be used to improve the energy performance of buildings. A window system based on a thermotropic glass pane was tested both in the laboratory and by means of an outdoor test cell facility.In this paper the full optical and thermal characterization of this glazing technology is presented. Experiments and data analysis led to the characterization of the behaviour of the thermotropic glazing both when this technology is used alone (single glass pane) and when it is integrated in a multilayer fenestration (a triple glazed unit).

A Versatile System for the In-Field Non-Destructive Characterization of Radioactive Waste Packages and of Objects in the Defense Against Nuclear Threats

In-filed non-destructive characterization of radioactive waste packages and of objects in the defense of nuclear threats requires purpose-built but similar equipment. Based on commercially available measuring devices like dose-rate and gamma detectors, X-ray and gamma-transmission sources etc. a versatile and mobile mechanical positioning system for these devices is designed, assembled and operated facilitating basic to even complex measuring procedures. Several in-field measuring campaigns resulted in its further optimization. Today an highly mobile and flexible mechanical manipulator system is available supporting nearly all types of required measuring devices thus rising to nearly all occasions.

Crystallinity and in-field characterization of high-Tc YBa2Cu408 and Y0.9Ca0.1Ba2Cu4O8 epitaxial films fabricated by low temperature flux method

REBa2Cu4O8 superconductor has an important advantage that the critical temperature (Tc) is improved by Ca substitution for RE site. We fabricated the YBa2Cu4O8 (Y124) and Y0.9Ca0.1Ba2Cu4O8 (YCa124) films by molten hydroxide method in ambient atmosphere and investigated the crystallinity and in-field characterization. Obtained samples show that the film alignment is biaxial orientation and the grain size is larger than 50 μm, and the irreversibility field of YCa124 film is superior to that of Y124 in all the measured magnetic fields

Pulsed laser deposition and in-field characterization of FeTe0.8S0.2 epitaxial thin films with enhanced superconducting properties

Fe–Te–S thin films deposited by pulsed laser deposition at 400°C on SrTiO3 (100) and MgO (100) single crystals showed epitaxy and 4-fold symmetry. Films deposited on both substrates reached zero resistance condition (Tc0=3.54K on STO and 5.37K on MgO) and presented large upper critical field (Bc2(0) = 61.1T on STO and 74.2T for MgO using 90% of the normal state resistance and Werthamer–Helfand–Hohenberg model), indicating that the coherence length ξ0 of the present films is very short (ξ0=2.3nm on STO and 2.1nm on MgO).

Evaluation of the possible use of a CdTe detector for the characterization of diagnostic X-ray beams

Abstract This work describes the initial stages in the development of a system which will allow a quick and easy in-field spectrometric characterization of diagnostic X-ray beams. The spectrometric approach to the quality control procedure on diagnostic X-ray beams constitutes an advanced investigation method for monitoring and evaluating the fundamental parameters (as kVp, exposure, HVL, total filtration, etc.) when compared to the classical methods performed by several and specific dedicated instruments. Toward this aim particular care has been taken in the choice and study of the best suited detector unit. Owing to the very promising characteristics of cadmium telluride (CdTe) as a room temperature semiconductor detector, the possibility was investigated of using it in order to elude the main technical problems associated with the use of cooled semiconductor detectors in such a specific application. The investigation was made both in term of dimensions and geometric configuration of the detector, in order to optimize the match between energy response and efficiency. The obtained results are reported and discussed.