Geometric Concentrations Research Articles

Optical design and validation of a solar concentrating photovoltaic-thermal (CPV-T) module for building louvers

This paper presents a solar concentrating photovoltaic-thermal (CPV-T) module for building louver which is designed to provide electricity and heat for buildings by capturing solar radiation in building vertical space. A specially designed concentrating blade used for louver is combined with a PV-T module. The concentrating blade enables incident sunlight converge to a solar cell, thus obtaining electricity. The heat generated in the solar cell is taken away and collected by thermal fluid, by which the deficiency of increasing extra cooling demand in summer existing in traditional building integrated photovoltaic is overcome. The concentrating blade is designed to work under the solar incident angle of 0–90°, and its high-efficiency photovoltaic-thermal working range is 20–70°. Optical simulations are conducted to illustrate the characteristics of the concentrating blade. Remarkably, the maximum geometrical concentration ratio is 2.96 at the incident angle of 20°. Over a wide range of incident angles between 12.5° and 52.5°, the geometrical concentration ratio maintains above 2. Finally, experiments are carried out to test the electrical and thermal performance of the CPV-T module. The results illustrate that its overall efficiency can reach above 55 % for nearly 5 h without tracking during the all-day experiment.

A Summary of Residential Radon Surveys and the Influence of Housing Characteristics on Indoor Radon Levels in Canada.

Based on community and nationwide radon surveys with long-term radon measurements in a total of 21,818 homes, radon distribution characteristics in Canada have been reassessed with the population-weighted arithmetic mean radon concentration of 82 Bq m−3, geometric mean radon concentration of 55 Bq m−3, and geometric standard deviation of 2.45. The major pathway for the influx of radon into Canadian homes is from the surrounding soil. Statistical analysis has shown that radon levels in houses with a basement are, on average, about twice the radon levels in houses without a basement, and houses with private wells also tend to have higher radon concentrations than houses with municipal water supply.

Enabling open sun cooling method-based estimation of effective concentration factor/ratio for concentrating type solar cookers

The solar cooker is a vital device to attain sustainable development goals. Solar concentrating cookers (SCCs) are preferred mostly for intermediate to high-temperature cooking applications. The solar flux reflected and concentrated by the reflecting surface of the collector of a particular design of SCC are mainly responsible for the heating of the cooking pot/receiver. Hence, the quantification of the concentration-effect and subsequent assessment of effectiveness and role of reflecting surface in the opto-thermal performance analysis and rating of the SCCs is an essential and critical requirement.This work proposes a thermal method to determine an Effective Concentration Ratio (Ceff.) for any design of SCC. Two thermal tests, with and without reflecting surface, were performed on the SCC. Results depict that determination ofCeff. allows the quantification of realistic concentration ratio and comments on the thermal and optical performance analysis of the SCC. The mean value ofCeff. is determined as 4.998 and the geometric concentration ratio computed to be ~ 12.35 for the SCC used in the present work. This result indicates the effectiveness of the concentrating surface. Thus,Ceff. is an effective tool to estimate the efficacy of/degradation in the performance analysis of reflecting surface of the different designs of the SCCs and can be effectively used for grading of SCCs. This method may be helpful for other solar concentrating collectors of several design configurations as well.

Safety and long-term immunogenicity of the two-dose heterologous Ad26.ZEBOV and MVA-BN-Filo Ebola vaccine regimen in adults in Sierra Leone: a combined open-label, non-randomised stage 1, and a randomised, double-blind, controlled stage 2 trial

Safety and long-term immunogenicity of the two-dose heterologous Ad26.ZEBOV and MVA-BN-Filo Ebola vaccine regimen in adults in Sierra Leone: a combined open-label, non-randomised stage 1, and a randomised, double-blind, controlled stage 2 trial

Antimicrobial Susceptibility of Urogenital and Extragenital Neisseria gonorrhoeae Isolates Among Men Who Have Sex With Men: Strengthening the US Response to Resistant Gonorrhea and Enhanced Gonococcal Isolate Surveillance Project, 2018 to 2019.

We investigated differences in gonococcal antimicrobial susceptibility by anatomic site among cisgender men who have sex with men (MSM) using specimens collected through the Centers for Disease Control and Prevention's enhanced Gonococcal Isolate Surveillance Project and Strengthening the US Response to Resistant Gonorrhea. During the period January 1, 2018-December 31, 2019, 12 enhanced Gonococcal Isolate Surveillance Project and 8 Strengthening the US Response to Resistant Gonorrhea sites collected urogenital, pharyngeal, and rectal isolates from cisgender MSM in sexually transmitted disease clinics. Gonococcal isolates were sent to regional laboratories for antimicrobial susceptibility testing by agar dilution. To account for correlated observations, linear mixed-effects models were used to calculate geometric mean minimum inhibitory concentrations (MICs), and mixed-effects logistic regression models were used to calculate the proportion of isolates with elevated or resistant MICs; comparisons were made across anatomic sites. Participating clinics collected 3974 urethral, 1553 rectal, and 1049 pharyngeal isolates from 5456 unique cisgender MSM. There were no significant differences in the geometric mean MICs for azithromycin, ciprofloxacin, penicillin, and tetracycline by anatomic site. For cefixime and ceftriaxone, geometric mean MICs for pharyngeal isolates were higher compared with anogenital isolates (P < 0.05). The proportion of isolates with elevated ceftriaxone MICs (≥0.125 μg/mL) at the pharynx (0.67%) was higher than at rectal (0.13%) and urethral (0.18%) sites (P < 0.05). Based on data collected from multijurisdictional sentinel surveillance projects, antimicrobial susceptibility patterns of Neisseria gonorrhoeae isolates may differ among MSM at extragenital sites, particularly at the pharynx. Continued investigation into gonococcal susceptibility patterns by anatomic site may be an important strategy to monitor and detect the emergence of antimicrobial resistant gonorrhea over time.

Analysis and Research on the Performance of Solar Concentration Based on Big Data and Machine Learning

Empirical formulas for PTC optical efficiency calculation are difficult and costly to obtain from rigorous comparative experiments, whereas simpler optical modeling methods inadequately incorporate realistic optical effects. In this article, algorithms are respectively developed to calculate the geometric concentration ratio (Cg) of linear Cassegrainian solar concentrators (CSC) with a secondary flat mirror based on the way of edge rays from solar sources to a flat-plate receiver. On the basis of the large amount of data generated, machine learning and Python language programming methods are used to analyze and process the data, and the functional relationship between the concentration ratio and each parameter is obtained. The learning and training effect is good, and the ideal result is achieved.

A pilot study of glyphosate, and preterm birth among blacks and whites

BACKGROUND AND AIM: Glyphosate was first registered as an herbicide in the United States in 1974. It has since been linked to birth defects in animal models. Additionally, in vitro studies suggest that glyphosate has anti-androgenic and anti-estrogenic activities including the ability to interfere with aromatase activity. One observational human study found a statistically significant correlation between higher maternal glyphosate levels and shortened gestational length. However, no studies have investigated potential race-disparities in gestational glyphosate exposure or effects. METHODS: A nested case control pilot study enrolled 26 women with a preterm birth (37 weeks completed gestation) and 26 term births matched by race from a larger cohort study. Second trimester urine samples, collected at 18-22 weeks of gestation, were analyzed for specific-gravity corrected glyphosate using liquid chromatography-tandem mass spectrometry. Logistic regression was used to estimate the association between gestational urinary glyphosate concentrations and preterm birth, adjusted for age, race, body mass index, season of specimen collection, education level and reported organic food consumption. RESULTS:Geometric mean glyphosate concentrations were 0.07 ng/mL (95% CI: 0.04-0.13) for preterm and 0.06 ng/mL for term births (95% CI: 0.03-0.10). Fewer term whites (n=4, 31%) were in the middle (range: 0.04-0.11 ng/mL) and highest (range: 0.17-1.25 ng/mL) tertiles of glyphosate exposure than term Blacks (n=7, 54%), although the difference was not statistically significant (p=0.43). Higher urinary glyphosate was associated with lower odds of preterm birth (odds ratio=0.75, 95% confidence interval 0.16-3.68), adjusted for covariates, although also not statistically significant. The odds varied by race, with OR=0.60 (95% CI: 0.11-3.4) among whites and OR=1.40 (95% CI: 0.28-7.02) among Blacks, although the interaction was not statistically significant. CONCLUSIONS:Glyphosate exposure varied by maternal race with elevated exposure in Blacks. There was no association found between urinary glyphosate levels and preterm birth, suggesting that glyphosate may not be a preterm birth risk factor. KEYWORDS: Glyphosate, Pregnancy Outcomes, Risk Assessment, Exposure assessment-biomarkers of exposure

Per-and Polyfluoroalkyl Substances (PFAS) Concentrations in Serum and Drinking Water in Pregnant Women from the Greater Cincinnati Area HOME Study

BACKGROUND AND AIM: The occurrence, fate, and transport of PFAS in the environment is understood, but the contribution of drinking water to serum PFAS concentrations in humans is poorly defined. METHODS: We examined data from a prospective pregnancy and birth cohort (HOME Study) in Cincinnati, Ohio. We quantified PFOA and PFOS in sera of 227 pregnant women at 16 weeks gestation between 2003 and 2006. Tap water was collected from the participants’ homes within one month of blood collection. We mapped serum and tap water PFAS concentrations using ArcGIS and examined clustering via spatial hotspot analyses for each participant. RESULTS:The median (range) of PFOA serum concentration in pregnant HOME Study participants between 2003-2006 was 5.4 (0.5-24.5) ng/ml, which is over twice the geometric mean serum concentration of 2.4 ng/l as measured in a representative sample of pregnant women in NHANES 2003 and 2004. Median PFOA drinking water concentrations in samples collected from participants’ homes were 3.7 ng/l in 2003, 4.5 ng/l in 2004, 6.4 ng/l in 2005 and 11.0 ng/l in 2006. For each doubling of water PFOA concentration, serum PFOA increased by 0.6 ng/l (95% CI: 0.02, 1.20) after adjusting for water source type (bottled/filtered vs tap water). For every doubling of water PFOS, serum PFOS increased 0.95 ng/l (95%CI: -0.10, 2.00). CONCLUSIONS:Drinking water is an important contributing source of PFAS exposure in pregnant women. This research adds to the literature, helping to delineate the relationship between drinking water and circulating serum concentrations of PFAS in pregnant women. The views expressed in this abstract are those of the authors and do not necessarily reflect the views or policies of the U.S. EPA. KEYWORDS: PFAS, drinking water, pregnant women, HOME Study, Cincinnati

High-performance 4096× ultra-high CPV module based on multiple concentrator units and optical guides.

Ultra-high concentrator photovoltaic systems aim to enhance the conversion efficiency of sunlight and to reduce the cost of electricity. However, it is still necessary to develop optical systems with higher efficiencies and angular tolerances for them to become a reality. This Letter proposes a novel design that is able to achieve a geometric concentration of 4096×. The system consists of four concentrator units based on parabolic mirrors and optical guides that concentrate the sunlight onto a single cell. Additionally, a preliminary proof-of-concept module has been assembled for validation purposes. The novel design exceeds the optical efficiency of the existing systems, ≈84%, and offers almost double acceptance angles, ≈0.6∘.

Unlocking Higher Power Efficiencies in Luminescent Solar Concentrators through Anisotropic Luminophore Emission.

The luminescent solar concentrator (LSC) offers a potential pathway for achieving low-cost, fixed-tilt light concentration. Despite decades of research, conversion efficiency for LSC modules has fallen far short of that achievable by geometric concentrators. However, recent advances in anisotropically emitting nanophotonic structures could enable a significant step forward in efficiency. Here, we employ Monte Carlo ray-trace modeling to evaluate the conversion efficiency for anisotropic luminophore emission as a function of photoluminescence quantum yield, waveguide concentration, and geometric gain. By spanning the full LSC parameter space, we define a roadmap toward high conversion efficiency. An analytical function is derived for the dark radiative current of an LSC to calculate the conversion efficiency from the ray-tracing results. We show that luminescent concentrator conversion efficiency can be increased from the current record value of 7.1-9.6% by incorporating anisotropy. We provide design parameters for optimized luminescent solar concentrators with practical geometrical gains of 10. Using luminophores with strongly anisotropic emission and high (99%) quantum yield, we conclude that conversion efficiencies beyond 28% are achievable. This analysis reveals that for high LSC performance, waveguide losses are as important as the luminophore quantum yield.

Concentrations of Lead, Mercury, Arsenic, Cadmium, Manganese, and Aluminum in the Blood of Pakistani Children with and without Autism Spectrum Disorder and Their Associated Factors.

Background: Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with early onset in utero or childhood. Environmental exposure to six metals (Pb, Hg, As, Cd, Mn, Al) is believed to be associated with ASD directly or interactively with genes. Objective: To assess the association of ASD among Pakistani children with the six metals and genotype frequencies of three GST genes (GSTP1, GSTM1, GSTT1). Methods: We enrolled 30 ASD cases, age 2–12 years old, and 30 age- and sex-matched typically developing (TD) controls in Karachi, Pakistan. We assessed associations of ASD status with various factors using Conditional Logistic Regression models. We also used General Linear Models to assess possible interaction of blood Mn and Pb concentrations with the three GST genes in relation to ASD status. Results: The unadjusted difference between ASD and TD groups in terms of geometric mean blood Pb concentrations was marginally significant (p = 0.05), but for Al concentrations, the adjusted difference was marginally significant (p = 0.06). Conclusions: This is the first study reporting six blood metal concentrations of Pakistani children with ASD. Estimates provided for possible interactions of GST genes with Mn and Pb in relation to ASD status are valuable for designing future similar studies.

Intrapulmonary pharmacokinetic profile of cefiderocol in mechanically ventilated patients with pneumonia.

ObjectivesLung penetration of cefiderocol, a novel siderophore cephalosporin approved for treatment of nosocomial pneumonia, has previously been evaluated in healthy subjects. This study assessed the intrapulmonary pharmacokinetic profile of cefiderocol at steady state in hospitalized, mechanically ventilated pneumonia patients.MethodsPatients received cefiderocol 2 g (or ≤1.5 g if renally impaired), administered IV q8h as a 3 h infusion, or 2 g q6h if patients had augmented renal function (estimated CLCR > 120 mL/min). After multiple doses, each patient underwent a single bronchoalveolar lavage (BAL) procedure either at the end of the infusion or at 2 h after the end of infusion. Plasma samples were collected at 1, 3, 5 and 7 h after the start of infusion. After correcting for BAL dilution, cefiderocol concentrations in epithelial lining fluid (ELF) for each patient and the ELF/unbound plasma concentration ratio (RC, E/P) were calculated. Safety was assessed up to 7 days after the last cefiderocol dose.ResultsSeven patients received cefiderocol. Geometric mean ELF concentration of cefiderocol was 7.63 mg/L at the end of infusion and 10.40 mg/L at 2 h after the end of infusion. RC, E/P was 0.212 at the end of infusion and 0.547 at 2 h after the end of infusion, suggesting delayed lung distribution. There were no adverse drug reactions.ConclusionsThe results suggest that cefiderocol penetrates the ELF in critically ill pneumonia patients with concentrations that are sufficient to treat Gram-negative bacteria with an MIC of ≤4 mg/L.

Hair to blood mercury concentration ratios and a retrospective hair segmental mercury analysis in the Northwest Territories, Canada

Concentrations of total mercury were measured in blood and hair samples collected as part of a human biomonitoring project conducted in First Nations communities of the Mackenzie Valley, Northwest Territories, Canada. Hair (n = 443) and blood (n = 276) samples were obtained from six communities in the Dehcho region and three communities in the Sahtú region of the Mackenzie Valley. The aim of this paper was to calculate hair to blood mercury ratios (for matched samples) and determine if: 1) ratios differed significantly between the two regions; 2) ratios differed from the 250:1 ratio proposed by the WHO; and, 3) point estimates of hair to blood mercury ratios could be used to estimate blood mercury concentrations. In addition, this paper aims to determine if there were seasonal patterns in hair mercury concentrations in these regions and if so, if patterns were related to among-season variability in fish consumption.The majority of mercury levels in hair and blood were below relevant health-based guidance values. The geometric mean hair (most recent segment) to blood mercury ratio (stratified by region) was 619:1 for the Dehcho region and 1220:1 for the Sahtú region. Mean log-transformed hair to blood mercury ratios were statistically significantly different between the two regions. Hair to blood ratios calculated in this study were far higher (2–5 times higher) than those typically reported in the literature and there was a large amount of inter-individual variation in calculated ratios (range: 114:1 to 4290:1). Using the 250:1 ratio derived by the World Health Organisation to estimate blood mercury concentrations from hair mercury concentrations would substantially over-estimate blood mercury concentrations in the studied regions. However, geometric mean site-specific hair to blood mercury ratios can provide estimates of measures of central tendency for blood mercury concentrations from hair mercury concentrations at a population level.Mercury concentrations were determined in segments of long hair samples to examine exposure of participants to mercury over the past year. Hair segments were assigned to six time periods and the highest hair mercury concentrations were generally observed in hair segments that aligned with September/October and November/December, whereas the lowest hair mercury concentrations were aligned with March/April and May/June. Mean log-transformed hair mercury concentrations were statistically significantly different between time periods. Between time periods (e.g., September/October vs. March/April), the geometric mean mercury concentration in hair differed by up to 0.22 μg/g, and the upper margins of mercury exposure (e.g., 95th percentile of hair mercury) varied by up to 0.86 μg/g. Results from self-reported fish consumption frequency questionnaires (subset of participants; n = 170) showed total fish intake peaked in late summer, decreased during the winter, and then increased during the spring. Visual assessment of results indicated that mean hair mercury concentrations followed this same seasonal pattern. Results from mixed effects models, however, indicated that variability in hair mercury concentrations among time periods was not best explained by total fish consumption frequency. Instead, seasonal trends in hair mercury concentrations may be more related to the consumption of specific fish species (rather than total wild-harvested fish in general). Future work should examine whether seasonal changes in the consumption of specific fish species are associated with seasonal changes in hair mercury concentrations.

Turning-induced surface integrity for a fillet radius in a 316L austenitic stainless steel

Turning is a machining process extensively applied to produce revolution parts. Durability of these parts are known to depend on the turning process signature that is often referred as surface integrity. The surface integrity generated in a fillet radius has been barely studied in the literature so far, despite the well-known geometrical stress concentration factor of such singularities. Therefore this paper deals with the investigation of machining-induced surface integrity when turning a fillet radius in a 316L austenitic stainless steel. Different characterization methods are used for that purpose - SEM, EBSD, nanoindentation and X-Ray diffraction. It points out that the turning-induced consequences are not homogeneous along the machined profile. Residual stresses are strongly affected and microstructure is highly modified over a depth of 80 μm that leads to a mechanical properties gradient. It is evidenced that the average uncut chip thickness is the main governing parameter regarding surface integrity. It is also reported that deformation twins appear in the affected zone. It highlights that turning-induced microstructure evolution at a given depth is rather a consequence of severe plastic deformation at high strain rate than dynamic recrystallization. • For the first time, turning-induced surface integrity in 316L is studied along a fillet radius. • Turning-induced affected depth depends on angular position in the fillet radius. • Affected depth is twice larger for longitudinal turning than for face turning. • Microstructure evolution is correlated with average uncut chip thickness parameter and cutting edge radius. • Severe plastic deformation at room temperature or/and high strain rate governs microstructural evolution (deformation twins).

Contamination of Air and Surfaces in Workplaces with SARS-CoV-2 Virus: A Systematic Review.

ObjectivesThis systematic review aimed to evaluate the evidence for air and surface contamination of workplace environments with SARS-CoV-2 RNA and the quality of the methods used to identify actions necessary to improve the quality of the data.MethodsWe searched Web of Science and Google Scholar until 24 December 2020 for relevant articles and extracted data on methodology and results.ResultsThe vast majority of data come from healthcare settings, with typically around 6% of samples having detectable concentrations of SARS-CoV-2 RNA and almost none of the samples collected had viable virus. There were a wide variety of methods used to measure airborne virus, although surface sampling was generally undertaken using nylon flocked swabs. Overall, the quality of the measurements was poor. Only a small number of studies reported the airborne concentration of SARS-CoV-2 virus RNA, mostly just reporting the detectable concentration values without reference to the detection limit. Imputing the geometric mean air concentration assuming the limit of detection was the lowest reported value, suggests typical concentrations in healthcare settings may be around 0.01 SARS-CoV-2 virus RNA copies m−3. Data on surface virus loading per unit area were mostly unavailable.ConclusionsThe reliability of the reported data is uncertain. The methods used for measuring SARS-CoV-2 and other respiratory viruses in work environments should be standardized to facilitate more consistent interpretation of contamination and to help reliably estimate worker exposure.

A spectral splitting planar solar concentrator with a linear compound parabolic lightguide for optical fiber daylighting

For the sake of taking full advantage of solar energy, an optical fiber daylighting system is proposed in this paper. To achieve a uniform irradiance distribution and a great concentration ratio at high level, innovative collectors and compound parabolic lightguide (CPL) are designed based on edge-ray principle and total internal reflection (TIR). The surface of the collectors is designed as paraboloid to drive the concentrated rays possessing a certain level of oblique angles before coupling into the lightguide, which simplifies the design difficulty and processing difficulty of the couplers and suppresses the light leakage. The beam splitters can separate full spectrum rays into visible and invisible parts. The invisible light for compensation is collected by collector array and reflected into the solar cell which converts solar energy to electricity and drives the LED array together with the extra electricity. The LED array is considered as the compensation part because it can adjust the luminous intensity at any time according to the changes of the illuminance from the visible part. The CPL can improve the geometric concentration ratio compared to traditional planar lightguide. The simulation and experimental results show that the proposed optical fiber daylighting has geometric concentration of 200 and optical efficiency of 50%, and its concentrating characteristics can maximize the use of solar energy.

Carbon monoxide exposures in wildland firefighters in the United States and targets for exposure reduction.

Background:Every year thousands of wildland firefighters (WFFs) work to suppress wildfires to protect public safety, health, and property. Although much effort has been put toward mitigating air pollutant exposures for the public and WFFs, the current burden in this worker population is unclear as are the most effective exposure reduction strategies.Objective:Quantify fireline carbon monoxide (CO) exposures in WFFs and identify predictors of exposures.Methods:We collected one-minute breathing zone CO measurements on 246 WFFs assigned to fires between 2015 and 2017. We used generalized estimating equations to evaluate predictors of CO exposure.Results:Approximately 5 percent of WFFs had fireline CO exposure means exceeding the National Wildfire Coordinating Group’s (NWCG) occupational exposure limit of 16 ppm. Relative to operational breaks, direct suppression-related job tasks were associated with 56% (95% CI: 47%, 65%) higher geometric mean CO concentrations, adjusted for incident type, crew type, and fire location. WFF perception of smoke exposure was a strong predictor of measured CO exposure.Significance:Specific job tasks related to direct suppression and WFF perceptions of smoke exposure are potential opportunities for targeted interventions aimed at minimizing exposure to smoke.

In Vitro Antifungal Activity of Luliconazole, Efinaconazole, and Nine Comparators Against Aspergillus and Candida Strains Isolated from Otomycosis

Background: Aspergillus and Candida species are the most commonly identified fungal pathogens in otomycosis. However, we usually encounter some difficulties in its treatment because many patients show resistance to antifungal agents and present a high recurrence rate. Objectives: The current research was conducted to compare the in vitro activities of luliconazole (LUL), and efinaconazole (EFN) and the nine comparators on Aspergillus and Candida strains isolated from otomycosis. Methods: The in vitro activities of nine common antifungal drugs (amphotericin B (AMB), voriconazole (VRC), fluconazole (FLU), itraconazole (ITC), ketoconazole (KTO), clotrimazole (CLO), nystatin (NYS), terbinafine (TRB), and caspofungin (CAS)) and two novel new azoles (LUL and EFN) against 108 clinical isolates of Aspergillus and Candida species obtained from otomycosis were assessed according to the CLSI broth microdilution document. Results: The LUL and EFN had the geometric mean minimum inhibitory concentrations (GM MICs) of 0.098 and 0.109 μg/mL against all Aspergillus strains, respectively. Furthermore, the GM MICs of all Candida isolates for LUL, EFN, CAS, CLO, VRC, AMB, ITC, KTO, FLU, NYS, and TRB were calculated to be 0.133, 0.144, 0.194, 0.219, 0.475, 0.537, 0.655, 1.277, 4.905, 9.372, and 13.592 μg/mL, respectively. Additionally, 6 (35.29%), 2 (11.7%), and 1 (5.88%) Candida isolates were resistant to FLU, CAS, and VRC, respectively. Conclusions: As the findings indicated, LUL and EFN showed the lowest GM MIC values against the examined species. Accordingly, these novel imidazole and triazole antifungal agents can be regarded as proper candidates for the treatment of otomycosis caused by Aspergillus and Candida strains.

Long term performance analysis of low concentrating photovoltaic (LCPV) systems for building retrofit

Low concentrating photovoltaic (LCPV) systems offer viable solution for generating higher energy output per unit cell area compared to a typical flat PV panel, making them potential candidates for building retrofit. However, the best LCPV geometry for a given location is yet to be identified. The current study investigates the technical, economic and environmental feasibility of three geometrically equivalent LCPV designs installed at a building within Brunel University London (UK). The studied LCPV systems comprised of Asymmetric Compound Parabolic Concentrating (ACPC), Compound Parabolic Concentrating (CPC) and V-Trough optical concentrators with the post-truncation geometric concentration ratios of 1.53, 1.46, 1.40 respectively. The performances of the prototypes have been monitored every 15 min over 10 months and analyzed on hourly, daily, and monthly basis. Performance parameters such as reference yield, array yield, performance ratio, electrical conversion efficiency and the generated energy output per unit area have been derived and presented. Payback periods have been estimated in two separate scenarios. Measurements have showed that the ACPC integrated LCPV achieved the highest annual optical efficiency generating the highest amount of electrical energy per unit cell area of 246.2 kWh/m2 compared to CPC-LCPV, V-Trough-LCPV and conventional flat modules which produced 224.6 kWh/m2, 196.1 kWh/m2 and 185.4 kWh/m2 respectively. One particular conclusion of the study is that the ACPC based LCPVs perform better in locations where diffuse component of solar radiation is predominant as in the case of the UK. Consequently, ACPC based LCPV modules are recommended for the building retrofit in such locations.

Design and testing of concentrated photovoltaic arrays for retrofitting of solar thermal parabolic trough collectors

A new design and retrofit approach for a concentrated photovoltaic thermal (CPV-T) system based on a parabolic trough collector is presented. The design differs from previous hybrid architectures, employing a significantly simplified topology in order to reduce costs while keeping electrical efficiency high. To achieve this ambitious goal, the absorber tube of a conventional parabolic trough collector used in thermal systems is replaced by a newly developed hybrid absorber equipped with multi-junction solar cells. This offers the advantage that existing solar thermal parabolic trough facilities can be easily retrofitted, making the system scalable and cost-effective. A scaled prototype of the system was designed and tested in Graz, Austria. During on-sun tests an average electrical system efficiency of 26.8% with a simultaneous thermal efficiency of 48.8% was measured using a geometric concentration ratio of 150 (DNI based). This leads to an overall average system efficiency of 75.5%. Moreover, a solar cell peak efficiency of 30% was achieved, one of the highest measured solar-to-DC efficiencies for a parabolic trough-based solar collector. Special attention was paid to the temperature difference between the solar cells and the heat transfer fluid in order to ensure sufficient cooling of the cells and maximize thermal efficiency. The electrical, thermal and overall efficiencies at different heat transfer fluid temperatures were measured (17°C - 90°C) and their coefficients were derived. This work serves as an experimental proof-of-concept for the application of solar cells in parabolic trough collectors, thereby opening up new possibilities for cost reduction of CPV-T systems.