Outdoor Test Results Research Articles

Theoretical and experimental investigation of a pilot-scale solar air-heated humidification dehumidification desalination system

Among the various humidification dehumidification desalination (HDD) system configurations, the air-heated cycle has demonstrated promising results in small lab-scale setup investigations, whereas pilot-scale studies are lacking. This study theoretically and experimentally investigates the performance of a pilot-scale flat-plate solar air collector-powered HDD unit. An optical-thermal model for a solar air collector and a transport model based on heat and mass transfer for the dehumidifier have been developed and validated using experimental data. The triangular-shaped turbulators on the absorber plate of a solar collector with relative roughness pitches of 2.3, 4.61, and 6.92 are built and optimized for maximum distillate yield. Perforated turbulators with open area ratios of 5.5 %, 12.25 %, and 21.8 % are evaluated. To reduce distillate production costs in the HDD system, naturally available wood apple shell with drilled holes is tested in the humidifier. Outdoor test results revealed that at an average solar intensity of 712 W/m2, the proposed system achieved a maximum distillate yield and gain output ratio of 17.34 kg/day and 0.65, respectively. Wood apple shell packing demonstrated better distillate yield, gain output ratio, and humidifier performance potential factor compared to the commercially available raschig ring and cascade mini-ring packings. Moreover, the optimal performance of the solar air collector with solid turbulators was obtained at a relative roughness pitch of 4.61 due to sufficient longitudinal space to effectively prevent flow separation and reattachment of the free shear layer. Turbulators with a 12.25 % open area ratio exhibited the highest Nusselt number and low friction factor.

Techniques to mitigate membrane displacement for vacuum-membrane solar-dish facets

The prospects of a multifaceted vacuum-membrane solar dish concentrator are considered in this work. The membrane depths of these facets can shift slightly due to varying ambient conditions throughout an operational day, leading to major focal point shifts and a reduced overall efficiency. The purpose of this work was to experimentally investigate different methods of membrane displacement mitigation. A controlled-environment (indoor) enclosure was employed to examine the effects of static ambient conditions, allowing for the independent manipulation of the surrounding pressure and temperature. Various manufacturing techniques were also investigated within the controlled-environment enclosure, which included alterations in pretension, changes in membrane thickness and adjustments to overall facet sizes. Furthermore, outdoor tests were conducted to determine how solar radiation and convection affected membrane displacement as well as to investigate the performance of various membrane depth control strategies using an Arduino Uno microcontroller. The indoor results showed that opting for a small facet would minimize membrane displacement. The results were supported by material tests and a finite element analysis. The outdoor test results indicated that solar radiation and wind affected the internal temperature and consequently also affected the membrane depth. Furthermore, a focus control system maintaining a constant differential pressure across the membrane achieved the required accuracy of ±2 mm membrane displacement limitation. However, another focus control system consisting of a Hall effect module actively monitoring membrane depth emerged as the most effective, with an increase of about 0.09 mm and a decrease of approximately 0.02 mm from an initial depth of 10 mm. This level of stability with a focus control system will ensure that the facet maintains a consistent optical performance, ultimately advancing the reliability and efficiency of low-cost vacuum-membrane technology.

A Novel Method for Increasing Phase‐Change Microcapsules in Nanofiber Textile through Electrospinning

AbstractPhase‐change textiles can achieve temperature regulation in variable ambient environments, however, augmenting the amounts of phase‐change materials (PCMs) in textiles remains a significant challenge due to the occurrence of leakage with higher amounts. Herein, a novel approach is proposed for the fabrication of a hierarchical nanofiber textile embedded with a substantial quantity of phase‐change microcapsules (PCMC) using electrospinning. Such nanofiber textile is composed of a polyvinylidene fluoride‐hexafluoropropylene fibers (PVDF‐HFP) layer and a polyvinyl butyral fibers doped with 60 wt% of PCMC (PVB/PCMC‐60) layer. Gratifyingly, doped PCMC shows no signs of rupture and exhibits excellent cycling stability. Furthermore, the incorporation of the PCMC does not affect the spectral characteristics of the PVDF‐HFP layer while providing a substantial enthalpy of fusion (92.6 J g−1) to the PVB/PCMC‐60 layer. This serves to compensate for the deficiency in radiative cooling capacity and effectively mitigates temperature fluctuations and overheating of the textile. Outdoor test results indicate that the nanofiber textile can achieve temperature drops of 3.7 and 14.8 °C compared to textile without the PCMC (namely PVDF‐HFP/PVB) and cotton, and attains a subambient temperature drop of 6.5 °C. Additionally, the nanofiber textile exhibits desirable mechanical strength, flexibility, washability, breathability, moisture permeability, and sun protection.

Self-Cleaning Solar Mirror Coatings: From the Laboratory Scale to Prototype Field Tests

In this study, a low-cost, scalable and robust process is proposed as an innovative method for coating solar mirrors with a self-cleaning, transparent in the full solar range and versatile material based on auxetic aluminum nitrides, previously obtained at the laboratory scale. This work presents the scaling-up of the fabrication process from the laboratory to prototypal scale and the preliminary results of outdoor self-cleaning solar mirror field tests in the demonstrative concentrating solar power (CSP) plant ENEASHIP located in Casaccia (Rome) ENEA Research Center. Prototypes with a size of 50 × 40 cm have shown stability in external conditions: no coating degradation occurred during the test campaign. Their washing restores the initial reflectance affected by soiling and the self-cleaning performance allows for the utilization of a reduced quantity of water for cleaning operations with respect to the uncoated glass of back surface mirrors. A similar self-cleaning AlN coating could be utilized on other solar components affected by soiling, such as the glass envelopes in heat-collecting elements, PV panels and other parts where a self-cleaning performance combined with an optical one is required.

From Sunrise to Sunset: Unraveling Metastability in Perovskite Solar Cells by Coupled Outdoor Testing and Energy Yield Modelling

AbstractPerovskite‐based solar cells exhibit peculiar outdoor performance which is not yet fully understood. The results of outdoor tests may contain hidden, but valuable information that cannot be fully extracted from measurements alone. One such phenomenon is the effect of nighttime degradation and the subsequent light‐soaking recovery, which can take from a few hours in the morning up to the entire day. In this work, long‐term outdoor monitoring is combined with energy yield modeling to qualitatively and quantitatively investigate the effect of light‐soaking recovery in both single junction and tandem perovskite‐based devices. Following the novel methodology presented in this study, it is observed that the light‐soaking effect depends not only on the daily irradiation but also on the device temperature, and it can be described using a simple empirical formalism. Incorporating this dependency into the energy yield model results in an excellent agreement between the simulated and the measured outdoor data, which allows to perform long‐term prediction studies. The model estimates that the light‐soaking metastability effect decreases the attainable annual energy yield by up to ≈5% for the studied single junction devices, and for tandems by up to ≈3%, depending on the geographical location, and even more for non‐optimal device orientation.

Study on shrinkage and creep effect of steel truss-stiffened continuous rigid frame bridge considering variable temperature and relative humidity

In this study, indoor-outdoor comparison tests of shrinkage and creep were carried out in northwest China. The experimental results were compared with commonly used models of shrinkage and creep, some of which have adapted different methods for temperature and humidity correction. A finite element model for a continuous rigid-frame bridge with steel truss bracing was established. The calculated values from different shrinkage and creep models were then compared with the measured deflection values. An analysis was conducted to determine the influence of variable temperature and humidity on the long-term mechanical behavior of the steel truss-stiffened continuous rigid-frame bridge.The results show that when the concrete reaches the age of one year, the creep coefficient for the outdoor environment is 18.5% smaller than that in the indoor environment, while the outdoor shrinkage strain is 16.0% smaller. The CEB 90 model agrees best with the indoor test results. The corrected shrinkage and creep model (CSCM) is the closest to the outdoor test results, and the fib2010 model ranked second. The predicted values from CSCM exhibit the best agreement with the measured deflection values after the bridge completion. The CEB 90 model's predicted values for deflection of the main girder, longitudinal displacement of the pier, the maximum stress in steel trusses, and prestressing loss are lower than those in the CSCM after 20 years of construction, indicating that the influence of temperature and relative humidity variations on shrinkage and creep effect of the bridge can not be negligible.

Investigations on a solar humidification dehumidification desalination system equipped with various packing materials and multi-stage bubble column dehumidifier.

This work presents the theoretical and experimental investigation of a solar-powered humidification dehumidification desalination (HDD) system with different humidifier packing materials and a two-stage bubble column dehumidifier (BCD). Naturally available coconut shells (CS) and coconut shells with drilled holes (CSH) on the surface to improve water permeability were used as packing materials in the humidifier, and their performance was compared with that of commercial-type pall ring (PR) and raschig ring (RR) packings. An in-house developed numerical model of the HDD system in conjunction with a flat plate solar water collector was used in this study. Steady-state experimental results showed that CSH packing exhibited the highest volumetric mass transfer coefficient (0.00852kg/s), resulting in maximum humidifier efficiency (96%) and freshwater yield (2.16kg/hr), followed by PR (0.00841kg/s, 94%, and 2.137kg/hr), CS (0.00831kg/s, 90%, and 2.127kg/hr), and RR (0.0081kg/s, 81%, and 2.087kg/hr) at feedwater mass flow rate of 1.5kg/min and humidifier inlet temperature of 75 [Formula: see text]. Furthermore, transient outdoor test results showed that using a two-stage configuration in a BCD increased the daily average effectiveness to 0.93, as against 0.79 for a single-stage BCD. Employing CSH instead of PR and RR packings in the humidifier reduced freshwater costs by 6.2% and 7.6%, respectively.

Effect of Curing Condition on the Strength Evolution of Polyether Polyurethane Concrete

Polyether polyurethane concrete (PPC) is a new type of cold-mixed and cold-paved material. In this study, the strength evaluation mechanism of PPC was systematically investigated through test methods at different scales. First, the strength evolution mechanism of the polyurethane binder itself was characterized by Fourier transform infrared spectrometer (FTIR). Subsequently, different significant influence factors including temperature, humidity, and catalyst dosage on the strength evolution of PPC were analyzed and quantified by indirect tensile test. Third, a systematic statistical analysis of these influencing factors was performed by statistical methods to quantify their contribution to the strength formation of PPC. The strength of PPC was closely related to the strength evolution of polyurethane binder, and the order of influence factors on strength evolution was temperature > humidity > catalyst dosage. Finally, considering these influence factors, a prediction model of PPC curing time was established. The predicted curing time was compared with the outdoor test results, and the results verified the validity and rationality of the model.

Robust Pedestrian Dead Reckoning Integrating Magnetic Field Signals and Digital Terrestrial Multimedia Broadcasting Signals

Currently, many positioning technologies complementary to Global Navigation Satellite System (GNSS) are providing ubiquitous positioning services, especially the coupling positioning of Pedestrian Dead Reckoning (PDR) and other signals. Magnetic field signals are stable and ubiquitous, while Digital Terrestrial Multimedia Broadcasting (DTMB) signals have strong penetration and stable transmission over a large range. To improve the positioning performance of PDR, this paper proposes a robust PDR integrating magnetic field signals and DTMB signals. In our study, the Spiking Neural Network (SNN) is first used to learn the magnetic field signals of the environment, and then the learning model is used to detect the magnetic field landmarks. At the same time, the DTMB signals are collected by the self-developed signal receiver, and then the carrier phase ranging of the DTMB signals is realized. Finally, robust pedestrian positioning is achieved by integrating position information from magnetic field landmarks and ranging information from DTMB signals through Extended Kalman Filter (EKF). We have conducted indoor and outdoor field tests to verify the proposed method, and the outdoor field test results showed that the positioning error cumulative distribution of the proposed method reaches 2.84 m at a 68% probability level, while that of the PDR only reaches 8.77 m. The proposed method has been validated to be effective and has good positioning performance, providing an alternative solution for seamless indoor and outdoor positioning.

Potential-induced degradation of n-type front-emitter crystalline silicon photovoltaic modules — Comparison between indoor and outdoor test results

We perform indoor and outdoor potential-induced degradation (PID) tests for n-type front-emitter (n-FE) crystalline Si (c-Si) photovoltaic (PV) modules and compare their results. The indoor/outdoor acceleration factor for the polarization-type PID (PID-p) of n-FE PV modules is found to be ∼1000 at an indoor test temperature of 85 °C. We observe the progression of the PID-p of n-FE PV modules in rainy days, while their performance is recovered in sunny days. This may be because of the formation of a water film on a module surface acting as a conductive film, resulting in a larger electric field near the n-FE cells in rainy days. The recovery of the PV performance of n-FE modules in sunny days can partly explain the large acceleration factor for the indoor PID test against the outdoor test. • We performed indoor and outdoor PID tests for n-FE PV modules. • n-FE PV modules show polarization-type PID (PID-p) both indoors and outdoors. • The acceleration factor for the PID-p is ∼1000 at an indoor test temperature of 85 °C. • We observe the recovery of PID-p for the outdoor modules in sunny days. • The recovery may be one of the reasons for the large acceleration factor.

Exercise-induced bronchoconstriction is associated with air humidity and particulate matter concentration in preschool children.

Long-term exposure to air pollution is connected to asthma morbidity in children. Exercise-induced bronchoconstriction (EIB) is common in asthma, and the free running test outdoors is an important method for diagnosing asthma in children. It is not known whether momentary air pollution exposure affects the results of outdoor exercise tests in children. We analyzed all reliable exercise challenge tests with impulse oscillometry in children (n = 868) performed between January 2012 and April 2015 at Tampere University Hospital. Pollutant concentrations (PM2.5 , NO2 , and O3 ) at the time of the exercise test were collected from public registers. We compared the pollutant concentrations with the proportion and severity of EIB and adjusted the analyses for air humidity and pollen counts. Pollution levels were rarely high (median PM2.5 6.0 µg/m3 , NO2 12.0 µg/m3 , and O3 47.0 µg/m3 ). The relative change in resistance at 5 Hz after exercise did not correlate with O3 , NO2 or PM2.5 concentrations (p values 0.065-0.884). In multivariate logistic regression, we compared the effects of PM2.5 over 10 µg/m³, absolute humidity (AH) over 10 g/m³ and alder or birch pollen concentration over 10 grains/m³. High (over 10 g/m3 ) AH was associated with decreased incidence (OR 0.31, p value 0.004), and PM2.5 over 10 µg/m³ was associated with increased incidence (OR 1.69, p value 0.036) of EIB. Even low PM2.5 levels may have an effect on EIB in children. Of the other properties of air, only AH was associated with the incidence of EIB.

A novel spectral-splitting solar indoor lighting system with reflective direct-absorption cavity: Optical and thermal performance investigating

Sunlight contains a wide range of the spectrum, and the spectrum used for plant photosynthesis is mainly located in the visible band (380–780 nm), while the spectral energy of other bands is not suitable for plant growth because it generates heat in summer. In this paper, a novel spectral-splitting solar indoor lighting system with a reflective direct-absorption cavity for Plant Factory was developed, which used the combination of pure water and spectrum splitting mirrors to perfectly separate the visible light and non-visible light of sunlight. Visible light was conducted to Plant Factory by optical fiber to provide illumination for plants, and non-visible light was trapped and then absorbed by a reflective direct-absorption cavity and convert into thermal energy. The structural parameters of the reflective direct-absorption cavity were optimized based on the Monte Carlo method, and the light conduction and heat transfer models were established to analyze the photo-thermal performance of the device. The results of indoor and outdoor tests showed that the solar energy utilization efficiency of the device could reach 50%, among which the light transmission efficiency and heat collection efficiency were 24.7% and 25.3%, respectively. The temperature of the optical fiber coupling end face was kept in the range of 27–37 °C, which can ensure the safe and efficient operation of the optical fiber. It provides a new idea for the protection of optical fiber, the efficiency improvement of sunlight conduction lighting technologies, and the energy saving of the Plant Factory lighting in the future.

Cooperative Navigation for Low-Cost UAV Swarm Based on Sigma Point Belief Propagation

As navigation is a key to task execution of micro unmanned aerial vehicle (UAV) swarm, the cooperative navigation (CN) method that integrates relative measurements between UAVs has attracted widespread attention due to its performance advantages. In view of the precision and efficiency of cooperative navigation for low-cost micro UAV swarm, this paper proposes a sigma point belief propagation-based (SPBP) CN method that can integrate self-measurement data and inter-UAV ranging in a distributed manner so as to improve the absolute positioning performance of UAV swarm. The method divides the sigma point filter into two steps: the first is to integrate local measurement data; the second is to approximate the belief of position based on the mean and covariance of the state, and pass message by augmentation, resampling and cooperative measurement update of the state to realize a low-complexity approximation to traditional message passing method. The simulation results and outdoor flight test results show that with similar performance, the proposed CN method has a calculation load more than 20 times less than traditional BP algorithms.

Smart Maintenance and Health Monitoring of Buildings and Infrastructure Using High-Resolution Laser Scanners

An integrated structural health monitoring system was proposed for the rapid assessment of damage on large structures such as high-rise buildings, industrial chimneys, long-span bridges, and similar facilities. The system used ground-based high-resolution IR (infrared) laser vibrometers to measure the dynamic response of structures. To utilize these devices as automated scanners in a fast and efficient way, a new targeting and control mechanism was developed. Different aspects of the proposed system, such as targeting precision and scanning efficiency, were discussed by presenting the results of laboratory experiments and outdoor vibration tests. In addition to the enhancements made in the measurement system, a new methodology was introduced to analyze the recorded vibration response. A novel data processing approach, based on a comparison of the mode shapes calculated on the healthy reference and damaged structures, made it possible to determine the location of the flaw. If available, a finite element model of the analyzed structure also enables the degree of the damage to be calculated very accurately. The reliability of the identification algorithm was demonstrated by conducting extensive numerical simulations and vibration tests on scale building models.

Development and Assessment of Methods for Predicting Rainfall in Unmeasured Watersheds Using the Relation Between Observed and Sensor-Measured Rainfall

Recently, with the development of information and communication technology and the Internet of Things (IoT), observation technology using sensors is being applied in a variety of ways, such as using a sensor to observe rainfall in an unmeasured area. In this study, the relationship between the rainfall sensor signal (S) and the amount of rainfall (R) was developed through an experiment in an artificial rainfall generator, and the applicability was evaluated through outdoor observation. The coefficient of determination of the relational expression developed through the indoor experiment was 0.95, the mean absolute error was 2.66 mm/hr, the root mean square error was 3.87 mm/hr, the efficiency coefficient was 0.89, and the concordance index was 0.97, showing very high reliability. In the outdoor test results, the error rate was 7.96% when comparing the data from the rainfall sensors in vehicles and the precipitation station, which were not observed at the same location. Despite such errors, it is judged that accurate rainfall observation using a rainfall sensor is possible in an area where a precipitation station is not installed.

제주형 태양광 시스템 실증 연구

Jeju island has unique weather such as strong and salty wind. Thus, it is necessary to select stronger PV modules and system components because of Jeju island own harsh weather conditions. To secure safety against harsh weather, more severe tests were carried out for selections of PV. Actually, only test-passed-PV-modules were installed. Lastly, A option of PV mount rotation was added to protect against winds. Herein we will introduce its outdoor test results and guidelines for Jeju application.

MFDC‐net: Multifeature‐based deep convolutional neural network for single image haze removal

SummaryWhen it comes to the dehazing method based on the ambient light scattering model, there are ill‐conditioning problems of great concern. Therefore, the inaccurate estimation of the global atmospheric light and transmittance can bring about hue error phenomena, halo artifacts, and image noises. In this paper, we present an effective and efficient approach to solve above problems. Firstly, we adopt single‐threshold segmentation method and quad‐tree algorithms, which can break through the limitation that the dark channel prior theory (DCP) is not suitable for sky region, to quickly and accurately locate and estimate the global atmospheric light. Secondly, we design a new deep convolutional network architecture, which can effectively suppress the halo effect of image edges and restrain image noises, to optimize transmittance. Numerous of outdoor and synthesis haze image test results indicate that the optimized approach could shorten the processing time greatly. Besides, with more accurate global atmospheric light value and transmittance, the image noise and the halo artifact can be effectively suppressed and removed respectively, the hue error phenomenon improved, and the image contrast significantly enhanced in the dehazing results.

Implementation of polymer optical fibre sensor system for monitoring water membrane thickness on pavement surface

ABSTRACT Water membrane thickness on the surface of pavements should be monitored constantly and accurately during high-intensity rainfall to evaluate pavement safety. This is critical to the realisation of smart roads. In this study, a water membrane thickness monitoring system is built based on reflective intensity-modulated fibre-optic sensor (RIM-FOS) technology. The system comprises a sensing unit and a weak signal detection circuit, and its monitoring range and accuracy are calibrated by a specific device. Considering the environmental influence, the water membrane thickness–voltage curves at different light intensities and temperatures are obtained. Subsequently, the accuracy and effectiveness of the proposed water membrane thickness–voltage function are validated by comparing them with the outdoor test results. Finally, to ensure the survival rate of the optical fibre and the accuracy of long-term monitoring, a polymer optical fibre (POF) packaged by a process using water-blocking paste and reinforcing steel bars is employed. To prevent the bending loss during embedding from affecting the measurement results, the bending radius is suggested. The results demonstrate that the POF sensor system shows remarkable performance in terms of accuracy and temperature stability. This research will help provide an inexpensive and comprehensive safety assessment method for asphalt pavement.

A novel perspective for reflective cooling composites: Influence of the difference between the effective refractive index of polymeric matrix and inorganic functional particles

Reflective cooling composites have been successfully developed and widely utilized in common life and production. Most of the previous works focused on the effect of reflective fillers with different crystal structures or sizes on the reflective performance of composites, whereas relatively few studies have studied the influence of polymeric matrix on the reflective performance. Hence, this study, applying theoretical analysis and experimental verification, investigated the impact of the difference between the refractive index (n) of the polymeric matrix and rutile titanium dioxide (TiO2, n = 2.74) on the reflective cooling property. The theoretical analysis indicated that the n of single material is positively correlative with the reflective performance, as well as the biggish difference between the refractive index of the polymeric matrix and reflective fillers can significantly improve the reflectance of composites. Herein, the polymeric matrix was acquired by blending high-density polyethylene (HDPE, n = 1.59) and ethylene-co-octene elastomer (POE, n = 1.48), yet the addition of rutile TiO2 remained the same content of 3 wt%. The experimental results show that the total solar reflectance of neat HDPE is three times higher than that of neat POE, while the total solar reflectance of the POE/TiO2 composite increases by 3.85% in comparison of the HDPE/TiO2 composite. Besides, the HDPE/POE samples without TiO2 also have a higher reflectance compared with the neat HDPE and POE, and the reflectance of HDPE/POE increases with increasing POE content. The results of reflective performance verify the conclusions of theoretical analysis. Moreover, the reflectance of HDPE/POE/TiO2 ternary system increases with the increase of POE content. Finally, the results of outdoor and indoor temperature tests are consistent with the results of reflective performance.

Reversible Efficiency Variation of Tandem Amorphous/Microcrystalline Si Photovoltaic Modules in Outdoor Operation

The Staebler-Wronski effect in amorphous silicon based photovoltaic devices is responsible for degradation of their power conversion efficiency, within approximately the first one thousand hours of light soaking. Several experimental studies led to highlight the performance instability phenomena for the mentioned devices, underling that recovery and improvement of such performance are observable, by subjecting such devices (both of single-junction and tandem types) to DC reverse bias stresses under illumination, or to operation in the Maximum Power Point (MPP) under variable conditions of temperature and illumination. In this work, we present and discuss the results of novel recent outdoor tests on stabilized specimens (i.e., exposed to 1000 h extended light soaking, before our tests) of tandem amorphous/microcrystalline Si (a-Si/µc-Si) photovoltaic (PV) minimodules operating in their MPP, by analyzing the causes of the performance instability effects, systematically observed on a daily scale. During the mentioned tests, we have monitored the solar cell operating temperature and the incident solar spectrum at various times in different days to verify the effect of cell temperature and solar spectrum changes on the cell performances. The experimental results show a clear correlation between performance improvements of the photovoltaic modules and their thermal history during the outdoor tests, proving the interplay between defect build-up at a lower temperature and defect annealing at a higher temperature, taking place in the solar cells operated in MPP during conventional outdoor operation.