Outdoor Field Test Research Articles

Moisture performance of a new thermal insulation composite for interior application

The paper introduces prototypes of a new composite insulation product for interior application. The product consists of a standard mineral fibre insulation batt, which is wrapped in a combination of a thin fabric of moisture absorbing, capillary active material and vapour retarding membranes. The insulation composite has been tested with small samples in a laboratory setup and in an outdoor field test on a full-scale brick wall, and has so far shown promising results in comparison with other products. The paper describes the new insulation composite and the initial moisture tests that have been made with its constituents as well as results from the laboratory and field tests of its ability to prevent moisture accumulation.

Corrosion Behavior of Steel Buried in Soil Under Natural Rainfall Conditions at Outdoor Test Field

Introduction Buried steel structures generally deteriorate due to soil corrosion. The corrosion rate depends on various soil environment factors such as the water content, pH value, resistivity, and oxygen concentration (1, 2). It is well known that these factors in shallow ground usually change with rainfall. However, the relationship between these factors and the corrosion rate of buried steel under natural rainfall conditions has not been clarified. Therefore, in this study, we used electrochemical impedance spectroscopy to evaluate the corrosion behavior of steel buried in shallow ground under natural rainfall conditions at outdoor test fields. Experimental The electrode cell for the AC impedance measurements was fabricated from a carbon steel plate with dimensions of 10 × 10 mm and embedded in epoxy resin. It was buried at a depth of 90 cm in the gley soil of the experimental system at outdoor test field. The soil conditions changed with rainfall. The AC impedance measurements were carried out at constant time interval to evaluate the changes in the corrosion rate with rainfall. They were conducted over the frequency range of 0.05 Hz to 10 kHz at the AC voltage of ± 50 mV. Results and discussion Figure 1 shows the Nyquist plot of the buried steel obtained from the AC impedance measurement with different voltage conditions. The equivalent circuit is also shown in Fig. 1, where R s, R ct, C dl, and Z w are the resistance in soil, charge transfer resistance, double-layer capacitance, and Warburg impedance, respectively. At the low AC voltage of ± 5 mV, the Nyquist plot could not be measured due to exogenous noise. On the other hand, as shown in Fig. 1, it could be obtained by increasing the AC voltage to ± 50 mV. It has been confirmed that the influence of the applied voltage of ± 50 mV on the Nyquist plot is small. Therefore, we set the AC voltage during the impedance experiments to ± 50 mV. Figure 2 shows the changes in the 1/R ct value of the buried steel over time under natural rainfall conditions. As shown in Fig. 2, the value of 1/R ct, which is proportional to the corrosion rate, decreased during rainfall and gradually increased over time after the rain stopped. During this experiment, the soil water content and oxygen concentration were kept almost constant at around 54% and 0.9%, respectively. In extremely low-oxygen soil, it is considered that the cathodic reaction on the steel surface is a reduction reaction of water, not a reduction reaction of oxygen. Since both the soil water content and oxygen concentration were almost constant, it is suggested that the cathodic reaction stayed constant during experiment. Therefore, in this study, the change in the corrosion rate with rainfall was thought to be due to changes in anodic reactions. Conclusion The corrosion rate of steel buried at a depth of 90 cm in gley soil under natural rainfall conditions at outdoor test fields was monitored by electrochemical impedance spectroscopy. It was observed that the 1/R ct value, which is proportional to the corrosion rate, decreased during rainfall and gradually increased over time after the rain stopped. From the changes in the AC impedance and soil environment factors with rainfall, it was found that the corrosion rate in gley soil was closely related to anodic reactions on the steel surface. References (1) R. Akkouche, C. Rémazailles, M. Barbalat, R. Sabot, M. Jeannin and Ph. Refait, J. Electrochem. Soc., 164(12). C626-C634 (2017). (2) S. Mineta, S. Ohki, M. Mizunuma, S. Oka, ECS Trans., 85(13), 599-604 (2018). Figure 1

Simultaneously enhanced solar absorption and radiative cooling with thin silica micro-grating coatings for silicon solar cells

Recently, the idea of radiative cooling by dissipating infrared thermal energy to the cold space through the atmospheric window, especially from 8 to 13 μm in wavelength, has become an attractive way to cool down outdoor devices. Here we show that thin silica (SiO2) micro-gratings as solar-transparent and radiatively cooling coatings for silicon solar cells. The well-designed silica micro-gratings were fabricated with plasma-enhanced chemical vapor deposition, photolithography, and reactive ion etching processes. Spectrometric measurements showed that the SiO2 micro-gratings atop doped silicon wafer could remarkably enhance the infrared emittance up to 100% within the atmospheric window and increase the solar absorptance with anti-reflection. Numerical modeling confirmed the measured optical and radiative properties and elucidated the underlying physical mechanisms for the anti-reflection in the solar spectrum and enhanced infrared thermal emission. The radiative cooling performance calculated based on a heat transfer model signified that by enhancing the radiative heat dissipation to the space, the grating structure could increase the radiative cooling power when the structure temperature is higher than 45 °C, and reduce the stagnation temperature by up to 20 °C depending on convective heat transfer coefficients. Furthermore, an outdoor field test has been conducted to experimentally demonstrate the cooling performance of the silica micro-gratings, where the grating covered sample showed a lower temperature than the bare silicon sample did under direct sunlight.

Experimental investigation of shading façade-integrated solar absorber system under hot tropical climate

In this paper, a shading façade-integrated solar absorber system has been assessed outdoors under the hot tropical climate. The system was developed, and its performance was tested for 79 days under a standard system operating condition. The outdoor field test has demonstrated that the system was principally dependent on the available global irradiance, and its performance was impaired by the high occurrence of afternoon rain. On average, the system was capable to achieve a daily efficiency of 50.5%, maximum daily water temperature attained at 48.9 °C, and solar water heating rate of 2.9 °C/h. Findings showed that the system could perform most frequently at a daily efficiency ranging from 45% to 60%, and the maximum daily water temperature attained from 45 °C to 57 °C during the test period. Empirical results indicate that there exist several linear regressions between the variables that show acceptable correlations. An additional experiment was carried out to assess the heat distribution mapping of the experimental model.

The prediction methodology for tire’s high speed durability regulation test using a finite element method

In the tire industry, indoor accelerated life tests as regulations have been performed to ensure tire durability performances instead of outdoor field test. The finite element method has been widely used to minimize real test time and cost, but prediction method for accelerated life test had hardly been made in the past. This study presents a rational methodology to predict the tire’s failure life at the steel belt edge region due to high speed regulation test. Based on the finite element analysis and fatigue characteristic of rubber material, a method to determine exact failure time is proposed. The steady-state rolling analysis by FEM to get strain energy density range(ΔSED) at the steel belt edge region and fatigue test of rubber compound to obtain ΔSED- number of cycle (Nf) curve were used. The reliability of proposed prediction method was verified by real indoor test.

Far-Field Antenna Pattern Measurement Using Near-Field Thermal Imaging

The Active Denial nonlethal weapon system utilizes a large millimeter-wave (mmW) antenna with over 66 dBi of gain operating at 95 GHz. In its final state, the active denial antenna cannot be characterized by conventional measurement techniques including direct far-field pattern characterization or near-field scanning. However, the high power transmitted from Active Denial (100 kW average) provides the means of rapidly recording near-field antenna beam patterns using infrared imaging. Although these thermal images provide a magnitude-only snapshot of the near-field antenna beam, phase can be retrieved from measurements at two different ranges using the iterative Gerchberg–Saxton algorithm. The resulting complex near fields can then be used to compute the antenna far-field pattern and the complex aperture fields. This method has been used to successfully characterize these mmW antennas in both indoor laboratory and outdoor field test environments.

MIMO Radar Calibration and Imagery for Near-Field Scattering Diagnosis

Multiple-input multiple-output (MIMO) radar is an enabling technique for high-resolution imaging, which is especially useful for near-field electromagnetic scattering diagnosis of complex targets. Among others, high sidelobes and radar cross section (RCS) calibration uncertainty are the major challenges for such applications, due to array nonuniformity, imperfect channels, and antenna pattern tapering. These shortcomings prevent a MIMO radar from obtaining high-quality images with enough dynamic range and RCS accuracy. In this paper, we develop a complete solution for these problems. A novel adaptive weighting technique is proposed, where the complex weights are optimized for exact amplitude and phase error calibration of a MIMO array and for azimuth sidelobe reduction. A MIMO filtered backprojection algorithm is developed for image formation with improved RCS calibration accuracy, where propagation path-loss, antenna pattern tapering, and phase distortion due to the near-field spherical wave front are compensated. Both indoor and outdoor field test results are presented to show the high-quality images obtained using the proposed techniques, demonstrating the applicability of a MIMO radar for diagnostic RCS imaging of complex targets.

Effects of 12 weeks of Nordic Walking and XCO Walking training on the endurance capacity of older adults

BackgroundSeveral studies have already examined the positive effects of various forms of endurance training in patient groups and in healthy adults up to 60 years old. The aim of this study was to analyse the effects of Nordic Walking (NW) and XCO Walking (XCO) training on endurance capacity in healthy older adults, aged 60 years and older.MethodsTwenty-three older participants (mean age: 69.9 ± 5.4 years) were randomly assigned to either the NW group or the XCO group. All participants were measured before and after the 12 weeks of endurance training (2 sessions/week) to examine oxygen uptake (VO2) and energy consumption during an outdoor field test. In addition, heart rates were recorded and lactate samples were collected.ResultsNW mainly demonstrated some significant (p < 0.05) decreases in heart rate, lactate concentration at lower to moderate walking speeds, whereas XCO Walking revealed significant (p < 0.05) decreases in lactate concentration and VO2 at low to higher walking speeds.ConclusionsNW as well as XCO training increase the efficiency of the cardio-vascular system in older subjects. Both training approaches are suitable options for endurance training, which may serve to counteract age- and inactivity-related decreases in cardio-vascular functioning as well as aid in maintaining overall performance in older adults.

Field Performance of a Novel Passive Bioaerosol Sampler using Polarized Ferroelectric Polymer Films.

Passive bioaerosol samplers can improve environmental and health protection by enhancing the practicality and cost-effectiveness of air sampling. Here, we present the outdoor field testing of a novel, passive bioaerosol sampler, the Rutgers Electrostatic Passive Sampler (REPS), based on the use of polarized, ferroelectric polymer film (poly(vinylidene fluoride)). Four 10-day-long field campaigns were conducted to compare total (culturable + non-culturable) and culturable bioaerosol collection efficiencies of REPS to passive samplers (PTFE settling filters and agar settling plates). These collection efficiencies were calculated relative to performance of an active, reference Button Sampler. Compared to passive PTFE filters, which exclusively rely on gravitational particle deposition, REPS collected a 7-fold higher total microorganism quantity. Relative to the Button Sampler, REPS collected 25% of the total number of bacteria and fungi and 65% of the culturable bacteria. Furthermore, REPS achieved this performance without any air movers, pumps, batteries or external power. Since the Button Samplers operated at 4 L/min, REPS was calibrated to have equivalent sampling rates of 2.6 L/min and 1.0 L/min for culturable bacteria and total microorganisms, respectively. These results suggest that REPS can passively collect airborne microorganisms, including culturable bacteria, with high efficiency over long-term sampling durations. REPS can provide better preservation of bacterial culturability because it has no active airflow, which desiccates microbes in active samplers. Since there are limited options available for long-term, unattended bioaerosol sampling, REPS can complement currently available bioaerosol sampling technologies for numerous environmental health applications, such as exposure assessment for epidemiology and monitoring aeroallergen trends.

Modelling the performance of amorphous and crystalline silicon in different typologies of building-integrated photovoltaic (BIPV) conditions

In this work we use and further elaborate a previously proposed model to describe the daily performance ratio of amorphous (a-Si) and crystalline silicon (c-Si) photovoltaic solar modules under real operating conditions. For both technologies, the model was validated against three years of data collected from the outdoor test field at Supsi for a conventional ventilated free-rack mounted installation (south-facing, 45°-tilt). In the present work, we expand the simulations to model the performance of the same technologies for the same location and to include building integrated (BIPV) installation conditions. For simplicity, we consider two extreme cases: (a) a south-facing façade installation (90°-tilt) and (b) a perfectly horizontal one (0°-tilt). The angle-of-incidence response of the modules is then used to quantify reflection losses, which are very significant in summer and winter for the façade and horizontal installation, respectively. Further, compared to ventilated ones, fully integrated PV modules exhibit average operating temperatures that can reach an offset of +20°C in days of clear sky conditions. This offset is used to model the operating temperatures – and performance losses – of the BIPV modules.The model, whose main limitation is the focus on days of clear sky conditions, allows assessing the distinguished contributions, and peculiar time-phases, of each effect to the yearly energy performance of the devices under test.

Design and development of a passive bioaerosol sampler using polarized ferroelectric polymer film

Passive samplers are needed to collect bioaerosols over broad spatiotemporal scales. Here, we present the design and development process of a novel, passive bioaerosol sampler using polarized, ferroelectric polymer film (poly(vinylidene fluoride), PVDF). First, the elution efficiencies of spiked bacteria and fungal spores from PVDF, prototype film holder materials (3D-printed plastics), and controls (PTFE filters and electrostatic dust cloths) were investigated. Second, a wind tunnel was used to determine optimal air channel widths between parallel sheets of PVDF for efficient collection of charge neutralized and non-charge neutralized test particles in viral, bacterial and fungal size ranges flowing with typical indoor air velocities. Particle collection efficiencies were then compared for PVDF, a PVDF copolymer (77% PVDF, 23% TrFE) and control materials (polyvinylchloride and polyfluoroalkoxy alkane). Third, a calm air settling chamber was used for proof of concept tests. Spiked microorganisms were removed with 100% elution efficiency from the PVDF and 3D-print materials. PVDF gave significantly greater collection efficiency (~30%) when using air channel widths of 2.25mm compared to other tested widths (p<0.001). Compared to control materials, PVDF gave 13% to 30% greater collection efficiencies across all tested particle size ranges for charge neutralized and non-charge neutralized particles (p<0.001). In the calm air chamber, a spiral film prototype sampler with poled PVDF provided a greater than six-fold increase in captured bacterial quantity compared to gravimetric settling onto a 25mm reference filter (p<0.05). This passive sampler concept offers many benefits compared to other active and passive bioaerosol samplers: small size and portability, increased bioaerosol collection compared to controls, capture of all bioaerosol particle sizes including nano-sized particles, expedited particle elution, and easy sampler production by 3D-printing. The next stage of research will be outdoor field testing to determine the collection efficiency for culturable and non-culturable samples.

Improvement of the self-cleaning capabilities and transparency of cover glasses for solar cell applications by modification with atmospheric pressure plasma

Using a cover glass is indispensable for protecting solar cells in photovoltaic systems. Herein, the surface of the cover glass was modified by atmospheric pressure plasma to enhance the self-cleaning effect without degrading the transmittance. A lower surface energy was achieved by depositing fluorocarbon polymers, and a micro-nano multi-scale morphology was built on the cover glass within 50 s. These two properties led to an increase in the hydrophobicity, which enhanced the self-cleaning effect of the surface. The morphology of the surface also helped to improve the transparency by reducing reflections. Both the enhanced self-cleaning effect and the improved transparency induced by the atmospheric pressure plasma treatment were confirmed by analyzing the total conversion efficiency of a solar cell by outdoor field testing.

A comprehensive study on partial shading response of c-Si modules and yield modeling of string inverter and module level power electronics

Building Integrated and Building Attached Photovoltaic (BIPV, BAPV) systems may suffer from lower performance than predicted as a result of not considered partial shading. New system architectures have been proposed to optimize performance. The common approach of these new architectures is to track the Maximum Power Point (MPP) of every solar module individually. A simulation model is developed to quantify the benefits and drawbacks of different PV system architectures. The model includes a shading evaluation of the installation with means of 3D modeling, irradiance calculations, PV cell modeling and finally an empirical power conversion model. The energy yield of three leading architectures is confirmed (string inverter, power optimizer, micro inverter) for clear and partial shading conditions by means of an outdoor field test. Results with the irradiance profile of the Netherlands show that the string inverter system outperforms MLPE in 2 out of 3 partial shading scenarios that were evaluated in this study. It is found that the energy yield benefit of MLPE has a seasonal and latitude variation with the highest contribution during winter months. Additionally a study was performed to evaluate the energy yield at different irradiance profiles. Results show that there is a marginal benefit of the micro inverter system at higher irradiance locations when partial shading is present. The analysis method can be used by PV installers and system designer to determine which is the optimal system architecture for maximum energy yield especially when partial shading is present.

Evaluating the Thermal and Electrical Performance of Several Uncovered PVT Collectors with a Field Test

Recently, there has been a lot of interest in PV thermal systems, which generate both heat and power. Within the WenSDak project, several companies and research institutes work together to (further) develop several uncovered PVT collectors. The outdoor performance of prototypes of these collectors is being evaluated in an outdoor test setup. The three types of uncovered PVT collectors in this paper can be distinguished as an un-insulated add-on PVT collector, a PVT collector with insulation at the back and a building integrated PVT collector.In this paper, we will describe the experimental outdoor field test facility used for measuring the electrical and thermal performance. Furthermore, the results of the steady state analysis and typical collector curves are presented. In the next phase of the project, results of this field test will be used for dynamic simulations of the annual electrical and thermal energy yields for typical system designs and heat loads in the Netherlands.

Efficient outdoor performance of esthetic bifacial a-Si:H semi-transparent PV modules

We developed bifacial transparent back contact (TBC) hydrogenated amorphous silicon (a-Si:H) semi-transparent glass-to-glass photovoltaic (PV) modules with emotionally inoffensive and esthetically pleasing colors have been developed by combining the transparent back contact and color of the back glass. Due to the high series resistance of the transparent back contact, the bifacial TBC a-Si:H semi-transparent PV modules had a lower rated power after light soaking than the monofacial opaque (metal) back contact (OBC) a-Si:H semi-transparent PV modules fabricated using the additional laser scribing patterns. However, the TBC a-Si:H semi-transparent PV module produced a higher annual electrical energy output than the OBC a-Si:H semi-transparent PV module thanks to bifacial power generation during the outdoor field test. In particular, the performance ratio of the TBC a-Si:H semi-transparent PV module measured at the optimal tilt angle of 30° surpassed its simulated prediction by a drastically high value of 124.5%. At a higher tilt angle of 85°, bifacial power generation produced a higher deviation between the measured and simulated annual performance of the TBC a-Si:H semi-transparent PV module. Since the reflected albedo has a tendency to increase toward higher tilt angles, bifacial power generation can compensate for the loss of lower direct plane-of-array irradiation at a higher tilt angle. Therefore, the TBC a-Si:H semi-transparent PV module is suitable for the vertically mounted building integrated photovoltaic modules for use in curtain walls, façades, roofs and traffic noise barriers by harvesting reflected and illuminated light.

Integrated control of dynamic facades and distributed energy resources for energy cost minimization in commercial buildings

Controllable window, shading, and daylighting technologies provide an interesting opportunity to manage end use demands on distributed energy resources (DER) in ways that both complements the peak output profile of solar photovoltaic (PV) electricity generation and counteracts the peak demands on the utility grid produced by daytime commercial activities. The objective of this study is to explore whether dynamic facade technologies can play an enabling role in supporting a desired level of electricity service at either minimum operating cost or minimum carbon footprint through optimized integrated control with distributed energy resources. A proof-of-concept control system was developed by approximating non-linearities as piecewise-linear and determining the control state of both the demand and supply side components through global optimization. Annual simulations of a south-facing office zone with switchable electrochromic windows, solar photovoltaic electricity generation, and battery storage indicated that with optimized integrated demand–supply side controls, the utility grid load profile could be lowered to nearly zero demand (5W/m2) during the daytime when energy costs are highest. A full-scale outdoor field test in Berkeley, California verified this performance, demonstrating that during a week of sunny winter weather, electricity bills could be reduced by 63% compared to heuristic control of electrochromic windows without the photovoltaics and electrical storage. In both the simulated and measured cases, the photovoltaic system was sized to meet the peak perimeter zone load and the electrical storage was sized to be fully discharged by the end of the peak day. Technical and market challenges for achieving reliable optimal control for widespread applications are discussed.

A 24.4% solar to hydrogen energy conversion efficiency by combining concentrator photovoltaic modules and electrochemical cells

The highest efficiency of 24.4% for the solar-to-hydrogen (STH) energy conversion was obtained in an outdoor field test by combining concentrator photovoltaic (CPV) modules with InGaP/GaAs/Ge three-junction cells and polymer-electrolyte electrochemical (EC) cells. The high efficiency was obtained by using the high-efficiency CPV modules (∼31% under the present operation conditions) and the direct connection between the CPV modules and the EC cells with an almost optimized number of elements in series. The STH efficiency bottleneck was clarified to be the efficiency of the CPV modules, the over-potential of the EC cells, and matching of the operation point to the maximal-power point of the CPV modules.

A simple approach to model the performance of photovoltaic solar modules in operation

In this work, we present a simplified model that describes the energy performance of solar photovoltaic (PV) modules under real operating conditions. The model, validated against three full years of data collected from our outdoor test field for amorphous (a-Si) and crystalline (c-Si) silicon PV modules, agrees well in describing the energy performance of both technologies, including their peculiar counter-cyclical seasonal oscillations.The model focuses on clear-sky conditions and on four main loss/gain mechanism: (1) temperature, (2) spectral-effects, (3) reflection, and (4) irradiance, with the addition for a-Si of the Staebler–Wronsky effect. From the device side, the model requires a limited characterisation of the device under test: (a) power rating, (b) temperature coefficients, (c) spectral, (d) angle-of-incidence response and (e) irradiance dependence.Compared to approaches that are more conventional, our model, rather than focusing on the instantaneous power, concentrates on the large picture and directly attempts at providing a description of the daily performance ratio of the device allowing us to introduce a number of simplifications and, most notably, work with much smaller data sets. Input for our simulations are daily aggregate meteorological, and solar data weighted on the irradiance profile.For the a-Si device, slight discrepancies on the long term are attributed to an intrinsic degradation of the module’s energy performance, which is not observed for c-Si. Moreover, for the devices investigated in this work we show that by neglecting the irradiance dependence parameter the model can further be simplified without loss of accuracy.

Poly(2,5-bis(N-Methyl-N-Hexylamino)Phenylene Vinylene) (BAM-PPV) as Pretreatment Coating for Aerospace Applications: Laboratory and Field Studies.

In this study, an electroactive polymer (EAP), poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAM-PPV) was investigated as a potential alternative surface pretreatment for hexavalent chromium (Cr(VI))-based aerospace coatings. BAM-PPV was tested as a pretreatment coating on an aerospace aluminum alloy (AA2024-T3) substrate in combination with a non-Cr(VI) epoxy primer and a polyurethane Advanced Performance Coating (APC) topcoat. This testing was undertaken to determine BAM-PPV’s adhesion, corrosion-inhibition, compatibility and survivability in laboratory testing and during outdoor field-testing. BAM-PPV showed excellent adhesion and acceptable corrosion performance in laboratory testing. The BAM-PPV aerospace coating system (BAM-PPV, non-Cr(VI) epoxy primer and polyurethane APC topcoat) was field tested for one year on the rear hatch door of the United States Air Force C-5 cargo plane. After one year of field testing there was no evidence of delamination or corrosion of the BAM-PPV aerospace coating system.

The importance of aerodynamics for prosthetic limb design used by competitive cyclists with an amputation

This study introduces the importance of the aerodynamics to prosthetic limb design for athletes with either a lower-limb or upper-limb amputation. The study comprises two elements: 1) An initial experiment investigating the stability of outdoor velodrome-based field tests, and 2) An experiment evaluating the application of outdoor velodrome aerodynamic field tests to detect small-scale changes in aerodynamic drag respective of prosthetic limb componentry changes. An outdoor field-testing method is used to detect small and repeatable changes in the aerodynamic drag of an able-bodied cyclist. These changes were made at levels typical of alterations in prosthetic componentry. The field-based test method of assessment is used at a smaller level of resolution than previously reported. With a carefully applied protocol, the field test method proved to be statistically stable. The results of the field test experiments demonstrate a noticeable change in overall athlete performance. Aerodynamic refinement of artificial limbs is worthwhile for athletes looking to maximise their competitive performance. A field-testing method illustrates the importance of the aerodynamic optimisation of prosthetic limb components. The field-testing protocol undertaken in this study gives an accessible and affordable means of doing so by prosthetists and sports engineers. Using simple and accessible field-testing methods, this exploratory experiment demonstrates how small changes to riders' equipment, consummate of the scale of a small change in prosthetics componentry, can affect the performance of an athlete. Prosthetists should consider such opportunities for performance enhancement when possible.