Outdoor Test Facility Research Articles

Experimental and computational fluid dynamics investigations of tracking CPC solar collectors

The aim of the paper was to investigate thermal performance of two newly developed 15.4 m2 compound parabolic concentrator (CPC) solar collectors both theoretically and experimentally. The two collectors are identical except that one collector is equipped with a transparent Ethylene tetrafluoroethylene (ETFE) foil and the other collector is not. Experimentally the solar collectors were tested in an outdoor test facility at different temperatures. Collector efficiencies were determined. Theoretically simplified CFD models of the CPC solar collectors were developed and validated against the measurements. A ray tracing tool Tonatiuh was used to calculate distribution of solar irradiance on the receiver. The influence of the ETFE foil on collector heat loss coefficient and efficiency was investigated. The results show that the CFD model predicts satisfactorily temperature rises of the collectors in the temperature range between 20 °C and 81 °C. The deviations between the measured and the calculated temperature rises were limited to ±0.3 K with a relative error less than 3.7%. By installation of the ETFE foil, the first order collector heat loss coefficient decreased from 1.42 to 0.82 W/m2/K. Efficiency of the collector with the ETFE foil was measured to be 63%, 55% and 54% for a mean collector fluid temperature of 27 °C, 63 °C and 81 °C respectively. For a solar irradiance of 895 W/m2 and a mean collector temperature of 133 °C, collector efficiency is predicted to increase from 36% to 41% by installation of the ETFE foil. Another 5% increase of collector efficiency is expected if installation of the foil is made airtight.

Evaluation of drawbar performance of winter tyres for special purpose vehicles

Driving on ice is still a risky activity. Research has investigated the factors contributing to the friction mechanism and has reported experimental studies of pneumatic tyres on ice in order to develop models that predict tractive and braking performance on ice/snow. Therefore, developing testing methods to obtain relevant experimental data for the validation of models is equally important.There are agricultural and industrial vehicles which are also designed for pulling but there are no specific studies reporting experimental tests on traction force of such machines in snowy conditions. However, this issue is very topical, as demonstrated by the appearance on the market of winter tyres for such vehicles.This study presents a method for testing winter tyres in outdoor test facilities with a focus on traction performance. The conclusions will serve in future investigations as a concise knowledge source to develop improved testing facilities and tyre–ice interaction models, aiding the development of better tyre designs and improved vehicle safety systems.The functional tests hereafter described have been carried out with the aim of evaluating the possibility of measuring the influences of different technique solutions on the performance of certain 17.5 R25 sized industrial tyres.

Identification of Tire Force and Moment (F&M) Characteristics That Improve Combined Slip Handling Performance

ABSTRACT Since tires generate the control forces required for the operation of a vehicle, the tire force and moment (F&M) characteristics have to be designed such that the vehicle can easily be kept under driver control under many driving conditions. However, the relationship between F&M characteristics and vehicle handling performance is not well understood for many driving maneuvers. A better understanding of this relationship would thus provide insight into how to improve the matching between tires and vehicles for increased vehicle stability. Building a large number of tires with different characteristics would be too expensive and time consuming, so an investigation using simulations is preferred. However, one problem with simulations is that handling performance cannot be evaluated by a professional driver (subjective metrics), unlike in outdoor tests. A way of evaluating handling performance in simulation through objective metrics is therefore necessary. In this study, the focus is on vehicle handling performance during simultaneous cornering and braking. Desirable F&M metrics were identified using the following process: Handling simulations were validated using instrumented vehicle measurements of handling behavior at outdoor test facilities. An objective handling metric (peak body slip angle) was identified that has high correlation with professional driver ratings (subjective metric) of combined slip handling performance. The objective metric could therefore be used with simulations to predict the professional driver rating. Many virtual tires were generated by changing F&M characteristics of Pacejka tire models. These virtual tires were used in simulations of combined slip handling maneuvers and evaluated for performance using the objective handling metric. By identifying which changes to F&M metrics had high correlation to changes in handling performance, the primary influencing characteristics were determined. These results were also confirmed by looking at the correlation between F&M metrics of actual tires and their subjective ratings.

Preliminary investigations on two different procedures to calculate the efficiency and performance ratio of PV modules

Short- and long-term outdoor performances of the photovoltaic (PV) modules are extremely important in reaching their economic viabilities. Such information is very valuable for the investors, customers and researchers of PV technologies. Two different procedures are possible, and both are used by many researchers. However, to the best of our knowledge, there is no comparative investigation to evaluate these two procedures. One of the methods uses instantaneous I–V curves of PV modules taken in a specified instant of time, while the others simply use the integrated energy values of the input and the yield of PV modules. In fact, both have advantages and disadvantages. In the present work, we outlined the advantages and disadvantages of both methods and compared them using the data of two different cell-type modules which are installed at GUNAM’s outdoor test facility. In the analysis, the data that we used are taken under the same outdoor test conditions and ambient weather conditions. The outcomes of these preliminary analyses can be summarized as follows: (1) The procedure that uses instantaneous I–V curves seems dependent on the specified time intervals and ambient weather conditions at that instant; (2) accordingly, we will propose how to determine an optimal time interval to reach better performance results; (3) using the integrated values, we achieved the variations in performances with different integration time periods; (4) preliminary comparisons of these two procedures resulted in key conclusions on performance and degradation calculations of PV modules.

The fire resistance of lightweight composite tanks depending on fire protection systems

To save weight and resources lightweight tanks with complex geometries made of glass-fibre reinforced plastics (GFRP) are a promising innovation for the transportation of dangerous goods. To realise the use of polymer tanks for such applications, their fire safety must be guaranteed. This paper presents solutions to protect fibre-reinforced plastic tanks from fire. The fire resistance of six GFRP tanks with different fire protection systems was tested in an outdoor full-scale fire test facility according to the regulation stipulated in the ADR (European agreement concerning the national carriage of dangerous goods by road). All tanks feature a complex geometry and a holding capacity of 1100 litres. The fire protection systems are composed of specialised resins as well as two intumescent coatings. All systems had a protective impact. The best results were achieved by the epoxy based intumescent coating, which was able to prolong the time needed to reach 150 °C inside the tank by 20 min. The emergence of a temperature holding point inside the tank due to condensation effects was observed at temperatures around 100 °C.

Potential energy yield increase of a solar spectra down-converter equipped photovoltaic device in real operational conditions

In this work, we evaluate the impact of solar spectrum down-converter (DC) on an energy yield of solar cells working in real world meteorological conditions. For this purpose, a simple model of PV device with a down-converting layer is used, with inputs (spectra, irradiance, temperature) taken from the public NREL database for their outdoor test facility. The model assumes ideal external quantum efficiency (EQE). The analysis showed that in these conditions the energy yield increase from the use of DC system is 23.64% which is bigger than improvement due to DC calculated for the standard test conditions (20.1%). This effect is more profound in summer (24.8% for June-August) than winter months (22.1% for December-February). The average photon energy (APE) turned out to reasonably well reflect the overall impact of the DC layer on the energy yields with R2 = 0.96. The primary conclusion is that the impact of spectral converters on PV device performance should be analyzed not only in the standard test conditions as in the real operating conditions the result of spectra converting layer may turn out substantially better, lowering the bar for commercialization and broad application of such layers.

Using a Hydrological Model to Simulate the Performance and Estimate the Runoff Coefficient of Green Roofs in Semiarid Climates

Green roofs offer a series of benefits to buildings and to the urban environment. Their use in dry climates requires optimizing the choice of their components (i.e., vegetation, substrate and drainage layer) for the specific local climatic conditions, in order to minimize irrigations needs while preserving the attributes of the roof. In this study, we calibrated and validated an existing hydrological model—IHMORS—for the simulation of the hydrological performance of green roofs. Simulated results were compared to experimental data obtained in an outdoor test facility on several green roof specimens, representing a variety of green roofs configurations. IHMORS was able to reasonably predict the soil moisture dynamics for all tested specimens. The specimens of 10 cm depth were the best simulated by the model, while some overestimation was observed during the model validation for the 5 and 20 cm depth specimens. The model was then used to estimate the number of days in which irrigation is needed, as well as analyze the water runoff control performance of all specimens. We related the amount of water retained by the substrate and depth, magnitude and intensity of precipitation event, and the initial substrate moisture. For all events, the lowest runoff coefficient was simulated for the 20 cm specimens. Our study showed the full potential of the model for estimating the water needs and the runoff control performances of different variants of green roofs.

Temperature impact on dusty and cleaned photovoltaic module exposed in sub-Saharan outdoor conditions

In this work, impacts of temperature and dust cleaning on photovoltaic module performance operating in sub-Saharan's climate are investigated. Two single junction technologies, monocrystalline and polycrystalline silicon, and one micromorph (amorphous/micrystalline) thin film silicon tandem technology are considered. We have recorded at the same time under real operating conditions, the module temperature and the current versus voltage characteristics of each module, and the local solar irradiation. All the measurements were performed with the outdoor monitoring and test facility located at Ouagadougou in Burkina Faso. The results show the drop of generated power of dusty modules for the same irradiation level. Between April and June (where temperatures are higher) a significant drop of output power is observed, despite a daily cleaning. Furthermore, performance losses are observed for all technologies compared to that under standard test conditions. However, the micromorph silicon tandem technology with low temperature sensitivity present the less losses in performance compared to the monocrystalline and the polycrystalline single junction modules, even if the modules are not cleaned.

Application of Tomo-PIV in a large-scale supersonic jet flow facility

Particle imaging velocimetry (PIV) has been used extensively at NASA GRC over the last 15 years to build a benchmark data set of hot and cold jet flow measurements in an effort to understand acoustic noise sources in high-speed jets. Identifying the noise sources in high-speed jets is critical for ultimately modifying the nozzle hardware design/operation and therefore reducing the jet noise. Tomographic PIV (Tomo-PIV) is an innovative approach for acquiring and extracting velocity information across extended volumes of a flow field, enabling the computation of additional fluid mechanical properties not typically available using traditional PIV techniques. The objective of this work was to develop and implement the Tomo-PIV measurement capability and apply it in a large-scale outdoor test facility, where seeding multiple flow streams and operating in the presence of daylight presents formidable challenges. The newly developed Tomo-PIV measurement capability was applied in both a subsonic M 0.9 flow and an under-expanded M 1.4 heated jet flow field. Measurements were also obtained using traditional two-component (2C) PIV and stereo PIV in the M 0.9 flow field for comparison and validation of the Tomo-PIV results. In the case of the M 1.4 flow, only the 2C PIV was applied to allow a comparison with the Tomo-PIV measurement. The Tomo-PIV fields-of-view covered 180 × 180 × 10 mm, and the reconstruction domains were 3500 × 3500 × 200 voxels. These Tomo-PIV measurements yielded all three components of vorticity across entire planes for the first time in heated supersonic jet flows and provided the first full 3D reconstruction of the Mach disk and oblique shock intersections inside of the barrel shocks. Measuring all three components of vorticity across multiple planes in the flow, potentially reduces the number of measurement configurations (streamwise and cross-stream PIV) required to fully characterize the mixing-enhanced nozzle flows routinely studied in aeroacoustics research.

그린인프라 및 저영향개발 기술의 검증 및 인증 기법 개발

본 연구는 최근 많은 관심을 받고 있는 그린인프라 및 저영향개발 (GI & LID) 기술에 대한 물순환 및 물환경 효율성 측정을 위한 실내 외 검증, 인증 시스템을 개발하였다. 기술의 검증 및 인증을 위한 실외시험시설은 건축형, 도로형, 주차장형, 빗물정원형, 생태공원형 등 크게 5구역으로 나누어 기술종류에 따라 시험이 가능하도록 시스템을 개발하였다. 또한, 실내실험으로는 수리/수문분야, 토질/지반분야, 환경분야 등 다양한 시험이 가능하도록 시험장비의 개발 및 구축을 하였다. 본 연구에서 개발한 GI & LID 검 인증시스템 구축을 위한 실내 및 실외 시험시설의 개발은 GI & LID 기술의 적용을 위한 객관적이고 신뢰성 있는 데이터 제공에 대한 기반을 마련함과 동시에 관련 사업의 활성화에 기여할 것으로 판단된다. This study developed a verification and certification method of technologies of green infrastructure (GI) and low impact development (LID) that gained interest recently. The outdoor testbed used in this study consisted of a building type, a road type, a parking lot type, a rain garden type and a bioretention type. Indoor test facilities were ready for testing using hydrology efficient analysis, pavement and soil analysis and water environment analysis. The development of outdoor and indoor test facilities were used to certify the efficiency of GI & LID technologies, and this was expected to contribute to the activation of the related projects by providing reliable data for the application of GI & LID techniques.

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.

MATRIX, a multi activity test-room for evaluating the energy performances of ‘building/HVAC’ systems in Mediterranean climate: Experimental set-up and CFD/BPS numerical modeling

Technology transfer, scientific research and education could have a key role in Mediterranean regions, in order to reduce the environmental impact of the building sector.Recently, the Department of Engineering of University of Sannio has developed a laboratory suitable for performing researches on the dynamic interactions between building envelope components, indoor environment and mechanical systems for a typical climate of south of Italy.The work described within this paper is a part of this large-scale project. Its goals are: (a) to design, test and validate a poly-equipped test room, (b) to perform transient tests to determine performances of common and innovative building components and alternative HVAC systems. More in detail, this paper focuses on the first goal, with the aim to generalize the design approach, requirements and capabilities of calibrated outdoor test facilities, specifically thought for Mediterranean climate. The facility has undergone a substantial amount of characterization tests, aimed at determining its response under yearly operations. The primary conclusions are that the new test facility is usable for a wide range of environmental and indoor conditions, it is functional and has been validated through characterization and preliminary investigations of the behavior of the thermal envelope.Moreover, some experimental results are here analyzed, by evidencing the potentialities of vacuum insulation panels for improving the performances of the thermal envelope, for what concerns both winter and summer seasons. Then, some numerical analyses have been carried out. A 3D CFD model has been calibrated for studying the real distribution of temperatures and water vapor partial pressures within VIP panels. Furthermore, a dynamic energy model of the test cell has been developed by means of Energy Plus, with the aim to use its capability to compare potential configurations that would be installed in future researches, or to evaluate energy, environmental and economic issues.

Design principles and field performance of a solar spectral irradiance meter

A solar spectral irradiance meter (SSIM), designed for measuring the direct normal irradiance (DNI) in six wavelength bands, has been combined with models to determine key atmospheric transmittances and the resulting spectral irradiance distribution of DNI under all sky conditions. The design principles of the SSIM, implementation of a parameterized transmittance model, and field performance comparisons of modeled solar spectra with reference radiometer measurements are presented. Two SSIMs were tested and calibrated at the National Renewable Energy Laboratory (NREL) against four spectroradiometers and an absolute cavity radiometer. The SSIMs’ DNI was on average within 1% of the DNI values reported by one of NREL’s primary absolute cavity radiometers. An additional SSIM was installed at the SUNLAB Outdoor Test Facility in September 2014, with ongoing collection of environmental and spectral data. The SSIM’s performance in Ottawa was compared against a commercial pyrheliometer and a spectroradiometer over an eight month study. The difference in integrated daily spectral irradiance between the SSIM and the ASD spectroradiometer was found to be less than 1%. The cumulative energy density collected by the SSIM over this duration agreed with that measured by an Eppley model NIP pyrheliometer to within 0.5%. No degradation was observed.

MagLev-Cobra Operational Tests

The Brazilian project MagLev-Cobra proposes a superconducting levitation vehicle for urban transportation in highly populated cities. The levitation technology is based on the diamagnetic behavior and flux pinning property of Y-Ba-Cu-O blocks in the proximity of the magnetic field of Nd-Fe-B magnets. The traction is given by a short primary linear induction motor. In previous editions of EUCAS conference, laboratory tests were presented to validate the levitation method and vehicle design. In this paper, recent operational results of the MagLev-Cobra traveling along an outdoor 200-m test facility constructed in the university campus will be reported. The full-scale vehicle is composed of four modules, interconnected by mechanical links. The transportation capacity is equivalent to 5 passengers/m 2 , a limit of transportation comfort and quality. Acceleration, braking, and also cruising speed conditions were analyzed. A data acquisition system monitored the levitation gap and other parameters along the track. This effort is an important step to certificate the operational safety, an indispensable condition before industrialization and commercialization.

Energy performance of different silicon photovoltaic technologies under hot and harsh climate

This paper presents a performance comparison study performed on four photovoltaic modules. Three silicon technologies are concerned: one monocrystalline module, two polycrystalline modules and one module of tandem structure (amorphous/microcrystalline) also known as micromorph module. The modules I–V data and meteorological data have been measured during one year using an outdoor monitoring test facility named “IV bench”. This set up is installed at Ouagadougou (Latitude 12.45° North, Longitude 1.56° West) in Sudano Sahelian climate. The actual maximum power, the average performance ratios, the series resistances and the maximum power temperature coefficient of tested modules are determined from the outdoor measurements and used for comparison study. The power of all the modules has been stabilized in outdoor conditions before the performance analysis. The results show that the micromorph module presents the best performance on the selected site, with an average performance ratio of 92%. The monocrystalline and polycrystalline modules from the same manufacturer, have both an average performance ratio of 84%. The second polycrystalline module from another manufacturer, strangely presents the lowest average performance ratio (80%) due to both its large series resistance and the high maximum power temperature coefficient in operating conditions.

Long-term soiling of silicon PV modules in a moderate subtropical climate

The results of 28 silicon-based PV modules which were installed from 1981 to 1985 in a free rack configuration in the outdoor test facility of the European Solar Test Installation (ESTI) and dismantled at the end of 2014 without cleaning were analysed. The system was composed of modules with two series-connected laminates mounted in a single frame produced by the same manufacturer but using different cell layouts and cover glasses (plain glass or textured glass). The effects of long-term soiling on the PV module performance for more than 30years of outdoor exposure in a moderate subtropical climate and the influence of different cleaning methods from manual cleaning to the use of high pressure water washing were investigated. The influence of the cover glasses and the mismatch due to the particular manufacturing design were also analysed. It was observed that a manual cleaning was effective at improving the output of all the module types. However, additional high pressure water spraying on plain glass modules showed no further improvement, but showed small improvements on the textured glass modules. Overall improvements in Pmax after cleaning ranged from 3.5% to 19.4%, with an average value of 9.8% and an average improvement in Isc of 6.7% were obtained.

Effect of environmental conditions on device and performance parameters of thin film photovoltaic modules

The effects of outdoor temperature and irradiance on the device and performance parameters of thin film amorphous hydrogenated silicon (a-Si:H) module are investigated. An outdoor test facility is installed to perform I-V measurements under different irradiance and temperature conditions. A numerical model considering the effect of series and shunt resistances is developed to determine different module parameters. The device parameters determined from I-V measurements are found to agree well with the corresponding parameters obtained from the developed model. The device parameters extracted from I-V measurements are then employed to investigate device parameters impacts on module performance parameters. Present results indicate that as outdoor temperature increases, the device parameters increase at all irradiance levels studied. Also, the device parameters decrease with increasing irradiance up to 800 W/m2 then the behaviour starts to be vice versa. While, Voc and Isc increase with irradiance but FF and η decrease.

Effect of environmental conditions on device and performance parameters of thin film photovoltaic modules

The effects of outdoor temperature and irradiance on the device and performance parameters of thin film amorphous hydrogenated silicon (a-Si:H) module are investigated. An outdoor test facility is installed to perform I-V measurements under different irradiance and temperature conditions. A numerical model considering the effect of series and shunt resistances is developed to determine different module parameters. The device parameters determined from I-V measurements are found to agree well with the corresponding parameters obtained from the developed model. The device parameters extracted from I-V measurements are then employed to investigate device parameters impacts on module performance parameters. Present results indicate that as outdoor temperature increases, the device parameters increase at all irradiance levels studied. Also, the device parameters decrease with increasing irradiance up to 800 W/m2 then the behaviour starts to be vice versa. While, Voc and Isc increase with irradiance but FF and η decrease.

Developing a method and simulation model for evaluating the overall energy performance of a ventilated semi‐transparent photovoltaic double‐skin facade

AbstractA comprehensive simulation model has been developed in this paper to simulate the overall energy performance of an amorphous silicon (a‐Si) based photovoltaic double‐skin facade (PV‐DSF). The methodology and the model simulation procedure are presented in detail. To simulate the overall energy performance, the airflow network model, daylighting model, and the Sandia Array Performance Model in the EnergyPlus software were adopted to simultaneously simulate the thermal, daylighting, and dynamic power output performances of the PV‐DSF. The interaction effects between thermal, daylighting, and the power output performances of the PV‐DSF were reasonably well modeled by coupling the energy generation, heat‐transfer, and optical models. Simulation results were compared with measured data from an outdoor test facility in Hong Kong in which the PV‐DSF performance was measured. The model validation work showed that most of the simulated results agreed very well with the measured data except for a modest overestimation of heat gains in the afternoons. In particular, the root‐mean‐square error between the simulated monthly AC energy output and the measured quantity was only 2.47%. The validation results indicate that the simulation model developed in this study can accurately simulate the overall energy performance of the semi‐transparent PV‐DSF. This model can, therefore, be an effective tool for carrying out optimum design and sensitivity analyses for PV‐DSFs in different climate zones. The methodology developed in this paper also provides a useful reference and starting point for the modeling of other kinds of semi‐transparent thin‐film PV windows or facades. Copyright © 2015 John Wiley & Sons, Ltd.

Design and long-term monitoring of DSC/CIGS tandem solar module

This paper describes the design and development of tandem dye-sensitized/Cu(In, Ga)Se (DSC/CIGS) PV modules. The tandem PV module comprised of the top DSC module and a bottom commercial 0,8 m2 CIGS module. The top DSC module was made of 10 DSC mini-modules with the field size of 20 × 20 cm2 each. Tandem DSC/CIGS PV modules were used for providing the long-term monitoring of energy yield and electrical parameters in comparison with standalone CIGS modules under outdoor conditions. The outdoor test facility, containing solar modules of both types and a measurement unit, was located on the roof of the Institute of Biochemical Physics in Moscow. The data obtained during monitoring within the 2014 year period has shown the advantages of the designed tandem DSC/CIGS PV-modules over the conventional CIGS modules, especially for cloudy weather and low-intensity irradiation conditions.