Reference rules-of-thumb advise equator-facing orientations and slopes near the site's latitude as the optimal conditions for photovoltaic (PV) systems to maximize annual solar electricity ...production. However, if the electricity consumption profile is considered, this layout will most likely increase net load variance on the electricity grid at sunrise and sunset, which ought to be avoided. Making use of a variety of orientations and inclinations can help to minimize this impact, especially in cities where plentiful area of diversely oriented façades and rooftops is particularly relevant for broadening the peak of PV production throughout the day. Providing electricity not only around solar noon but also in the morning and late afternoon, when demand from residential buildings increases, helps to maximize self-consumption/-sufficiency and reduces costs for end-users and utilities.
Until recently, due to high installation costs, there was little interest in this non-optimal PV systems configurations. In the last five years, however, the paradigm started to shift, triggered by the growing interest from municipalities that seek energy transition through currently more affordable PV systems and, on the other hand, by the duck-curve phenomena reported in pioneering “solar cities”. This paper reviews studies that address the use of non-optimal azimuths and tilts to better match utility- and distributed-scale demand and supply.
•Review of PV systems in non-optimal conditions and their value to the prosumers and the electricity system.•Reference rule of “south-/northwards, latitude ±10°" rarely applies.•Load-matching should be the main driver for PV systems sizing.•Urban environment has potential to load-match with PV at utility-scale.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sensory representations are typically endowed with intrinsic noise, leading to variability and inaccuracies in perceptual responses. The Bayesian framework accounts for an optimal strategy to deal ...with sensory-motor uncertainty, by combining the noisy sensory input with prior information regarding the distribution of stimulus properties. The maximum-a-posteriori (MAP) estimate selects the perceptual response from the peak (mode) of the resulting posterior distribution that ensure optimal accuracy-precision trade-off when the underlying distributions are Gaussians (minimal mean-squared error, with minimum response variability). We tested this model on human eye- movement responses toward broadband sounds, masked by various levels of background noise, and for head movements to sounds with poor spectral content. We report that the response gain (accuracy) and variability (precision) of the elevation response components changed systematically with the signal-to-noise ratio of the target sound: gains were high for high SNRs and decreased for low SNRs. In contrast, the azimuth response components maintained high gains for all conditions, as predicted by maximum-likelihood estimation. However, we found that the elevation data did not follow the MAP prediction. Instead, results were better described by an alternative decision strategy, in which the response results from taking a random sample from the posterior in each trial. We discuss two potential implementations of a simple posterior sampling scheme in the auditory system that account for the results and argue that although the observed response strategies for azimuth and elevation are sub-optimal with respect to their variability, it allows the auditory system to actively explore the environment in the absence of adequate sensory evidence.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Until now, hydraulic fracturing has played prominent role in increasing production of hydrogen energy such as natural gas, geothermal energy, natural gas hydrate. Hydrogen energy stimulation is ...realized by many methods. Such as multiple-clusters in staged fracturing, and fracture propagation guided by combined radial boreholes in different azimuths. In order to extend lateral stimulation area, the zipper fracturing is investigated continuously. However, the report on the zipper fracturing is limited to the post-frac productivity. In this study, model of simultaneous and zipper fracturing was established in ABAQUS to investigate the effect of six factors on the fracture propagation. The results showed that in simultaneous fracturing, the fracture network is formed spontaneously. With same brittleness of reservoir, fracture in zipper fracturing always propagates slightly longer than that in simultaneous fracturing. The results provide theoretically support for both fracturing modes, which helps design of well completion and fracturing operation parameters.
•The effects of multiple factors on fracture propagation of the new crafts on hydraulic fracturing was studied.•Simulation experiments of zipper fracturing were in-depth carried out.•Simulation of fracturing cracking stress was studied.•Difference of fracture propagation between simultaneous fracturing and zipper fracturing was discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Sansha Yongle Blue Hole (SYBH) is the deepest blue hole found anywhere to date. Study of the SYBH can provide insight into the interactions between hole wall morphology and many ...geological/hydrological mechanisms. A comprehensive investigation of the SYBH was carried out for the first time in 2017 using a professional-grade underwater remotely operated vehicle (ROV) to obtain accurate depth and three-dimensional (3D) topographic data. The SYBH resembles a ballet dancer's shoe and has a volume of ~499609 m
. The observed deepest portion of the SYBH is at 301.19 m below the local 10-year mean sea level. The cave bottom laterally deviates from its entrance by 118 m at an azimuth of 219 degrees. The cave entrance is shaped like a comma and has an average width of 130 m; the widest part is 162.3 m wide, while the narrowest part is 26.2 m wide and is at 279 mbsl (meters below sea level). The 3D topography of the SYBH and underwater photography revealed two large transitions at ~76 to 78 mbsl and at 158 mbsl, indicating that the initiation of the blue hole was likely a step wise process and that the hole wall morphology was subsequently remolded through a paleo-sea level stillstand (at or near Younger Dryas). The topographic data also indicated that the blue hole is situated within an isolated environment with no water or material exchange with the outside open sea.
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•An optimized tracking strategy of double-axis PTC is proposed.•A novel normalized rating method is proposed for performance evaluation.•The recommended region for optimized tracking strategy is −60° ...to 60° (latitude).•The recommended period for optimized tracking strategy is 266–80 (day number).•Experiment shows 15–17 percentage points boost in collector efficiency.
Small-scale double-axis parabolic trough collector (PTC) is suitable for solar thermochemical reactions and solar-aided coal-fired power plants. In the present work, the double-axis PTC is numerically investigated and an optimized tracking strategy is proposed. That is to maintain PTC at the half-day optimal azimuth angles in the morning and afternoon, shifting at solar noon, in order to maximize the annual received solar radiation amount. The half-day optimal azimuth angle is found correlated to the latitude and varies diversely through a year. A normalized rating method is proposed to generally evaluate the performance of the proposed tracking strategy under theoretical and practical conditions. The results indicate that the recommended regions and periods to apply the proposed tracking strategy are low and middle latitudes (φ=−60° to 60°) and autumn and winter seasons (Nday=266–80), respectively, where the performance is rated above 0.6 regarding the traditional single-axis and double-axis tracking strategies. Experiments have been carried out on a 300kWt double-axis PTC rig in Langfang, Hebei, China, in early November. Compared to the north-south single-axis tracking strategy, the proposed optimized tracking strategy (14° NW) shows roughly 68.8% higher in heat gain and 15–17 percentage points boost in collector efficiency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In archaeological remote sensing, space-borne Synthetic Aperture Radar (SAR) has not been used so far to monitor ‘looting’ (i.e. illegal excavations in heritage sites) mainly because of the spatial ...resolution of SAR images, typically not comparable to the ground dimensions of looting features. This paper explores the potential of the new TerraSAR-X beam mode Staring Spotlight (ST) to investigate looting within a workflow of radar backscattering change detection. A bespoke time series of five single polarisation, ascending mode, ST scenes with an unprecedented azimuth resolution of 0.24m was acquired over the archaeological site of Apamea in western Syria, from October 2014 to June 2015 with a regular sampling of one image every two months. Formerly included in the Tentative List of UNESCO, the site has been heavily looted from at least early 2012 to May 2014, as confirmed by Google Earth Very High Resolution (VHR) optical imagery. Building upon the theory of SAR imaging, we develop a novel conceptual model of ‘looting marks’, identify marks due to occurrence of new looting and discriminate them from alteration (e.g. filling) of pre-existing looting holes. ‘Looting marks’ appear as distinctive patterns of shadow and layover which are visible in the ground-range reprojected ST image and generated by the morphology of the holes. The recognition of looting marks within ratio maps of radar backscatter (σ0) between consecutive ST scenes allows quantification of the magnitude, spatial distribution and rates of looting activities. In agreement with the estimates based on Google Earth imagery, the ST acquired in October 2014 shows that ~45% of the site was looted. In the following eight months new looting happened locally, with holes mainly dug along the margins of the already looted areas. Texture values of ~0.31 clearly distinguish these holes from the unaltered, bare ground nearby. Hot spots of change are identified based on the temporal variability of σ0, and colour composites indicate where repeated looting and alteration of existing holes occurred. Most looting marks are observed north of the two main Roman decumani. Looting intensified almost steadily from December 2014, with over 1500 new marks in February–April 2015. The estimated rates of looting increased from 214 looting marks/month in October–December 2014 to over 780marks/month in April–June 2015, and numerically express the dynamic nature of the phenomenon to which Apamea is still exposed. The method of identifying looting marks in VHR radar images therefore proves a reliable opportunity for archaeologists and image analysts to measure remotely the scale of looting and monitor its temporal evolution.
•A novel conceptual model of ‘looting marks’ in SAR imaging is developed.•TerraSAR-X Staring Spotlight (ST) is used to detect looting rates in Apamea, Syria.•Consistently with Google Earth, ST of October 2014 shows that ~45% of the site was looted.•New looting marks in 2014–2015 are mostly observed north of the main Roman decumani.•Looting has intensified in 2015, with 780 new marks/month in April–June.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In traditional solar desalination systems, the solar collector and demineralizer are separate components with a large thermal resistance and pipeline heat loss between them. This paper introduces the ...concept of a floating solar desalination film, which uses concentrated light to directly evaporate seawater. The greatest advantage of this design is that it combines solar energy collection and seawater demineralisation as an integrated system, eliminating pipeline heat losses and realising large-scale desalination on the surface of the sea, saving space on the land. This paper describes the operating principle of the floating solar desalination film, carries out an optical simulation for the light concentration process, analyses heat and mass transfer processes for theory calculation in the film's microstructure, and investigates optimisation of the device structure. A performance test was conducted on the device, showing water production and temperature measurements at different weather conditions. In addition, the average daily efficiency of the system was calculated. According to the test results, with comprehensive tracking of the sun, the water production per unit area of this test device reached 1.38 kg/m2·day. With azimuth-only tracking of the sun, the water production was 1.19 kg/m2·day, and the daily solar-thermal conversion rate reached 22.7%.
•A solar desalination film that floats on the sea surface and produces freshwater is introduced.•Optical simulation was used to investigate light concentration performance.•Energy transfer within the device microstructure was analysed.•Under actual weather conditions, the freshwater yield reached 1.38 kg/m2·day.•Under actual weather conditions, the solar-thermal conversion efficiency reached 22.7%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A numerical model is developed to analyze underwater explosion of slender explosive and structure responses.•Slender explosive will generate a directional pressure field in the surrounding ...water.•The shape of explosive strongly influences shock wave dynamics in the near-field.•The direction effect of pressure and energy flux is significant.•The response of a plate subjected to near-field underwater explosion of a slender explosive is studied.
The shape of a high-explosive is an important factor to consider in the near-field and contact explosion, but this has been rarely studied previously. In this paper, we first conduct experiments to study the directional effects of the underwater explosion shock wave of slender explosives. A numerical model based on the multi-material arbitrary Lagrangian Eulerian (MM–ALE) technique is then developed to study the influence of the explosive slender ratio on the generated shock waves. The numerical model is validated by experiment data. Then, tests are conducted with constant-mass cylindrical explosives with slender ratios ranging from 2.0 to 9.2. By comparing with the center-detonated spherical explosive, the peak pressure, pulse duration, impulse and energy flux of the underwater explosion of slender explosives are analyzed in detail. Furthermore, the effectiveness of the fluid-structure interaction algorithm is verified through the experimental data of a plate subjected to underwater contact explosion. Finally, the response of plates subjected to the underwater explosion of a slender explosive at different azimuths is studied. The interaction between the plate and the directional loads is analyzed. We conclude that the loads and structure responses of the near-field underwater explosion of slender explosives are different from those of spherical explosives. The analyses and results provide a reference for the near-field underwater explosion loads and structural response studies.
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The aeroelastic modeling of Tjæreborg wind turbine blades was performed based on the unsteady Reynolds Averaged Navier-Stokes equations (URANS) combined with Finite Element Method (FEM) in a loosely ...coupled manner. This method was verified by comparing numerical and experiment results at four axial inflow wind speeds. Furthermore, the aeroelastic performance of Tjæreborg wind turbine under yaw angle of 10°, 30° and 60°were computed and analyzed. The results showed that the average power and thrust of the wind turbine decreased with increasing yaw angle, along with the increasing oscillation amplitude under large yaw angle. The aerodynamic load showed periodic change within one revolution of rotor, resulting in the blade deflection and the strain present considerably asymmetric distributions. The maximum deflection and strain occurred at azimuth angle of about90° and their minimum values occurred at azimuth angle of about 270°. Besides, both the maximum deflection and strain under yaw conditions became larger than those in axial inflow condition do. For Tjæreborg wind turbine, the coupled solver gave a higher average power and thrust than the CFD solver alone. The aerodynamic performances showed more asymmetrical characters under the combined effect of yaw and fluid structure interaction (FSI).
•A coupled CFD-CSD method was presented for aeroelastic analysis of HAWTs rotor blades.•Effects of yaw angle on aerodynamic performance of rotor blades were investigated.•Effects of FSI on aerodynamic performance of rotor blades were investigated.•Maximum deflection and stress of rotor blades in yaw conditions increased.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Carbon-fiber-reinforced plastic (CFRP) is of low conductivity and has a layered structure. High-frequency transmitter-receiver (T-R) probes are widely chosen to inspect CFRPs using eddy current ...testing (ECT). However, in these works, the variation in the distance between the probe and test sample can cause a larger signal than that caused by defects and may cover up the defect. The detection sensitivity was also reduced by random noise resulting from lift-off change. To address these issues, it is meaningful to design a probe which can overcome the effect of lift-off variation and meanwhile offer high sensitivity to defects in CFRPs. In this study, a T-R probe with a special structure for detection of CFRPs was developed. The probe contains an 8-shaped transmitter coil (TX coil) and a circular receiver coil (RX coil), which is placed on a line equidistant from the two parts of the transmitter coil. Theoretically, regardless of how the lift-off changes, the output signal is always 0 if the azimuth of the probe agrees with one of the fiber orientations of an intact CFRP. Experimental studies demonstrate that the proposed probe is insensitive to lift-off compared with a traditional T-R probe and offers high sensitivity to defects. For defect detection, in-plane waviness can be detected with the proposed probe. Quantitative experiments for crack detection were performed. The cracks were clearly visualized in the scanning images. The length and location of the cracks can also be estimated from the scanning images.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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