Certain advantages of using mountainous terrain for the installation of solar plants are well known, such as lower temperature, higher solar irradiance present at high altitudes, and economic aspects ...related to the lower cost of land. This paper highlights another one: the higher annual solar irradiation incident of single-axis N-S trackers installed on sloping terrain, as compared to horizontal ones. After a theoretical study in which the relevant formulas are derived, numerical simulations are presented. Then we showcase the results of a year-long experiment in which a N-S aligned single-axis tracker prototype was used, at the location of our Department (Gijón, Spain). The experimental results confirm the trends in the formulas and simulations. Finally, theoretical values for the energy gain for different slopes, at locations over the northern hemisphere between latitudes of 6° and 60° are provided. These gains can reach values up to 13.5%.
•N-S oriented solar trackers in sloped terrain receive higher solar irradiation.•Formulas and simulations are included for irradiation in sloped terrains.•Results of a year-long experiment are included for a location in Gijón (Spain).•Experiment confirms the theoretical and numerical ones. Gains can be up to 10%.•Numerical estimations for latitudes between 6° and 60° are provided.
•Solar tracking is a crucial task in efficiently harvesting solar power in a PV plant.•Horizontal Single-axis tracking systems require a precise estimation of its axis’ orientation.•This methodology ...uses available data to accurately estimate the tracker’s orientation.•This methodology estimates height differences in adjacent trackers.•The improve tracking and backtracking strategies increase production by 1%.
Photovoltaic (PV) energy production is becoming a more significant part of the energy mix world-wide due to its clean origin, supportive and cost reductions. Therefore, it is increasingly important to develop methodologies to improve efficiency and reduce energy losses. Solar tracking is a way of increasing the irradiance over the PV field and, subsequently, boosting energy production. Both single-axis and double-axis tracking systems (SATS & DATS) are well known methods but both require not only a proper estimation of the sun’s position but also precise knowledge of the tracker’s position and orientation. Several factors (construction, design, configuration) can cause the values used to calculate the optimal tracking to be inaccurate, thus increasing production losses. This paper proposes a methodology to calculate the actual orientation of the trackers’ axis based on the energy production of its associated strings. Additionally, it provides the height differences between adjacent trackers by detecting shading patterns. This information is key to defining more efficient tracking and backtracking strategies the avoid row-to-row shading and, overall increasing energy production. The proposed method is applied to a real 5 MW facility, identifying misalignments of several degrees in most trackers that were causing annual losses (1 %), not only due to inaccurate tracking but also row-to-row shading.
This paper examines the multifaceted effect of the effective spatial baseline, as expressed through the vertical (interferometric) wavenumber, on the inversion of forest height from polarimetric ...interferometric synthetic aperture radar (Pol-InSAR) data. First, the role of the vertical wavenumber in relating forest height to the interferometric (volume) coherence is introduced. Through the review of the forest height inversion from Pol-InSAR data, the effect of the vertical wavenumber on the inversion performance is evaluated. The selection of optimum with respect to forest height inversion performance, vertical wavenumbers is discussed. The impact of the acquisition geometry and terrain slopes on the vertical wavenumber and their consideration in the inversion methodology is addressed. The individual effects discussed are demonstrated by means of airborne repeat pass Pol-InSAR acquisitions in L- and P-band acquired over different forest conditions, including a boreal, a temperate, and a tropical forest test site. The achieved forest height inversion performance is validated against reference height data derived from airborne LIDAR acquisitions.
•A LID effect experiment considering different storm intensities and terrain slopes is presented.•Experimental LID measures could reduce the peak runoff compared to the traditional ...development.•Runoff reduction rate is sensitive to storm intensities, the heaver storm, the lower impact.•Runoff reduction effect of the LID measures becomes lower as the slope turns to be more abrupt.
To quantitatively investigate the LID (Low Impact Development) effects under different storms and terrain conditions, an experimental urban catchment with LID measures is developed in this work. The surface runoff control effects of the experimental LID measures are evaluated by quantifying and comparing the peak runoff reduction rate to a traditional infrastructure with no LID. The experimental results on three cross and longitudinal slopes under three storm intensities show that the measured peak runoff of the traditional infrastructures is higher than that of the LID, indicating that LID reduces the peak runoff considerably. As the storm intensities are increased from 0.47 mm/min to 0.84 mm/min, the peak runoff reduction rates decrease from 14.48% to 4.91%, highlighting that LID effects are more significant for low to moderate intensity of storms. The effect of LID in reducing the peak runoff is more significant for a gentler cross or longitudinal slope, for example, the highest reduction in peak runoff (14.48%) occurs when a gentle longitudinal and cross slope of 1° is incorporated. Moreover, the effect of LID is more sensitive to the longitudinal slope when compared to the cross slope. The findings from this study quantify that the LID measures are more effective for low intensity storm across gentler slopes. While the results help in understanding the mechanism of LID effects for optimizing infrastructure planning, they also provide a systematically measured data for numerical model validation and coefficient calibration.
The present study aims to evaluate the TOPODATA Digital Elevation Model (DEM) as a source of relevant altimetric information for urban cycling planning. A case study was conducted in the city of ...Bariri-SP. The Cartographic Accuracy Standard of Digital Cartographic Products (PEC-PCD), assessed by comparing the TOPODATA altitudes with homologous altitudes surveyed by a precise satellite method (GNSS), suggests that the DEM may not be adequate for phases of cycling planning that require greater detailing of the elements to be designed. A moderate to strong positive spatial autocorrelation was observed between the DEM errors. Regarding its usability for estimating the average slopes of the road segments, however, the results suggest that TOPODATA average slopes do not differ statistically from those estimated with field-surveyed data and, for the two criteria adopted for acceptable gradient lengths for cycling, more than 82% of the road segments were classified similarly using both sources of information.
•Modelling and characterization of fire-spotting generated fires through mesoscale factors.•Theoretical determination of the relationship between the flame length and the fire intensity.•Stating the ...Rate of Spread of the front in terms of the flame geometry.•Study of the role of the flame geometry and of the terrain slope on the emerging of fire-spotting generated fires.
This is the second part of a series of two papers concerning fire-spotting generated fires. While, in the first part, we focus on the impact of macro-scale factors on the growth of the burning area by considering the atmospheric stability conditions, in the present study we focus on the impact of meso-scale factors by considering the effects of the flame geometry and terrain slope. First, we discuss the phenomenological power law that relates flame length and fireline intensity by reporting literature data, analysing a formula originally proposed by Albini, and deriving an alternative formula based on the energy conservation principle. Subsequently, we extend the physical fire-spotting parametrisation RandomFrontadopted in the first part by including flame geometry and slope. Numerical examples show that fire-spotting is affected by flame geometry and, therefore, cannot be neglected in simplified fire-spread models used in operational software codes for wildfire propagation. Meanwhile, we observe that terrain slope enhances the spread of a fire at a higher rate than the augmentation of fire-spotting generated fires, such that a rapid merging occurs among independent fires.
Gravimetric measurements allow monitoring mass transport in the Earth system and one example is temporal variations in the global water cycle including the cryosphere. Coupling gravity observations ...to the underlying processes requires modeling of the relevant mass elements. When observing the gravity field from space (i.e., by satellites), point mass models or simple spherical surface layers (mascons) are a reasonable choice. However, for terrestrial observations taken right on the surface of the relevant masses, precise modeling of the geometry of those mass elements and the related gravitational effects becomes crucial for the quality of the modeling and the correct interpretation of the results. In this study, two different modeling techniques are investigated, the right rectangular prism and the general polyhedron. Both approximations provide the possibility to analytically calculate the corresponding gravitational signal. Although modeling in terms of polyhedrons is numerically more complex and less efficient, the representation of the actual surface is superior as the inclined polyhedral surface fits much better to the actual topographic surface than the step function implied by rectangular prisms with horizontal top plane. The case study presented here is related to the gravimetric mass balance of a mountain glacier (Vernagtferner in the Ötz valley, Austria) where on the one hand high resolution digital terrain models (DTM of resolution 1 m × 1 m) are available, while on the other hand, the accuracy requirements are very high (on the level of 10−7 m/s2, i.e., 10 μGal). We evaluate first and second order derivatives of the gravitational potential induced by the melting of ice masses between epochs 2009 and 2016 at gravity sites on and off the actual glacier body. Furthermore, the relation of ground surface slope to the differences between the modeling approaches is investigated for a small part of the DTM, containing a variety of different slope regimes. Besides the original grid spacing, denser and coarser grids are also evaluated in order to examine the relation of the considered DTM resolution to the modeling differences. The modeling choice, the location of the computation points and the morphology of the mass distribution are the main factors that determine the quality of the results. The comparison of the two methods for the original 1 m resolution, provides differences up to 2.9 μGal for the vertical component of the attraction Vz, 9.1 μGal/m for the gradient Vzx, 4.6 μGal/m for Vzy and 17.1 μGal/m for Vzz. Coarser grid resolutions increase these values significantly, up to 500 μGal at specific locations, while grids denser than the 1 m resolution decrease them for about 48%.
•Gravitational effect due to ice melting of Vernagtferner glacier during 2009–2016 is evaluated analytically.•Prism and polyhedral modeling applied for gravitational effects at gravity stations situated on and around the glacier.•The difference between the two techniques defines a range well inside the measurement accuracy of terrestrial gravimeters.
Zhejiang Province, located in the southeast coastal region of China, is highly prone to rainfall-triggered landslides because of its geologic, geomorphologic, and climatic settings. The ...rainfall–landslide relationship is critically important for predicting rainfall-induced landslides. This study defines landslide-triggering rainfall intensity–duration thresholds for the entire Zhejiang region; and the 62 individual areas that comprise the region, based on 1569 shallow landslides which occurred from 1990 to 2013 and their corresponding detail rainfall records from 2457 rain gauges in the region. The results indicate that the rainfall thresholds vary spatially over the region. For rainfall durations from 1 to 24h, the threshold tends to increase from the northwestern part of Zhejiang to its southeastern coastal region; and it is lower in the central and coastal hill–basin regions than that in the western and southern mountainous regions. Variability of the threshold in space is mainly affected by the slope-forming materials and terrain slope gradients. Different soil types have different thresholds, and the thresholds for weathered rock slides are generally higher than those for soil slides. For the soil–weathered rock on slopes, the slope gradient has no obvious influence on the thresholds when the slope angle is <30°; the thresholds have an obviously increasing trend with the increase of slope angles in the range of slope angles from 30 to about 40°; and when slope angle is larger than about 40°, the thresholds rapidly decrease with gradient on the whole. These findings will facilitate the improvement of warning systems for regional rainfall-triggered landslides.
•We studied rainfall data with 1569 landslides in Zhejiang between 1990 and 2013.•We defined the regional and 62 subregional rainfall intensity–duration thresholds.•Spatially distributed rainfall threshold maps over the entire region were prepared.•We discussed the correlations of threshold with soil types and slope gradients.•Variation of threshold is affected by slope-forming materials and terrain slopes.
PDF
