Subsequent Rows Research Articles

Boosting electricity generation associated with Saudi Arabi buildings using PCM and PV cells on walls and roof leading to a sustainable building

In Saudi Arabia, where the majority of regions receive a minimum incident shortwave solar energy exceeding 4 kWh/(m2.year), there is a high potential for electricity generation and simultaneously, a challenge in building cooling. In this study, by adding photovoltaic (PV) on the roof and wall, as well as using phase change material (PCM) inside the walls, electricity production and energy consumption of Saudi residential buildings were investigated. Taking into account the effects of radiation on vertical and horizontal envelopes as well as phase change in PCM, the energy equation was solved using DesignBuilder to specify hourly energy consumption and electricity generation. When installing PV cells at the optimal tilt, incoming radiation to the cells increases. However, creating shadows on subsequent rows of cells diminishes the effective PV surface area. Surprisingly, calculations revealed that if PV cells are installed at zero angle, owing to installing more PV cells, up to 31% extra electricity is produced than when installed at the optimal tilt. As a side effect, the cooling load decreases by 5.1% due to reduced radiation intensity on the roof. The orientation of the walls significantly impacts both phase change material (PCM) and PV-associated electricity generation. Placing PCM on the east wall optimizes its performance, while walls containing PV panels perform best when facing south. To further enhance cooling and reduce electricity demand, phase change material was incorporated into both the roof and wall, resulting in a 2% reduction in overall electricity demand. Notably, in eight major populated areas across Saudi Arabia, under the constraint of the constant PV cell area, installing PV cells on the roof proves three times more advantageous than placing them on the walls.

Dynamical Electron Correlation and the Chemical Bond. IV. Covalent Bonds in A2 Molecules (A = N-As and F-Br).

In a series of recent papers, we investigated the effect of dynamical electron correlation on the potential energy curves and spectroscopic constants of several diatomic molecules, including the simple diatomic hydrides (AH) and the more complex diatomic fluorides (AF) and homonuclear diatomic molecules (A2) with A = B-F (AF) or A = C-F (A2), respectively. Our goal was to understand the dependence of the dynamical electron correlation energy, EDEC, on the internuclear distance, R, and quantify how dynamical electron correlation influences the spectroscopic constants (De, Re, and ωe) of these molecules. At large R, we found that the magnitude of EDEC(R) had a simple dependence on R, with EDEC(R) increasing nearly exponentially with decreasing R. However, as R continued to decrease, there were significant variations in EDEC(R). These variations led to differing changes in the predicted spectroscopic constants of the molecules. In many molecules, the changes in EDEC(R) could be correlated with changes in the underlying spin-coupled generalized valence bond wave function, either in the orbitals or the spin-coupling coefficients. In the current paper, we extend these studies to higher main group elements, comparing the effects of EDEC(R) on P2 and As2 versus N2, and on Cl2 and Br2 versus F2. We find that there are significant differences between the effects of dynamical electron correlation on the molecules in the first and subsequent rows of the periodic table.

Analytical assessment of pullout capacity of reinforcements in unsaturated soils

The effective interaction mechanisms in the pullout resistance of reinforcements include skin friction mobilized at the soil-solid surface, soil-soil shear resistance, and compressive resistance created against transverse elements. The third component is obtained from passive lateral pressure (LPM) or bearing capacity (BCM) methods. An analytical solution is proposed to determine the pullout capacity of geocell, geogrid, and strengthened geogrids embedded in ordinary and unsaturated soils. For unsaturated soils, the effective stress approach was employed. The solution-predicted results were compared with those obtained from large-scale pullout tests reported in the literature. Results indicated that considering LPM for 2D and 3D reinforcements better agrees with experimental results. The mobilized frictional rib-soil interfaces and the soil-soil shear resistance components generally contribute more to the pullout capacity of the geocell and geogrid, respectively. For the extensibility represented by mpi and flexibility of geocell denoted by αpi, the values of mpi = 1, 0.7, and 0.3 for the first, second, and third row of geocell, αpi= 0.4 for the first row of geocell and 0.25 for the second and subsequent rows are suggested to be considered. Parametric studies showed that the optimum transverse rib spacing is over 50 times the equivalent rib thickness (Beq).

A DEIM-CUR factorization with iterative SVDs

A CUR factorization is often utilized as a substitute for the singular value decomposition (SVD), especially when a concrete interpretation of the singular vectors is challenging. Moreover, if the original data matrix possesses properties like nonnegativity and sparsity, a CUR decomposition can better preserve them compared to the SVD. An essential aspect of this approach is the methodology used for selecting a subset of columns and rows from the original matrix. This study investigates the effectiveness of one-round sampling and iterative subselection techniques and introduces new iterative subselection strategies based on iterative SVDs. One provably appropriate technique for index selection in constructing a CUR factorization is the discrete empirical interpolation method (DEIM). Our contribution aims to improve the approximation quality of the DEIM scheme by iteratively invoking it in several rounds, in the sense that we select subsequent columns and rows based on the previously selected ones. Thus, we modify A after each iteration by removing the information that has been captured by the previously selected columns and rows. We also discuss how iterative procedures for computing a few singular vectors of large data matrices can be integrated with the new iterative subselection strategies. We present the results of numerical experiments, providing a comparison of one-round sampling and iterative subselection techniques, and demonstrating the improved approximation quality associated with using the latter.

Simulation of the Multi-Wake Evolution of Two Sandia National Labs/National Rotor Testbed Turbines Operating in a Tandem Layout

The future of wind power systems deployment is in the form of wind farms comprised of scores of such large turbines, most likely at offshore locations. Individual turbines have grown in span from a few tens of meters to today’s large turbines with rotor diameters that dwarf even the largest commercial aircraft. These massive dynamical systems present unique challenges at scales unparalleled in prior applications of wind science research. Fundamental to this effort is the understanding of the wind turbine wake and its evolution. Furthermore, the optimization of the entire wind farm depends on the evolution of the wakes of different turbines and their interactions within the wind farm. In this article, we use the capabilities of the Common ODE Framework (CODEF) model for the analysis of the effects of wake–rotor and wake-to-wake interactions between two turbines situated in a tandem layout fully and partially aligned with the incoming wind. These experiments were conducted in the context of a research project supported by the National Rotor Testbed (NRT) program of Sandia National Labs (SNL). Results are presented for a layout which emulates the turbine interspace and relative turbine emplacement found at SNL’s Scaled Wind Technologies Facility (SWiFT), located in Lubbock, Texas. The evolution of the twin-wake interaction generates a very rich series of secondary transitions in the vortex structure of the combined wake. These ultimately affect the wake’s axial velocity patterns, altering the position, number, intensity, and shape of localized velocity-deficit zones in the wake’s cross-section. This complex distribution of axial velocity patterns has the capacity to substantially affect the power output, peak loads, fatigue damage, and aeroelastic stability of turbines located in subsequent rows downstream on the farm.

Geometric modification and placement of high heat flux ic chips on substrates of different materials for enhanced heat transfer

This article presents the significance of using different sizes and positions of IC (Integrated Circuit) chips that are mounted on substrates of different materials. The ICs are cooled by forced convection in a horizontal wind tunnel. COMSOL Multiphysics 5.4 solve the IC chip cooling problem by selecting a conjugate heat transfer module with laminar flow. FR4, ba-kelite, single and multi-layer copper clad boards are used as substrate materials. Numerical simulations are performed for FR4, bakelite with a constant heat flux of 5000 W/m2, at 2.5 m/s air velocity. In contrast, single and multi-layer copper clad boards are studied for 10000 W/m2 with 1.5 m/s air velocity. The prime objective of this research is to use adequate size and placement of chips generating high heat fluxes for enhanced heat transfer. Results showed that larger chips placed at bottom rows and sequentially decreasing sizes in the subsequent rows for the same overall input for high substrate thermal conductivity give more heat dissipation. Among all configurations A0 – F considered in the study, case E provides minimum tempera-ture using single and multi-layer copper clad boards. In addition to modification of chip sizes, geometric spacing of X1/X2 = 1.8 results in lower maximum temperature.

Generating binomial coefficients in a row of Pascal's triangle from extensions of powers of eleven

Sir Isaac Newton noticed that the values of the first five rows of Pascal's triangle are each formed by a power of 11, and claimed that subsequent rows can also be generated by a power of 11. Literally, the claim is not true for the 5th row and onward. His genius mind might have suggested a deep relation between binomial coefficients and a power of some integer that resembles the number 11 in some form. In this study, we propose and prove a general formula to generate the values in any row of Pascal's triangle from the digits of (10⋯0︸Θ zeros1)n. It can be shown that the numbers in the cells in nth row of Pascal's triangle may be achieved from Θ+1 partitions of the digits of the number (10⋯0︸Θ zeros1)n, where Θ is a non-negative integer. That is, we may generate the number in the cells in a row of Pascal's triangle from a power of 11, 101, 1001, or 10001 and so on. We briefly discuss how to determine the number of zeros Θ in relation to n, and then empirically show that the partition really gives us binomial coefficients for several values of n. We provide a formula for Θ and prove that the (n+1)th row of Pascal's triangle is simply Θ+1 partitions of the digits of (10⋯0︸Θ zeros1)n from the right.

Numerical Assessment of Vertical Axis Tidal Turbine Performances in Shallow Water

Although blessed with plenty of natural resources, Malaysia has now begun transitioning away from them towards renewable energy alternatives. This is evidenced by various initiatives and plans made towards reducing dependency on hydrocarbons, such as a pledge to “become a carbon neutral country by 2050 as outlined in 12th Malaysia Plan. Among the green energy that can be considered, explored, and focused on by Malaysia is marine renewable energy, such as tidal, since the country is surrounded by large oceans. Nonetheless, there is currently insufficient data regarding the behaviour of the flow when passing through the devices downstream, especially in shallow water applications. Thus, this paper aims to highlight on the turbulence wake characteristics, and also to analyse the behaviour of wake produced by the vertical axis tidal turbine (VATT) in harnessing tidal energy at shallow water application, specifically further downstream of the device. Comparison will be made against the horizontal axis tidal turbine (HATT) to highlight their differences. Numerical analysis using the CFD method is used to analyse the model of turbines, which is represented by cylindrical and disc geometries. The simulation is evaluated in terms of the wake characteristic for both single and array configurations of the turbine. From a previous study, it has been demonstrated that the wake distance has a significant influence on the performance of tidal devices on the subsequent rows. Hence, this statement is examined in this research work to verify its validity for vertical axis tidal turbines.

Effects of wind loads on the solar panel array of a floating photovoltaic system – Experimental study and economic analysis

Floating photovoltaic systems have been installed around the world as solar energy is powerful renewable energy source, but they can sink or overturn depending on harsh environmental conditions. Analyzing the wind load on a solar panel array is important for designing an appropriate supporting structure for floating photovoltaic systems. In this study, the local pressure distributions on a solar panel array were experimentally measured and economic analysis was conducted for reduced manufacturing cost. The results showed that the first and last rows of panels had the highest drag and lift coefficients because they were the first to encounter the wind. The drag and lift coefficients gradually decreased in subsequent rows because of the sheltering effect. When the wind flowed from the side, the leftmost and rightmost columns provided a sheltering effect, which reduced the drag and lift coefficients for the center of the solar panel array by 45%–86%. From these results, the middle regions of floating bodies could be changed to the lower-cost materials which showed the 19% reduced manufacturing costs for 2.5 MW system (20 × 30). If the size of the floating PV system increases further, many floating bodies could be changed to lower-cost materials which will be more economical.

Investigating wind farm blockage in a neutral boundary layer using large-eddy simulations

Understanding how blockage influences large wind farms is essential as the first row produces the most energy and is often used as a reference for the subsequent rows. We use large-eddy simulations to investigate wind farm blockage by comparing a stand-alone turbine, an infinite row of turbines, and a wind farm with eight rows. We find that the blockage effect for dense turbine arrays is highly dependent on the non-dimensional turbine spacing. Spanwise neighboring turbines appear to benefit from deflected flow, while close downstream turbines enhance flow over the wind farm, reducing productivity at the front. In agreement with the uniform inflow wind tunnel measurements by Segalini and Dahlberg (2020), we find that the effect of downstream turbines follows a universal trend as a function of the average inter-turbine spacing when the performance of the first wind farm row is normalized with the corresponding isolated row case. However, we also demonstrate that the wind farm layout strongly affects blockage as the results do not follow a universal trend when normalized with the performance of a stand-alone turbine.

Shading and Masking of PV Collectors on Horizontal and Sloped Planes Facing South and North—A Comparative Study

With the increase in PV system installations, the available free land and rooftops for these systems may become scarcer, and therefore sloped fields facing the north may be utilized for that purpose. In deployments of PV collectors in multiple rows, either on horizontal or sloped planes, the second and subsequent rows are subject to two effects: shading and masking. Both effects reduce the electric energy generated by the PV systems. Multiple rows of collectors are deployed on horizontal planes and on sloped planes facing south, and literature on the topic has been published. No literature deals analytically with deployments of PV fields on north-facing slopes in the northern hemisphere, to the best of our knowledge. The present study develops explicit analytical expressions for the shadow height and length cast on a collector row by a row in front in multiple-row PV systems installed on slopes facing north. In addition, analytical expressions are developed for row spacing and sky view factors, altogether leading consequently to the determination of shading and masking losses. Having the developed expressions, a comparison was made between PV deployments on north-facing sloped planes to PV deployments on horizontal and south-facing slopes regarding shading and masking losses. The main finding is that the percentage of masking losses (diffuse radiation) may exceed the percentage of shading losses (beam radiation) in PV fields. At the local site 32∘ N, collector inclination angle β=25∘ and sloped-plane ε=10∘, for example, the percentage of masking losses for a horizontal plane is 6.90%; for a sloped plane facing south, the losses are 5.39%, and for a sloped plane facing north, the losses are 6.86%. In comparison to the masking losses, the percentage of shading losses for the horizontal plane is 0.83%; for the sloped plane facing south, the losses are 0.42%, and for the sloped plane facing north, the losses are 1.37%.

Modification of circumsolar radiation for anisotropic diffuse radiation models: Photovoltaic collectors on sloped planes

Photovoltaic fields are deployed in multiple collector rows on horizontal and on sloped planes, therefore the second (and subsequent rows) sees the sky dome with a smaller angle than the first (front) row

Numerical Analysis of a Flow over Spheres Embedded on a Flat Wall

This paper presents the results of numerical simulations of flow in a periodic channel with the walls covered in the central part by spherical elements that have the same overall surface areas but different radii. Two distributions of the sphere are considered, with the subsequent rows placed one after another or shifted. The computations are performed using the high-order code, whereas the solid elements are modelled with the help of the immersed boundary method. For selected cases, the results are validated by comparison with the solutions obtained using the ANSYS Fluent code on a very dense body-fitted mesh. It was found that the increase in the sphere diameter slows down the flow, which is attributed to the larger blockage of the channel cross-section caused by larger spheres and the occurrence of intense mixing (recirculation) between the spheres. The velocity profiles in the vicinity of the sphere are largely dependent on sphere diameter and rise when it increases. It was found that the distribution of the spheres plays an important role only when the spheres are large. In the part of the channel far from the sphere, the velocity profiles are significantly influenced by the sphere diameter but seem to be independent of the sphere distributions.

Numerical prediction of vortex trajectories and vortex–blade interaction on the CROR engine

PurposeThe exponential growth in computational capabilities and the increasing reliability of current simulation tools have fostered the use of computational fluid dynamics (CFD) in the design of pioneering aircraft engine architectures, such as the counter rotating open rotor (CROR) engine. Today, this design process is led by tight performance and noise constraints from a very early stage, thus requiring deep investigations of the aerodynamic and acoustic behaviour of the fluid flow. The purpose of this study is to track the trajectory of tip vortices, which is of critical importance to understand and prevent potential vortex–blade interactions with subsequent rows, as this condition strongly influences the aerodynamic and structural performance and acoustic footprints of the engine.Design/methodology/approachIn this paper, a flow feature detection methodology is applied to a particular CROR test case with the goal of visualizing and tracking the development of these coherent structures from the tip of front rotating blades. The suitability and performance of four typical region-based methodologies and one line-based (LB) criteria are firstly evaluated. Then, two novel seeding methodologies are presented as an attempt to improve the performance of the LB algorithm previously investigated.FindingsIt was demonstrated that the new seeding algorithms increase the probability of the selected seeds to grow into a tip vortex line and reduce the user’s dependence upon the selection of candidate seeds, providing faster and more accurate answers during the design-to-noise iterative process.Originality/valueApart from the new vortex detection initialization methodologies, the paper also attempts to assist the user in the endeavour of extracting rotating structures from their own CFD simulations.

PROXIMITY EFFECT OF SPRING CEREALS AND LEGUMES IN STRIP INTERCROPPING. PART IV. RESPONSE OF TRITICALE TO THE PROXIMITY OF WHEAT, BARLEY, PEA AND YELLOW LUPINE

Background. Because of its relatively low soil requirements and resistance to abiotic stress spring triticale is potentially a good component of mixtures (intercropping). The technologically easiest to use type of this agricultural method, i.e. mixed intercropping, despite having many advantages is not, unfortunately, gaining in importance due to problems related to crop protection and the variable composition of yield. An alternative is strip intercropping, which combines the advantages of pure sowing and intercropping. The production value of such cultivation depends on mutual interactions at the junction of neighbouring rows of different plant species. The aim of the undertaken experiments was to find out the response of spring triticale to the neighbouring occurrence of wheat, barley, pea and yellow lupine and to estimate the production effects of strip intercropping of triticale in the vicinity of plants of these species.
 Material and methods. This study uses the results of field experiments conducted as part of research on mixed sowings carried out in 2008–2010 in Mochełek near Bydgoszcz (53o13’ N; 17o51’ E). The experimental factor was the location of a plant row, within a strip, for the first four rows into the strip from the neighbouring species. The first row (contact row) was 12.5 cm away from the first row of the neighbouring species. The experimental unit was subsequent plant rows each four metres long.
 Results. Proximity of spring wheat, spring barley and pea was unfavourable for the growth and yield of spring triticale, especially in the row directly adjacent to a stand of the indicated species. The estimated reduction in triticale yield in strip intercropping, with three-meter wide strips in the two-sided neighbourhood of wheat, barley and pea, would amount to 2.67%, 4.85% and 4.36%, respectively. On the other hand, the proximity of yellow lupine resulted in a slight increase in the plant mass, including straw, the number of grains per spike and in grain yield, but only in the first row. The estimated increase in the yield of spring triticale grown in strip intercropping with yellow lupine, in 3-m-wide strips, was small and only amounted to 1.45%.
 Conclusion. The selection of plant species to neighbour with spring triticale in strip intercropping had a significant impact on the effect of spring triticale cultivation.

Is Compositional Data Analysis (CoDA) a theory able to discover complex dynamics in aqueous geochemical systems?

The study of the structure of compositional changes characterizing a geochemical system in time or space could be the key to understand its dynamics and resilience to environmental and anthropic perturbations. Variables characterizing the composition of an aqueous system (river or ground waters) constitute a multivariate system that moves as a whole due to multiple interrelationships and feed-back mechanisms. If the goal of the research is to understand how the whole moves, the Compositional Data Analysis (CoDA) theory offers the correct statistical framework since aqueous geochemical data pertaining to the simplex sample space. Cases of a compositional matrix can be ranked by using some criterium (e.g. increasing runoff or conductivity values), and the differences between subsequent rows calculated by using the perturbation operator that measures the change in the simplex geometry. The obtained perturbation matrix can be then analyzed by using robust Principal Component Analysis (robust-PCA) to discover the association between variables subjected to proportional perturbations during geochemical processes. The calculus of the robust Mahalanobis distance from the barycenter of this matrix appears to be also useful to reveal presence of intermittency in time or space. Intermittency is highly related to the fractal nature of variability representing an emergent property of self-organized complex dissipative systems since it optimizes the dissipation energy gradients and maximize entropy production. Application examples for the surficial waters of the Alps region and the Arno river basin (Tuscany, Central Italy) reveal that the methodology is powerful and able to discover complex dynamics moving on the boundary between different sample spaces, from the Euclidean one to the fractal one. The proposed approach allows us to shift the perspective to the nature of the dynamic interactions and transitions affecting a geochemical landscape revealing how variability moves and how presence of intermittency and resilient behavior affects evolution and prediction.

Experimental Verification of the Sky View Factor Model in Multiple-Row Photovoltaic Fields

Abstract In multiple rows of photovoltaic fields, the rows may be installed with several modules placed along the row width. The verification of the sky view factor model pertains to the second and subsequent rows. Photovoltaic (PV) modules along the row width experience uneven incident diffuse radiation caused by differences in the sky view factor of the modules. The present experimental study verifies first the sky view factor model, and second shows the differences in output power of the PV modules (affected by the sky view factors) placed in different locations along the width of the second row. This work complements the theoretical previous work and emphasizes the importance of the incident diffuse radiation, associated with the sky view factor, on the energy loss of the PV field. Two rows deployed with PV modules were tested on the laboratory roof for several days for different inclination angles and distances between rows. The results show that a top module on a row may generate 8% more power than a bottom module at noontime. The findings of this experimental study have technical significance in designing PV systems.

Corrections to anisotropic diffuse radiation model

Solar diffuse radiation models are based on isotropic and on anisotropic models. The anisotropic models take also into account the circumsolar and horizon brightenings. Both types of models were developed for a single row. A photovoltaic field is deployed in multiple rows, therefore the second (and subsequent rows) “sees” the sky dome with a smaller angle than the first row. Obscuring part of the sky affects the diffuse incident radiation. The present article modifies the anisotropic model by three factors: (a) Sky view factor of a second row (b) Correction to circumsolar brightening, (c) Correction to horizon brightening. The modified model is demonstrated on Klucher model for diffuse radiation. The study compares the differences in the diffuse incident irradiation on rows for isotropic, anisotropic and modified anisotropic Klucher models for the first and the second row. For latitude 32°N and relative low percentage of diffuse radiation, the horizon brightening may not be taken into account in the diffuse radiation calculations as it constitutes only about 0.1%. The isotropic model resulted in 9.56% less annual diffuse incident irradiation as compared to Klucher original model for the front row. The isotropic model predicts 5.83% less annual diffuse incident irradiation compared to the modified Klucher model for the second and subsequent rows. The proposed modified anisotropic model enables to calculate the incident solar radiation on photovoltaic fields more accurately.

The Effect of Collector Shading and Masking on Optimized PV Field Designs

Photovoltaic (PV) solar fields are deployed with multiple rows. The second and subsequent rows are subject to shading and masking by the rows in front. The direct beam incident radiation on the second row is affected by shading and the diffuse incident radiation is affected by masking, expressed by sky view factor. Hence, all rows, besides the first one, receive lower incident radiation. The design of PV fields must take into account the decrease in the incident radiation caused by these two effects. The paper investigates by simulation the annual incident diffuse, direct beam and global radiation on the first and on the second row for optimized PV fields at two sites: Tel Aviv, Israel, with low diffuse component, and Lindenberg–Germany monitoring station, with a high diffuse component. The study emphasizes the importance of the diffuse incident radiation on the energy loss of the PV field. The percentage annual global energy loss due to shading and masking on the second row amounts to 1.49% in Tel Aviv and 0.46% in Lindenberg. Isotropic and anisotropic diffuse models were considered. The calculated diffuse incident energy for the isotropic model is lower than the values for anisotropic model by about 8% in Tel Aviv and 3.75% in Lindenberg.

Numerical Simulation of Flapping Wing MAVs in V-formation

The purpose of this research is to understand the aerodynamics of Flapping wing Micro Aerial Vehicles (FMAVs) flying in V-formation and how V-formation can improve the endurance of FMAVs. We tested FMAVs with two types of flapping kinematics: (1) idealized sinusoidal flapping/pitching motion, (2) actual FMAV wing deformation capture. Using the design of experiment methodology, together with an immersed boundary method numerical solver, we investigate the effects of phase angle and x, y, z separation between the wings on the FMAVs’ performance. Results show that it is possible to obtain an overall thrust and lift improvement of up to 25% and 14% respectively, or a reduction of both 19%, compared to the single wing configuration. Lastly, for certain cases, we extend another row, leading to a total of five wings. Results show that in general, the additional thrust or lift experienced by the second row of wings is also experienced by the third row of wings. Hence, this may apply to subsequent rows too.