Performance Evaluation of Different PV-Array Configurations under Weak Light Conditions and Partial Shadings

The paper analyses empirical performance data of five commercial PV-plants in Germany. The purpose was on one side to investigate the weak light performance of the different PV-modules used. On the other hand it was to quantify and compare the shading losses of different PV-array configurations. The importance of this study relies on the fact that even if the behavior under weak light conditions or the shading losses might seem to be a relatively small percentage of the total yearly output; in projects where a performance guarantee is given, these variation can make the difference between meeting or not the conditions.When analyzing the data, a high dispersion was found. To reduce the optical losses and spectral effects, a series of data filters were applied based on the angle of incidence and absolute Air Mass. To compensate for the temperature effects and translate the values to STC (25°C), five different methods were assessed. At the end, the Procedure 2 of IEC 60891 was selected due to its relative simplicity, usage of mostly standard parameters found in datasheets, good accuracy even with missing values, and its potential to improve the results when the complete set of inputs is available.After analyzing the data, the weak light performance of the modules did not show a clear superiority of a certain technology or technology group over the others. Moreover, the uncertainties in the measurements restrictive the conclusiveness of the results.In the partial shading analysis, the landscape mounting of mc-Si PV-modules in free-field showed a significantly better performance than the portrait one. The cross-table string using CIGS modules did not proved the benefits expected and performed actually poorer than a regular one-string-per-table layout. Parallel substrings with CdTe showed a proper functioning and relatively low losses. Among the two product generations of CdTe analyzed, none showed a significantly better performance under partial shadings.

Electrical Evaluation of a Low Concentrating PVT Collector Based on Performance Ratio

Photovoltaic Thermal/Hybrid collectors are an emerging technology that combines PV and solar thermal collectors by producing heat and electricity simultaneously. In this paper, the electrical performance evaluation of a low concentrating PVT collector was done through two testing parts: power comparison and performance ratio testing. For the performance ratio testing, it is required to identify and measure the factors affecting the performance ratio on a low concentrating PVT collector. Factors such as PV cell configuration, collector acceptance angle, flow rate, tracking the sun, temperature dependence and diffuse to irradiance ratio. Solarus low concentrating PVT collector V12 was tested at Dalarna University in Sweden using the electrical equipment at the solar laboratory. The PV testing has showed differences between the two receivers. Back2 was producing 1.8 energy output more than Back1 throughout the day. Front1 and Front2 were almost the same output performance. Performance tests showed that the cell configuration for Receiver2 with cells grouping (6- 32-32-6) has proved to have a better performance ratio when to it comes to minimizing the shading effect leading to more output power throughout the day because of lowering the mismatch losses. Different factors were measured and presented in this thesis in chapter 5. With the current design, it has been obtained a peak power at STC of 107W per receiver. The solar cells have an electrical efficiency of approximately 19% while the maximum measured electrical efficiency for the collector was approximately 18 % per active cell area, in addition to a temperature coefficient of -0.53%/ ˚C. Finally a recommendation was done to help Solarus AB to know how much the electrical performance is affected during variable ambient condition and be able to use the results for analyzing and introducing new modification if needed.

Performance evaluation of ventilation radiators

A ventilation radiator is a combined ventilation and heat emission unit currently of interest due to its potential for increasing energy efficiency in exhaust ventilated buildings with warm water heating. This paper presents results of performance tests of several ventilation radiator models conducted under controlled laboratory conditions.   The purpose of the study was to validate results achieved by Computational Fluid Dynamics (CFD) in an earlier study and indentify possible improvements in the performance of such systems. The main focus was on heat transfer from internal convection fins, but comfort and health aspects related to ventilation rates and air temperatures were also considered.   The general results from the CFD simulations were confirmed; the heat output of ventilation radiators may be improved by at least 20 % without sacrificing ventilation efficiency or thermal comfort.   Improved thermal efficiency of ventilation radiators allows a lower supply water temperature and energy savings both for heating up and distribution of warm water in heat pumps or district heating systems. A secondary benefit is that a high ventilation rate can be maintained all year around without risk for cold draught.

The importance of body-mass exponent optimization for evaluation of performance capability in cross-country skiing

Introduction Performance in cross-country skiing is influenced by the skier’s ability to continuously produce propelling forces and force magnitude in relation to the net external forces. A surrogate indicator of the “power supply” in cross-country skiing would be a physiological variable that reflects an important performance-related capability, whereas the body mass itself is an indicator of the “power demand” experienced by the skier. To adequately evaluate an elite skier’s performance capability, it is essential to establish the optimal ratio between the physiological variable and body mass. The overall aim of this doctoral thesis was to investigate the importance of body-mass exponent optimization for the evaluation of performance capability in cross-country skiing. Methods In total, 83 elite cross-country skiers (56 men and 27 women) volunteered to participate in the four studies. The physiological variables of maximal oxygen uptake (V̇O2max) and oxygen uptake corresponding to a blood-lactate concentration of 4 mmol∙l-1 (V̇O2obla) were determined while treadmill roller skiing using the diagonal-stride technique; mean oxygen uptake (V̇O2dp) and upper-body power output (Ẇ) were determined during double-poling tests using a ski-ergometer. Competitive performance data for elite male skiers were collected from two 15-km classical-technique skiing competitions and a 1.25-km sprint prologue; additionally, a 2-km double-poling roller-skiing time trial using the double-poling technique was used as an indicator of upper-body performance capability among elite male and female junior skiers. Power-function modelling was used to explain the race and time-trial speeds based on the physiological variables and body mass. Results The optimal V̇O2max-to-mass ratios to explain 15-km race speed were V̇O2max divided by body mass raised to the 0.48 and 0.53 power, and these models explained 68% and 69% of the variance in mean skiing speed, respectively; moreover, the 95% confidence intervals (CI) for the body-mass exponents did not include either 0 or 1. For the modelling of race speed in the sprint prologue, body mass failed to contribute to the models based on V̇O2max, V̇O2obla, and V̇O2dp. The upper-body power output-to-body mass ratio that optimally explained time-trial speed was Ẇ ∙ m-0.57 and the model explained 63% of the variance in speed. Conclusions The results in this thesis suggest that V̇O2max divided by the square root of body mass should be used as an indicator of performance in 15-km classical-technique races among elite male skiers rather than the absolute or simple ratio-standard scaled expression. To optimally explain an elite male skier’s performance capability in sprint prologues, power-function models based on oxygen-uptake variables expressed absolutely are recommended. Moreover, to evaluate elite junior skiers’ performance capabilities in 2-km double-poling roller-skiing time trials, it is recommended that Ẇ divided by the square root of body mass should be used rather than absolute or simple ratio-standard scaled expression of power output.

Modelling solute transport in structured soils: performance evaluation of the ADR and TRM models

The movement of chemicals through the soil to the groundwater or discharged to surface waters represents a degradation of these resources. In many cases, serious human and stock health implications are associated with this form of pollution. The chemicals of interest include nutrients, pesticides, salts, and industrial wastes. Recent studies have shown that current models and methods do not adequately describe the leaching of nutrients through soil, often underestimating the risk of groundwater contamination by surface-applied chemicals and overestimating the concentration of resident solutes. This inaccuracy results primarily from ignoring soil structure and nonequilibrium between soil constituents, water, and solutes. A multiple sample percolation system (MSPS), consisting of 25 individual collection wells, was constructed to study the effects of localized soil heterogeneities on the transport of nutrients (NO−3, Cl−, PO3−4) in the vadose zone of an agricultural soil predominantly dominated by clay. Very significant variations in drainage patterns across a small spatial scale were observed (one-way ANOVA, p < 0.001 indicating considerable heterogeneity in water flow patterns and nutrient leaching. Using data collected from the multiple sample percolation experiments, this paper compares the performance of two mathematical models for predicting solute transport, the advective-dispersion model with a reaction term (ADR), and a two-region preferential flow model (TRM) suitable for modelling nonequilibrium transport. These results have implications for modelling solute transport and predicting nutrient loading on a larger scale.

Performance evaluation of the concurrent execution of NAS parallel benchmarks with BYTE sequential benchmarks on a cluster

Computers of a non-dedicated cluster are often idle (users attend meetings, have lunch or coffee breaks) or lightly loaded (users carry out simple computations). These underutilized computers can be employed to execute parallel applications not only during weekends and at nights but also during office hours. Thus, they have to be shared by parallel and sequential applications which could lead to the improvement of their execution performance. However, there is a lack of experimental study showing the behavior and performance of parallel and sequential applications executing concurrently on clusters. We present here the result of an experimental study into load balancing based scheduling of a mixture of parallel and sequential applications on a non-dedicated cluster.

Sustainable components of leadership effectiveness in organizational performance

Purpose – The objective is to describe a selection of sustainability components of leadership effectiveness in organizational performance.
Design/methodology/approach – The paper is based on a conceptual discussion. Findings – The paper contributes to descriptive models that address sustainability components of leadership effectiveness in organizational performance. The study highlights some common views that exist in the management literature and in prosperous management practice related to the direct impact of the relationship in organizational performance between leadership and effectiveness. In fact, it also highlights the critical or sceptical views of leadership effectiveness in organizational performance raised in the literature. Research limitations/implications – The paper contends that the actual leadership effectiveness in organizational performance varies over time and across contexts. At times, the achievement in organizational performance is the outcome of prosperous and conscious leadership, while it at other times may be the outcome of poor and deficient leadership. The topic at hand is positioned and limited to the interface that may describe and explain the connection between these two views. Furthermore, it is limited to corporate decision making and business behaviour in relation to leadership effectiveness and organizational performance. Practical implications – The leadership of an organization need not only to be successful today, but they also need to be successful tomorrow to stay in control and to flourish. Quality control and quality assurance are no longer enough for most organizations. They need to build an awareness of the sustainability components into processes of their management and business practices (i.e. internal and external ones) in order to be judged as successful in corporate decision-making and business behaviour in organizational performance in the long term. Originality/value – The principal contributions of the study are a model of timely leadership effectiveness, a model of contextual leadership effectiveness, and a typology of leadership effectiveness in corporate decision-making and business behaviour. These contributions provide theoretical and managerial ideas and insights into the sustainability components of leadership effectiveness in organizational performance.

Evaluation of construction contractor performance: a critical analysis of some recent research

International comparisons of construction industry performance are notoriously difficult. A recent comparative study, extensive in scope and using an innovative approach, is reviewed and questions raised regarding various aspects of the methodology adopted, the validity of the conclusions drawn and manner in which outcomes were reported. Particular areas of concern include the unequivocal statement of conclusions that are based on a small sample, and the use of data from that sample that are, in fact, no more than estimates of project performance. Attention is drawn to the limitations of the research reported and the reliability of the methods used, and the data gathered is examined.

Reflexive and critical views of leadership performance in corporate accomplishment : framework and illustration

Purpose – This paper intends to shed some light on the relationship between leadership performance and corporate accomplishment through the aid of complexity sciences. The objective is to describe leadership performance in corporate accomplishment using different teleological approaches.

Design/methodology/approach – The paper discusses the underlying criteria of the relationship between leadership performance and corporate accomplishment. Case illustration and narrative analogy are also provided.

Findings – The authors believe that the discussion highlights a potential downside of leadership performance in corporate accomplishment and its precision rarely highlighted in practice and literature.

Research limitations/implications – There is a reigning assumption in management practice that is based on the belief that a top-down approach of leadership performance in management and business practices is superior to the bottom-up approach. It proffers the assumed importance of strategic management issues, but neglects the knowledge, experience, competence and awareness inherent among employees at tactical and operational levels of business practices. It also proffers a mechanical view of employee performance and ignores the worth of the generation of ideas from subordinates in management and business practices that contribute to corporate achievements. Furthermore, it neglects the fact that it is not possible to know the future nor it is predictable.

Practical implications – The paper contends that the importance of top management tends to be inflated in respect to corporate achievements in the management/leadership literature. It also contends that it should be questioned as to whether the top management of corporations are largely responsible for the corporate results on which they attempt to justify their salaries and other benefits. Furthermore, the paper contends that it also should be questioned as to what extent corporate accomplishment may be derived from the performance of the top management in organizations.

Originality/value – The paper strives to contribute to the ongoing discussion of leadership performance in corporate accomplishment in various ways. The principal contributions are: a set of teleological sub-processes of leadership performance and a case illustration and narrative analogies of teleological leadership performance patterns, in respect to corporate accomplishment in management and business practices. These contributions provide theoretical and managerial ideas and insights to anticipate and avoid deficient or erroneous grounds of leadership performance evaluation in corporate accomplishment.

A comparison of student evaluation of teaching with student performance

This study measures the evaluation of teaching given by students against their final outcomes in a subject. The subject in question had an enrolment across four campuses of 1073 students at the time of the evaluation and is a statistics subject that is core (i.e. compulsory) to several undergraduate business degrees. This study is based on the 373 students (34.8%) who responded to the survey, and their final results. The evaluations were open for a period of six weeks leading up to and just after the final exam. The study matches the responses to the question “This unit was well taught” to final outcomes, in an attempt to ascertain whether there is a link between student evaluation of teaching and performance. The analysis showed that for the students who self -selected to complete the survey:

· Students who perform well in the subject generally give higher scores than lower performing students.

· The same general pattern prevailed when other secondary factors were taken into account, such as, when the evaluation was completed, campus and gender.

· The timing of when a student completes the evaluation seems the most important of these secondary variables.

· In general, students who submitted their evaluations after the exam gave higher ratings if they eventually obtained a pass grade or better, and lower grades if they failed.

Preliminary evaluation of monolithic column high-performance liquid chromatography with tris(2,2’-bipyridyl)ruthenium(II) chemiluminescence detection for the determination of quetiapine in human body fluids

High-performance liquid chromatography (HPLC) with tris(2,2-bipyridyl)ruthenium(II) chemiluminescence detection methodology is reported for the determination of the atypical antipsychotic drug quetiapine and the observation of its major active and inactive metabolites in human urine and serum. The method uses a monolithic chromatographic column allowing high flow rates of 3mL min−1 enabling rapid quantification. Flow injection analysis (FIA) with tris(2,2-bipyridyl)ruthenium(II) chemiluminescence detection and HPLC time of flight mass spectrometry (TOF-MS) were used for the determination of quetiapine in a pharmaceutical preparation to establish its suitability as a calibration standard. The limit of detection achieved with FIA was 2×10−11 mol L−1 in simple aqueous solution. The limits of detection achieved with HPLC were 7×10−8 and 2×10−10 mol L−1 in urine and serum, respectively. The calibration range for FIA was between 5×10−9 and 1×10−6 mol L−1. The calibration ranges for HPLC were between 1×10−7–1×10−4 and 1×10−8–1×10−4 mol L−1 in urine and serum, respectively. The quetiapine concentrations in patient samples were found to be 3×10−6 mol L−1 in urine and 7×10−7 mol L−1 in serum. Without the need for preconcentration, the HPLC detection limits compared favourably with those in previously published methodologies. The metabolites were identified using HPLC-TOF-MS.

Performance evaluation of different ultrafiltration membranes for the reclamation and reuse of secondary effluent

This study investigates and compares the performance of two different types of ultrafiltration (UF) membranes in the recovery of water from secondary treated wastewater. Filtration experiments were carried out on a pilot scale cross-flow unit using synthetic wastewater similar to the quality of secondary treated wastewater by varying the operating parameters such as transmembrane pressure (TMP), feed composition and membrane configuration. The filtration experiments demonstrated that the flux recovery through spiral polymeric UF membrane was more sensitive to the variation in TMP compared to the tubular ceramic UF membrane over the range of TMP studied. The resistance in series model was used for the evaluation of the resistance to the permeate flux. The fouling resistance, particularly irreversible resistance compared to reversible resistance plays a major role in the total resistance for the tubular ceramic membrane. In contrast clean membrane resistance is the major contributor for the total resistance of the spiral polymeric membrane. Finally, the effectiveness of the filtration treatment was determined by evaluating the rejection coefficients for various pollution indices of the wastewater. Significant differences in the performance of the membrane types were observed which are likely to impact on the selection, operation and maintenance of the membrane system.