Technical and economic considerations on induction motor oversizing

In industry, due to conservative system design, safety factors associated with uncertainty in the load requirements, discrete availability of commercial rated power, and/or load power variation, most three-phase squirrel-cage induction motors are oversized. Besides the extra capital investment, the oversizing of direct-on-line fixed-speed induction motors can lead to a significant efficiency and power factor reduction. However, the part-load efficiency of oversized motors can still be higher than the full-load efficiency of well-sized smaller motors because, in general, the nominal efficiency increases with the rated power. In this paper, an analysis of potential benefits and drawbacks of motor oversizing is carried out. On the basis of the catalogue technical data provided by one of the largest motor manufacturers for IE1-, IE2-, IE3-, and IE4-class four-pole induction motors, the main results of a simulation-based study on the oversizing energy efficiency and cost-effectiveness are presented. A method to estimate the motor efficiency and power factor for any load level using commercial catalogue data is proposed and applied. Some technical issues associated with motor oversizing are also briefly addressed. It is shown that, if the additional reactive energy consumption due to poorer power factor and the slight speed increase are ignored, for IE1-, IE2- and, to a much less extent, IE3-class motors, oversizing can be cost effective for many motor rated powers, resulting in a higher average efficiency and a lower motor lifecycle cost, as well as in an extended motor lifespan. For most IE3- and IE4-class motors, the oversizing is not cost effective because of the lower nominal efficiency gain when moving to a higher oversized rated power. Additionally, the oversizing impact on the motor energy consumption strongly depends on the load profile of the application. When an old motor fails, it will probably be an IE0- or IE1-class equivalent motor, and this situation provides a golden opportunity for replacing the old motor with a properly sized IE3- or IE4-class motor, which offers significantly higher efficiency for a wide range of loads.     

Lipid Metabolism and Cardiovascular Morbidity and Mortality in Hemodialysis Patients: Role of Factors Modulating Cytosolic Calcium

Animal studies indicate that insulin resistance and glucose intolerance leading to dyslipidemia in uremic rats are associated with increased cytosolic calcium ([Ca⁺⁺ i]). The resistance and intolerance are reversed with verapamil, but recur after its discontinuation. This finding suggests that hyperparathyroid‐induced [Ca ⁺⁺ i] increase is responsible for the metabolic derangement. We retrospectively examined, over a 12‐year period, the effects of factors that lower [Ca ⁺⁺i] on total serum cholesterol and triglycerides in 332 hemodialysis (HD) patients. Because the study was retrospective, detailed lipid profiles were not available. We therefore relied on morbidity and mortality outcomes related to atherosclerotic vascular disease. Patients with diabetes mellitus were excluded, because their dyslipidemia and vascular disease are mediated via a different mechanism. Four groups emerged: group I [high parathormone (PTH) in the absence of calcium channel blockers (CCBs), n = 107], representing the highest [Ca⁺⁺ i]; group II (high PTH in the presence of CCBs, n = 76) and group III (lower PTH in the absence of CCBs, n = 66), representing intermediate [Ca ⁺⁺ i]; and group IV (lower PTH in the presence of CCBs, n = 83) representing the lowest [Ca ⁺⁺i]. The theoretically lower [Ca ⁺⁺ i] was achieved via CCB therapy or lower PTH, or both. The mean serum cholesterol in group I was 322 ± 24 mg/dL and the level of triglycerides was 398 ± 34 mg/dL. Group II had mean serum cholesterol of 196 ± 16 mg/dL and triglycerides of 157 ± 17 mg/dL. Group III had a mean serum cholesterol of 202 ± 19 mg/dL and triglycerides of 160 ± 15 mg/dL. Group IV had a mean serum cholesterol of 183 ± 9 mg/dL and triglycerides of 94 ± 6 mg/dL. The differences in cholesterol and triglyceride levels among four groups were significant (p < 0.001) by one‐way analysis of variance (ANOVA). The incidence of cardiovascular morbidity and mortality events was 61% in group I, 24% in group II, 28% in group III, and 18% in group IV (χ ² = 47.7, p < 0.001). We conclude that, in non diabetic HD patients, hyperparathyroidism, especially in the absence of CCBs, is associated with severe dyslipidemia and increased risk of cardiovascular morbidity and mortality. Dyslipidemia may be related to a hyperparathyroid‐induced increase in cytosolic calcium [Ca⁺⁺i]. Lowering [Ca⁺⁺i] by decreasing PTH or by blocking calcium entry into cells (via CCBs), or both, is associated with less dyslipidemia and improved long‐term cardiovascular morbidity and mortality. Prospective randomized studies, with actual measurement of [Ca ⁺⁺i], are needed to verify the results of this study.     

Bumblebee communities as an indicator for landscape monitoring in the agri-environmental programme

The current article focuses on the possibilities of applying bumblebees as one of the biodiversity indicators in the monitoring and evaluation of the Estonian Agri-Environmental Programme (AEP) at landscape level. The need for agri-environmental indicators arises, at least partially, because the desired state of the environment sought by policy makers may not be directly observable. To develop agri-environmental measures favourable to landscape quality, it is necessary to know more about the relationship between landscape structure and composition and the number of different species. This study tested the relationship between the data sets of landscape elements and bumblebee communities from 11 agricultural areas in Estonia. The localities were divided into two groups: intensively used agricultural areas (IA) (the percentage of arable land was >65%) and less intensively used agricultural areas (LIA) (the percentage of arable land was <45%). The following elements of landscape structure were analysed: buffer zones narrower than 5 m and wider than 5 m, ecotones between cultivated land and broad-leaved forests, ecotones between cultivated land and mixed or coniferous forests, ditches and brooks, fallow land, mixed forests, coniferous forests, broad-leaved forests, bushes, wetlands, cultivated grasslands, pastures, legumes, arable land, semi-natural grasslands. Fifteen bumblebee species were recorded in LIA and 13 in IA. The most widely distributed and abundant species were Bombus lucorum, Bombus pascuorum and Bombus lapidarius. These species dominated in both types of agricultural area. Two species, Bombus jonellus and Bombus hypnorum were found only in LIA. Principal component analysis (PCA) was applied to the landscape elements and the bumblebee species found. Results showed that there was a significant co-structure between the data sets of landscape elements and bumblebee communities. The most important landscape features that correlated with the distribution of the bumblebee species were the ecotone length between cultivated land and forests, and the size of the area covered with mixed forests and wetlands.     

Bioflocculation of (Iron oxide – Silica) system using Bacillus cereus bacteria isolated from Egyptian iron ore surface

In mineral bio-beneficiation, it is very important to understand the microbial surface characteristics and its behaviour onto the mineral surface. Bacillus cereus bacterium has never been used before as a bio-reagent for separation of different mineral systems. In this work, complete characterization of such type of bacteria, isolated from Egyptian iron ore surface, including gram stain, growth curve, Biolog microbial identification, Zeta potential characterization, Fourier Transform Infrared Spectrometer, FTIR characterization as well as protein and polysaccharide analysis have been studied. The results confirmed that Bacillus cereus is a gram positive bacterium, rod shaped, smooth and circular with different types of by-products as polysaccharides, carboxylic acids and amino acids that gives an amphoteric behaviour on the cell surface. The results of zeta potential showed that the iso-electric points (IEP) of iron oxide (≈6.3) and silica (≈1.8) were significantly displaced to low values (≈2.2) and (≈1) respectively after treatment with the bacterial isolates. The results obtained showed a better affinity of Bacillus cereus to hematite mineral surface rather than silica surface and could be used in separation of such mineral from its associated gangue minerals. On applying B. cereus bacterial strain as a sole flocculating agent, to selectively separate hematite from its mixture with silica, succeeded in the removal of 80% of SiO₂ as a concentrate containing about 2% SiO₂ and 98% Fe₂O₃ with 82% flocculated by Wt. and a good recovery of 89.20%.     

Utilization of surface modified phyllosilicate mineral for heavy metals removal from aqueous solutions

The objective of this work is to enhance the adsorbing performance of the natural Egyptian phyllosilicate mineral, glauconite (greensand), through surface modification to obtain a particular combination of physical and chemical properties. It was found that Zn removal increased from 84% to 94%, while Pb removal varied from 96.67% to 99% by using 10–25 g/l modified glauconite in a solution having 50 mg/l Zn²⁺ and 30 mg/l pb²⁺ ions. Adsorption data were investigated using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Linear regression methods are used to determine adsorption capacities and optimum adsorption isotherms. R² value of Langmuir isotherm model for pb²⁺ is higher than other models. The maximum monolayer coverage (Q_o) from Langmuir isotherm model was calculated to be 15.363 and 21.654 mg/g and the separation factor indicating a favorable sorption experiment is 0.0324 and 0.13207 for Zn²⁺ and Pb²⁺ respectively. Also from Freundlich isotherm model, the intensities of adsorption (n) that indicated favorable sorption are 1.3036 and 1.364 for Zn²⁺ and Pb²⁺ respectively. The heat of sorption process was calculated from Temkin isotherm model to be 6.44101 and 4.1353 J/mol for Zn²⁺ and Pb²⁺ respectively, that indicated to the physisorption process which B < 20 kJ/mol so, Temkin isotherm is not fitted with experimental adsorption but the mean free energy was calculated from DRK isotherm which are 24.693 and 47.093 kJ/mol, where E_D < 8 proved that the adsorption experiment followed a chemisorption process. So the relative adsorption capacity for metals was in the order Pb < Zn.     

Mathematical modeling of thin-layer drying kinetics and moisture diffusivity study of apple slices using infrared conveyor-belt dryer

The drying features of apples at different infrared drying settings were investigated. The drying time, moisture-effective diffusion, and activation energy of infrared dried apples were measured experimentally and statistically as a function of slice thicknesses, radiation intensity, and air velocity. The infrared intensity of 0.225, 0.130, and 0.341 W/cm², slice thicknesses of 6, 4, and 2 mm, and airflow of 0.5, 1.0, and 1.5 m/s were used to dry apple slices. The data shows that the drying time reduced as IR increased, but airflow and slice thickness increased. Eight statistical factors were used to compare 11 alternative mathematical drying models. The experimentally acquired drying curves were matched to the thin-layer drying equations. According to the calculations, the Midilli et al. equation had the greatest (efficiency and R²) and lowest (χ², sum of squared errors, standard error of estimate, standard error, standard deviation of difference) values. As a result, this equation is the best for modeling the drying curves of apple slices across all drying circumstances. The optimum moisture diffusivity value varied from 2.59 to 9.07 × 10⁻¹⁰ m²/s. The mean activation energy was determined to be 19.02–29.83 kJ/mol under various experimental conditions.     

Semi-natural grassland continuity, long-term land-use change and plant species richness in an agricultural landscape on Öland, Sweden

The study characterizes historical land-use change and the development of semi-natural grassland habitats, over 274 years, within a mosaic agricultural landscape (22 km²) on the island of Öland (Sweden). We also explore the relationship between previous land-use, habitat continuity and present-day vascular plant species richness in grassland patches. Land-cover maps, based on cadastral maps and aerial photographs, were produced for six time-periods between 1723/1733 and 1994/1997. In 1723/1733, the landscape was dominated by grasslands, with arable land surrounding the villages. The grassland area decreased throughout the study period and grassland patches became progressively more fragmented. Present-day grasslands represent 18% of the grassland area in 1723/1733. The land-use structure of the early 18th century is still evident in the modern landscape. The majority of the present-day grasslands are situated on former common grazing land and have had a continuity of at least 274 years: the remaining grasslands are younger and developed during the 20th century on arable or forested land. The proportion of plant species that depend on grazing and are characteristic of semi-natural grasslands significantly reflects the continuity and previous land-use of grassland sites. The study illustrates the way in which information on historical land-use and habitat continuity can help to explain the structuring of plant assemblages in semi-natural grasslands within the modern landscape.     

Driving forces for and barriers to providing energy services—a study of local and regional energy companies in Sweden

Improving energy efficiency is a cornerstone in climate change mitigation, and energy services are portrayed as a promising market-based approach to achieve this. This paper examines the barriers to, and driving forces needed for, the implementation of energy services from the perspective of Swedish local and regional energy companies. This includes an analysis of the resources needed in three phases of energy service implementation, i.e., development, sales, and deployment. The results indicate a supply-side interest in providing energy services, with the major challenges being related to (a) intra-organizational issues such as a lack of strategic direction and intent and (b) a perceived lack of knowledge, interest, and trust on the part of potential energy service customers. The paper concludes with managerial and policy implications on how an increased focus and impact of energy service can be achieved among local and regional companies.