			Home About us Contact

Energy Utilization Efficiency (energy + utilization_efficiency)

Distribution by Scientific Domains

Chemistry	40%

Selected Abstracts

Assessment of the energy and exergy utilization efficiencies in the Turkish agricultural sector

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2006
Zafer Utlu
Abstract This study deals with evaluating the energy and exergy utilization efficiencies in the Turkish agricultural sector over a 12-year period from 1990 to 2001. In the energy and exergy analyses, two main energy sources, namely fuels and electricity, are taken into consideration, while the sectoral energy and exergy efficiencies are compared for this period. These main energy sources include diesel for tractors and other vehicles, and electricity for pumps. Overall energy utilization efficiencies are obtained to vary between 29.1 and 41.1%, while overall exergy utilization efficiencies are found to range from 27.9 to 37.4% in the analysed years, respectively. It may be concluded that the present technique proposed here may be used as a useful tool in analysing and evaluating the energy and exergy utilization efficiencies, identifying energy efficiency and/or energy conservation opportunities and dictating the energy strategies of countries. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Optimum matching parameters of an MPPT unit used for a PVG-powered water pumping system for maximum power transfer

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2006
Mehmet Akbaba
Abstract Photovoltaic generator (PVG)-powered water pumping has the potential to bring potable water to millions of people in developing countries. However, due to the high initial cost of PVG units, sophisticated load matching is required between the water pumping system and PVG, in order to be able to extract maximum available power from an available PVG unit at all solar radiation levels. This requires an intermediate circuitry between the PVG unit and the motor driving the water pump, which is usually termed as maximum power point trackers (MPPT). This present paper therefore investigates the optimum matching parameters of a power conditioning circuit, which is composed of a double step-up dc,dc converter (DSUC). This MPTT circuit is used for interfacing a permanent magnet (PM) motor-driven water pumping system to a PVG for extracting maximum available power from PVG, hence maximizing the energy utilization efficiency and price,performance ratio of the whole system. It is shown that two key parameters of the DSUC, which are the duty cycle and chopping frequency, are dominating the performance of the whole system, and they are interrelated and load dependent. Therefore, optimum values of these parameters need to be determined. An example system is provided in which a complete modelling is presented in time domain and through numerical experiments it is demonstrated how the optimum values of these two key matching parameters can be determined for a given system. The MPPT circuit used in this investigation is suitable for optimum matching of all types of loads to PVG units, provided that an optimum frequency,duty cycle pair is determined for the choppers in DSUC for every 5% bands of solar radiation between 20 and 100%. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A multi-objective optimization approach to polygeneration energy systems design

AICHE JOURNAL, Issue 5 2010
Pei Liu
Abstract Polygeneration, typically involving co-production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. The optimal design of such a complex, large-scale and highly nonlinear process system poses significant challenges. In this article, we present a multiobjective optimization model for the optimal design of a methanol/electricity polygeneration plant. Economic and environmental criteria are simultaneously optimized over a superstructure capturing a number of possible combinations of technologies and types of equipment. Aggregated models are considered, including a detailed methanol synthesis step with chemical kinetics and phase equilibrium considerations. The resulting model is formulated as a non-convex mixed-integer nonlinear programming problem. Global optimization and parallel computation techniques are employed to generate an optimal Pareto frontier. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Energy Efficiency of Two-Phase Mixing in a Modified Bubble Column

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
Subrata Kumar Majumder
Abstract Energy efficiency for gas liquid mixing in a modified downflow bubble column reactor has been analyzed in this paper. Efficiencies of the different parts of the bubble column have been assessed on the basis of energy dissipation. Prediction of the energy dissipation coefficient as well as energy utilization efficiency due to gas-liquid mixing as a function of different physical, geometric and dynamic variables of the system has been done by correlation method. The distribution of energy utilization in the different zones of the column has also been analyzed. Experiments were carried out with air-water and air-aqueous solutions of carboxy methyl cellulose with different concentrations. Dans cet article on a analysé l'efficacité énergétique pour le mélange gaz-liquide dans un réacteur à colonne à bulles à écoulement descendant modifié. Les efficacités des différentes régions de la colonne à bulles ont été évaluées sur la base de la dissipation d'énergie. On a utilisé une méthode de corrélation pour prédire le coefficient de dissipation d'énergie ainsi que l'efficacité d'utilisation de l'énergie due au mélange gaz-liquide en fonction des différentes variables physiques, géométriques et dynamiques du système. La distribution de l'utilisation de l'énergie dans les différentes régions de la colonne a également été analysée. Des expériences ont été menées avec des solutions air-eau et air-solutions aqueuses de carboxyméthylcellulose à différentes concentrations. [source]

Reduced water oxygen levels affect maximal feed intake, but not protein or energy utilization efficiency of rainbow trout (Oncorhynchus mykiss)

AQUACULTURE NUTRITION, Issue 1 2009
B.D. GLENCROSS
Abstract This study examined the effect of reduced water oxygen levels on the utilization efficiencies of energy and protein from a diet fed to rainbow trout. An experimental diet was fed at one of the four ration levels with an additional starved treatment also included in each oxygenation regime. Oxygen levels in each oxygenation regime varied with ration level, but averaged 9.3 ± 0.36 mg L,1 for the normal regime and 5.7 ± 1.4 mg L,1 for the hypoxia regime. Significant differences were observed in the apparent satietal feed intake levels in each oxygenation regime, but not at any of the pair-fed restricted levels. No significant effects of oxygenation regime were observed on the utilization of either energy or protein by the fish. Efficiency of protein use varied depending on the protein intake level, but was not significantly affected by oxygenation regime. This study demonstrates that a reduction in the oxygen levels of the water does not affect the utilization efficiency of dietary digestible protein and energy in rainbow trout, but does result in a downregulation of feed intake when the fish is fed to apparent satietal levels. [source]