Energy and Metabolism

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I NTERNATIONAL J OURNAL OF E NERGY AND E NVIRONMENT Volume 3, Issue 4, 2012 pp.521-530 Journal homepage: www.IJEE.IEEFoundation.org ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2012 International Energy & Environment Foundation. All rights reserved. Integration of energy and environmental systems in wastewater treatment plants Suzanna Long 1 , Elizabeth Cudney 2 1 Department of Engineering Management and Systems Engineering, 600 W, 14 th Street, 215 EMGT Building, Rolla, MO-65401, 573-341-7621, U.S.A. 2 Department of Engineering Management and Systems Engineering, 600 W, 14 th Street, 217 EMGT Building, Rolla, MO-65401, 573-341-7931, U.S.A. Abstract Most wastewater treatment facilities were built when energy costs were not a concern; however, increasing energy demand, changing climatic conditions, and constrained energy supplies have resulted in the need to apply more energy-conscious choices in the maintenance or upgrade of existing wastewater treatment facilities. This research develops an integrated energy and environmental management systems model that creates a holistic view of both approaches and maps linkages capable of meeting high-performing energy management while meeting environmental standards. The model has been validated through a case study on the Rolla, Missouri Southeast Wastewater Treatment Plant. Results from plant performance data provide guidance to improve operational techniques. The significant factors contributing to both energy and environmental systems are identified and balanced against considerations of cost. Copyright © 2012 International Energy and Environment Foundation - All rights reserved. Keywords: Energy conservation; Environmental management; Process integration; Strategic management; Wastewater treatment systems. 1. Introduction Green environmental practices are increasingly important in combating serious global energy and environmental issues. Water and wastewater facilities are among the largest and most energy-intensive systems owned and operated by local governments and account for approximately 30 to 50% of municipal energy use. Most wastewater treatment facilities were built when energy costs were not a concern; however, increasing energy demand, changing climatic conditions, and constrained energy supplies have resulted in the need to apply more energy-conscious choices in the maintenance or upgrade of existing wastewater treatment facilities. Energy represents the largest controllable cost of water and wastewater treatment since energy use directly affects the amount of greenhouse gas (GHG) emissions, and indirectly affects the biological oxygen demand (BOD), chemical oxygen demand (COD), and pollutions levels. By controlling the level of energy consumption, wastewater treatment facilities can reduce the operating costs, increase efficiency, and reduce pollution in an effort to provide cleaner environments. In addition, increased training on advanced equipment by well-trained employees can lead to improved effluent and surface water quality and more compliant facilities [1, 2]. A strategic process to control these various factors could provide significant benefits to local governments and the communities they serve. International Journal of Energy and Environment (IJEE), Volume 3, Issue 4, Energy and Metabolism Energy and Metabolism Bởi: OpenStaxCollege Scientists use the term bioenergetics to describe the concept of energy flow ([link]) through living systems, such as cells Cellular processes such as the building and breaking down of complex molecules occur through stepwise chemical reactions Some of these chemical reactions are spontaneous and release energy, whereas others require energy to proceed Just as living things must continually consume food to replenish their energy supplies, cells must continually produce more energy to replenish that used by the many energy-requiring chemical reactions that constantly take place Together, all of the chemical reactions that take place inside cells, including those that consume or generate energy, are referred to as the cell’s metabolism Ultimately, most life forms get their energy from the sun Plants use photosynthesis to capture sunlight, and herbivores eat the plants to obtain energy Carnivores eat the herbivores, and eventual decomposition of plant and animal material contributes to the nutrient pool 1/16 Energy and Metabolism Metabolic Pathways Consider the metabolism of sugar This is a classic example of one of the many cellular processes that use and produce energy Living things consume sugars as a major energy source, because sugar molecules have a great deal of energy stored within their bonds For the most part, photosynthesizing organisms like plants produce these sugars During photosynthesis, plants use energy (originally from sunlight) to convert carbon dioxide gas (CO2) into sugar molecules (like glucose: C6H12O6) They consume carbon dioxide and produce oxygen as a waste product This reaction is summarized as: 6CO2 + 6H2O > C6H12O6 + 6O2 Because this process involves synthesizing an energy-storing molecule, it requires energy input to proceed During the light reactions of photosynthesis, energy is provided by a molecule called adenosine triphosphate (ATP), which is the primary energy currency of all cells Just as the dollar is used as currency to buy goods, cells use molecules of ATP as energy currency to perform immediate work In contrast, energystorage molecules such as glucose are consumed only to be broken down to use their energy The reaction that harvests the energy of a sugar molecule in cells requiring oxygen to survive can be summarized by the reverse reaction to photosynthesis In this reaction, oxygen is consumed and carbon dioxide is released as a waste product The reaction is summarized as: C6H12O6 + 6O2 > 6H2O + 6CO2 Both of these reactions involve many steps The processes of making and breaking down sugar molecules illustrate two examples of metabolic pathways A metabolic pathway is a series of chemical reactions that takes a starting molecule and modifies it, step-by-step, through a series of metabolic intermediates, eventually yielding a final product In the example of sugar metabolism, the first metabolic pathway synthesized sugar from smaller molecules, and the other pathway broke sugar down into smaller molecules These two opposite processes—the first requiring energy and the second producing energy—are referred to as anabolic pathways (building polymers) and catabolic pathways (breaking down polymers into their monomers), respectively Consequently, metabolism is composed of synthesis (anabolism) and degradation (catabolism) ([link]) It is important to know that the chemical reactions of metabolic pathways not take place on their own Each reaction step is facilitated, or catalyzed, by a protein called an enzyme Enzymes are important for catalyzing all types of biological reactions—those that require energy as well as those that release energy 2/16 Energy and Metabolism Catabolic pathways are those that generate energy by breaking down larger molecules Anabolic pathways are those that require energy to synthesize larger molecules Both types of pathways are required for maintaining the cell’s energy balance Energy Thermodynamics refers to the study of energy and energy transfer involving physical matter The matter relevant to a particular case of energy transfer is called a system, and everything outside of that matter is called the surroundings For instance, when heating a pot of water on the stove, the system includes the stove, the pot, and the water Energy is transferred within the system (between the stove, pot, and water) There are two types of systems: open and closed In an open system, energy can be exchanged with its surroundings The stovetop system is open because heat can be lost to the air A closed system cannot exchange energy with its surroundings Biological organisms are open systems Energy is exchanged between them and their surroundings as they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release energy to the environment by doing work and releasing heat Like all things in the physical world, energy is subject to physical laws The laws of thermodynamics ... I NTERNATIONAL J OURNAL OF E NERGY AND E NVIRONMENT Volume 1, Issue 3, 2010 pp.445-458 Journal homepage: www.IJEE.IEEFoundation.org ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2010 International Energy & Environment Foundation. All rights reserved. Energy and exergy analysis of particle dispersed latent heat storage system S. Jegadheeswaran, S. D. Pohekar Mechanical Engineering, Tolani Maritime Institute, Induri, Pune 410 507, India. Abstract Latent heat thermal storage (LHTS) system has been attractive over the years as an effective energy storage and retrieval device especially in solar thermal applications. However, the performance of LHTS systems is limited by the poor thermal conductivity of phase change materials (PCMs) employed. A numerical study is carried out to investigate the performance enhancement of a LHTS unit of shell and tube configuration due to the dispersion of high conductivity particles in the PCM during charging process (melting). Temperature based governing equations have been formulated and solved numerically following an alternate iteration between the temperature and thermal resistance. Exergy based performance evaluation is taken as a main aspect. The numerical results are presented for several mass flow rates and inlet temperatures of heat transfer fluid (HTF). The results indicate a significant improvement in the performance of the LHTS unit when high conductivity particles are dispersed. Copyright © 2010 International Energy and Environment Foundation - All rights reserved. Keywords: Latent heat storage system, Phase change material, Melting, Exergy, Thermal resistance. 1. Introduction The large scale utilization of the many sources of thermal energy like solar thermal energy, hot waste streams available in industries etc., may be handicapped, if not properly managed. The major problem in managing energy from the above-mentioned sources is the time gap between availability and need. The storage of thermal energy has been emphasized as an attractive solution for such kind of problems on energy management and conservation, in both industrial and domestic sectors. For the last three decades, there has been a growing interest in latent heat thermal storage (LHTS) technique, which has been proved as a better engineering option over sensible heat storage. They offer several advantages such as high energy storage, uniform temperature of operation, simple configuration, etc. In spite of the relative merits, the phase change material (PCM) loaded in the LHTS unit possesses a very low thermal conductivity, which drastically affects the performance of the unit. The various performance techniques proposed and studied are employing fins [1-3], multiple PCMs [4, 5] and increasing the thermal conductivity of conventional PCMs with the help of additives [6-8]. For the recent review on the various performance enhancement techniques employed for LHTS units, readers are referred to the paper by Jegadheeswaran and Pohekar [9]. However, only a limited number of works is reported on dispersion of high conductivity particles, although a large number of studies have focused on other performance enhancement techniques. Seeniraj et al. [6] investigated the effect of high conductivity particles dispersed in the PCM on the performance during the melting process. It is reported that though the 446 International Journal of Energy and Environment (IJEE), Volume 1, Issue 3, 2010, pp.445-458 ISSN 2076-2895 (Print), ISSN A New AC Current Switch Called MERS with Low On-State Voltage IGBTs (1.54 V) for Renewable Energy and Power Saving Applications Ryuichi Shimada ∗ , Jan A. Wiik ∗ , Takanori Isobe ∗ , Taku Takaku † , Noriyuki Iwamuro † , Yoshiyuki Uchida ‡ , Marta Molinas § and Tore M. Undeland § ∗ Tokyo Institute of Technology, N1-33, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550, Japan, Email: rshimada@nr.titech.ac.jp † Fuji Electric Device Technology Co., Ltd, 4-18-1, Tsukama, Matsumoto, Nagano 390-0821, Japan ‡ Curamik Electronics KK, Assorti Takanawa, 3-4-13 Takanawa, Minato-ku, Tokyo 108-0074, Japan § Norwegian University of Science and Technology, Institutt for elkraftteknikk, 7491 Trondheim, Norway Abstract— Emergence of new power electronics configurations have historically been one of the important drivers for improve- ment of the IGBT technology. Development of new IGBTs is said to be a trade-off between saturation voltage, short-circuit capability and switching losses. With the common applications requiring high switching frequency and short-circuit capability, the saturation voltage performance has not been fully optimized. This paper describes a new configuration called the Magnetic Energy Recovery Switch (MERS). It is characterized by using simple control and low switching frequency, where saturation voltage is the main contributor to losses. The semiconductor requirements of this configuration have led to the development of a new low on-state voltage IGBT. Application in the area of wind power conversion shows potential for efficiency improvements. Additionally, due to the soft-switching nature of the MERS application, series connection of the new IGBTs in variable frequency induction heating application is shown to be easy without voltage sharing problems. I. I NTRODUCTION Emergence of new power electronics configurations have historically been one of the important drivers for improvement and development of the IGBT technology. Since the introduc- tion of the IGBT in the early 1980s have need for higher power and reduced losses been given main attention. Several technologies have resulted, such as various trench structures and field stop layer. In a majority of the application areas, high frequency switching and need for short circuit capacity have been impor- tant requirements. In motor drive applications, usually there is no internal output impedance, meaning that a short-circuit at the inverter terminals is a direct short-circuit of the inverter transistors [1]. As a result, turn-off of the IGBTs must be managed in the case of a short circuit without being destructed. Several trade-offs exist in the development of IGBTs, some of them being switching losses, short circuit capability and on-state losses. With the typical existing applications, low switching losses and high short circuit capability have been prioritized. This paper looks at a new power electronics configuration called the Magnetic Energy Recover Switch (MERS). The Fig. 1. Configuration of the MERS. configuration is characterized by low switching speed, reduced need for short circuit capability and simple control. The special features of the configuration have led to the development of a new type of IGBT with lower conduction losses. The characteristics of the MERS are first discussed. This is fol- lowed by a description of the newly developed low saturation voltage IGBT. Q UANTITATIVE A SPECTS OF R UMINANT D IGESTION AND M ETABOLISM Second Edition This page intentionally left blank Q UANTITATIVE A SPECTS OF R UMINANT D IGESTION AND M ETABOLISM Second Edition Edited by J. Dijkstra Animal Nutrition Group Wageningen University The Netherlands J.M. Forbes Centre for Animal Sciences University of Leeds UK and J. France Centre for Nutrition Modelling University of Guelph Canada CABI Publishing CABI Publishing is a division of CAB International CABI Publishing CABI Publishing CAB International 875 Massachusetts Avenue Wallingford 7th Floor Oxfordshire OX10 8DE Cambridge, MA 02139 UK USA Tel: þ44 (0)1491 832111 Tel: þ1 617 395 4056 Fax: þ44 (0)1491 833508 Fax: þ1 617 354 6875 E-mail: cabi@cabi.org E-mail: cabi-nao@cabi.org Web site: www.cabi-publishing.org ßCAB International 2005. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners. A catalogue record for this book is available from the British Library, London, UK. A catalogue record for this book is available from the Library of Congress, Washington, DC, USA. Library of Congress Cataloging-in-Publication Data Quantitative aspects of ruminant digestion and metabolism / edited by J. Dijkstra, J. M. Forbes, and J. France.- -2nd ed. p. cm. Includes index. ISBN 0–85199–814–3 (alk. paper) 1. Rumination. 2. Digestion. 3. Metabolism. 4. Ruminants. I. Dijkstra, J. (Jan), 1964– II. Forbes, J. M. (John Michael), 1940–III. France, J. IV. Title. QP151.Q78 2005 573.3’1963- -dc22 2004029078 ISBN 0 85199 8143 Typeset by SPI Publishing Services, Pondicherry, India Printed and bound in the UK by Biddles Ltd, King’s Lynn Contents Contributors ix 1. Introduction 1 J. Dijkstra, J.M. Forbes and J. France DIGESTION 2. Rate and Extent of Digestion 13 D.R. Mertens 3. Digesta Flow 49 G.J. Faichney 4. In Vitro and In Situ Techniques for Estimating Digestibility 87 S. Lo ´ pez 5. Particle Dynamics 123 P.M. Kennedy 6. Volatile Fatty Acid Production 157 J. France and J. Dijkstra 7. Nitrogen Transactions in Ruminants 177 J.V. Nolan and R.C. Dobos 8. Rumen Microorganisms and their Interactions 207 M.K. Theodorou and J. France v 9. Microbial Energetics 229 J.B. Russell and H.J. Strobel 10. Rumen Function 263 A. Bannink and S. Tamminga METABOLISM 11. Glucose and Short-chain Fatty Acid Metabolism 291 R.P. Brockman 12. Metabolism of the Portal-drained Viscera and Liver 311 D.B. Lindsay and C.K. Reynolds 13. Fat Metabolism and Turnover 345 D.W. Pethick, G.S. Harper and F.R. Dunshea 14. Protein Metabolism and Turnover 373 D. Attaix, D. Re ´ mond and I.C. Savary-Auzeloux 15. Interactions between Protein and Energy Metabolism 399 T.C. Wright, J.A. Maas and L.P. Milligan 16. Calorimetry 421 R.E. Agnew and T. Yan 17. Metabolic Regulation 443 R.G. Vernon 18. Mineral Metabolism 469 E. Kebreab and D.M.S.S. Vitti THE WHOLE ANIMAL 19. Growth 489 G.K. Murdoch, E.K. Okine, W.T. Dixon, J.D. Nkrumah, J.A. Basarab and R.J. Christopherson 20. Pregnancy and Fetal Metabolism 523 A.W. Bell, C.L. Ferrell and H.C. Freetly 21. Lactation: Statistical and Genetic Aspects of Simulating Lactation Data from Individual Cows using a Dynamic, Mechanistic Model of Dairy Cow Metabolism 551 H.A. Johnson, T.R. Famula and R.L. Baldwin vi Contents 22. Mathematical Modelling of Wool Growth at the Cellular and Whole Animal Level 583 B.N. Nagorcka and M. Freer 23. Voluntary Feed Intake 3 Digesta Flow G.J. Faichney School of Biological Sciences A08, University of Sydney, NSW 2006, Australia Introduction The structural carbohydrates that constitute plant fibre represent a major feed resource. Herbivorous animals, unable to produce fibre-degrading enzyme systems of their own, have evolved a range of strategies (Hume and Sakaguchi, 1991) to make use of a consortium of microbes, including bacteria, protozoa and anaerobic fungi, for this purpose. The strategy adopted by the ruminants involves the development of a compound stomach in which the feed eaten can be fermented by the microbes before being subjected to attack by the animal’s own enzymes and, finally, to a second fermentation in the hindgut before the undigested residues are voided in the faeces. This strategy suits the domestic ruminants to the utilization of diets of moderate fibre content for the production of food and fibre and the provision of motive power. They are not so well adapted to poor quality diets of high fibre content because the extended time required to break down the fibre for passage out of the stomach severely limits the amount of such diets that can be eaten. Thus a knowledge of digesta flow through the ruminant gastrointestinal (GI) tract, and of the factors that affect it, is important because of its role both in the processes of digestion and absorp- tion and in the expression of voluntary feed consumption. The Nature of Digesta The ruminant GI tract consists of a succession of mixing compartments – the reticulorumen, abomasum and caecum/proximal colon, in which residues from successive meals can mix – and connecting sections in which flow is directional and axial mixing is minimal. Of these latter, the small intestine and the distal colon (consisting of the spiral colon, terminal colon and rectum) are tubular in nature. However, the omasum is a bulbous organ whose lumen is largely ß CAB International 2005. Quantitative Aspects of Ruminant Digestion and Metabolism, 2nd edition (eds J. Dijkstra, J.M. Forbes and J. France) 49 occupied by leaves of tissue (the laminae) so that, although particulate matter may be retained between them, little mixing can occur. The digesta in the GI tract consist of particulate matter, including microorganisms, and water, in which is dissolved a range of organic and inorganic solutes of both dietary and endogenous origin. The relative proportions of these digesta components are different in the different sections of the tract. The particles exist in a continuous range of sizes from the very small to pieces of plant material up to several centimetres long that can be found in the rumen when a diet of long hay is given. In order to study the characteristics of these particles, various sieving procedures have been devised which divide the continuum of sizes into fractions of defined size range. Both dry- and wet-sieving procedures have been used but it is now generally accepted that a wet-sieving procedure is preferable for digesta particles (Kennedy, 1984; Ulyatt et al., 1986). However, plant particles are generally elongated, often having a length/width ratio in excess of six (Evans et al., 1973), and there remains uncertainty regarding the relative importance of length and diameter in the separations achieved during sieving. McLeod et al. (1984) concluded that discrimination in their wet-sieving procedure was mainly on the basis of diameter. However, examination of their data indicates that for three of five fractions, particle ... shifting kinetic and potential energy of a pendulum in motion 6/16 Energy and Metabolism Free and Activation Energy After learning that chemical reactions release energy when energy- storing bonds... electrical energy, light energy, and heat energy are all different types of energy To appreciate the way energy flows into and out of biological systems, it is important to understand two of... potential 5/16 Energy and Metabolism energy (highest at the top of the swing) to kinetic energy (highest at the bottom of the swing) Other examples of potential energy include the energy of water