DOCSLIB.ORG

Implementation of a Low-Cost Smart Grid Device to Prevent Brownouts in Village Micro-Hydro Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Implementation of a Low-Cost Smart Grid Device to Prevent Brownouts in Village Micro-Hydro Systems Implementation of a Low-­‐Cost Smart Grid Device to Prevent Brownouts in Village Micro-­‐Hydro Systems by Thomas Quetchenbach A Project Presented to The Faculty of Humboldt State University In Partial Fulfillment Of the Requirements for the Degree Master of Science In Environmental Systems: Environmental Resources Engineering Option August, 2011 Abstract Implementation of a Low-­‐Cost Smart Grid Device to Prevent Brownouts in Village Micro-­‐ Hydro Systems Thomas Quetchenbach Brownouts are a common problem in micro-­‐hydro mini-­‐grid systems due to the limited supply of power and the difficulty of restricting usage. The GridShare is a device designed to alleviate brownouts by limiting peak power and encouraging load-­‐shifting to off-­‐peak times. The device is installed at each household’s electrical service entrance and measures voltage and current consumption. Indicator lights inform the customer whether a brownout is occurring; if the customer attempts to use large appliances, such as rice cookers, during a brownout, the GridShare disconnects power to the house until appliance is turned off. The objective of this master’s degree project was to advance the design of the GridShare device from a prototype to a production design ready for small-­‐ scale manufacturing and to manufacture, assemble, and test enough GridShare devices to perform an installation in the village of Rukubji, Bhutan. Based on our testing and a field visit by the GridShare team in June 2010, several changes were made to the circuit design, and several prototype devices were built. To enable the production of 120 GridShare devices, a printed circuit board was designed, allowing automated fabrication and assembly. A comprehensive testing protocol was developed to evaluate the device’s ability to withstand the electrical and environmental conditions at the installation site, including exposure to low voltage and frequency and low and high ambient temperatures. The final version of the GridShare passed all tests; 120 devices were manufactured, shipped to Bhutan, and installed in Rukubji in June 2011. Further work will be needed to assess effectiveness and user satisfaction. ii Acknowledgments Funding for the GridShare project was provided by a grant from the United States Environmental Protection Agency’s People, Prosperity, and the Planet (P3) program. My participation in the project was made possible by a fellowship from the National Science Foundation (Award #1011464) through the Division of Graduate Education. In addition, sponsorships from Sunstone Circuits, Screaming Circuits, and Industrial Electric in Arcata helped make the GridShare a reality. The Schatz Energy Research Center provided financial and administrative support as well as laboratory space and machine shop services. The GridShare project would not have been possible without the help of so many people that it is impossible to name them all. Special credit goes to my supervisory committee, which consisted of Dr. Eileen Cashman, who provided invaluable assistance in writing this report and navigating uncharted waters of administrative paperwork; Dr. Peter Lehman, who also served as a faculty mentor to the GridShare team and was instrumental in keeping the project on track; and Dr. Charles Chamberlin, whose high standards for technical writing helped prepare me for this project. In addition, special thanks are due to Dr. Arne Jacobson for getting me involved with this project and for taking time from his busy schedule while on sabbatical to continue to provide the group with valuable advice. I extend special gratitude to James Apple for laying the groundwork for my project; to Meg Harper for her organizational skills, motivation, and encouragement; to Kyle Palmer for his technical expertise; and to Nathan Chase and James Robinson for their enthusiasm and dedication. Thanks are due to Kirstin Hervin for her excellent work on the educational materials and help with assembly, as well as to the many people who helped with assembly and testing, including but not limited to Kristen Radecsky, Zachary Stanko, Mark Rocheleau, and Rowan Beckensten. I would also like to thank Allison Oakland, Carolyn Ortenberger, and Alina Taalman for their efficient handling of finances, purchasing, and administrative paperwork, as well as the rest of the staff of the Schatz Energy Research Center for their support, encouragement, and advice. The project would not have happened without our in-­‐ country contact, Chhimi Dorji, who was essential in our communications with Bhutanese corporations and the Bhutanese government and in arranging our travel, or without the support of the Bhutan Power Corporation and the Bhutan Department of Energy. Rick Mayberry provided the group with valuable technical oversight and advice. Last-­‐minute packing assistance from Jessica, Chris, and the rest of the team at Post Haste in Arcata was also greatly appreciated. I would also like to extend special thanks to everyone who assisted us with our installation efforts in Bhutan, including Chhejay Wangdi and his staff at BPC Electricity Services Division Wangdue Phodrang office, who did excellent work and helped us finish the installations ahead of schedule, and to Phub Gyeltshen and the people of Rukubji for their incredible hospitality. Finally, I would like to thank Shilo for her assistance with proofreading and for her constant support and encouragement and for her willingness to not only put up with me during this process but to get married to me at the end of it. iii Table of Contents Chapter 1. Introduction and Background ...................................................................................................... 1 1.1. Introduction .................................................................................................................................................. 1 1.2. Project Site ..................................................................................................................................................... 1 1.3. Micro-­‐Hydro overview ............................................................................................................................. 2 1.4. Mini-­‐grids ....................................................................................................................................................... 3 1.5. Mini-­‐Grids and Brownouts ..................................................................................................................... 4 1.6. Micro-­‐Hydro in Bhutan ............................................................................................................................ 5 1.7. Rukubji Micro-­‐Hydro System ................................................................................................................ 6 1.8. The Brownout Problem in Rukubji ..................................................................................................... 9 1.9. Cooking and Appliance Usage ............................................................................................................. 10 1.10. House wiring in Rukubji ..................................................................................................................... 10 1.11. Project History and People ................................................................................................................ 11 Chapter 2. GridShare Circuit Design .............................................................................................................. 12 2.1. First Prototypes ......................................................................................................................................... 12 2.2. GridShare Installation Options ........................................................................................................... 13 2.3. Design criteria ............................................................................................................................................ 14 2.4. Changes Identified by GridShare Team ........................................................................................... 15 2.5. Voltage regulator selection ................................................................................................................... 16 2.6. Transformer upgrade ............................................................................................................................. 16 2.7. Relay upgrade ............................................................................................................................................ 17 2.8. Current transformer change ................................................................................................................ 17 2.9. Frequency measurement ...................................................................................................................... 17 2.10. Circuit protection ................................................................................................................................... 18 2.11. Software changes ................................................................................................................................... 19 2.12. PCB design and construction ............................................................................................................ 24 2.13. Prototypes ................................................................................................................................................. 26 2.14. Enclosure
Load more

Recommended publications
  • Cities, Climate Change and Multilevel Governance
    Cities, Climate Change and Multilevel Governance J. Corfee-Morlot, L. Kamal-Chaoui, M. G. Donovan, I. Cochran, A. Robert and P.J. Teasdale JEL Classification: Q51, Q54, Q56, Q58, R00. Please cite this paper as: Corfee-Morlot, Jan, Lamia Kamal-Chaoui, Michael G. Donovan, Ian Cochran, Alexis Robert and Pierre- Jonathan Teasdale (2009), “Cities, Climate Change and Multilevel Governance”, OECD Environmental Working Papers N° 14, 2009, OECD publishing, © OECD. OECD ENVIRONMENT WORKING PAPERS This series is designed to make available to a wider readership selected studies on environmental issues prepared for use within the OECD. Authorship is usually collective, but principal authors are named. The papers are generally available only in their original language English or French with a summary in the other if available. The opinions expressed in these papers are the sole responsibility of the author(s) and do not necessarily reflect those of the OECD or the governments of its member countries. Comment on the series is welcome, and should be sent to either [email protected] or the Environment Directorate, 2, rue André Pascal, 75775 PARIS CEDEX 16, France. ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ OECD Environment Working Papers are published on www.oecd.org/env/workingpapers ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Applications for permission to reproduce or translate all or part of this material should be made to: OECD Publishing, [email protected] or by fax 33 1 45 24 99 30. Copyright OECD 2009 2 ABSTRACT Cities represent a challenge and an opportunity for climate change policy. As the hubs of economic activity, cities generate the bulk of GHG emissions and are thus important to mitigation strategies.
    [Show full text]
  • Breadboards for Beginners Created by Lady Ada
    Breadboards for Beginners Created by lady ada Last updated on 2018-08-22 03:56:03 PM UTC Guide Contents Guide Contents 2 Introduction 3 What's up with the name? 4 ~~ Interlude ~~ (Wire Wrapping) 5 1971 - The Breadboard Is Invented! 6 Breadboards 8 The curse of the flaky breadboard 10 Other Breadboard Sizes 11 Half Size 11 Tiny Breadboard 12 Little Breadboard Bits 13 Large Breadboard 15 Breadboard Usage 17 Adding DIPs and Modules 19 Jumper Wires 21 DIY Solid Core Wire Jumpers 21 Multi-size wire stripper & cutter 21 Hook-up Wire Spool Set - 22AWG Solid Core - 6 x 25 ft 21 Pre-made Jumper Wires 26 Premium Male/Male Jumper Wires - 40 x 3" (75mm) 26 Premium Male/Male Jumper Wires - 40 x 6" (150mm) 26 Premium Male/Male Jumper Wires - 40 x 12" (300mm) 26 Perma Protos 27 Adafruit Perma-Proto Quarter-sized Breadboard PCB - Single 29 Adafruit Perma-Proto Full-sized Breadboard PCB - Single 30 Adafruit Perma-Proto Mint Tin Size Breadboard PCB 30 Adafruit Perma-Proto Small Mint Tin Size Breadboard PCB - 3 pack 30 Breadboard Tips & Tricks 31 Connecting the two power rails 31 Watch Out For Split Rails! 32 Using Fritzing! 32 © Adafruit Industries https://learn.adafruit.com/breadboards-for-beginners Page 2 of 34 Introduction When you start on your electronics journey, you will eventually need to wire up some parts to follow along with some project. And, chances are, you will be prodded towards using a breadboard. These ubiquitous pale slabs of plastic are everywhere when it comes to electronics hacking.
    [Show full text]
  • Breadboarding And, As You’Ll See, More Flexible When Using the Techniques I’M Going to Tell You About
    circuits and is best suited for building digital circuits. These techniques can FEATURE also be applied to analog or RF designs. The basic prototyping material is ARTICLE perfboard, such as that sold at Radio Shack. This material has holes on 0.1² (2.54-mm) centers and is available in Stuart Ball several sizes. The holes match the pin spacing on DIP ICs and many other components. You can get perfboard with plated- through pads on every hole, but I pre- fer the type without pads. It’s cheaper Breadboarding and, as you’ll see, more flexible when using the techniques I’m going to tell you about. GROUNDING A key area where many digital and microprocessor designs have problems is grounding. Early digital designs often used two-layer printed circuit boards, ometimes the with power and ground traces mixed s best way to test a with the signal traces on the top and With this offering, Stuart new circuit is to pro- bottom layers. pumps new life into the dy- totype it. If you are plan- As clock speeds and edge rates go ning to build only one, the prototype up, simple grounds such as this are less ing technique of may be the only one you ever put to- effective. A modern production digital prototyping. For electronics gether. Unfortunately, prototyping is design will typically use one or more slowly dying out in the electronics ground planes between the signal lay- experimenters, the cost of industry. Modern CAD tools let you ers to get a low-impedance ground. It is making a circuit board is too produce a circuit board layout in a few difficult to duplicate this with most hours.
    [Show full text]
  • Policy Brief
    Policy brief Energy Transition in Europe’s Power House. Alleingang, avant-garde or blackout? Issue 2012/03 • October 2012 by Thomas Sattich he transformation of Germany’s energy Tsector will further exacerbate current The German government proclaimed its “revolution of Germany’s network fluctuations and intensify the need energy sector” (Angela Merkel) without consulting its neighbours. The neglect of Europe’s Internal Electricity Market is one of the most for modifications in Europe’s power system. surprising aspects of the German Energiewende (energy transition) Cross-border power transfers will have project, which aims at substantially increasing the share of rene- to increase in order to overcome national wables in the German energy mix while phasing out nuclear power. limitations for absorbing large volumes In Europe, national power systems do not function in isolation from of intermittent renewables like wind and one another; cross-border power flows are daily routine. In addi- solar power. In order to establish such an tion, the Internal Electricity Market helped with the first steps of infrastructure on a European scale, the energy Germany’s energy transition: interconnections with neighbouring transition needs to be guided by an economic countries not only enabled wind energy surpluses to be exported, approach designed to prevent further fractures but also permitted electricity imports to bridge the supply gap after in the Internal Electricity Market. Moreover, the rapid phase-out of nuclear plants in the wake of the Fukushi- constructive negotiations with neighbouring ma disaster. Increasing the input of renewables therefore not only countries on market designs and price subverts the hierarchical top-down logic of electricity distribution signals will be important preconditions for a on the national level, but has implications for the supranational di- successful energy transition in Europe.
    [Show full text]
  • NV Energy Reliability and Power Quality Brochure
    CUSTOMER SERVICE Reliability and Power Quality How To Safeguard The Life And Reliable Operation Of Your Home Appliances And Business Equipment Electricity powers our everyday lives. From specialized care equipment such as dialysis machines to everyday heating and cooling devices like air conditioners or furnaces and appliances, the impact of a power interruption on consumers can be significant. NV Energy places the highest priority on providing safe and reliable electric energy to all customers. However, there are situations where disturbances beyond human control cause momentary disruptions or other power quality issues. This Power Quality brochure outlines the power disturbances that happen in residential, industrial and commercial customers and how to protect against them. What Are The Different Types Of How Does NV Energy Deliver Electricity? Power Disturbances I Can Experience? NV Energy operates an extensive, sophisticated generation, transmission and distribution power management system that supplies most of southern and northern Nevada with There are several types of power disturbances that may affect your home or business. These electricity. This system delivers a reliable supply of power that satisfies national voltage may or may not impact you, depending on the magnitude, frequency and duration of the standards. Occasionally however, electric systems experience voltage disturbances from event, as well as the sensitivity of your electrical appliance or equipment. natural or man-made causes (e.g., lightning, wind, cars hitting power poles, etc.) that are impossible to predict or control. These disturbances can interfere with your appliances and If you have ever experienced any of the following, you may have a power quality concern: even damage some of your more sensitive equipment such as computers.
    [Show full text]
  • The Smart Grid
    Privacy in the Smart Grid ISED 2018 Alfredo Rial [email protected] Table of Contents • Challenges of the Current Grid • The Smart Grid • Privacy Problems • Possible Privacy-Friendly Solutions Current Challenges in the Grid Integration of renewable sources of energy Integration of renewable sources of energy: • Solar panels • Wind mills From centralized to distributed power generation: • Transmission and distribution borders blur • Requires bidirectional energy flows • More resilience to attacks against plants • Help meeting demand grow Improving the load factor • Short peaks caused, e.g., by heating and air conditioning • Costly gas turbines employed to match peak loads • They can be started and shut down fast • Peak power plants only on several hours a day • Electricity prices are incremented Incorporation of Demand Response To reduce the load, customers are requested to reduce their load. Currently, this is mainly done with large industrial customers. Load Control Switch Integration of Advance Electricity Storage • Renewable sources are variable, so electricity generation can be higher than demand. • Electricity is stored to be used during peak demand periods • Different methods (not cheap): • Batteries. • Pumped water • Electric vehicles • Hydrogen • Compressed air Obsolescence • Aging Equipment • Obsolete layout – insufficient facilities • Outdated Engineering Deregulation of the Electricity Market Operating a system using concepts and procedures that worked in vertically integrated industry exacerbate the problem under a deregulated
    [Show full text]
  • Brownout-Oriented and Energy Efficient Management of Cloud Data Centers
    Brownout-Oriented and Energy Efficient Management of Cloud Data Centers Minxian Xu Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy November 2018 School of Computing and Information Systems THE UNIVERSITY OF MELBOURNE Copyright c 2018 Minxian Xu All rights reserved. No part of the publication may be reproduced in any form by print, photoprint, microfilm or any other means without written permission from the author except as permitted by law. Brownout-Oriented and Energy Efficient Management of Cloud Data Centers Minxian Xu Principal Supervisor: Prof. Rajkumar Buyya Abstract Cloud computing paradigm supports dynamic provisioning of resources for deliver- ing computing for applications as utility services as a pay-as-you-go basis. However, the energy consumption of cloud data centers has become a major concern as a typical data center can consume as much energy as 25,000 households. The dominant energy efficient approaches, like Dynamic Voltage Frequency Scaling and VM consolidation, cannot func- tion well when the whole data center is overloaded. Therefore, a novel paradigm called brownout has been proposed, which can dynamically activate/deactivate the optional parts of the application system. Brownout has successfully shown it can avoid overloads due to changes in the workload and achieve better load balancing and energy saving effects. In this thesis, we propose brownout-based approaches to address energy efficiency and cost-aware problem, and to facilitate resource management in cloud data centers. They are able to reduce data center energy consumption while ensuring Service Level Agreement defined by service providers. Specifically, the thesis advances the state-of-art by making the following key contributions: 1.
    [Show full text]
  • Brownout Based Blackout Avoidance Strategies in Smart Grids
    Brownout Based Blackout Avoidance Strategies in Smart Grids Basina Deepak Raj Satish Kumar Sambit Padhi IIT Guwahati IIT Guwahati IIT Guwahati Arnab Sarkar Arijit Mondal Krithi Ramamritham IIT Guwahati IIT Patna IIT Bombay ABSTRACT during demand overloads, such that uninterrupted power supply to Power shortage is a serious issue especially in third world countries, essential appliances/establishments may be selectively maintained and is traditionally handled through rolling blackouts. Today, smart while cutting down supply to less critical loads (lower priority). grids provide the opportunity of avoiding complete blackouts by In [1], authors introduced the brownout based approach and pre- converting them to brownouts, which allow selective provisioning sented a customer-end hardware prototype system to support the of power supply to support essential loads while curtailing supply to brownout based energy distribution scheme. less critical loads. In this work, we formulate brownout based power Our Contributions: Informed distribution of available Power. distribution scheduling as an optimization problem and propose In this paper, we develop the algorithmic support to answer the a modified Dynamic Programming (DP) based optimal algorithm following question: Given a system-wide upper-bound on consump- (suitable for moderate sized grids) that is 9 to 40 times faster than tion in times of power scarcity, how do we ensure that the available the conventional DP approach. power is equitably distributed to the consumers, taking into account the criticality of their needs. KEYWORDS First, we devise a comprehensive framework for brownout based electricity scheduling. The framework is guided by the following Smart Grids, Rolling Blackouts, Brownout. soft real-time specification (governed by recommendations of IEEE ACM Reference Format: standards on power quality [2]): Brownout based mitigation of im- Basina Deepak Raj, Satish Kumar, Sambit Padhi, Arnab Sarkar, Arijit Mon- balances in demand-supply must be conducted quickly and within dal, and Krithi Ramamritham.
    [Show full text]
  • Cleaning up America's Coal: an Analysis of States' Potentials For
    Intersect, Vol 9, No 1 (2015) Cleaning up America’s Coal: An Analysis of States’ Potentials for Carbon Capture and Storage Jessica Nicole Farrell Morehead State University Abstract Coal-fired power plants across the United States, though affordable and reliable providers of approximately 39% of the nation’s power, emit approximately 25% of total greenhouse gas emissions in the country. Therefore, in moving forward with legislation to reduce the amount of emissions, coal-fired power plants are among the first emitters to be targeted. This research examined individual power plants and states across the country, and after determining the energy profile and amount of coal emissions for each state and analyzing the unique characteristics of each power plant, an analysis was conducted to determine which power plants would benefit most from a Carbon Capture and Storage (CCS) retrofit. CCS, which captures carbon and prevents it from being released into the atmosphere, provides a unique solution for coal-fired power plants in that it allows them to continue their normal use while reducing emissions. In the framework of the Environmental Protection Agency’s regulations for coal-fired power plants through the Clean Power Plan, several states were ranked based on their energy profiles, emission amounts, and CCS retrofit value. With this research, a quantitative outreach strategy was designed for the Department of Energy to implement CCS technology in a select group of states, focusing on cost-effectiveness and efficiency of CCS in each state. The states that were identified as ideal candidates for CCS retrofits included: Illinois, Missouri, North Dakota, and West Virginia.
    [Show full text]
  • The Seven Types of Power Problems
    The Seven Types of Power Problems White Paper 18 Revision 1 by Joseph Seymour Contents > Executive summary Click on a section to jump to it Introduction 2 Many of the mysteries of equipment failure, downtime, software and data corruption, are the result of a prob- Transients 4 lematic supply of power. There is also a common problem with describing power problems in a standard Interruptions 8 way. This white paper will describe the most common types of power disturbances, what can cause them, Sag / undervoltage 9 what they can do to your critical equipment, and how to Swell / overvoltage 10 safeguard your equipment, using the IEEE standards for describing power quality problems. Waveform distortion 11 Voltage fluctuations 15 Frequency variations 15 Conclusion 18 Resources 19 Appendix 20 RATE THIS PAPER white papers are now part of the Schneider Electric white paper library produced by Schneider Electric’s Data Center Science Center [email protected] The Seven Types of Power Problems Introduction Our technological world has become deeply dependent upon the continuous availability of electrical power. In most countries, commercial power is made available via nationwide grids, interconnecting numerous generating stations to the loads. The grid must supply basic national needs of residential, lighting, heating, refrigeration, air conditioning, and transporta- tion as well as critical supply to governmental, industrial, financial, commercial, medical and communications communities. Commercial power literally enables today’s modern world to function at its busy pace. Sophisticated technology has reached deeply into our homes and careers, and with the advent of e-commerce is continually changing the way we interact with the rest of the world.
    [Show full text]
  • How to Solder Electronics 15 Rules for Successful Soldering
    How to Solder Electronics 15 Rules for Successful Soldering i www.sra-solder.com How to Solder Electronics 15 Rules for Successful Soldering Written and published by SRA Soldering Products www.sra-solder.com How to Solder Electronics: 15 Rules for Successful Soldering Written and Published by SRA Soldering Products 24 Walpole Park South, Suite #10, Walpole, MA 02081 www.sra-solder.com © 2020 SRA Soldering Products All rights reserved. No portion of this book may be reproduced in any form without permission from the publisher, except as permitted by U.S. copyright law. For permissions contact: [email protected] ISBN: 9798656683746 iii www.sra-solder.com Contents Introduction .......................................................................................viii Rule #1 – Know the Fundamentals ��������������������������������������������1 What is Flux? ......................................................................................1 What is Solder? ...................................................................................1 What is Wetting? ���������������������������������������������������������������������������������2 Methods of Heat Transfer ....................................................................3 The Difference Between Soldering, Brazing, and Welding .................4 When Do I Need to Solder? ����������������������������������������������������������������6 Rule #2 – Identify the Construction Method �����������������������������8 Breadboards and Learning Labs .........................................................8
    [Show full text]
  • Surface Mount Technology in the Educational Environment
    Electronics Technical Sameul Ginsberg Surface mount technology in the educational environment by Samuel Ginsberg, University of Cape Town The consumer-driven demand for electronic devices to become smaller, lighter and more functional has been driving electronic components into ever smaller packages. The early development of integrated circuits mount technology (SMT) has brought great This article proposes a shift in thinking and focused on increasing the number of transistors variation in the physical size and shape of suggests methods of implementing that shift. per package, leading to very large scale devices and is commonly believed to require The shift in thinking is that SMT must be embraced integration (VLSI) devices but in the last few great skill in handling because of the smallness wholeheartedly by educators, an investment in decades the limitations of traditional through- of the connections that it requires. equipment and skills must be made and the full hole integrated circuit packaging have SMT has been seen as unfriendly in the benefits of this technology reaped. become clear and industry has moved steadily educational environment since it became The differences between educational and away from this cumbersome but easily-handled available. Educators actively avoid the use of production environments technology. Educational institutions have been surface mount devices (SMDs) in their teaching slow to follow this trend and now face increasing work and some educational institutions actively SMT is well accepted in commercial products, limitations in the variety of usable devices. avoid stocking SMDs in their component stores. and many designers prefer to use SMDs even when more traditional packaging is Some of the advantages of through-hole The problem with this approach is that in available.
    [Show full text]