Solar Water Heating Systems

Solar Water Heating Systems

SolarWater Heating Systems Proceedings of the Workshop on Solar Water Heating Systems New Delhi, India 6-10 May, 1985 edited by H.P. Garg Professor of Solar Energy, Centre of Energy Studies, Indian Institute of Technology, New Delhi, India D. Reidel Publishing Company A MEMBER OF THE KLUWER ACADEMIC PUBLISHERS GROUP Dordrecht / Boston / Lancaster / Tokyo

library of Congress Cataloging in Publication Data Workshop on Solar Water Heating Systems (1985 : New Delhi, India) Solar water heating systems. Includes indexes. 1. Solar water heaters-congresses. TH6561.7.w67 1985 697'.78 I. Garg, H. P. 85-19386 II. Title. ISBN -13: 978-94-010-8920-3 e-isbn -13: 978-94-009-5480-9 DOl: 10.1007/978-94-009-5480-9 Published by D. Reidel Publishing Company, P.O. Box 17, 3300 AA Dordrecht, Holland Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 190 Old Derby Street, Hingham, MA 02043, U.S.A. In all other countries, sold and distributed by Kluwer Academic Publishers Group, P.O. Box 322, 3300 AH Dordrecht, Holland All Rights Reserved 1986 by D. Reidel Publishing Company, Dordrecht, Holland Softcover reprint of the hardcover 18t edition 1986 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

Dedicated to my parents who always believed in Honesty I Sincerity and Hardwork

CONTENTS Preface Acknowledgements xi xiii Inaugural Address Maheshwar Dayal Solar Hot Water Technology and Approach to Popularise the same G.D. Sootha Solar Radiation Anna Mani Components of Solar Water Heaters H.P. Garg Materials for Low Temperature Solar Thermal Applications S.K. Gupta Design Optimization of Collector Plates Arun G. Joshi Absorber Plate Configuration and Optimization H.P. Garg Hot Water Storage Systems S.P. Sukhatme 5 15 37 61 85 93 113 The Use of Fibreglass ~n A. Sharif Solar Water Heating Systems 125 Insulation Materials for Solar Heating Systems and their Application T. Udayakumar 129 Thermal Insulation in Solar Thermal Devices 133 B.C. Raychaudhuri Paints and Painting Procedures for Solar Energy Collectors 153 S.M. Singh

viii Low Cost, High Performance Solar Selective Paints O.P. Agnihotri Selective Coatings for Photothermal Conversion L.K. Malhotra and K.L. Chopra Instrumentation and Controls for Solar Water Heating System M. Ramakrishna Rao CONTENTS 159 169 179 Galvanised Steel Solar Absorber - Rate and Expected Life R.S. Soin Welding Technology and Procedures R.S. Parmar Its Choice, Corrosion 199 231 Glazing Materials for Solar Collectors N.K. Bansal and V.K. Sharma Heat Exchanger Optimization for Hot Water Heating System N.K. Bansal and Jugal Kishor Pumps for Use with Hot Water D.P. Agrawal Flow and Heat Transfer of Water Ln Pipes Ashok Malhotra Domestic Thermosyphon Water Heating Systems S.S. Mathur and N.K. Bansal How to Get the Most Solar Heated Water for the Least Cost in India Walt Chappell Novel Design Concepts in Solar Water Heating Atam Kumar Solar Water Heating System Ln a Textile Industry - A Case Study K.S. Rao Industrial Experiences with Solar Water Heaters M.S. Ramaprasad and Sudhir Mohan Solar Water Heating-Design Methods C.L. Gupta Testing of Solar Collectors A.K. Sharma and M.S. Sodha 243 257 279 291 299 327 337 347 361 371 383

CONTENTS ix Technoeconomics of Solar Forced Flow Hybrid Hot Water Systems Arvind Goyal, Ashvini Kumar and M.S. Sodha Author Index Subject Index 399 417 421

PREFACE H.P. Garg Centre of Energy Studies Indian Institute of Technology Hauz Khas, New Delhi 110 016 India Heating of water using solar energy is not new and by using a little science and technology in it, the solar energy can be utilized more effectively and economically for heating the water both for domestic and industrial applications. Solar Water Heaters are popular for the last three decades in countries like USA, Australia, Israel, Japan, India. This is the only solar energy application which is commercially, technically and economically viable and has been studied for more than 30 years in many countries. Technical advances in solar water heating have been very rapid in the last 30 years. These are becoming popular not only for domestic use but for large establishments like hostels, hotels, hospitals, industries such as Textile, Paper and Food Processing and even in heating of swimming pools in winter. In few instances the cost of solar water heating systems may be higher than those operated by electricity, gas or other fuel but over a period of time this is more than recovered by the savings in the cost of operations and maintenance. In some cold countries about 20% of the total energy demand of a family is required for heating of water, may be for taking bath, cleaning of clothes and utensils, and heating of space. In Developing as well as in Developed countries, it has been estimated that more than 20% of all the industrial heat is directly used in processes at temperatures below 100oC. In the remaining 80%, where high temperatures are required, considerable amount of heat can be supplied to pre-heat the water up to 1000C. There are many small industries where 100% of the heat is required up to only l40 o C, which can easily be supplied by using solar energy employing simple solar energy collection devices like flatplate collectors, solar ponds, evacuated collectors and linear concentrators, where the technology is sufficiently advanced. The editor has visited many countries of the world and found that there is a large variation in the design, operation, testing and evaluation procedures of water heating systems. Even in India, where more than 1000 large solar water heaters have been installed, there is no standard procedure for their design or evaluation. A few of these solar water heaters are working satisfactorily but few have failed due

PREFACE to leakage, poor quality materials, poor maintenance, poor design procedures, etc. The need of such a national effort to sit together and discuss at a common platform and discuss a single topic like that of Solar Water Heating was therefore long felt since this application has got an immediate market and if used in industries, considerable amount of energy can be saved. Even in a small country like Cyprus, where only domestic solar water heaters are used on a large scale, the country is able to save about 4% of the total energy consumed in the country. The National Workshop on Solar Water Heating Systems was organised by me with support from DNES, to discuss various aspects of solar water heating systems and to give training to the engineers from industries manufacturing the solar water heating systems, officers from nodal agencies involved in the extension programmes, scientists from national laboratories/organisations, academicians from universities/institutions, and officers/planners from Government organisations. In order to guarantee excellent quality, we had selected and invited more than 25 speakers to speak on the topics suggested to them falling in their field of specializations. More than 200 experts from different industries, nodal agencies, universities, IITs, Government organisations, etc., participated in this training workshop. There were 10 technical sessions on policies and incentives, solar energy materials, selective coatings and paints, solar radiation measurement and computation, solar water heating components, glazing materials, insulation materials, heat exchangers, controls, welding technology, pumps and control, collector plate configurations and domestic and large industri~ systems. Some typical case studies, collector testing procedure and economics of solar/hybrid heating systems are also discussed. I hope the present compilation of papers will be useful to industries, extension workers, designers, policy makers, students and teachers.

ACKNOWLEDGEMENTS H.P. Garg Centre of Energy Studies Indian Institute of Technology Hauz Khas, Ne~ Delhi 110 016 India The Organising Secretary, ~ho is also the editor of this book, is grateful to Shri Mahesh~ar Dayal, Secretary, Department of Non-Conventional Energy Sources (Government of India), New Delhi, who has given the idea of convening such a 'National Training Workshop on Solar Water Heating Systems' at lit Delhi. The Workshop is fully sponsored by Department of Non-Conventional Energy Sources, Ne~ Delhi. I am also grateful to Prof. M.S. Sodha, lit Delhi, and Dr.G.D.Sootha, Department of Non-Conventional Energy Sources, Ne~ Delhi, for helping me in organising the Workshop and for conducting the technical sessions. I ~ish to convey my gratitude to the Non-Conventional Energy Development Agency (NEDA), D.P., B-46 Mahanagar Extension, Luckno~ (D.P.), India for the financial grant for preparing the manuscript of this Proceeding. I am particularly grateful to Shri D.K. Mittal, Director, Non-Conventional Energy Development Agency, D.P., ~ho has ~hole-heartedly supported the idea to convene this Workshop and provided the financial support for preparing the manuscript of the Proceeding. I ~ish to thank Dr. V.K. Sharma, ~ho has assisted me in organ~s~ng the above Workshop and in other routine matters while preparing the manuscript of the Proceeding. I am also grateful to Shri M.P. Joseph, ~ho has typed the manuscript efficiently and in a record time. I am also thankful to Shri Kirpa1 Singh and Shri Sushil who have prepared the art ~ork of this Proceeding. I also thank the Speakers for submitting the papers for including in the Proceeding and giving permission for their publication. The participants of the Workshop also deserve appreciation for supporting the idea of holding the Workshop and for useful discussions and recommendations. I ~ould like to express my appreciation to my wife Kusum Garg, daughters Minu, Neelu and Naina, and son Darpan for their patience and moral support during the conduct of the Workshop and preparation of the manuscript. xiii