© 2011 by Taylor and Francis Group, LLC GREEN NANOTECHNOLOGY Solutions for Sustainability and Energy in the Built Environment Geoffrey B. Smith Claes G. Granqvist Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business © 2011 by Taylor and Francis Group, LLC CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2011 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number: 978-1-4200-8532-7 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmit- ted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright. com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging‑in‑Publication Data Smith, Geoffrey B. (Geoffrey Burton) Green nanotechnology : solutions for sustainability and energy in the built environment / authors, Geoffrey B. Smith and Claes-Goran S. Granqvist. p. cm. “A CRC title.” Includes bibliographical references and index. ISBN 978-1-4200-8532-7 (alk. paper) 1. Sustainable buildings--Design and construction. 2. Nanotechnology. 3. Buildings--Electric equipment. 4. Buildings--Energy conservation. 5. Sustainable construction. 6. Electronic apparatus and appliances. I. Granqvist, Claes G. II. Title. TH880.S65 2010 690.028’6--dc22 2010007968 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com © 2011 by Taylor and Francis Group, LLC Contents Preface xiii Chapter 1 Green Nanotechnology: Introduction and Invitation 1 1.1 What Is Nanotechnology? 1 1.2 What Is Green Nanotechnology? 4 1.3 Some Basic Issues in Nanoscience 5 1.4 Nanoscience, Dimensionality, and Thin Films 1 1 1.5 Outdoing Nature in Exploiting Complexity 12 1.6 Energy Supply and Demand 1 4 1.7 Energy and Development 2 0 References 21 Chapter 2 In Harmony with the Environment: Nature’s Energy Flows and Desired Materials Properties 2 5 2.1 Global Energy Flows 2 6 2.2 Radiation in Our Ambience: An Overview 2 8 2.3 Interaction between Radiation and Materials 3 3 2.3.1 Fundamentals Based on Energy Conservation 3 3 2.3.2 Directionality and Polarization Dependence 3 4 2.4 Beam and Diffuse Radiation 3 6 2.4.1 General Considerations 3 6 2.4.2 Energy Flows in Diffuse and Nonparallel Radiation Beams 3 7 v © 2011 by Taylor and Francis Group, LLC vi Contents 2.5 Hemispherical Absorptance 4 2 2.6 Solar and Daylighting Performance Parameters 4 4 2.7 Thermal Radiation and Spectral Properties of the Atmosphere 4 5 2.7.1 Blackbody Emittance 4 6 2.7.2 The Sky Window 47 2.8 Dynamical Environmental Properties 5 0 2.8.1 General Considerations 5 0 2.8.2 Solar Energy and Daylight Dynamics: The Sun’s Path 5 1 2.9 Materials for Optimized Use of the Spectral, Directional, and Dynamical Properties of Solar Energy and Sky Radiation 5 3 2.9.1 Opaque Materials 5 5 2.9.2 Transparent Materials 5 7 2.9.3 Other Generic Classes of Optical Properties for Radiation Control 5 8 2.10 Thermal and Density Gradients in the Atmosphere and Oceans 6 0 2.11 Performance of Energy Systems: Thermodynamics and Value 61 References 64 Chapter 3 Optical Materials Science for Green Nanotechnology: The Basics 6 7 3.1 Light and Nanostructures 6 9 3.1.1 Local Fields and Far Fields 6 9 3.1.2 Refractive Index and Absorption Coefficient 7 0 3.2 Spectral Properties of Uniform Materials 7 3 3.2.1 Insulators and Liquids 7 4 3.2.2 Conductors, Semiconductors, and Superconductors 7 5 3.2.3 Chromogenic Materials 7 6 3.3 Plasmonic Materials in General 77 3.4 Materials for Electron-Based Plasmonics: Mirrors for Visible and Infrared Light 7 9 © 2011 by Taylor and Francis Group, LLC Contents vii 3.5 Ionic-Based Materials with Narrow-Band Infrared Properties 8 5 3.5.1 Plasmonics Once Again 8 5 3.5.2 Phonon Absorption 8 7 3.5.3 Infrared Transparency 8 8 3.6 Generic Classes of Spectrally Selective Materials 8 8 3.7 Thin Films for Controlling Spectral Properties and Local Light Intensities 89 3.8 Nanoparticle Optics 9 2 3.8.1 Transparent and Translucent Materials 9 2 3.8.2 Some Basic Models 9 4 3.9 Optical Homogenization of Nanocomposites 9 8 3.9.1 Models for Particle- and Inclusion- Based Composites 9 9 3.9.2 Invisibility, Effective Medium Models, and Critical Percolation 100 3.9.3 Core-Shell Random Unit Cells and Actual Core-Shell Particles 104 3.10 Surface Plasmon Resonances in Films, Particles, and “Rectennas” 107 3.11 Temporary “Storage” of Light at Resonances and in Evanescent Fields 111 3.11.1 General Considerations 111 3.11.2 Evanescent Optical Fields and How They Can Be Used 113 References 116 Chapter 4 Visual Indoors–Outdoors Contact and Daylighting: Windows 123 4.1 General Introduction 124 4.1.1 Strategies for Energy Efficiency 125 4.1.2 Uncoated Glass and Plastic Foil 126 4.2 Spectral Selectivity: The Energy Efficiency That Is Possible 128 4.3 Spectral Selectivity of Noble-Metal-Based Films 132 4.3.1 Thin Metal Films Are Not Bulk-Like 133 © 2011 by Taylor and Francis Group, LLC viii Contents 4.3.2 Very Thin Metal Films Are Nanomaterials 134 4.3.3 Toward a Quantitative Theoretical Model for the Optical Properties 137 4.3.4 Multilayer Films for Spectrally Selective Windows 141 4.4 Spectral Selectivity of Oxide-Semiconductor- Based Films 145 4.4.1 Some Characteristic Properties 147 4.4.2 Typical Nanostructures of ITO Films 148 4.4.3 Theoretical Models for the Optical and Electrical Properties of ITO Films 151 4.4.4 Computed Optical Properties 154 4.5 Spectral Selectivity: Novel Developments for Films and Foils 156 4.5.1 Silver-Based Nanowire Meshes 156 4.5.2 Carbon Nanotubes and Graphene 158 4.5.3 Foils with Conducting Nanoparticles 160 4.5.4 “Holey” Metal Films 161 4.5.5 Photonic Crystals 162 4.6 Optimized Angular Properties: The Energy Efficiency That Is Possible 163 4.7 Angular Selectivity of Films with Inclined Columnar Nanostructures 166 4.8 Chromogenics: The Energy Efficiency That Is Possible 167 4.9 Photochromics 175 4.10 Thermochromics 177 4.10.1 Metal-Insulator Transition and Its Nanofeatures in VO 178 2 4.10.2 Thermochromism in VO -Based Films, 2 and How to Adjust the Metal-Insulator Transition 179 4.10.3 How to Enhance the Luminous Transmittance in VO 183 2 4.11 Electrochromics 187 4.11.1 How Do Electrochromic Devices Work? 188 © 2011 by Taylor and Francis Group, LLC Contents ix 4.11.2 Facile Ion Movement Due to Favorable Nanostructures 190 4.11.3 What Causes the Optical Absorption? 193 4.11.4 Some Device Properties 193 4.11.5 Alternative Electrochromic Devices 196 References 199 Chapter 5 Electric Lighting and Daylighting: Luminaires 207 5.1 Lighting: Past, Present, and Future 208 5.2 Daylighting Technology: The “Cool” Option 212 5.2.1 Roof Glazing and Skylights 213 5.2.2 Mirror Light Pipes 216 5.2.3 Daylight Redirecting Structures for Façades 221 5.3 Dielectric Mirrors Based on Nanostructure 224 5.4 Luminescent Solar Concentrators for Daylighting and Solar Power 228 5.4.1 Devices for Generating Daylight-Like Radiation 228 5.4.2 Devices with Solar Cells and Mirrors 233 5.4.3 Light Trapping in Light Guides: Getting It All Out 233 5.5 Light-Diffusing Transmitting Materials 236 5.5.1 Polymer Diffusers 237 5.5.2 End-Lit Long Continuous Light Sources 240 5.5.3 Light Extraction from Light Pipes and in LCD Displays 244 5.6 Advanced Electronic Lighting Concepts 245 5.6.1 Semiconductor Light-Emitting Diodes 246 5.6.2 Organic Light-Emitting Diodes 249 5.6.3 Nanostructures for Improved LED Performance 250 5.6.4 Emerging Lamp Technologies 254 5.6.5 Concluding Remarks 255 References 256 © 2011 by Taylor and Francis Group, LLC x Contents Chapter 6 Heat and Electricity: Solar Collectors and Solar Cells 261 6.1 Solar Thermal Materials and Devices 261 6.1.1 Spectral Selectivity and Its Importance 263 6.1.2 Principles for Spectral Selectivity 265 6.1.3 Selectively Solar-Absorbing Coatings Based on Nanoparticles: Some Practical Examples 269 6.1.4 Colored Absorbers and Paints: Novel Developments 277 6.2 Photovoltaic Materials and Devices 279 6.2.1 Technology Overview 281 6.2.2 Nanofeatures for Boosting the Efficiency of Silicon-Based Solar Cells 284 6.2.3 Dye-Sensitized Solar Cells 288 6.2.4 Organic Solar Cells 292 References 297 Chapter 7 Coolness: High-Albedo Surfaces and Sky Cooling Devices 303 7.1 Two Cooling Strategies 305 7.1.1 High-Albedo Surfaces 305 7.1.2 Sky Cooling 307 7.2 City Heating, Global Cooling, and Summer Blackouts 307 7.2.1 Urban Heat Islands 307 7.2.2 Global Cooling by Increased Albedo 310 7.2.3 Avoiding Summer Blackouts 312 7.3 High-Albedo Paints for Cool Buildings 313 7.3.1 How Cool Can a Solar Exposed Roof Get? 314 7.3.2 Colored Paints with High Solar Reflectance 318 7.3.3 Mechanisms and Nanostructures for Colored “Cool” Paints 319 7.4 Sky Cooling to Subambient Temperatures 322 7.4.1 Sky Radiance 324 © 2011 by Taylor and Francis Group, LLC Contents xi 7.4.2 Spectral Selectivity and Sky Cooling: Idealized Surfaces 327 7.4.3 Calculated Cooling for Ideal and Practical Materials 329 7.4.4 Some Practical Surfaces for Sky Cooling: Bulk-Type Solids 332 7.4.5 Nanotechnology for Optimum Sky Radiators: Computed and Measured Data 332 7.4.6 Practical Sky Cooling: Systems and Data 337 7.4.7 Amplifying Sky Cooling with Heat Mirrors 342 7.4.8 Impact of Solar Irradiance on Sky Cooling 345 7.5 Water Condensation Using Sky Cooling 346 7.6 A Role for Cooling and Waste Heat in Electric Power Generation 348 7.7 Electronic Cooling and Nanotechnology 350 7.8 Whither Cooling? 353 7.8.1 Some Environmental and Health-Related Benefits 353 7.8.2 Cooling Plus 353 References 354 Chapter 8 Supporting Nanotechnologies: Air Sensing and Cleaning, Thermal Insulation, and Electrical Storage 361 8.1 Air Quality and Air Sensing 361 8.1.1 The Sick Building Syndrome 361 8.1.2 Gas Sensing with Nanoporous Metal Oxides: General 363 8.1.3 Gas Sensing with Nanoporous Metal Oxides: Illustrative Examples 365 8.2 Photocatalysis for Cleaning 368 8.2.1 General 368 8.2.2 Self-Cleaning Surfaces 372 8.2.3 Air Purification 377 © 2011 by Taylor and Francis Group, LLC