Table Of ContentPico-solar Electric Systems
This book provides a comprehensive overview of the technology behind the pico-solar revolution
and offers guidance on how to test and choose quality products. The book also discusses how
pioneering companies and initiatives are overcoming challenges to reach scale in the market-
place, from innovative distribution strategies to reach customers in rural India and Tanzania,
to product development in Cambodia, product assembly in Mozambique and the introduction
of ‘pay as you go’ technology in Kenya.
Pico-solar is a new category of solar electric system which has the potential to transform the
lives of over 1.6 billion people who live without access to electricity. Pico-solar systems are
smaller and more affordable than traditional solar systems and have the power to provide useful
amounts of electricity to charge the increasing number of low power consuming appliances
from mobile phones, e-readers and parking meters, to LED lights which have the power to light
up millions of homes in the same way the mobile phone has connected and empowered
communities across the planet.
The book explains the important role pico-solar has in reducing reliance on fossil fuels while
at the same time tackling world poverty and includes useful recommendations for entrepreneurs,
charities and governments who want to participate in developing this exciting and rapidly
expanding market.
John Keane is Managing Director and a founding member of SunnyMoney, the largest
distributor of pico-solar lighting products in Africa. Previously, he was Head of Programmes
for SolarAid, the international NGO that set up and owns SunnyMoney. He became acutely
aware of the pressing need for affordable, renewable energy in off-grid communities from living
in the village of Uhomini in rural Tanzania as a volunteer in 2000. He has since spent more
than a decade leading and developing solar projects across east and west Africa and has played
an instrumental role in building both SolarAid and SunnyMoney into respected international
organisations.
Earthscan Expert Series
Series editor Frank Jackson
Solar:
Grid-Connected Solar Electric Systems
Geoff Stapleton and Susan Neill
Pico-solar Electric Systems
John Keane
Solar Domestic Water Heating
Chris Laughton
Solar Technology
David Thorpe
Stand-alone Solar Electric Systems
Mark Hankins
Home Refurbishment:
Sustainable Home Refurbishment
David Thorpe
Wood Heating:
Wood Pellet Heating Systems
Dilwyn Jenkins
Renewable Power:
Renewable Energy Systems
Dilwyn Jenkins
Energy Management:
Energy Management in Buildings
David Thorpe
Energy Management in Industry
David Thorpe
Pico-solar
Electric Systems
The Earthscan Expert Guide
to the Technology and Emerging Market
John Keane
Solar:
Solar:Routledge
SSoollaarr::Taylor &. Francis Group SЭolaЯr: ПШШ]
LONDON AND NEW YORK from Routledge
First edition published 2014
by Routledge
2Park Square, Milton Park, Abingdon, Oxon OX14 4RN
Simultaneously published in the USA and Canada
by Routledge
711 Third Avenue, New York, NY 10017
Routledge is an imprint of the Taylor & Francis Group, an informa business
©2014 John Keane
The right of John Keane to be identified as author of this work has been asserted by him in
accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form
or by any electronic, mechanical, or other means, now known or hereafter invented, including
photocopying and recording, or in any information storage or retrieval system, without
permission in writing from the publishers.
Trademark notice:Product or corporate names may be trademarks or registered trademarks,
and are used only for identification and explanation without intent to infringe.
British Library Cataloguing in Publication Data
Acatalogue record for this book is available from the British Library
Library of Congress Cataloging in Publication Data
Keane, John (Urban planner)
Pico-solar electric systems : the Earthscan expert guide to the Technology and Emerging
Market / John Keane. — First edition.
pages cm — (Earthscan expert series)
Includes bibliographical references and index.
1. Building-integrated photovoltaic systems. 2. Small power production facilities.
3. Solar houses. I. Title.
TK1087.K43 2014
621.31¢244—dc23 2013035359
ISBN: 978-0-415-82359-3 (hbk)
ISBN: 978-1-315-81846-7 (ebk)
Typeset in Sabon
by Keystroke, Station Road, Codsall, Wolverhampton
Contents
Illustrations vii
Preface xiii
Acknowledgments xvii
List of Abbreviations xix
1 Introducing Pico-Solar 1
2 The Solar Resource 15
3 Solar PV Cells and Modules 23
4 Batteries 39
5 Lighting 53
6 Appliances and Energy Use 59
7 Product Quality 85
8 Using, Maintaining and Repairing Pico-Solar Systems 97
9 The Impact of Pico-Solar in Developing Countries 109
10 Selling Pico-Solar at the Base of the Pyramid 123
11 Case Studies 147
12 Resources 169
Bibliography 173
Glossary 177
Index 181
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Illustrations
Figures
1.1 Selection of pico-solar lights and charging systems, principally designed
for use in areas without access to electricity 3
1.1a Pico-solar systems are used to provide power for a wide range of
applications 4
1.1b Asmall portable charger with an integrated battery, PV module and LED
light, also recharges mobile phones 4
1.1c Asmall, pico-solar powered, bike light 4
1.2 The sale of pico-solar lights in Africa, approved for quality by the Lighting
Global programme, has increased significantly between 2009 and 2012 5
1.3a Pico-solar systems are smaller than traditional solar home systems 6
1.3b Large solar module dwarfing a pico-solar light and module 6
1.3c Asolar light and phone charger taken apart to show the main components 6
1.4 Map demonstrating the largest un-electrified populations of the world in
2009 7
1.5 Acomposite image of the world at night 7
1.6 Incident solar radiation map 8
1.7 Kerosene lamps are a dangerous fire hazard, and are polluting, costly and
emit low levels of light 9
1.8 The majority of households in rural Africa are not connected to the
electricity grid 9
1.9 Children light candles in a school in Malawi during a power cut 10
1.10 Two students studying with one pico-solar light 10
1.11 Children playing with disposable batteries which have reached the end
of their life in Rema, Ethiopia 11
1.11a Battery recycling box in Rome, Italy 11
2.1 Energy is transferred from the sun as light energy and then converted
into electrical energy which charges up a rechargeable battery, where it
is stored as chemical energy 16
2.2 1350 W/m2of solar radiation arrives in the earth’s atmosphere 17
2.3 Direct and diffuse radiation 18
2.4 Solar irradiance in watts per square metre (W/m2), received over time on
aflat surface in an equatorial region 19
2.5 The solar incident angle 20
2.6 Symbols used for direct current and alternating current 20
2.7 Voltage, current and power within the context of a simple circuit 21
3.1 Asolar cell producing electricity 23
3.2 Sunlight hits the surface of the PV cell, which converts the light energy
(photons) into electric current which flows to the terminals which are
connected to a circuit 24
viii LISTOFILLUSTRATIONS
3.3 Thirty-six solar cells wired together in series so as to achieve a higher
voltage 25
3.3a Asolar module made up of solar cells wired together 25
3.4 The back of a pico-solar module provides information such as power
rating and operating specifications under test conditions 26
3.5 Silicon solar cell I-V curve which shows the maximum power point
‘the knee’ of the curve 28
3.6 Effects of radiation intensity on module output 29
3.7 Effects of temperature on module output 29
3.8 In full sunlight, the module shows a Voc reading of 21.24 V 30
3.9 The Voc reading drops to 20.73 V when the module is in the shade 30
3.10 In full sunlight, the Isc reading is 0.305 A 31
3.10a This reading drops significantly to 0.071 A 31
3.11 Monocrystalline cells 33
3.11a Monocrystalline modules 33
3.12 Polycrystalline cells 34
3.12a Polycrystalline modules 34
3.13 Athin film module can be recognised by its dark uniform appearance
with lines running along the module 35
3.14 Flexible, Unisolar multi-junction thin film solar module 35
3.15 The junction box at the rear of a module projects the points where the
cable and wiring connects to the module’s terminals 36
3.16 Average solar PV price per watt have fallen significantly between 2008
and 2012 37
4.1 Rechargeable batteries come in a range of different shapes, sizes and
chemistries as well as different voltages and energy capacities 40
4.2–4.2a Pico-solar products typically incorporate the rechargeable battery 40
4.3 Circuit board of a pico-solar lantern and phone charger which
incorporates charge control circuitry and a fuse 41
4.4 Apico-solar light with a digital display which tells the user how many
hours of light remain 42
4.5 It is common to see a battery’s capacity defined as mAh on the side of the
battery 43
4.6 Battery SoC at 20 per cent and 80 per cent 44
4.7 Measuring the voltage of a battery 44
4.8 The percentage degree to which a battery is discharged is referred to as
depth of discharge (DoD) 45
4.9 3.6 V NiMH battery pack made up of three 1.2 V NiMH batteries
connected together in parallel 48
4.10 3.2 V, 600 mAh LFP battery 48
4.11 6V, 4.5 Ah sealed lead-acid battery 49
4.12 1.2V, 600 mAh NiCd battery 50
5.1 Luminous flux refers to visible light in every direction 54
5.2 One lux equates to the even distribution of 1 lumen over an area of 1m2 54
5.3 Atypical LED 55
5.4 LEDs come in a range of different shapes and sizes 55
5.5 This light has seven LEDs in the centre, surrounded by a large metallic
plate which acts as a ‘heat sink’ 55
LISTOFILLUSTRATIONS ix
5.6 Chart showing luminous efficacy of LEDs, CFLs and incandescent bulbs
over time 57
6.1 AC/DC power adaptor for a laptop 60
6.2 AC/DC power adaptor for a mobile phone 60
6.3 The micro USB connector has become fairly standard as a connection
type 61
6.4 This voltage converter converts 12 V (typical voltage of car batteries)
down to 5 V (typical voltage of USB outlets) 63
6.5 Pico-solar module facing the overhead sun 65
6.6 Designers of portable pico-solar chargers often have to compromise the
size of the PV module so that the product can be carried around easily 68
6.7 Anincreasing number of pico-solar lamps incorporate a USB outlet 69
6.8 Solar module being used to charge a mobile phone directly in Zambia 70
6.9 Awide range of specialised solar chargers exist 70
6.10 Radio with an integrated solar module and rechargeable battery 71
6.11 This radio available in the Kenyan market uses a 3.7 V, 800 mAh
rechargeable mobile phone battery instead of traditional disposable
batteries to operate 72
6.12 This pico-solar light comfortably recharges a basic e-reader device 73
6.13 Atablet computer being recharged by a portable solar powered charger 74
6.14 This pico-solar system uses a 5 Wp PV module and a 12 V, 7.7 Ah SLA
battery, which is capable of recharging a tablet computer 74
6.15 Hand-held mobile television 75
6.16 Pico-projector with a 3.7 V, 1600 mAh battery 75
6.17 This pico-solar lantern has an integrated solar module and rechargeable
battery 76
6.18 This light, charged by a separate solar module, can produce over 300
lumens for an hour at its maximum setting 76
6.19 This phone comes with an integrated pico-solar module of around
0.3 Wp 77
6.20–6.20a Device designed to provide useful back-up power for laptops on the go 78
6.21 Laptops with integrated pico-solar modules are appearing on the market 79
6.22 Solar backpacks come with an integrated solar module 80
6.23 Solar charged parking meter in Sicily, Italy 80
6.24 Asolar-powered city bike hire station in Toronto 81
6.25 Asolar powered electric fence unit 82
6.25a The unit can send an electric pulse along up to 30 km of electric fencing
and is used to keep cows and other livestock at bay 82
6.26 Solar module being used to recharge an SLA battery 82
6.27 A30 Wp solar lighting system with a 12 V 24 Ah SLA battery 83
7.1 To measure illuminance, position the photo detector of the lux meter so
that it faces the light source 91
8.1 Instructions for how to use and recharge a pico-solar light 99
8.2 Keep modules free of dust and anything which prevents sunlight reaching
the surface to maximise electricity generation 100
8.3 Customers need to know how to use systems properly to get the best
out of them 100
8.4 Good products are built to withstand use in harsh conditions 101
