developing a next generation solar lantern

Panel Presentation: Energy Author: Chris White Institution: University of Cambridge

Developing

Keywords

Solar Lantern, Off-Grid Lighting, Kerosene,

Abstract

The Glowstar lantern was developed to meet the needs of the 1.6 billion people worldwide who live without electricity anddepend on kerosene for lighting. The lantern has sold in large numbers across the world but has not achieved the levelsexpected or fulfilled the need. This project examines the Glowstar project and attempts to identify the reasons for it notmeeting expectations. In addition a new desi

The Glowstar lantern is regarded as a high performance and quality product but the price (US$150) at which it is sold istoo high. This combined with a limited distribution network put the product out of the reaat which the development was targeted. A new design of lantern is presented that comprises three multiand flexible modules that provide the functionality of a solar lantern for a projected cost of US$50 whilehigher powers and better performance and providing auxiliary functions.

Introduction

Worldwide 1.6 billion people live without access to electricityfor light after dark. Kerosene for lighting can absorb up to 15% of household income and produces very poor quality light.Grid expansion is expensive and happening very slowly and so a new solution was sought. In 2003 the Glowstar lanternwas released to market. Developed by Practiccompany Sollatek Ltd, it was designed to serve the world’s poorest people by providing low cost, high quality lighting to

eliminate the need for kerosene lanterns. The Glowstar is abattery that continues to sell worldwide but has never enjoyed the success that was anticipated and has not spread as faras the need for improved lighting. This project investigates the reasons focase study for the global situation and seeks to design and prototype a lantern that can meet the needs of the targetmarket more successfully.

Solar Lighting

The provision of electric lighting can provide aproductivity resulting from an extended working day, enabling children to study effectively after dark, reducingexpenditure on consumables and improving the health of the whole famiElectric lighting can also improve business performance through the extension of working and trading hours and improvedconditions from brighter and more consistent light.

Photovoltaic (PV) systems are well suitedinsolation. In addition PV systems can be low maintenance and installed in a variety of situations. The main drawback inthis context is the price which is falling as the globalincome levels of the poorest people.

The challenges with the cost of PV systems can be combated through the development of small scale PV appliancesdubbed ‘micro’ or ‘Pico PV’ that can be produced at a cost that is compatible with rural household income in developingcountries. The solar lantern is one example of this that offers the potential to meet this large market.

Methods

The work in this project falls broadly into two areas, firstdevelopment of a new lantern. The research into the Glowstar project focused around a field trip to Kenya to investigatethe market performance of Glowstar and obtain opinions from across the didistributers, agents and end users as well as NGOs working in related areas. The trip was also used develop anunderstanding of the general state of the offresearch using reports and papers produced by a wide range of stakeholders in the Glowstar project and the offlighting market in general.

The development of a new lantern followed on from the first phase, using the knowledge of the marketdesign. Consideration has also been given to the distribution and marketing of a solar lantern.

EWB-UK National Research & Education Conference 2011

Developing a next generation solar lantern Chris White

University of Cambridge

Grid Lighting, Kerosene,

The Glowstar lantern was developed to meet the needs of the 1.6 billion people worldwide who live without electricity and. The lantern has sold in large numbers across the world but has not achieved the levels

expected or fulfilled the need. This project examines the Glowstar project and attempts to identify the reasons for it notmeeting expectations. In addition a new design for a lantern is developed and presented.

The Glowstar lantern is regarded as a high performance and quality product but the price (US$150) at which it is sold istoo high. This combined with a limited distribution network put the product out of the reach of the rural poor householdsat which the development was targeted. A new design of lantern is presented that comprises three multiand flexible modules that provide the functionality of a solar lantern for a projected cost of US$50 whilehigher powers and better performance and providing auxiliary functions.

Worldwide 1.6 billion people live without access to electricity [1], relying on expensive and dangerous kerosene lanternse for lighting can absorb up to 15% of household income and produces very poor quality light.

Grid expansion is expensive and happening very slowly and so a new solution was sought. In 2003 the Glowstar lanternwas released to market. Developed by Practical Action Consulting (formerly ITC) and produced and distributed by solarcompany Sollatek Ltd, it was designed to serve the world’s poorest people by providing low cost, high quality lighting to

eliminate the need for kerosene lanterns. The Glowstar is a solar charged compact fluorescent lantern with a lead acidbattery that continues to sell worldwide but has never enjoyed the success that was anticipated and has not spread as faras the need for improved lighting. This project investigates the reasons for Glowstar’s level of success using Kenya as acase study for the global situation and seeks to design and prototype a lantern that can meet the needs of the target

The provision of electric lighting can provide a boost to families attempting to break away from poverty through increasedproductivity resulting from an extended working day, enabling children to study effectively after dark, reducingexpenditure on consumables and improving the health of the whole family by removing exposure to kerosene smoke.Electric lighting can also improve business performance through the extension of working and trading hours and improvedconditions from brighter and more consistent light.

Photovoltaic (PV) systems are well suited to applications in the developing world as many areas receive high levels ofinsolation. In addition PV systems can be low maintenance and installed in a variety of situations. The main drawback inthis context is the price which is falling as the global market develops but is still high, especially when compared to the

The challenges with the cost of PV systems can be combated through the development of small scale PV appliancesproduced at a cost that is compatible with rural household income in developing

countries. The solar lantern is one example of this that offers the potential to meet this large market.

The work in this project falls broadly into two areas, firstly the investigation of the Glowstar project and secondly thedevelopment of a new lantern. The research into the Glowstar project focused around a field trip to Kenya to investigatethe market performance of Glowstar and obtain opinions from across the distribution network from importers,distributers, agents and end users as well as NGOs working in related areas. The trip was also used develop anunderstanding of the general state of the off-grid lighting market in Kenya. This field trip was complimentedresearch using reports and papers produced by a wide range of stakeholders in the Glowstar project and the off

The development of a new lantern followed on from the first phase, using the knowledge of the marketdesign. Consideration has also been given to the distribution and marketing of a solar lantern.

UK National Research & Education Conference 2011

‘Our Global Future’

4th March 2011

28

The Glowstar lantern was developed to meet the needs of the 1.6 billion people worldwide who live without electricity and . The lantern has sold in large numbers across the world but has not achieved the levels

expected or fulfilled the need. This project examines the Glowstar project and attempts to identify the reasons for it not

The Glowstar lantern is regarded as a high performance and quality product but the price (US$150) at which it is sold is ch of the rural poor households

at which the development was targeted. A new design of lantern is presented that comprises three multi-purpose smart and flexible modules that provide the functionality of a solar lantern for a projected cost of US$50 while being scalable to

, relying on expensive and dangerous kerosene lanterns e for lighting can absorb up to 15% of household income and produces very poor quality light.

Grid expansion is expensive and happening very slowly and so a new solution was sought. In 2003 the Glowstar lantern al Action Consulting (formerly ITC) and produced and distributed by solar

company Sollatek Ltd, it was designed to serve the world’s poorest people by providing low cost, high quality lighting to

solar charged compact fluorescent lantern with a lead acid battery that continues to sell worldwide but has never enjoyed the success that was anticipated and has not spread as far

r Glowstar’s level of success using Kenya as a case study for the global situation and seeks to design and prototype a lantern that can meet the needs of the target

boost to families attempting to break away from poverty through increased productivity resulting from an extended working day, enabling children to study effectively after dark, reducing

ly by removing exposure to kerosene smoke. Electric lighting can also improve business performance through the extension of working and trading hours and improved

to applications in the developing world as many areas receive high levels of insolation. In addition PV systems can be low maintenance and installed in a variety of situations. The main drawback in

market develops but is still high, especially when compared to the

The challenges with the cost of PV systems can be combated through the development of small scale PV appliances produced at a cost that is compatible with rural household income in developing

countries. The solar lantern is one example of this that offers the potential to meet this large market.

ly the investigation of the Glowstar project and secondly the development of a new lantern. The research into the Glowstar project focused around a field trip to Kenya to investigate

stribution network from importers, distributers, agents and end users as well as NGOs working in related areas. The trip was also used develop an

grid lighting market in Kenya. This field trip was complimented by UK based research using reports and papers produced by a wide range of stakeholders in the Glowstar project and the off-grid

The development of a new lantern followed on from the first phase, using the knowledge of the market to inform the


Results and discussion

Glowstar

The Glowstar lantern (Fig 1) is widely regarded in Kenya as a high quality and robust product that performs welsimple to use. This is backed up by the excellent 5 year warranty offered bythe manufacturer Sollatek. There are some commonly reported faults withthe battery management system leading to reduced battery lifetimes and thereported lifetimes varied widely between users with some requiringreplacement within a year and others lasting in excess of six years. A cleartheme emerged from many users of disappointment with the battery life.

A technical assessment of a range of solar lanterns undertaken bplaced the Glowstar 7th out of the 12 lanterns tested. Thecriticised for wrongly designed circuitry’ and scored poorly on efficiency, runtime and deviation from specifications. The report concluded thatGlowstar failed both the technical test and in terms of value for money. Thisunusually heavy and cumbersome lantern was a pioneer of the marketsector, but exhibits defects in workmanship and offers only a poor solarfraction and modest light duration.’

The Glowstar lantern typically sells for around US$100 without a solarmodule, rising to US$150 with a solar module which puts it out of reach formany of the rural poor for whom the lantern was designed. This combinedwith a limited distribution network focusing mainly on regimajority of sales taking place in Nairobi “61 out of 100 last month”regional sales manager for Sollatek) and not on rural areas hascontributed to the poor penetration of the rural market by the Glowstar inKenya. Sales of the Glowstar in Kenya are dominated by NGOs who havethe capital available to purchase the lanterns and value their rugged and robust construction. A common use for thelanterns is in remote field sites in Northern Kenya and South Sudan. This demand has maintained saland it appears that Sollatek have settled on pursuing this high margin market rather than actively targeting the ruralmass market.

Glowstar Impacts

The Glowstar lantern has had a number of impacts in the area of off grid lighting whicreaching than simply providing lighting solutions to poor rural people.

The project successfully developed a good quality lantern that was taken on by a private company and marketed

worldwide. This has been an experiment in parfuture.

The direct social impact of the lantern on poor rural people has been very limited due to poor market penetration. Wherethe product has been used within this market users repolighting. In addition to this most of the users interviewed for this research now have alternative supplies of electricityinstalled either from a solar system or mains. This is not a strong bappears to suggest that the Glowstar lantern was a first step on the energy ladder.

The lantern has been used extensively by NGOs in remote areas and continues to sell today inworldwide.

The Glowstar was one of the first lanterns designed for this market and as such played a role in establishing the marketthat has continued to develop.

Off-Grid Lighting market

The solar market in Kenya is well established and growing with a high levelgrid is limited with poor reliability and high costs. This, combined with a growing awareness of environmental concerns,has led to a high level of enthusiasm for solar power. The government has responded tointroducing strict import standards and rigorous checks to ensure that products are not substandard and has removedVAT (16%) from solar products.

The wider off grid lighting market is quite broad incorporating solar lanterns, solar hgenerators as well as traditional kerosene lamps and candles. In addition new schemes are being trialled based on anenergy kiosk idea where energy is bought as a product from a central kiosk, mini grids covering one village andgenerating local power from alternative fuels e.g. biogas.

The solar lantern market is also developing rapidly with two generations of lantern evident. The first generation,contemporaries of Glowstar, tend to be large CFL and lead acid based lanterns. Theemerging on the market now and is often LED based with a range of prices and power options. The companies producingthe new generation include number of social enterprises including Barefoot Power and Tough Stuff Solar,


The Glowstar lantern (Fig 1) is widely regarded in Kenya as a high quality and robust product that performs welsimple to use. This is backed up by the excellent 5 year warranty offered by the manufacturer Sollatek. There are some commonly reported faults with the battery management system leading to reduced battery lifetimes and the

ed widely between users with some requiring replacement within a year and others lasting in excess of six years. A clear theme emerged from many users of disappointment with the battery life.

A technical assessment of a range of solar lanterns undertaken by GTZ [2] out of the 12 lanterns tested. The ‘Glowstar was

and scored poorly on efficiency, run time and deviation from specifications. The report concluded that ‘The

he technical test and in terms of value for money. This unusually heavy and cumbersome lantern was a pioneer of the market sector, but exhibits defects in workmanship and offers only a poor solar

ypically sells for around US$100 without a solar module, rising to US$150 with a solar module which puts it out of reach for many of the rural poor for whom the lantern was designed. This combined with a limited distribution network focusing mainly on regional centres (the majority of sales taking place in Nairobi “61 out of 100 last month” - regional sales manager for Sollatek) and not on rural areas has contributed to the poor penetration of the rural market by the Glowstar in

in Kenya are dominated by NGOs who have the capital available to purchase the lanterns and value their rugged and robust construction. A common use for thelanterns is in remote field sites in Northern Kenya and South Sudan. This demand has maintained saland it appears that Sollatek have settled on pursuing this high margin market rather than actively targeting the rural

The Glowstar lantern has had a number of impacts in the area of off grid lighting which are potentially much widerreaching than simply providing lighting solutions to poor rural people.


worldwide. This has been an experiment in partnerships of this nature which will provide interesting lessons for the

The direct social impact of the lantern on poor rural people has been very limited due to poor market penetration. Wherethe product has been used within this market users reported that the lantern was very useful and replaced kerosene forlighting. In addition to this most of the users interviewed for this research now have alternative supplies of electricityinstalled either from a solar system or mains. This is not a strong basis for conclusions without further research butappears to suggest that the Glowstar lantern was a first step on the energy ladder.

The lantern has been used extensively by NGOs in remote areas and continues to sell today in

The Glowstar was one of the first lanterns designed for this market and as such played a role in establishing the market

The solar market in Kenya is well established and growing with a high level of awareness of solar power. The extent of thegrid is limited with poor reliability and high costs. This, combined with a growing awareness of environmental concerns,has led to a high level of enthusiasm for solar power. The government has responded to support the market byintroducing strict import standards and rigorous checks to ensure that products are not substandard and has removed

The wider off grid lighting market is quite broad incorporating solar lanterns, solar home systems and fuel basedgenerators as well as traditional kerosene lamps and candles. In addition new schemes are being trialled based on anenergy kiosk idea where energy is bought as a product from a central kiosk, mini grids covering one village andgenerating local power from alternative fuels e.g. biogas.

The solar lantern market is also developing rapidly with two generations of lantern evident. The first generation,contemporaries of Glowstar, tend to be large CFL and lead acid based lanterns. The new generation of solar lighting isemerging on the market now and is often LED based with a range of prices and power options. The companies producingthe new generation include number of social enterprises including Barefoot Power and Tough Stuff Solar,

Figure 1 - Glowstar lantern



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29

The Glowstar lantern (Fig 1) is widely regarded in Kenya as a high quality and robust product that performs well and is

the capital available to purchase the lanterns and value their rugged and robust construction. A common use for the lanterns is in remote field sites in Northern Kenya and South Sudan. This demand has maintained sales of the Glowstar, and it appears that Sollatek have settled on pursuing this high margin market rather than actively targeting the rural

h are potentially much wider


resting lessons for the

The direct social impact of the lantern on poor rural people has been very limited due to poor market penetration. Where rted that the lantern was very useful and replaced kerosene for

lighting. In addition to this most of the users interviewed for this research now have alternative supplies of electricity asis for conclusions without further research but

The lantern has been used extensively by NGOs in remote areas and continues to sell today in significant numbers

The Glowstar was one of the first lanterns designed for this market and as such played a role in establishing the market

of awareness of solar power. The extent of the grid is limited with poor reliability and high costs. This, combined with a growing awareness of environmental concerns,

support the market by introducing strict import standards and rigorous checks to ensure that products are not substandard and has removed

ome systems and fuel based generators as well as traditional kerosene lamps and candles. In addition new schemes are being trialled based on an energy kiosk idea where energy is bought as a product from a central kiosk, mini grids covering one village and

The solar lantern market is also developing rapidly with two generations of lantern evident. The first generation, new generation of solar lighting is

emerging on the market now and is often LED based with a range of prices and power options. The companies producing the new generation include number of social enterprises including Barefoot Power and Tough Stuff Solar, but also include

Glowstar lantern


some big corporate names including Phillips and Osram. These companies are pursuing enthusiastic marketing and educational campaigns targeting rural populations with low cost, good quality products that appear to be selling well. There is a wide range of price points in the market, with some lanterns retailing at UD$10, however these tend to have low light outputs, providing an improvement on kerosene, but significantly dimmer than Glowstar. There did not appear to be a direct replacement for Glowstar that offered a similar level of light output, battery life and 360 degree room lighting in a portable package.

Distribution

For a product to be self sustaining it needs to be sold on a commercial basis. Charity funded givenot self sustaining and they degrade the perceived value of the product with the risk of market spoiling. To quote Tough Stuff Solar “There’s a built in feedback loop when you sell something just doesn’t happen when you give things away.”[3]

The Glowstar distribution network in place in Kenya is inadequate for rural market penetration. The product must be available locally and coupled with knowledgeable advisors for effective distribution.

Utilising the mobile phone distribution network is a possible solution that could provide an extensive distribution network very rapidly. Partnerships with micro credit agencies and community groups has been explored by the Glowstar project but could be expanded to provide an effective distribution network by combining a solution to capital availability access to large numbers of people. A potential method of providing flexible payment programs is through the use of mobile money transfers that have become widespread acrossmoney.

Next Generation Lantern

Requirements for a next generation lantern

It would seem that little has changed to the requirements for a solar lantern since the market research was carthe Glowstar except for the desire for six hours of light. Detailed market research by Lighting Africa [4, 5] and this projecresearch have led to the summary of key requirements as follows:

• Cost – below $50 and as low as possible• Light Duration – minimum of 6 hours on a day’s charge• Easy to operate and maintain • 360 degree light distribution • Some industry experts felt that general room lighting, rather than directional task lighting is a higher priority for

domestic users.

Proposed design

Solar lanterns are a very good first step on the energy ladder, but they are not a long term solution and it is likely that customers will seek to upgrade to higher power systems with more functionality when their finances permit, perhaps using the money saved by not buying kerosene for lighting. When a larger system is installed the solar lanterns become redundant, or act as a backup light source and new lighting systems are purchased.

This concept aims to improve the scalability of Pico solar systems and allow them to be easily upgraded to suit all requirements. The lighting system concept is described in Figure 2.

The basis of the system is a smart solar lighting unit that offers flexibility while remaining simple to use and maintain. The basic lantern is split into three elements: the lamp, Battery pack and solar module. Each is a standalone appliance and can be used seamlessly with the others as well as other products.


some big corporate names including Phillips and Osram. These companies are pursuing enthusiastic marketing and educational campaigns targeting rural populations with low cost, good quality products that appear to be selling well.

a wide range of price points in the market, with some lanterns retailing at UD$10, however these tend to have low light outputs, providing an improvement on kerosene, but significantly dimmer than Glowstar. There did not appear to

for Glowstar that offered a similar level of light output, battery life and 360 degree room lighting

For a product to be self sustaining it needs to be sold on a commercial basis. Charity funded givenot self sustaining and they degrade the perceived value of the product with the risk of market spoiling. To quote Tough Stuff Solar “There’s a built in feedback loop when you sell something – people only pay for something they want. That

ings away.”[3]

The Glowstar distribution network in place in Kenya is inadequate for rural market penetration. The product must be available locally and coupled with knowledgeable advisors for effective distribution.

bile phone distribution network is a possible solution that could provide an extensive distribution network very rapidly. Partnerships with micro credit agencies and community groups has been explored by the Glowstar project

e an effective distribution network by combining a solution to capital availability access to large numbers of people. A potential method of providing flexible payment programs is through the use of mobile money transfers that have become widespread across Kenya allowing anyone with a mobile phone to electronically transfer

Requirements for a next generation lantern

It would seem that little has changed to the requirements for a solar lantern since the market research was carthe Glowstar except for the desire for six hours of light. Detailed market research by Lighting Africa [4, 5] and this projecresearch have led to the summary of key requirements as follows:

below $50 and as low as possible minimum of 6 hours on a day’s charge

Some industry experts felt that general room lighting, rather than directional task lighting is a higher priority for

lar lanterns are a very good first step on the energy ladder, but they are not a long term solution and it is likely that customers

systems with more functionality when their finances permit, perhaps using the money

ed by not buying kerosene for lighting. When a larger system is installed the solar

This concept aims to improve the scalability llow them to be

easily upgraded to suit all requirements. The

remaining simple to use and maintain. The split into three elements: the

lamp, Battery pack and solar module. Each is a standalone appliance and can be used seamlessly with the others as well as other

Figure 2 Function diagram of the next generation concept



4th March 2011

30

some big corporate names including Phillips and Osram. These companies are pursuing enthusiastic marketing and educational campaigns targeting rural populations with low cost, good quality products that appear to be selling well.

a wide range of price points in the market, with some lanterns retailing at UD$10, however these tend to have low light outputs, providing an improvement on kerosene, but significantly dimmer than Glowstar. There did not appear to

for Glowstar that offered a similar level of light output, battery life and 360 degree room lighting

For a product to be self sustaining it needs to be sold on a commercial basis. Charity funded give-aways are inherently not self sustaining and they degrade the perceived value of the product with the risk of market spoiling. To quote Tough

people only pay for something they want. That

The Glowstar distribution network in place in Kenya is inadequate for rural market penetration. The product must be

bile phone distribution network is a possible solution that could provide an extensive distribution network very rapidly. Partnerships with micro credit agencies and community groups has been explored by the Glowstar project

e an effective distribution network by combining a solution to capital availability access to large numbers of people. A potential method of providing flexible payment programs is through the use of mobile money

Kenya allowing anyone with a mobile phone to electronically transfer

It would seem that little has changed to the requirements for a solar lantern since the market research was carried out for the Glowstar except for the desire for six hours of light. Detailed market research by Lighting Africa [4, 5] and this project

Some industry experts felt that general room lighting, rather than directional task lighting is a higher priority for

Figure 2 Function diagram of the next generation concept


Lamp

The lamp consists of a high power, high efficiency LED with a driver circuit tallows the lamp to be run from a 4xAA NiMH battery pack or a 12V lead acid solar battery in a solar home system (SHS). Therefore if the household upgrades to a SHS they can use their existing high quality la

Battery pack

The battery pack holds four AA NiMH batteries which can be replaced by the owner and used as individual batteries in other appliances as well as in the battery pack. The battery pack has overcharge controller that will accept power between 6 and 24 volts allowing a range of solar modules to be used to charge it. This allows seamless upgrading to higher power solar modules without rendering the battery pack useless. The battery pack can clip into the lamp to provide a single lantern unit, or it can be attached via wires for permanent light fittings in the house with the batteries at a central location. The battery pack can also be utilised for other applications e.g. phone charging or powering a radio.

Solar module

The basic lighting pack would be supplied with a 2Wp solar module to minimise cost but as described above any other size of panel could be used to suit the household budget.

Technical implementation

The prototype design is based around switchThe battery pack employs a micro-controller controlled DCsource) to the charging characteristics of the battpower output from the solar module and also controlling the charge of the batteries to prevent damage from overcharging and over discharging. The lamp module uses a DC

Cost

The cost of the parts for the prototype lantern is around £40 (approximately US$65). To produce 1000 prototype lanterns would reduce the cost per lantern below £35 (approximately US$55). This is still too expeUS$50 as this does not include the casings, transport, markmarket. There are going to be savings in the economies of mass production that will drive the cost down butto quantify that amount. The total production cost will have to be brought down to around US$25 in order for the final retail price to be on target, however this should be possible to achieve with the current design.

Return on Investment

Typical running costs are US$2.80 and US$8.06 per month for a simple wick lamp and a hurricane lantern respectively [5]. At a retail cost of US$50 a solar lantern would have a payback period of 6 to 18 months if seen as a direct replacement. This is obviously a significant capital outlay necessitating a suitable finance provision to enable poor households to purchase one. The extra benefits of replacing a kerosene lantern are obviously not accounted for in this simplistic equation and nor are the additionlikely to use in addition to kerosene lanterns. Once purchased a solar lantern should be expected to operate without any additional costs for around two years before replacemen

Remaining challenges

Challenges remain over the optimisation of the circuitry to maximise the efficiency and performance of the lantern and the embodiment of the design into a robust and intuitive package that is easy to uselement that requires further work is the lens to distribute the light into a 360 degree room light. The directional nature oLEDs makes this difficult to achieve but there are some interesting possible solutions available ibulb enclosures that achieve a very uniform light distribution through to cheap and simple machined acrylic attachments.


The lamp consists of a high power, high efficiency LED with a driver circuit that allows input voltages of 4 to 15 volts. This allows the lamp to be run from a 4xAA NiMH battery pack or a 12V lead acid solar battery in a solar home system (SHS). Therefore if the household upgrades to a SHS they can use their existing high quality lamps.

The battery pack holds four AA NiMH batteries which can be replaced by the owner and used as individual batteries in other appliances as well as in the battery pack. The battery pack has over-discharge protection for the batteries and a charge controller that will accept power between 6 and 24 volts allowing a range of solar modules to be used to charge it. This allows seamless upgrading to higher power solar modules without rendering the battery pack useless. The battery

to the lamp to provide a single lantern unit, or it can be attached via wires for permanent light fittings in the house with the batteries at a central location. The battery pack can also be utilised for other applications e.g. phone

The basic lighting pack would be supplied with a 2Wp solar module to minimise cost but as described above any other size of panel could be used to suit the household budget.

nd switch-mode DC-DC converters that allow for high efficiency utilisation of energy. controller controlled DC-DC converter to match the solar module (or other input power

source) to the charging characteristics of the batteries, providing maximum power point tracking to achieve the optimum power output from the solar module and also controlling the charge of the batteries to prevent damage from overcharging and over discharging. The lamp module uses a DC-DC converter to efficiently drive the high brightness LED.

The cost of the parts for the prototype lantern is around £40 (approximately US$65). To produce 1000 prototype lanterns would reduce the cost per lantern below £35 (approximately US$55). This is still too expensive to meet the target of sub US$50 as this does not include the casings, transport, mark-ups and taxes that will be imposed on a product going to market. There are going to be savings in the economies of mass production that will drive the cost down butto quantify that amount. The total production cost will have to be brought down to around US$25 in order for the final retail price to be on target, however this should be possible to achieve with the current design.

Typical running costs are US$2.80 and US$8.06 per month for a simple wick lamp and a hurricane lantern respectively [5]. At a retail cost of US$50 a solar lantern would have a payback period of 6 to 18 months if seen as a direct

ously a significant capital outlay necessitating a suitable finance provision to enable poor households to purchase one. The extra benefits of replacing a kerosene lantern are obviously not accounted for in this simplistic equation and nor are the additional lighting costs such as batteries for torches and candles that a household is likely to use in addition to kerosene lanterns. Once purchased a solar lantern should be expected to operate without any additional costs for around two years before replacement of the batteries is required.

Challenges remain over the optimisation of the circuitry to maximise the efficiency and performance of the lantern and the embodiment of the design into a robust and intuitive package that is easy to use and maintain. One particular element that requires further work is the lens to distribute the light into a 360 degree room light. The directional nature oLEDs makes this difficult to achieve but there are some interesting possible solutions available ibulb enclosures that achieve a very uniform light distribution through to cheap and simple machined acrylic attachments.



4th March 2011

31

hat allows input voltages of 4 to 15 volts. This allows the lamp to be run from a 4xAA NiMH battery pack or a 12V lead acid solar battery in a solar home system (SHS).

The battery pack holds four AA NiMH batteries which can be replaced by the owner and used as individual batteries in discharge protection for the batteries and a

charge controller that will accept power between 6 and 24 volts allowing a range of solar modules to be used to charge it. This allows seamless upgrading to higher power solar modules without rendering the battery pack useless. The battery

to the lamp to provide a single lantern unit, or it can be attached via wires for permanent light fittings in the house with the batteries at a central location. The battery pack can also be utilised for other applications e.g. phone

The basic lighting pack would be supplied with a 2Wp solar module to minimise cost but as described above any other size

DC converters that allow for high efficiency utilisation of energy. DC converter to match the solar module (or other input power

eries, providing maximum power point tracking to achieve the optimum power output from the solar module and also controlling the charge of the batteries to prevent damage from overcharging

iciently drive the high brightness LED.

The cost of the parts for the prototype lantern is around £40 (approximately US$65). To produce 1000 prototype lanterns nsive to meet the target of sub

ups and taxes that will be imposed on a product going to market. There are going to be savings in the economies of mass production that will drive the cost down but it is difficult to quantify that amount. The total production cost will have to be brought down to around US$25 in order for the final retail price to be on target, however this should be possible to achieve with the current design.

Typical running costs are US$2.80 and US$8.06 per month for a simple wick lamp and a hurricane lantern respectively [5]. At a retail cost of US$50 a solar lantern would have a payback period of 6 to 18 months if seen as a direct

ously a significant capital outlay necessitating a suitable finance provision to enable poor households to purchase one. The extra benefits of replacing a kerosene lantern are obviously not accounted for in this

al lighting costs such as batteries for torches and candles that a household is likely to use in addition to kerosene lanterns. Once purchased a solar lantern should be expected to operate without any

Challenges remain over the optimisation of the circuitry to maximise the efficiency and performance of the lantern and e and maintain. One particular

element that requires further work is the lens to distribute the light into a 360 degree room light. The directional nature of LEDs makes this difficult to achieve but there are some interesting possible solutions available including commercial LED bulb enclosures that achieve a very uniform light distribution through to cheap and simple machined acrylic attachments.


Conclusions

Glowstar pioneered a new market sector ten years ago and was in many ways a ground breaking inintervening decade great advances have been made in technology that now allows new options to be explored and thereare many factors both social and technological that make a next generation lantern development a very exciting prospect

Technical:

• LED technology has developed new, efficient and robust lighting possibilities that are proven in service andcontinues to develop rapidly.

• A great array of very capable and affordable ICs is now available on the market that can simplify the dereduce costs.

• Battery technology has advanced significantly and continues to expand the options for offincluding NiMH and lithium chemistries.

Social:

• The need for improved off-grid lighting has not diminished with a huge and un• There is great desire and enthusiasm amongst un• The potential benefits to people are huge and potentially life• There is an unprecedented global focus on off• Access to relevant information is easier than ever before• Governments, communities and individuals are increasingly aware of the potential benefits including

environmental issues resulting from the worldwide concern over climate change.

The coincidence of the above factors makes now a very good time for a new lantern development and indeed there aremany companies in various stages of the process. The design proposed here perhaps offers a new level of modularity andflexibility of use to the design that can benefit u

With further development this design could form the basis of a high performance, scalable and affordable solar lanternthat can help to address the need for off-of people through a suitable and scalable development, manufacturing and distribution program building on the lessonslearnt from the Glowstar project and subsequent market experience. A proportion of local manufacture and assembly is afeasible option given the design of the lantern with benefits for both the host country and the business viability throughimproved maintainability, local servicing and building of local skill which may help to stimulate the local market throughindigenous innovation.

The challenges in a lantern development are clearly large and numerous, but not insurmountable. The mainconsiderations are:

• Obtaining funding to pursue the development as returns on investments is likely to be slow due to the nature ofthe market and the need to sell many products at low mark

• Setting up a successful distribution network which to be effective is likely to be highly labour intensive and

geographically diverse.• Marketing the product successfully to a target group who are geographicall

aware and have little spare cash available.• Making the product affordable by keeping the cost to a minimum and seeking ways to enable poor people to

purchase the product• Building a strong brand through high product performa

For more information please see www.solarclever.co.uk

Acknowledgements Dr Patrick Palmer, Project supervisor, Cambridge University Engineering DepartmentLighting Africa Sollatek Kenya Barefoot Power Practical Action and Practical Action ConsultingScode Nakuru

References Chris White. 2010. Developing the Next Generation Solar Lantern. www.solarclever.co.uk [1] Lighting Africa. Lighting and Development.http://www.lightingafrica.org/node/326. [2] GTZ. Grüner, Roman, et al. 2009. Solar Lanterns Test: Shades of Light.[3] Rocky Radar. 2009. Tough Stuff: Bringing Solar to the Developing World.23 05 2010.] http://www.rockyradar.com/cleantech/?p=341.[4] Lighting Africa. 2008. Kenya Qualitative Off[5] Lighting Africa. 2008. Lighting Africa Market Assessment Results: Quantitative ResultsBank, 2008.


Glowstar pioneered a new market sector ten years ago and was in many ways a ground breaking inintervening decade great advances have been made in technology that now allows new options to be explored and thereare many factors both social and technological that make a next generation lantern development a very exciting prospect

LED technology has developed new, efficient and robust lighting possibilities that are proven in service and

A great array of very capable and affordable ICs is now available on the market that can simplify the de

Battery technology has advanced significantly and continues to expand the options for offincluding NiMH and lithium chemistries.

grid lighting has not diminished with a huge and under-served marketThere is great desire and enthusiasm amongst un-electrified communities The potential benefits to people are huge and potentially life-changing There is an unprecedented global focus on off-grid lighting through projects such as LightingAccess to relevant information is easier than ever beforeGovernments, communities and individuals are increasingly aware of the potential benefits includingenvironmental issues resulting from the worldwide concern over climate change.

nce of the above factors makes now a very good time for a new lantern development and indeed there aremany companies in various stages of the process. The design proposed here perhaps offers a new level of modularity and

hat can benefit users.

With further development this design could form the basis of a high performance, scalable and affordable solar lantern-grid lighting in Kenya and beyond. There is the potential to reach huge

of people through a suitable and scalable development, manufacturing and distribution program building on the lessonslearnt from the Glowstar project and subsequent market experience. A proportion of local manufacture and assembly is a

tion given the design of the lantern with benefits for both the host country and the business viability throughimproved maintainability, local servicing and building of local skill which may help to stimulate the local market through

The challenges in a lantern development are clearly large and numerous, but not insurmountable. The main

Obtaining funding to pursue the development as returns on investments is likely to be slow due to the nature ofhe need to sell many products at low mark-ups.

Setting up a successful distribution network which to be effective is likely to be highly labour intensive and

Marketing the product successfully to a target group who are geographically diverse, may not be technologyaware and have little spare cash available.Making the product affordable by keeping the cost to a minimum and seeking ways to enable poor people to

Building a strong brand through high product performance and providing good after sales service.

For more information please see www.solarclever.co.uk

Dr Patrick Palmer, Project supervisor, Cambridge University Engineering Department

Action and Practical Action Consulting

Chris White. 2010. Developing the Next Generation Solar Lantern. www.solarclever.co.uk [1] Lighting Africa. Lighting and Development. Lighting Africa. [Online] [Cited: 21 05 2010.]

Solar Lanterns Test: Shades of Light. s.l. : GTZ, 2009. [3] Rocky Radar. 2009. Tough Stuff: Bringing Solar to the Developing World. Rocky Radar. [Online] 01 09 2009. [Cited:

tp://www.rockyradar.com/cleantech/?p=341. Kenya Qualitative Off-Grid Lighting Market Assessment. s.l. : IFC - World Bank, 2008.Lighting Africa Market Assessment Results: Quantitative Results - Kenya.



4th March 2011

32

Glowstar pioneered a new market sector ten years ago and was in many ways a ground breaking innovation. During the intervening decade great advances have been made in technology that now allows new options to be explored and there are many factors both social and technological that make a next generation lantern development a very exciting prospect.

LED technology has developed new, efficient and robust lighting possibilities that are proven in service and

A great array of very capable and affordable ICs is now available on the market that can simplify the design and

Battery technology has advanced significantly and continues to expand the options for off-grid applications

served market

grid lighting through projects such as Lighting Africa

Governments, communities and individuals are increasingly aware of the potential benefits including

nce of the above factors makes now a very good time for a new lantern development and indeed there are many companies in various stages of the process. The design proposed here perhaps offers a new level of modularity and

With further development this design could form the basis of a high performance, scalable and affordable solar lantern grid lighting in Kenya and beyond. There is the potential to reach huge numbers

of people through a suitable and scalable development, manufacturing and distribution program building on the lessons learnt from the Glowstar project and subsequent market experience. A proportion of local manufacture and assembly is a

tion given the design of the lantern with benefits for both the host country and the business viability through improved maintainability, local servicing and building of local skill which may help to stimulate the local market through

The challenges in a lantern development are clearly large and numerous, but not insurmountable. The main

Obtaining funding to pursue the development as returns on investments is likely to be slow due to the nature of

Setting up a successful distribution network which to be effective is likely to be highly labour intensive and

y diverse, may not be technology

Making the product affordable by keeping the cost to a minimum and seeking ways to enable poor people to

nce and providing good after sales service.

[Online] 01 09 2009. [Cited:

World Bank, 2008. Kenya. s.l. : IFC - World

developing a next generation solar lantern

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