Report 5 of 5: Glowstar - Kenya

Introduction

	© Phil Webb - Solar lantern with radio

In many parts of the developing world people who live in rural areas have no access to electricity (around two billion people). As a result, most families are forced to rely on candles or kerosene lamps to provide basic lighting in their homes. In Kenya, for example, 96% of householders rely upon kerosene lighting lamps, and 70% supplement this lighting with battery powered torches. Kerosene lamps are potentially hazardous and the running costs are high, with rural households spending about £5 per month on fuel and batteries. This recurrent cost every month eats up valuable financial resources that could otherwise be directed towards children’s education or family health. For many people, the provision of light in their homes can compete directly with other household essentials.

Energy from the sun is freely available and many countries in the developing world have it in plentiful supply. As a result there has been a growing interest in the use of Photo-Voltaics (the technology used to convert the sun’s energy into electricity) as a renewable and environmentally friendly source with which to provide low cost light and power in rural communities. Unfortunately, the cost of installing even a modest Solar Home System puts it out of the reach of most rural families in the developing world.

Solar Lanterns

The Solar Lantern, "GLOWSTAR", designed by Intermediate Technology Consultants (ITC - the consulting subsidiary of ITDG) has been designed as a low-cost alternative to a Solar Home System and is intended to allow rural families to climb the first step on the "energy ladder". The lantern is cheap to maintain and harnesses a free and plentiful source of energy as it is powered by sunshine.

The solar lantern kit consists of a Photo-Voltaic panel, and a lantern containing a high efficiency lamp, a rechargeable battery and a charge control circuit. The lantern uses the latest technology to provide a simple solution to a very basic problem. During daytime, sunlight falling onto a Photo-Voltaic panel generates a small electrical voltage. This is used to charge the lantern’s battery so that the lamp can provide light and power during the hours of darkness.

The solar lantern is ideal for any application where there is no local connection to grid electricity such as rural households and farms, schools and colleges, hospitals, health clinics and other community centres. It also has important applications where there is an inconsistent or unreliable supply of electricity.

Manufacturing Options

There are a range of options in terms of manufacturing techniques that are available to the designer today, and the choice of the most appropriate comes down to considerations of scale of production and cost. As a general rule, individual component part costs come down as production levels increase.

Specifications of the solar lantern

Service characteristics:

• The maximum price of the lantern should be no more than US$100 if possible

• The lantern should provide light for up to 4 hours each evening

• Customers should have access to affordable and readily available spares

• Customers expect an overall lifetime of the lantern of 6 years

• Customers expect a 12 months warranty for the product

The lantern should give a 360 degree spread of light

The bulb enclosure should allow maximum transmission of light with minimum dispersion effects

The carry handle should be sturdy and comfortable

The lamp should be portable and weigh no more than 2.5 kg

The lantern should be stable with a good base

• An indicator to show that the battery is charging

• A warning light to show that the lamp is about to switch off when the battery is low

• A power output socket to allow a small radio to be connected to the unit

The Photo-Voltaic Solar Panel collects light energy from the sun and converts it into electrical current. The energy is stored as charge within the battery of the lantern.

The lamp

The lantern uses a high efficiency compact florescent tube as its light source. These lamps are almost six times more efficient than a standard incandescent light bulb and have an effective life which is eight times longer. In normal use, the lamp can be expected to last for about four years.

	© Zul Mukhida

Power storage

The rechargeable lead acid Gel-cell is located in the base of the lantern. It has been specially designed to give reliable performance over numerous charge and discharge cycles.

Charging the lantern

To charge the lantern, simply plug the PV panel into the clearly marked INPUT socket. Alternatively, if there is a supply of mains electricity nearby then the lantern can be charged using a simple AC adapter. With an appropriate plug and lead the lantern may also be charged through the cigarette lighter socket found in many vehicles.

The OUTPUT socket supplies 9V DC which is sufficient to power a small radio or cassette player. Both sockets are protected against short circuit and reverse polarity connections.

Suspending the lantern

To maximise the spread of light over an area indoors, the folding hook on the base of the lantern may be used to suspend it, for example, in the middle of a room.

Battery technology

A crucial component for any rechargeable device is the battery. The project activities have included research into available battery technologies to identify a battery which

• has the capacity to store charge sufficient for the required period of lighting

• is suitably robust to withstand the heavy duty cycle required for daily charge and discharge

• requires no customer maintenance (also spill and leak proof)

• has minimum impact to the environment if disposed of at the end of its life cycle

• could be manufactured locally in the medium term in developing countries

• provides a cost effective solution

Charge control circuit

The charge control circuit housed within the lantern is the "brain" of the unit. It ensures that the battery is charged and discharged correctly so that it gives a lifetime of maintenance free service, and it can also "decide" to give the battery an extra top-up charge if the panel has gone without its full quota of sunlight for a few days. Its on-board microprocessor will even store information (which can be downloaded later for "interrogation") on how the lantern has been used over a period of time. This information is extremely useful and will help the designers build a picture of how customers use their lanterns to help improve designs in the future.
 

For further information, please contact:
 

Intermediate Technology Consultants Schumacher Centre for Technology and Development Bourton Hall Bourton on Dunsmore Rugby Warwickshire CV23 9QZ United Kingdom Tel: +44 (0) 1788 661103 Fax: +44 (0) 1788 661105 E-mail: glowstar@itdg.org.uk Website: www.itcltd.com/solar

The ITC Solar Lantern is a UK Registered Design No.2083358. The Solar Lantern Project has been funded by the UK Department for International Development (DFID). This information has been reproduced with the kind permission of ITC Ltd.

This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.

TVE/ Practical Action gratefully acknowledge support for the HANDS ON programmes from the UK's Department for International Development (DFID), the European Commission (EC), the UN Foundation and UNDP/The Equator Initiative in collaboration with the Government of Canada, IDRC, IUCN, BrasilConnects and the Nature Conservancy.