In an effort to curb wasteful use of resources, development organizations have been propagating alternative lighting technologies for two decades, among them solar lanterns. In these devices, solar cells convert sunlight into electricity during the day that charges a battery, which then produces light for use after dark.
The most common lighting source used in such solar systems is the compact fluorescent lamp (CFL), though recently more efficient light emitting diodes (LEDs) have become more widespread.
Types of solar lanterns
Progress in solar technology has recently led to a growing use of solar-powered lighting solutions in developing countries. Particularly in rural areas with a dispersed population, where connection to the electricity grid would be uneconomic, solar lighting systems are a promising alternative.
Solar lighting systems may broadly be divided into three classifications: simple models, similar to ordinary torches, are already available in many countries. These are sometimes sold with a crank dynamo in place of the solar cells. Luminous efficacy and durability are usually poor. Such low-cost lanterns often last for only a month, or give light for only a few minutes.
At the other end of the price scale are ‘solar home systems’ with a solar module of 20 to 100 watts and an optimized car battery, capable of powering several lights, a radio and a TV set simultaneously. Although some three million such solar home systems have already been installed worldwide, for most users they remain unaffordable.
Affordability of solar lanterns
In Africa and Latin America they are quite expensive. Only in Asia are they somewhat less expensive. A third product category, which is rapidly gaining importance, solar lanterns or ‘pico-PV systems’ whose retail prices currently fall between the two extremes above.
In their outward appearance they resemble kerosene lamps but they promise greater lighting convenience and minimal running costs. In most models available so far, a small solar module typically with a capacity of 3 to 10 watts is separate from the lantern, so that it can be placed outdoors without the lantern being exposed to the weather.
The best of these lanterns can be hung indoors or placed on a table, but are also portable enough to light the way when walking at night.
Another way in which these solar lanterns or ‘pico-PV systems’ stand out from simple solar torches is the auxiliary uses available on many newer models. These offer outputs for a radio, a mobile phone charger or other functions, thus making a minimal basic provision of electrically powered micro devices conceivable for all poor rural populations in the near future.