Pay as you go solar power makes energy cheaper

Pay as you go is a common way of paying for calls on your cellphone. Now the idea could help make solar power a more realistic option for families in Kenya and other African countries.

The system, called IndiGo, consists of a low-cost flexible plastic 2.5W solar panel that charges a battery. This is connected to a USB mobile phone charger and an LED lamp that provides around 5 hours of light from one day's charge.

Developed by solar energy firm Eight19, based in Cambridge, UK, IndiGo costs $1 a week to run, though the unit itself must be leased for an initial $10 fee. Users add credit by buying a scratchcard that they validate by sending a text message from their phone.

IndiGo is being trialled in Kenya and will be tested in other countries in the next few months. Eight19 hopes the device will go on sale early next year. The company also plans to offer higher-power systems as demand for solar energy increases, such as a 50W system that could power a small TV.

No more kerosene

Many rural areas of countries such as Kenya are not connected to the electricity grid, so people light their homes using kerosene lamps. As well as being relatively expensive, these create smoke pollution and carbon emissions. Simon Bransfield-Garth, CEO of Eight19, says the high cost of fuel locks people into a cycle of poverty. "They're paying disproportionately large amounts for their energy," he says – typically $2 or £3 a week.

Bransfield-Garth says the benefits of his firm's solar power system aren't just economic - it will improve access to power too. People in rural Kenya currently pay around $0.20 to charge their phone, and many also have to travel to a charger. One man in the trial used to make a 2-hour round-trip each week and wait another 2 hours to actually charge his phone. He can now do it at home.

"There's no doubt it's a great development," says Sabah Abdullah , who researches sustainable energy development in developing countries at the University of Bath, UK. But she warns that the system could be hard for people with low literacy levels to use and that relying on a mobile phone for payment could marginalise those who can't afford such devices. "These are the people who really need a step up in terms of electrification."

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Sateesh.smart