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Lighting up the developing world

03 July 2017

Imagine there is a solar light that could help to lift hundreds of millions of people in the developing world out of poverty and into a safer, healthier and brighter future.

Field testing the solar lamp (Credit: Patrick Bently)

This light is called the SM100. Hundreds of hours of detailed  research went into the design of the SM100 solar light to meet the needs of  families living without mains electricity in Africa, where it is being retailed for as little as $5, subject to local taxes and levies, making it the lowest cost solar light available in the market. 

It is the result of a collaboration between inventid, a UK strategic design consultancy, and Yingli Europe, to meet critical price and performance specifications of SolarAid, an international charity which seeks to combat poverty and climate change. 

Yingli Europe is a wholly owned subsidiary of Yingli Green Energy Holding Company Ltd., a solar panel manufacturer. Yingli manufactures the SM100, with distribution managed by SolarAid’s SunnyMoney sales teams across Africa, where the charity has been working for more than a decade to improve lives with a range of solar powered products. 

The design

The foundations for the SM100 design project began when inventid co­founder Henry James was on a design degree course at Leeds University in 2007 where he worked alongside SolarAid on a separate design challenge. He and fellow former student Bryn Morgan went on to establish inventid together in Manchester in 2012. 

The first phase consisted of low-fidelity model making in cardboard, foam and clay to explore form, balance and the fit of typical electronics. Many previous solar lights are round but when it comes to the SM100, its rectangular shape fits more readily with the standard shape of a solar panel, reducing the cost per unit and size of the solar light. 

Henry James explains “as we started to resolve ideas in parallel to design sketching we built the 3D product forms in Solidworks, allowing us to refine the design and render out visuals in Keyshot. This CAD data was translated into 3D printed parts. We probably made circa 30 prototypes refining even a simple structure. It meant we could explore and resolve ideas like using the AA battery as a counterbalance or fixing it comfortably to a person's head.”

The first phase consisted of low-fidelity model making in cardboard, foam and clay (Credit: inventid)

Adding two slots for a head strap adds no additional cost but means that the SM100 is also thought to be the world’s first integrated, low cost, solar head torch. 

Prototype feedback established that users preferred a cooler white light to a warm glow as it is perceived to feel modern and less flame like by people in Africa. 

Solar lights commonly have dual layer Printed Circuit Boards (PCBs), whereas the SM100 has a single layer PCB –reducing the cost of electronic components. Using a single layer PCB also means that the charging indicator light and switch are located on the front of the unit, conveniently making the SM100 more intuitive to use as a head torch. 

inventid also prototyped real-world experience to test the appropriate level of  power for the SM100’s LED light sources – using it to cook a meal and change a bicycle tyre in a darkened room of their Manchester studio, which  was approximate in size to the home of an African family. Further testing included a small run of 25x prototypes for testing in Malawi, Uganda and Zambia. 

The SM100 has a battery life of up to eight hours when fully charged; it produces an 18 lumen light – two times brighter than kerosene; its integrated solar panel is 50mA. This has led to the SM100 passing stringent Lighting Global test standards. 

Design work was finished on the SM100 solar light prototype in 2015, with delivery of the first product batch completed in autumn 2016. Every SM100 light bought in the UK (£10) includes a donation to support SolarAid’s work distributing solar lights in rural off-grid Africa.  

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