Let there be light

One in five people in the world has no access to electricity, a proportion that is predicted to remain the same for the next 20 years due to the pressures of population growth. In such electricity deprived areas the source of light is often the Kerosene lamp.

The World Bank estimates 780million women and children breathe Kerosene fumes equivalent to 40 cigarettes a day. In India 1.5 million people suffer severe burns caused by such lamps being knocked over. And they are expensive – in the poorest countries Kerosene can represent 30% of household income. In other words – kerosene lamps are not ideal.

So this month’s challenge is to come up with an alternative. The key requirements are that it is cheap, reliable and safe. Batteries are expensive and raise their own environmental issues, so we don’t want them. It needs to be constantly available, day and night, so a solar panel based solution is unlikely to satisfy demands. And while a wind up torch might offer us a short relief in a power cut, anyone who has used one will know it is never going to provide a constant light source unless you have a team of super fit ‘winders’ on the case.

Although there is no reason why this should not have applications in every environment, the target is those places where poverty prevails, so keeping upfront and running costs low is critical.

Any ideas? We will publish the solution we have in mind next month, but if in the meantime you have any entertaining or interesting solutions then feel free to leave a comment or email the editor at tfryer@findlay.co.uk.

Our solution is provided by GravityLight, the name describing the basic principle. Gravity transfers potential energy to kinetic, which produces electricity to light an LED.

GravityLight is installed to provide a 1.8m drop of a 12kg weight. This weight is lifted and on release starts falling very slowly (about 1mm / second). This movement powers a drive sprocket, which rotates very slowly with high torque. A polymer geartrain running through the product turns this input into a high speed, low torque output that drives a DC generator at thousands of rotations per minute. This generates just under a tenth of a watt, a deciwatt, to power an onboard LED and ancillary devices. Given the ever-increasing efficiency of LEDs, this produces a light over five times brighter than a typical open-wick kerosene lamp. Once the weighted bag reaches the floor, which depends on how high it was installed, it is simply lifted to repeat the process.

GravityLight has been through trials with its first generation model and intends to start mass production with the second generation model in the autumn 2015. For more information visit www.gravitylight.org