Cape Town trials solar-powered traffic lights

Cape Town has joined forces with South African power giant Eskom and the National Energy Efficiency Agency to try out an innovative project. Four pairs of solar-powered traffic lights have been installed in the southern suburb of Ottery. If the pilot is successful, many more such lights could be installed across South Africa within the next few years.

Explaining the rationale behind the project, Eddie Chinnappen, Cape Town municipality's director of transport, roads and stormwater, said the purpose was twofold: "The city is very much environmentally conscious."

"Also, we are hoping to get uninterrupted power supply for traffic lights in Cape Town so when there are power outages like we have had over the past two years, we will not have traffic jams."

Power interruptions mean traffic officers have to be sent to the affected junctions, says Mr Chinnappen, "and given the limited resources it is near impossible to get to all the junctions around the city".

The traffic lights are powered by a 3.6 m2 solar panel, tilted at a 30-degree angle to ensure maximum efficiency in capturing the sun's rays.

According to Mr Chinnappen, the panel converts these rays into electric power which is transmitted to a set of batteries which can provide eight hours of power to service the lights.

To prevent vandalism, the solar panel is located at the top of a 6m (18-foot) pole while the batteries are located in a thief-proof concrete casing which authorities say would require a mini-limpet mine to open.

The power-saving traffic lights have been fitted with hundreds of light-emitting diodes (LEDs) which use seven times less electricity than conventional light bulbs.

LEDs also last for a minimum of five years as opposed to the three-month lifespan of the conventional light bulbs in traffic lights.

"Because the solar-powered system is more expensive than the conventional traffic lights, we will do an evaluation to see the cost-effectiveness of it after three months," says Mr Chinnappen.

There will be a separate evaluation during Cape Town's winter months when there is much less sunlight.

But the director of transport, roads and storm water is optimistic about this 21st Century solution to controlling traffic.

"So far it seems like it is working reasonably well... but we have not had any power outages recently, so we will have to cut the power at some stage to look at the implications." -BBC