Solar traffic

Monday, 07 April 2008 14:07

South Africa’s first solar-powered traffic lights became operational in early October as a pilot project in one of Cape Town’s southern suburbs. This signalled the start of a programme aimed at having solar-powered traffic lights at all 1 300 intersections in the city by 2015. The project will not only save the city millions of rands on its electricity bill but will also make traffic lights immune to power cuts.

The initiative takes place under a plan to produce a wireless system independent of the national grid.
The first environmentally friendly lights have been installed at the intersection of Edna Street and Montague’s Gift Road south of Ottery at a cost of R150 000. A conventional set of lights costs R80 000 to install. Once the solar lights are installed on a large scale, the unit cost will drop to about R110 000 per set, but will pay for itself over time in electricity consumption savings.

The four pairs of lights are powered by batteries charged from solar panels mounted on poles.
The solar-powered traffic lights followed on the installation of solar-powered speed cameras deployed at strategic spots on some of the city’s throughways.

At the time the pilot traffic light project was launched, National Efficiency Agency operations manager Barry Bredenkamp said it would be monitored to quantify the fuel and time motorists would save in the event of power failures.

According to Bredenkamp, an eight-pole set of traffic lights uses the same amount of electricity as a four-member family living in a three-bedroom house.

To counter the danger of theft, the batteries are located in a theft-proof enclosed concrete casing at the bottom of the poles, while the solar panels are installed on high poles to counter possible theft and vandalism.

In the meantime, the city is also switching from using conventional bulbs in traffic lights to low-voltage, low-maintenance components, particularly light-emitting diodes (LEDs). Until the solar-powered system is fully operational, the new traffic light LEDs will be powered by uninterrupted power systems (UPS) in the event of power outages. One UPS system costs R50 000.

Previous experiences of power outages, particularly in February last year, when the city’s 1 300 traffic light-controlled intersections were all reduced to potentially fatal four-way stops, causing untold financial losses to the city’s transport-driven economy, have spurred the city into action.

The City of Cape Town had long been aware of the need to conserve traffic-light electricity in general and, in particular, to keep them operational during major power failures and those blackouts provided further incentive to our search for solutions,” said Councillor Elizabeth Thompson, Mayoral Committee Member for Transport, Roads and Stormwater.

We have, accordingly, constantly urged our suppliers to source low-voltage, low-maintenance components for our traffic lights. Replacing conventional light bulbs in traffic lights with light emitting diodes or the LEDs proved extremely encouraging.”

The LEDs use seven times less electricity than conventional light bulbs. Ordinary light bulbs also have high maintenance costs, needing to be replaced every three months. LEDs, on the other hand, last at least five years.

Cape Town hopes to have the LEDs installed at all 1 300 traffic light intersections by 2015. In the meantime, to keep all forms of traffic lights functioning during blackouts, 200 uninterrupted power systems have been installed at major traffic intersections, with more planned as budgetary constraints allow.

"Our ultimate goal for Cape Town is a wireless-driven, computer-controlled and -monitored traffic light system which is energy efficient and not dependent upon the vicissitudes of our electricity supply,” Ms Thompson said.

The solar-powered, LED-equipped traffic lights backed up by UPS systems for extra security are part of a continuing endeavour to make traffic light failures something of the past, she said.

State-owned electricity utility Eskom, which provides almost all of the country’s electricity, has been campaigning for the widespread use of energy-efficient systems for more than a year now.

This comes as rapid economic growth is straining the country’s energy supplies and Eskom embarks on a massive five-year R150-billion capital expenditure programme to boost the overall energy supply to the country.

The city has been assisted in its long-term solar energy plan for traffic light systems by the National Energy Efficiency Agency, a Central Energy Fund project set up last year at the behest of Minister of Minerals and Energy Buyelwa Sonjica.

The agency was formed as part of a broader strategy to reduce overall energy demand in South Africa by 12% by 2015.

Working with the agency, the city recently installed solar-powered, LED-equipped traffic lights – backed up by UPS – at an intersection in the northern part of Cape Town.

According to Eddie Chinnappen, the city’s executive director for Transport, Roads and Stormwater, the traffic lights at the intersection are powered by a 3.6 square metre solar panel placed on a conventional six-metre light pole angled at 30 degrees south to capture the maximum amount of sunlight.

The system will be tested for three months to see if it remains functional. The city will then take a decision on the viability of the project.

This will greatly improve energy efficiency and at the same time be more environmentally friendly.
Barry Bredenkamp, agency operations manager, said the project is a step towards energy efficiency in a nation renowned for year-round sunny conditions.

"Besides the obvious benefits for motorists, being solar powered means the traffic lights are more environmentally friendly, because they draw less electricity that has been generated by the predominant burning of fossil fuels,” he said.

Piet Coetzer