Monday, March 30, 2009

New sensors in street lamps 'to save 9,000 hours of energy a night'

Street-lamp sensors which react to changing light conditions are being upgraded across Southwark to reduce energy usage.

The sensors measure outdoor brightness and then switch lights on or off as required.

Sensors have been in use for several years, but Southwark's engineers have carried out several studies allowing them to reduce the time each light is on by 30 minutes per day.

Council bosses say this will reduce energy consumption by thousands of hours a night, and called for the scheme to be rolled out across London.

Eddie Henry, Southwark council's director of street lighting, said: "We looked at schemes like dimming, or turning off lights altogether. But in London, for safety reasons these are just not viable options, so we decided to experiment with changing the light levels at which we actually turn the lights on."

The unit of measurement for light is the "lux". Daylight is defined as 100 lux and street lamps were programmed to come on when that dimmed to 70. However, work by Southwark Council's street lighting team has shown that lights do not actually have to be turned on until brightness drops to 55 lux.

Mr Henry said: "We found it makes absolutely no difference. People will see no change at all, yet we will save 9,000 hours per night of electricity if all our lights are upgraded."

Southwark has already installed the new system on 2,000 street lamps, and hopes to double that number by the end of the year.

Councillor Jeff Hook, Southwark council executive member for environment, said: "Southwark is committed to achieving a number of carbon reduction targets over the next few years.

"We are calling on residents to switch off and save energy. But we have to walk the walk too. The council provides more than 200 services for its residents and is always looking for ways to reduce emissions across the organisation."