Making Street Lights Green

There are few homes left that do not have at least some energy saving light bulbs. As the availability of standard light bulbs dwindles, even the laziest of us will have no excuse for changing over to energy efficient lighting. Outside the house is a different story, however. Street lights, which are much more powerful than domestic lighting, and so use more power, emit more carbon dioxide and are on all night, have been slow to become more environmentally friendly.

Current Street Lamps

The street lights that we have today tend to be one of two types. Those that line most streets in towns and cities are high pressure sodium lamps. The other type, metal halide lamps, tend to be brighter and are often used at busy motorway junctions and – of course – in football and sports stadiums. Both consume a lot of electricity and produce a lot of waste heat and high carbon emissions. High pressure sodium lamps need 150 watts to run for an hour, metal halide lamps need 163 watts. This compares unfavourably to the 105 watts per hour used by LED lamps that produce an equivalent amount of light.

The Future is LED Bright

A recent study by researchers in an American university school of engineering has tested standard metal halide and high pressure sodium lamps and compared them with an alternative – LED lamps. The report leaves no room for doubt: LED lamps use only about 50% of the power of standard street lamps, they last around 5 times as long and they produce more light. The downside is that they are more expensive to make and install new but the savings over the life of the street lamp offset this eventually.

In the USA, different cities are already thinking hard about replacing older high pressure sodium lamps, which have a characteristic yellow glow, with new lights with LEDs. The city of Pittsburgh, which was behind the feasibility report, has just ordered 40 000 of them and other cities such as San Francisco and Los Angeles are following suit.

Green Street Lamps Save Money

In large trials of LED street lights, one other advantage became obvious when LED street lamps were installed. Due to their longer life, LED lamps do not need to be changed very often, and do not ‘blow’ or malfunction. This means that maintenance time is much lower and the crews of maintenance workers normally kept busy by traditional street lamps have more time to commit to other pressing maintenance projects. The city of Ann Arbor in Michigan found that it saved just under $1.4 by making the change to LED street lamps, just on the energy that the lamps used. The savings on maintenance could easily amount to another $1 million.

LED Street Lamps in Europe?

LED street lamps will come to Europe but we seem to be slightly behind the USA in terms of testing. A project is currently being run by the European Commission to test LED street lamps in four European countries – Poland, Latvia, Portugal and France. The system under test is an intelligent lighting system that allows the lamp to respond to ambient light. LED street lamps that are able to automatically dim at dawn and light up at dusk, without needing to be continually programmed with the time, could save power and maintenance. Safety would also be increased, because the street lamps would always provide the optimum light level for any given situation.

LED Street Lights in the UK?

Although the UK is not yet part of the EU trial, several privately run tests are underway here. In March 2008 Southampton Airport won an innovation award for developing an energy lighting system for its airport, all based on LED outside lighting. The people running the project estimated that the LED lamps reduced carbon emissions by 70% and the new LED systems produced far less waste heat and glare They were also capable of running for 10 years continuously before wearing out. The company who provided the LED lamps, Gemma Lighting of Portsmouth, is now working with other large organisations to revolutionise lighting systems in shopping centres and hospitals all over the country.