LED news and insight from our technology editor Steve Bush, who has been messing with LED lighting for more years than he would care to remember.
Life cycle and energy costs of street lighting
By Steve Bush (click on image to expand)
The city of Pittsburgh is replacing all of its streetlights, and a friend drew my attention to a report from the University of Pittsburgh on life cycle and energy costs of street lighting, including with LEDs.
The report is a year old now, but still valid as it assumes efficiencies of up to 90 lm/W for lighting LEDs – still a reasonable figure.
It concludes that LED lighting is the best, but induction lighting – where induction fields energise a gas mixture in a sealed glass cell – comes a close second.
In fact, LEDs only win because they are still becoming more efficient, while induction sources are mature.
Low pressure sodium lighting – the almost monochromatic yellow lighting used in the UK – which delivers 300 lm/W – is sadly omitted.
I suppose this is not surprising as it is not at all common in the US where energy has traditionally cheaper than in the UK and less efficient, but whiter, high-pressure sodium lighting has dominated.
Page 47 includes an excellent graph which compares the efficiency of light sources from the year 1850 until the era of lighting LEDs.
If I have understood the references, this graph comes from Azevedo and Morgan, F, The Transition to Solid-State Lighting, proceedings of the IEEE, 2009.
Click on the image, above right, to see the full scale graph.Tags: azevedo, gas mixture, induction, scale graph, steve bush