Not kept in dark (From York Press)
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Not kept in dark
11:15am Monday 25th June 2012 in Letters By Reader's letter
THE story headlined “Energy saving hits streets lights” (The Press, June 20) suggested that in the Harrogate area certain street lights would be turned off from midnight to 5am.
Could I suggest the idea of a sensor on each lamppost, so when someone is passing it lights up and switches off after a minute?
Should you really be keeping your community in the dark when the nights draw in, or will those who live in there have to carry a torch?
Also one does need to feel safe in their neighbourhood.
After midnight one needs to see any unwanted visitors who might be around.
Keith Chapman, Custance Walk, Nunnery Lane, York.
Magicman! says...
3:13am Tue 26 Jun 12
Unless you are using expensive LED fittings, the lamps need time to warm up (even fluorescents do, to a point)... sodium vapour ones start red as the neon gas energises, and it is only after about 5 minutes that the sodium in the tube has warmed enough to give off the yellow glow - High Pressure Sodium is similar, but start off dim until the mercury in the tube kicks in - and white light lamps that use halide salts are similar to HPS in that the mercury inside has to be energised for a short while before enough stable light is given off... and when the light is switched off, it needs a few minutes 'recovery time' before it'll switch back on again.
It isn't the same as sticking a halogen floodlight up on a pole!
LED lights can instantly switch on and off, but are very expensive to buy - and whilst a movement sensor on each column for its lantern would work on a footpath, for a road you'd need to have the sensor a few columns back so as to illuminate a block of lighting before the vehicle was at the section. Doing this would require complex wiring systems underground that would run into £1000's to install (just changing the supply from a single old column to a new one is £5000)... and then you have the factor to consider for locals who might not like their street light going on and off every few minutes as people/cars pass under.
An easier answer is simply to use better light sources. On main roads in Acomb, 90w sodium vapour lights (roughly 120w real power) were replaced by 57w fluorescent lights (~60w real power) which has a 50% saving per column. a few years ago 80w and 125w Mercury lights (average 100w real power, 140w for the 125's) were replaced by 42w fluorescent (~45w real power) - you multiply that saving over the nearly 2,000 lights that were changing and you can see why York doesn't need to switch it's lights off for half the night.
By comparison, in Harrogate and North Yorkshire I have seen 90w sodium vapour lights replaced by 150w High Pressure Sodium lights (in Leeds the same setup would see a 250w HPS installed)... and then their council wonders why they've got a high leccy bill!