Reducing energy used by street lighting.

[adam2]

I was recently invited to a meeting regarding this.
A brief presentation was given by a consultant, and questions then invited from the public.
These questions were then answered, by the consultant, by a local councilor, or by myself.

Summary of presentation.

Energy used by public lighting may be reduced in several ways, including;

1) Turning off lights that are considered to be no longer needed.
2) Part night operation, typically from dusk until midnight, and then from 06-00 until dawn, if still dark. Rather than the usual dusk till dawn operation.
3) Slightly "trimming" operating hours to take advantage of shorter warm up times of modern lamps.
4) Reducing lighting levels where these are greater than needed, either permanently by use of lower output lamps, or by dimming for part of the night as above.
5) Use of more efficient light sources, LED in most cases.
6) Use of better designed lanterns that direct more of the light onto the road and footway, with less wasted in other directions.
7) Replacing illuminated road signs with retro reflective types.

Questions were then invited, see following posts.

[adam2]

Questions and answers, selected ones relying on my imperfect memory.
Answers are identified as follows. All questions asked by members of the public unless stated otherwise.

R==answered by councillor.
T ==answered by consultant.
M ==answered by myself.

1) Could existing time controls be adjusted to reduce operating hours ? M answered, not in general as virtually all street lighting is controlled by photocells, not time switches.

2) Could part night operation be until 01-00 rather than midnight or half past midnight ? T replied, yes but only if specified thus initially, not readily adjustable afterwards.

3) Should we return to gas lighting ? gas is much cheaper than electricity. M replied, no because gas is cheaper per KWH than electricity but gas lighting is much less efficient than electric lighting.
3a) But Buckingham palace uses gas lighting to save money ! M replied, I feel that you are mistaken regarding the relative costs of gas and electric lights. Gas may be justified for heritage and historical reasons, or to protect against power failures, but is more expensive in both energy costs and also in maintenance.

4) Returning to part night lighting, how is this controlled, and what is the labour cost in setting it up ?
T replied, it is fully automatic, with a once only labour cost to fit a part night photocell. If done as part of other works, labour cost is zero.

5) Can LED bulbs be fitted to existing street lights. T and M replied jointly, not in general for various reasons.

6) Are there any street lights that use incandescent bulbs ? R replied, not so far as am aware.
6a) What about the ones at {location redacted} M replied, those are privately owned, not part of the public lighting scheme. I fitted LED bulbs to them recently, for the owner.

To be continued.

[kenneal - lagger]

When our council went over to LEDs a few years ago the local paper had loads of letters complaining about the new lights and how awful they were; how they were much brighter than the old lights; basically how people didn't like change. Also all the people walking home from work after midnight couldn't see their way, were going to be raped or robbed, or even worse, both.

Complaints dried up after about a year!

[adam2]

Other questions asked;

Could solar powered street lights be installed, to avoid electricity bills ? T answered, these are widely available. M added, only worth considering in locations without readily available electricity. PV modules cost money and most of the energy is wasted in street lighting by sizing the module for reliable mid winter operation it will be very over specified for the rest of the year.
As an aside, I said that grid tied PV arrays can be most worthwhile as virtually all the output is used.

Could street lights be controlled by motion sensors to save energy ?
T replied, it is certainly possible with LED street lights, but has found little favour in practice.
M replied also, with the light nearest a person lit, they may feel nervous at proceeding into the darkness ahead. Also residents found that lights going on and off are much more displeasing than continual lighting, or no lighting.

The street light near my home flashes on and off about every 10 minutes, why.
M replied most likely a worn out lamp of the high pressure sodium variety, report it.

Will street lighting be affected by the EU ban on certain types of light bulb ?
R replied, In general, no though there might be a handful of exceptions.

But I heard that low pressure sodium lamps are now banned.
M replied, I am not aware of any such ban, but manufacture has now ceased for commercial reasons of declining demand.

Local farmer asked, am I allowed to replace the lamps on my farm that are low pressure sodium ?
M replied, there is no prohibition, but replacement lamps may be hard to find.

What about decorative Christmas lighting put up by the council ? Are the bulbs still allowed ?
R replied, the great majority have been LED for some years.

Can the police turn on otherwise extinguished street lights ? R replied, no. Police cars and police officers are properly equipped for dark conditions.

[adam2]

When our council went over to LEDs a few years ago the local paper had loads of letters complaining about the new lights and how awful they were; how they were much brighter than the old lights; basically how people didn't like change. Also all the people walking home from work after midnight couldn't see their way, were going to be raped or robbed, or even worse, both.

Complaints dried up after about a year!

At the above meeting, some expressed similar views, others criticised the fact that the new lights do not properly light their front gardens or front doors.

[kenneal - lagger]

.................At the above meeting, some expressed similar views, others criticised the fact that the new lights do not properly light their front gardens or front doors.

With the earlier LED fittings we had the opposite complaint, that they were shining into bedrooms, etc. The newer low spill fittings direct light downwards very well indeed.

[PS_RalphW]

Our village was converted to LED a few years ago. The white light is much easier on the eye than the sodium yellow. The lamp outside our house does light our front garden much more, but probably because I cut down the 10 foot ivy hedge, and I keep the replacement I have grown at 6 feet.

The transition took over a year being put out to private contract, with the whole village looking like a building site for that time. However, I have heard no complaints about the new lights themselves.

The number of lamps was reduced slightly, and there are a few dark corners now, but our village has low crime and only a few youths of poor reputation. I am happy to walk across the unlit playing fields at night

[adam2]

Until fairly recently, replacing low pressure sodium lamps with LEDs was a low priority because low pressure sodium are highly efficient.
This has recently changed because production of replacement lamps has now ceased. Some lamps are still in the supply chain, but so far as is known, no more are being manufactured anywhere in the world.
The energy saving by changing to LED from low pressure sodium is modest but light quality is much improved and lamp costs much reduced.

High pressure sodium lamps are still readily available.

Mercury lamps are now little used for street lighting, except at pedestrian crossings. Some countries have prohibited the manufacture or import of mercury lamps.
These lamps remain popular for decorative outdoor lighting as foliage lit thus looks most attractive.

Blended light mercury tungsten lamps are of poor efficiency and not used significantly for street lighting.
The main merits of such lamps are extreme long life, stable operation and no requirement for control gear.

[adam2]

The above recent meeting has resulted in a number of follow up discussions, some sensible, some less so.

Q, could smart meters be fitted to street lights to save money ? I replied not in general because most street lights are not metered. The energy used is determined by knowledge of wattage and operating hours.

Q, Why have the council fitted green bulbs in the street lights at [location redacted] Coloured bulbs waste most of the light.
I replied, those are not council street lights, they are on private property.
The green LED bulbs are very efficient and use only 4 watts each.

Q What can be done to stop mischievous youths turning out the street lights in [location redacted] ?
I answered, not much ! Contrary to the general practice, many street lights in that place are centrally controlled, and mischievous persons have discovered how to subvert the automatic control.
Q, Could not the police do anything ? I replied, that I would be pleased to advise the police as to how they may restore the affected lights to automatic control.

Q Why were all the street lights lit during the day a local road junction ?
I replied, there are several possibilities.
Firstly, in exceptionally dark weather they may come on automatically.
Secondly, they may have been turned on manually to facilitate daytime inspection.
Or there may be a fault, don't worry about a "one off" but report this is if it recurs.

Q, I think that one or more street lights are connected to my electricity meter, which is unfair. (This question or variants thereof was widely asked)
I replied that I have never found this to be the case, not once !
The matter may be determined by a very simple test.
When the street lights are lit, turn your main switch to OFF. The street lights should remain lit as normal.
Then with your main switch still turned off, observe the electricity meter, no consumption should be recorded with your main switch off.
Do be aware that your home may be fitted with external lights, that incidentally light the road. These should be connected to your meter and you will have to pay for the energy that they use.

[adam2]

Two interesting follow up points.

Firstly, if street lighting is actually removed, then this might mean that the default speed limit for road traffic increases from 30 MPH to 60 MPH.
At present the default limit in built up areas is 30 MPH and one deciding factor in determining if an area is built up, is the provision of street lighting.
"30 MPH" road signs could be supplied, but this is a slight extra cost.

The second point, raised by myself is regarding the unit cost of electricity for street lighting for part night operation.
Street lighting is not normally metered, charging is based on knowledge of the number of lights, installed wattage, operating hours, and fixed costs.

If part night operation replaces all night operation, then I would expect the unit cost of the electricity to increase for two reasons.
Firstly, the fixed costs of providing the supply remain constant but are spread over fewer operating hours.
Secondly, all night operation incudes in winter both the evening peak hours (expensive to supply) and the off peak hours that are cheap to supply.
The electricity supplier take both factors into account when determining charges.
If part night operation is chosen, then this still includes the early evening peak, but includes a much smaller number of off peak hours. The electricity supplier might therefore charge a higher price per unit.