Glentrool Village - LED

Location: Glentrool Village, Galloway Forest

Client: The Forestry Commission

Products:

Ledway Road Lantern, 20 LED (x23)

Objectives

Galloway Forest was awarded Dark Sky Park status in November 2009 by the International Dark Sky Association (IDA) and conditions are about to get even darker without switching off street lights. The development of an external lighting management plan covering domestic, commercial and public lighting was an essential element in achieving the IDA award. Jim Paterson, director of LCADS Ltd, pioneered the first UK dark sky master plan for the Galloway Forest Park. In addition to recommending good lighting practice for all the private properties within the park boundary, the plan also contained forward recommendations to replace all the old low pressure sodium lighting in Glentrool Village. The village is located within the park buffer zone where the master plan recommends environmental zone E1 stray light limits.

The village, complete with a primary school and post office, was built in the late 1950's to house Forestry Commission workers and rangers and through time has seen many changes. The recent closure of the primary school triggered the implementation of a village regeneration initiative. Upgrading the street lighting to comply with the strict light control recommended in the lighting management plan was put high on the agenda. There is nothing new about using full cut-off lighting but when the plan was written, more than two years ago, there were only two flat glass lanterns utilising LED light sources. Both could achieve zero intensity at and above the horizontal thus providing G6 glare restrictions. However, in addition to achieving G6 the Ruud Ledway Road luminaire was the only LED luminaire which had been provided with an IDA Dark Sky Fixtures award and was therefore chosen for the master plan concept study. Within a 40 metre square illuminance grid a single Ruud 30 LED luminaire provided, at that time, about the same average and minimum illuminance values as a single 35 watt low pressure sodium luminaire.

During the period of waiting for the IDA approval for the Forestry Commission Scotland application an electronic visualisation of the village was developed by LCADS to show the night time comparison between the present low pressure sodium lighting and that which would be achieved by retrofitting the Ruud Ledway Road luminaires on to the existing electricity distribution poles. Spacing distances of up to 42 metres is a common feature with wooden electricity poles and there was a little concern that minimum illuminance values would not be achieved.

Solutions

Since writing the master plan more than two years ago there has been an explosion in LED development and many more LED sourced luminaires have come on the market. So instead of switching lights off the local authority wanted to see the illuminance implications of retrofitting luminaires from other manufacturers.

A test area was agreed with the Dumfries and Galloway Council and the comparison test grids were established by LCADS. For each luminaire a traditional straight road maximum spacing test was undertaken together with a section of site specific curved roadway to establish the usual average and minimum illuminance values. Additionally, a grid to cover an area of private garden behind the road and a vertical grid to cover a house front from ground to chimney pot, to check front door and bedroom window values, completed the in depth comparison study.

Apart from the traditional roadway test, which could be compared with BS EN 13201 criteria, the other grids were added as comparison reference points. One point of concern for the local authority was that dark areas by the front doors may give cause for a proliferation of security spotlights.

The existing SOX and eight flat glass luminaires from different market leaders were subjected to the same geometry calculation conditions. After running 40 separate lighting calculations the Ruud Ledway luminaire was deemed to achieve the best technical performance to suit the village site specific test layout. It was the only luminaire to pass BS EN 13201 criteria for an S5 lighting objective over the test section. The number of LED's could be reduced to 20 and the straight road test achieved 42 metres. This spacing was equalled by only one other luminaire which subsequently failed the curved road test. Bedroom window light reduced from a calculated 2 lux from the existing lighting to 0.3 lux with the Ruud Ledway Road.

	New design - Straight Road				Existing Mid Road			Existing Backlight			House Vertical
	Dmax (m)	Eav (lux)	Emin (lux)	Uo	Eav (lux)	Emin (lux)	Uo	Eav (lux)	Emin (lux)	Uo	EVav (lux)	EVw (lux)	EVd (lux)
SOX Baseline	41	3.48	0.61	0.18	3.64	0.52	0.14	2.16	0.25	0.12	1.38	1.9	3
Luminaire 1	42	4.5	0.63	0.14	4.48	0.81	0.18	1.88	0.03	0.01	0.53	0.3	1.3
Luminaire 2	28	3.08	1.29	0.42	2.15	0.38	0.17	0.72	0.01	0.01	0.05	0.1	0.1
Luminaire 3	34	5.17	1.1	0.21	3.08	0.3	0.08	0.23	0.1	0.03	0.04	0	0
Luminaire 4	30	3.81	0.64	0.17	2.97	0.1	0.03	1.78	0.03	0.01	0.55	0.1	2.5
Luminaire 5	38	6.65	1.1	0.16	6.28	0.61	0.1	1.93	0.04	0.02	0.61	0.2	2.5
Luminaire 6	40	4.44	0.69	0.15	4.33	0.53	0.12	1.34	0.04	0.03	0.48	0.2	1.5
Luminaire 7	42	6.2	1.1	0.18	5.75	0.8	0.14	0.71	0.03	0.04	0.12	0	0.3
Luminaire 8	41	5.4	0.65	0.12	5.5	0.61	0.11	1.81	0.03	0.01	0.19	0.2	0.3

Dmax = New design maximum spacing
Eav = Average illuminance over calculation area
Emin = Minimum spot illuminance in calculation area
Uo = Overall uniformity
Evav = Vertical average illuminance on test house front
Evw = Vertical illuminance on bedroom window (1st upper left of luminaire in test house)
Evd = Vertical illuminance on front door

Response

The before and after visualisations were constructed as a virtual reality drive round each street covering about half the village roads and were able to demonstrate to the Community Council and the Forestry Commission that the new lighting would reduce light into upper floor front bedroom windows. The overriding consensus of the residents has been that this reduction is a great benefit.