Improving your Lighting Street Lighting. Public lighting is one of the greatest consumers of energy and the greatest emitters of carbon. Changing to LED.

Improving your Street Lighting

Public lighting is one of the greatest consumers of energy and the greatest emitters of carbon. Changing to LED street lighting is more energy efficient, it is also more reliable and

requires less maintenance once installed – which is good for everyone, not just the environment.

The use of LED lighting in other cities around the UK have resulted in an average 50% reduction in energy costs with a predicted 35% saving in their carbon footprint as a result of these changes. Also LED street lighting helps reduce traffic

accidents, crime and the fear of crime, improving safety for all, due to the white LED lighting producing clearer and cleaner light

Introduction

VEM LED Lighting The Power of Illumination

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LEDs were invented by NASA in 1962 as low power sources of light for control panel

status indication. More recently they have been developed for high power applications

in vehicle lighting and now road lighting.


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In recent years much effort has been used to improve energy efficiency and decrease energy consumption. This has resulted in new legislation in the European Union on energy efficiency in general, but also for the lighting sector. This Directive will phase out a number of products with poor energy efficiency within the very near future, such as high pressure mercury lamps, which are widely used in road lighting. Switching to LED lighting with their increased luminous efficacy makes them a viable street light source that offers excellent energy savings. LEDs also provide other advantages such as reduced maintenance costs and longer service life (No replacement of lamps).


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Typical Returns on Investment (ROI) are 3 to 7 years (depending to the price of electricity and type of lamp in use). It can be expected that electricity prices will increase in the coming years, bringing down typical return times even further.Our LED lamps are constructed to have a lifetime of up to 60,000 hours of light output. The specially designed aluminum heat sink with optimised heat dissipation for the led lamp keeps the lamp operating at ambient temperatures of -40 to + 65c well below the critical current and temperature requirements. Because of these electrical properties and our heat dissipation design our lamp is extremely durable.

Last but not least, our lamps contain no hazardous substances such as mercury, which are commonly needed in conventional lighting solutions.


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Over a 15 year lifetime you will need to replace lamps which are an enormous amount of waste and cost. Maintenance for conventional lighting mainly consists of replacing the light source, the bulb. The lifetime of conventional lamps typically is about 8,000 - 12,000 hours, equal to average use over 2-3 years. Our LED light sources have a life time up to 60,000 hours, typically 12-18 years for street lighting. Less replacement of lamps means less maintenance, fewer road closures and therefor less congestion. Furthermore, LED lighting is much better able to withstand mechanical impact than conventional lighting . Corrective maintenance due to the failure of damaged bulbs is thus reduced to a minimum.


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With ever increasing costs of traffic management and H & S related costs when relamping, the saving in

maintenance frequency equates to a very substantial amount in any council maintenance budget.

The lower operational expenses provide a substantially lower Total Cost of Ownership (TCO)


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The International Commission on Illumination (CIE) has recently published a Technical Report recommending a System

for Mesopic Photometry based on Visual Performance. This new CIE Mesopic photometry is valid between 0.005 – 5

cd/m2, that is, it covers luminance encountered in outdoor street lighting. The new mesopic system provides for the first

time the means to evaluate lighting in terms of an internationally accepted system of mesopic photometry.


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MESOPIC VISIONIn medium light intensity areas the eye’s spectral sensitivity lies somewhere in the area between night vision and day vision. This is often true at dusk and dawn or under street lights and in our homes. The eye responds not only to brightness, but to the spectral distribution of incoming light when deciding when to shift between the Photopic and the Scotopic states

Mesopic Photometry


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This vision is called Mesopic vision and is due to both rods and cones being required for vision. Traditional methods of using ‘Photopic Lumens’ to describe light intensity in such an area grossly underestimates the light intensity, as it totally ignores the contribution of rod cells to vision or the ‘Scotopic Lumens’.Scientists at the Lawrence Berkley Laboratory developed a factor called Scotopic/Photopic [S/P] ratio. This ratio helps convert traditional Lumens into actual lumens (Pupil Lumens)perceived by the eye under Mesopic light conditions and gives a more accurate estimate of the amount of light


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Photopic Lumens * [S/P ratio] = Pupil LumensHere are various light sources S/P ratio. This ratio determines the

apparent visual brightness of a light source.

This is why a lower watt LED, which produce a high S/P ratio, appears as bright or brighter to the human eye, than a High Pressure Sodium of more than twice the wattage. They just don’t have the spectrum of light needed to illuminate objects properly and elicit the optimum response from the human retina in Mesopic lighting conditions. EXAMPLE60 Watt LED 106 lm/w – 6,360 [Photopic] * 1.96 [S/P]= 12,465 [Pupil Lumens]150 Watt HPS 90 lm/w- 13,500 [Photopic] * 0.62 [S/P]= 8,370 [Pupil Lumens]


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The most important metric of efficiency is the wattage required to provide the desired light

levels. In other words, “Pupil Lumens (Scotopic Lumens)on your street/per watt” is more important than “lumens per watt of the

Lamp (Photopic Lumens)”. The basic principle is a high S/P ratio for

maximum energysavings.

Photopic Lumens * [S/P ratio] = Pupil Lumens


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150W HPS VS 40W LED

= 13,000 X 0.62 = 8060

Photopic Lumens S/P Ratio Scotopic Lumens

= 4, 010 X 1.96 = 7860

Photopic Lumens S/P Ratio Scotopic Lumens

150w HPS

40w LED


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LEDs provide a higher quality of lightLED’s provide large energy & CO2 savings

LED technology offers the ultimate solution. No other light source allows you to improve optical performance while reducing energy consumption and maintenance.


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Whether you’re directing a new lighting project in your city, or developing a private property that requires outdoor lighting, please get in touch, our experienced professionals at VEM Lighting can go over your project specifications and brainstorm whether an LED solution would be cost effective and smart for you.

We would be more than happy to provide a free, strategic, and thorough consultation about your needs. Please give us a call, or email us to plan your next steps


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Thank

You

Improving your Lighting Street Lighting. Public lighting is one of the greatest consumers of energy and the greatest emitters of carbon. Changing to LED.

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