Why street lighting is important

The street light is often automated in such a way that when it dawns, it goes off automatically and when dusk comes, it lights up. This however is not the case to all street lights as some of them depend on being switched in order to function properly. Whatever the case, street lights are very important and sometimes basic parts of our lives because of their significance.

To begin with, street lights are basically for lighting purposes. They are very beneficial especially at night considering the state of nature. With the current state of things, there are quite a number of cases of insecurity. The people who take part in bringing insecurity often take advantage of the dark to cause chaos and further injure people. It is only in a few cases that crime always happens in broad daylight or when there are lights. When a place is well lit, it becomes quite difficult to attack because the security officers and even members of the public will be able to easily spot the attacker and sue them in a court of law. Street lighting products therefore help to boost security.

Street lights are also important in avoiding accidents. This is especially true in traffic places where both motor cars and pedestrians coexist. Since pedestrians never have torches, street lights enable drivers to see them and thus drive carefully to avoid knocking them down.

Conventional lighting is costly – household example

Despite its higher initial purchase cost, an in depth analysis into LED technology reveals that it is economically, environmentally and technically feasible to invest in LED’s now.

Cost of bulbs: LED bulb has a much longer life (30,000 hrs) than an incandescent bulb (2,500 hrs). So over the total life of one LED bulb, one will have to purchase 12 incandescent bulbs:

Bulb Type Bulb Life Cost/Bulb Cost of bulbs over 30,000 hours
Incandescent 2500 hrs $4.90 $58.80
LED 30000 hrs $28.35 $28.35

bulbs-cost

Cost of electricity: A 6 watt LED bulb gives the same intensity of light as a 50-60 watt incandescent bulb. For an average price of 0.12 $/kWh and average use of 10 hrs/day, the cost of using 45 incandescent bulbs would be $972 per year while the cost of using 45 LED lamps would be $116.6, a savings of $855/year or 88%!

Bulb Type Hours/Day Watts/Bulb Cost of Electricity (US Average) Bulbs in Household Cost/Month Cost/Year
Incandescent 10 50 0.12 100 $81 $972
LED 10 6 0.12 100 $21.6 $116.6

Conventional lighting is costly – Street light example

There are four major drivers to the cost of a street lighting system:

1)    Material cost of bulb, poles and electrical wires and labor cost of installing the light – the cost of installing one street light pole is generally around $4,000. It depends on the height of the pole, the rated power and efficiency of the light, type of foundation needed and length of wiring from the nearest source of electricity. When the nearest source of electricity is too far away as in rural communities it is obvious to install solar powered street lights instead of laying down miles of wire to energize the light.

2)    Cost of energy consumed by the bulb – LED Street light consumes 80 watts and produces 5600 lumens of high quality light. By comparison the 209,000 street lights of Los Angeles use 197,000,000 kWh of electricity every year at the rate of 250 watts per hour. Cost savings in electricity costs by adapting the LED alternative is what is propelling Los Angeles and many other cities towards LED lighting systems.

Added to this is the fact that LPS lights that produce the most light per watt have a Color Rendering Index (CRI) of ‘ZERO’. For good visibility they need to be combined with incandescent bulbs. The 5% efficiency rating of incandescent bulbs pulls down the efficiency of LPS lights as well. LPS lights are thus not suited for general purpose street lighting.

Visual evidence of the superiority of LED lights

LED-lights-superiority

The function of providing security is compromised with lights with low CRI. Police forces dislike low CRI lights because they make it impossible to tell colors apart. Yellow is the only color that is reflected. If an object does not reflect yellow light it appears black. Disruptions in the road are also difficult to visualize because the road and the dents all appear yellow! Poor contrast and color rendering necessitate that more powerful lights are needed to achieve the objectives of street lighting. Powerful lights in turn lead to glare which again compromises the ability of the human eye to see objects clearly. Indeed in areas where security is important mercury and metal halide lamps are preferred despite their inefficiencies and are rapidly being replaced by LED lights that cost a fraction to operate and maintain.

A comparison of good CRI lights shows that LED lights outperform the others by a wide margin on all parameters.

LED Lights HPS Mercury Vapor Incandescent
Lumen 5600 28000 28000 5600
Watts 80 250 400 400
Lumens/Watt 70 112 70 14
Wastage % 0.00 0.50 0.50 0.50
Wasted Light 0 14000 14000 2800
Actual light availability (Lumens) 5600 14000 14000 2800
Available Lumens/Watt 70 56 35 7
Hours of operation per night 10 10 10 10
Cost of electricity ($/kWh) 0.10 0.10 0.10 0.10
Annual Consumption (kWh) 292 913 1460 1460
Annual electricity charges ($) 29 91 146 146
Available Lumens/$ 192 153 96 19
Cost per 100 Lumens 0.52 0.65 1.04 5.21
Wastage (kwh) 0 456.25 730 730
Wastage ($) 0 45.625 73 73
Average Life Span (years) 12 5 4 3

3)    Cost of replacing burnt out bulbs and disposal of bulbs – We may not realize it but the cost of monitoring and replacing bulbs can be very high for street lights. Los Angeles spends 42 million dollars for monitoring and maintaining 209,000 street lights. This works out to more than $200 per street light per year.  The reason for the high cost is that street lights are placed at a height that necessitates the use of a cherry picker to carry workers to the light and a U haul truck to carry the cherry picker. Research shows that LPS lamps last 6000 hours less than HPS lamps leading to higher maintenance costs. Besides ‘zero’ color rendering ability, this is an important reason why LPS lights have not become widely accepted.

Cost of replacing one bulb = Cost of replacement bulb + Salary of 2 people + rental of cherry picker + rental of U haul truck = $800 (Assuming cost of one bulb to be $150).

Cities have found that funds available for maintenance have been frozen while expectations of service quality remain unchanged. Technology offers the only way out of the dilemma. Remote monitoring systems pare the cost of physical verification of lights while LED technology has extended the life of each light to 12 to 15 years from the current 5 years. The city of Ann Arbor had estimated that the savings in maintenance costs are higher than the savings in energy.

4)    Environmental impact of lights – The first 3 are easy to estimate while the fourth is not. Carbon dioxide emissions, mercury and heavy metal release in the environment, cost of treating water, land and light pollution, impact on ecosystems and human health- the ramifications of the lighting decision are manifold and covering all of them here is not possible. Suffice it to say that on all of these parameters LED lighting systems outperform all others.

Why LED lights are better than normal lights?

night-street-lampThe light which is used in houses is created by incandescent sources. A filament will be there inside a bulb which is thin and fragile. To generate light, electricity is passed through the conductor in a bulb. But, they consume more energy. Compared to these bulbs, LED lights have more and more advantages. The formation of LED light is different than normal bulb lights. The semiconductor inside this light gives the color to it.

These are becoming more popular because they consume less energy, provides less radiation, more reliable and gives more durability. They do not get damaged frequently.

Solar LED Street Lighting – The best of all Worlds

solar-lamp Besides from uniting all the advantages cited above, the sunRvest Solar LED Street Lighting (SL2) eliminates totally electricity costs for the lifetime of the LED (up to 50,000 hours) and all the civil works involved in digging trenches, lining electrical cables, connectors and electrical meters, thus eliminating all the reliability issues and costs of maintenance associated with it.The sunRvest SL2 is an All-In-One 20-60 Watt solar PV module charging an 8-40Ah battery with an intelligent charge controller that enables autonomy up to three days of overcast weather conditions. This low 12V battery system ensures safety and powers an advanced 20W LED producing 2,000 lumens in normal mode and 400 in dim mode.

It is designed to withstand the harshest and most extreme environments has to offer from blistering heat to driving rain, hail and sub-zero temperatures. Whatever the environment is, rugged construction is up for the challenge. Its internal components offer IP65 weather protection and its external components are built with marine grade aluminum and stainless steel mounting bracket.

The All-In-One concept and mounting bracket reduce dramatically the cost of installation labor and transportation costs thanks to its compact dimensions and weight.

Related Links

What is a LED?

LED versus traditional lamps

The true cost of LED Lighting

Street Lighting Design Guideline – Part 1

Street Lighting Design Guideline – Part 2