Light pollution has not occupied the limelight like water and air pollution. Even people who religiously recycle their waste and try to minimize their carbon footprint are often unaware of this silent enemy. Yet the impact of this lesser known evil is no less than its more famous peers.
Sample Some Data
Light pollution is a quite new topic when talking about outdoor lighting systems.The lighting systems should illuminate their purpose only like streets, sideways, parkways, parking spaces and so on. A lot of products don't care about the amount of light that is wasted by not directing the light on the area that should be illuminated. Scientists who are watching the sky, starts and planets are complaining that they can't see their objects of interest at night any more because the world is getting so bright. Just imagine you sit in a dark room and look outside the window, you can see quite well what is going on outside. As soon as you switch on the light in the room, the outside is getting dark. Another point is that peoples sleep is affected by light. Humans are "programmed" to sleep and rest at night when it is dark. If it is not dark anymore our hormone system is getting confused. The receptors, that are measuring the lighting level, tell us if it is time to rest or to be awake, detect a sufficient lighting level to be up although it is two o'clock in the morning and we should sleep and rest. To reduce the influence of light pollution, agreements have been signed.
BE CARFUL when choosing a luminaire for your application. Watch the downward, upward light ratio. Streetlights should have a very good one (0% at 0°). Decorative luminaires are not illuminating an area but giving emotion to it. They are not that powerful and can therefore have a worse ratio than streetlight luminaires.
There are an estimated 35 million street lights in United States and the $ value of the electricity wasted works out to a stupendous $ 958,125,000! All this is public money collected from tax payers. Instead of making life difficult for scientists, killing insects and damaging the environment, this money could provide employment to 19,162 people at an annual salary of $ 50,000. Clearly, light pollution is not just about dark skies and the environment alone.
Besides wasting light what else does light pollution do?
Reduced visibility Light that is not directed downwards can strike the eyes of the viewer horizontally, thereby, increase glare and reduce clarity of vision. So be careful that your luminaire is having a good glare rating index, especially if you want to choose streetlight luminaires.
Over lighting – If a large percentage of the light is wasted more powerful lights will be needed to achieve the objective of sufficient illumination. If light pollution were curtailed a 2000 lumen light could easily substitute one producing 2800 lumens. LED lights that direct all their output downwards are, therefore, more efficient than either LPS or HPS lamps.
Fixtures that are directing the light to more directions can cause a waist of light, by means up to 70%! As a result many more poles are needed to provide a sufficient lighting level on the ground, not talking about the additional cost of the fixtures and wiring that is adding too.
Each additional pole costs around $4,000 to install! Lighting engineers have realized the need to curb the wastage and are increasingly recommending directional Light Emitting Diode based lights.
Impact on Biological Rhythms – Animals and plants have a 24 hour cycle programmed into their genes by millions of years of evolution. Human beings for example secrete more growth hormone during sleep. 10 – 15% of human genes are believed to be affected by light! The deleterious impact of unwanted light on delicate biological systems is to be expected. A hormone Melatonin is secreted by the pineal gland. This hormone is responsible for reducing the amount of estrogen secreted at night. Excess light is thus linked to lower melatonin levels resulting in higher estrogen secretion, premature puberty and has also been implicated in breast and prostate cancer. No time of the day is now suited for nocturnal insects. Devoid of their predator detection system they have lost the ability to evade their predators. This in turn has serious consequences for not just insects but their predators too. Research has demonstrated that a million insects are killed due to the 50,000 street lights of Zurich. You can extrapolate to estimate the impact of the 35 million street lights in the United States.
Combating Light Pollution
The fix for Light pollution is surprisingly easy. Here are the options
- Install protective skirting around existing lamps
- Install box type lamp shades that direct light downwards
- Install LED based outdoor lights
The cost of material, manpower to rental cost of equipment to install either a skirting or box shaped lamp shades is US $ 800 - 900 per light. No benefit other than reduced light pollution and more available light on the ground is forthcoming from this exercise. But pay attention to the lighting distribution curve. Make sure it is still the same, otherwise your street or pathway won't be illuminated equally any more. Future maintenance and energy consumption remain unaffected. It is far better to replace HPS lamps with LED lighting devices that by design direct light downward, consume 30 to 70 % less energy.
LED light sources have no UV part in their spectrum. Insects feel attracted by UV light. They collect around streetlights, which are equipped with discharge lamps at night. The CRI of a streetlight is not that important. High pressure sodium lamps with a single peak regarding their spectrum have been used for years because the important point is not to see the color of the car first. Most important is the uniform illumination of the street and furthermore the possibility to detect obstacles, the visibility of people running over the street or just other cars to prevent accidents. When it comes to the maintenance of streetlights, the UV-free topic is coming up. Insects cause the luminaire to get dirty really fast. With the use of LED streetlights the maintenance costs will reduce dramatically while the lighting quality will stay high.
LED systems provide the ultimate answer to light pollution. Asymmetric lighting angles are recommended. A wide beam asymmetric light distribution will illuminate the street best. According to the height of the luminaires and the width of the street, the number of lanes and the amount of traffic, the ideal LED streetlight can provide a lighting system with as little poles as necessary to illuminate the street well.
Many adopters of LED technology have done so to eliminate the hassle of replacing bulbs. Given their long life these are semi permanent light fixtures. With LEDs there is hardly ever a dark moment. Made of a cluster of light producing devices these fail gradually over a period of time and the likelihood of all the LEDs failing together is very remote.
Intelligent Lights for a Smarter World
Full spectrum light, excellent color rendition, high lumen per watt consumed, wide angle of light, zero wastage of light, zero mercury pollution, no moving parts or fragile filaments, very little risk of breakage, low power consumption, ability to transmit data and facilitate networking, possibility of remote management and intelligent controls, possibility of changing light output to optimize power consumption and visibility, possibility of changing light color on the basis of ambient light color to maximize contrast and enhance visibility – LED lighting systems are the holy grail of lighting technology on more ways than one.