Energy efficient street lighting reduces the electricity demand and is a cost effective method of street lighting system compared to conventional street lighting methods.
In trending years, the gap between power generation figures and demand figures is a matter of concern, as it implies the failure of power supply system to meet the power demand, thus a warning about lack of conservation of energy.
According to the international agencies lighting accounts for 19 percent of the global electricity and 25-30% of home energy consumption.
What is Energy Efficient Street Lighting?
Street Lighting is necessary for visibility of objects in dark places or situations. Efficiency refers to how well the street light is produced for a given input power.
In conventional lamps like incandescent and gas discharge lamps, most of the electricity is wasted in terms of heat and also since ballast requires high voltage at the time of starting these consumes more power.
Energy Efficient Street Lighting
Energy efficient Street lighting includes the use of more illumination from less power lights by replacing high power consumption street lights like incandescent, high discharge lamps, etc. This is also used in various control technologies like GPRS or GSM or SCADA based controls. It is also replacing high power lighting accessories by low power devices such as electronic ballasts, fixtures, etc.
3 Energy Efficient Street Lighting Techniques
Replacing an ordinary bulb
In incandescent lamps, 90 percent of the electricity is wasted as heat rather than street light and also 3-5 times more power is consumed. So replacing these bulbs with energy saving bulbs gives efficient energy street lighting system. There are two main types of energy efficient street lights or blubs. 1. Compact fluorescent lamps (CFL) 2. Light Emitting Diode (LED) lamps
Compact Fluorescent Lamps (CFL) These are the most common type of energy saving lamps. These are available at different sizes, shapes and ratings and uses more advanced technology than the incandescent lamps.
They use 75 percent less power and last 10-15 times as longer as an ordinary bulb. CFL bulbs take high current during starting and low current while working in mean time.
Compact Fluorescent Lamps
CFL bulbs consist of a glass tube with phosphorus coating (for color rendering), filled with argon gas and mercury vapor.
Electronic ballast is used to create high voltage during the starting to create an arc between electrodes. Its operation is same as all the fluorescent lamps. When this lamp is powered, electricity running between the electrodes excites the mercury vapor. This mercury vapor causes to emit an ultraviolet light which in turn causes visible light by phosphorous coating.
LED Lamps (Light Emitting Diode)
These are also the most energy efficient and most durable type of bulbs, the only constraint being their expensiveness. These are different from ordinary lamps because they don’t get burn-out or get hot.
They produce equivalent illumination as incandescent lamps while consuming 80 percent less electricity compared to incandescent bulbs and fluorescent lamps. LED lamps last longer as their life is as long as 50000 hrs of life cycle rating.
Below figure shows how these lamps are rated for same light output or illumination. Higher the rated wattage more is the current drawn from the supply.
Comparision of Lamps by wattage
For the same illumination, incandescent lamps are rated at somewhat higher than the LED and CFL bulbs so the energy consumption is high in this case.
Compared to CFL lamps, LED lamps are rated somewhat lower so the energy consumption is too low in this case. Hence energy efficient lamps conserve the supply as compared with ordinary lamps. And also in life cycle perspective these lamps reduces CO2 emission and mercury pollution while going through fossil fuel burning process.
Using Lighting Controls
Another key for reducing street lights energy consumption is using the street light energy as much as needed with available street lights. This is possible by keeping various sensing devices to switch the lights such as motion sensors, infrared sensors, automatic timers, etc. These sensors sense the day light availability, presence of humans and other living species, instruction for remote operating, etc.
Wireless Street Light Control
GSM/SCADA/GPS based centralized systems also monitor and control the lighting system efficiently and reliably to save energy as shown in figure. Auto intensity of street lights can also be controlled through setting timer which gradually reduces the intensity as reducing traffic on late nights and ensures completely shutdown at morning periods.
Replacing with energy efficient accessories
Accessories of lamps such as ballasts, fixtures, etc also play an essential role in energy saving. Ballasts or chokes to be installed with lamps, including non integrated ballasts in CFL bulbs should be electronic or low loss copper ballasts to save some extent of energy compared to conventional ballasts. This also improves the power factor.
New way to save energy is by using energy efficient street lights fixtures which uses 75 percent less energy than standard street lights. These fixtures not only increase the illumination by low energy consumption but also protect the lamps for longer life.
This is all about energy efficient street lighting. Re-lamping by energy efficient lamps and ballasts uses advanced control techniques for better street lighting system. Hope that you have understood this concept.