Efficient Outdoor Lighting Sources

From Swikipedia

Introduction

The efficient and effective use of electrical lighting outdoors can offer major energy and cost savings. New, much improved light sources are now available which provide considerably more light per unit of energy. Most newer fixtures offer better light control, putting light where it is needed rather than wasting a great deal of the light produced by the lamp. Replacement of older fixtures and lamps with the newer, improved ones can greatly improve efficiency.

Brief Description

Energy Efficient Outdoor Lighting

Some useful tips for energy efficiency in outdoor lighting are:

 Use photo-sensors with fluorescent, high-intensity discharge, or low-pressure sodium lights.

 Make sure outdoor light fixtures have reflectors, deflectors, or covers to make more efficient use of the light source and help reduce light pollution.

 Use timers and other controls to turn decorative lighting on and off.

 Use outdoor solar lighting where and if applicable

Energy Efficient Outdoor Lighting Sources

Lamp efficiency is measured in lumens per watt. A lumen is a unit for measuring the amount of light; a watt is a unit for measuring the amount of electrical energy used. The lamp that gives the most lumens per watt is the most efficient lamp.

1. High Pressure Mercury Vapour (HPMV) Lamps

In an HPMV lamp, mercury, along with argon gas is used within a quartz glass tube. This tube is mounted within an outer bulb of borosilicate glass. Light is produced when electricity is passed through gaseous mercury. These lamps have a moderate efficacy of approximately 50 lumens/watt. The colour rendering index of a HPMV is not very good but it is better than that of HPSV lamps. The life of a typical HPMV is about 12000 hours.

These are very popular in outdoor lighting applications like street lighting, parking areas, lawn lighting and in godowns, storage yards, docks. The new fluorescent lamps of today have a much better efficacy than HPMV.

2. High Pressure Sodium Vapour (HPSV) Lamps

In HPSV lamps, light is produced when electricity is passed though a mixture of mercury and sodium vapours. Main source of light from the HPSV lamp is the sodium D-line and the light that is produced covers a good part of the visible spectrum. However, it has a poor colour rendering index. These lamps are characterized by high efficacy of around 100 lumen/watt and have a long life.

Most common uses include street lighting, security lighting, industrial lighting, public lighting, storage yards, docks and station platforms.

3. Metal Halide Lamps

These are also known as ‘metal arc’ lamps. Metal halide lamps belong to the high-intensity discharge (HID) category of lamps. In these lamps, high pressure mixture of mercury vapours along with other metal compounds known as halides is contained in a compact arc tube. These lamps have high efficacy and the light produced by these lamps has a natural white colour.

These are commonly used for spot lighting in areas like city centres and parks. These are also widely used in factories where high colour rendering indices are required. The disadvantages of metal halides are that they have a relatively high cost and a short life ranging from 6000-15000 hours.

References:

http://data.nextrionet.com/site/idsa/is052.pdf

http://www.energysavers.gov/your_home/lighting_daylighting/index.cfm/mytopic=12020