Sodium Vapour Lamp and CFL

Sodium Vapour Lamp and CFL

Sodium Vapour Lamp

• A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.
• They are some of the most efficient lamps in the world. They have an efficiency of up to 190 lumens per watt compared to an incandescent street lamp which has between 15 and 19 lumens per watt.

There are two varieties of such lamps:

– Low-pressure sodium lamps: They are highly efficient electrical light sources, but their yellow light restricts applications to outdoor lighting such as street lamps.
– Low-pressure sodium lamps only give monochromatic yellow light and so inhibit color vision at night
– High-pressure sodium lamps produce a broader spectrum of light than the low-pressure lamps, but they still have poorer color rendering than other types of lamps.
• Sodium lighting has the highest efficiency of all lighting.

How it works?

• The tube is made of borosilicate glass to withstand pressure and temperature and contains some sodium metal, neon and argon.
• When the lamp is switched on, the sodium vaporises and an arc is established.


• Low pressure sodium lamps:

– Outdoor lighting, security lighting, long tunnel lighting (the light seems to give less fatigue in tunnel driving than white lights flashing by at close proximity).

• High Pressure sodium lamps:

– Outdoor lighting, municipal lighting, home yard lighting, high bay lighting


• Good efficiency (lumens per watt).
• Smaller size than LPS or fluorescent, the HPS fits into many fixture types.
• Can be retrofitted into older Mercury Vapor fixtures.
• Better bulb life than LPS lamps.

CFL (Compact Fluorescent Lamp)

• CFL, energy-saving light, and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb;
• Some types fit into light fixtures designed for incandescent bulbs.
• The lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and compact electronic ballast in the base of the lamp.
• CFLs use one-fifth to one-third the electric power, and last eight to fifteen times longer.

There are two types of CFLs:

• Non-integrated ballast CFL: It is the type of CFL technology that we typically call a “plug-in.”

This means you will purchase the ballast separate from the lamp and the ballast will be configured in the fixture. This is similar to linear fluorescents but is far smaller than linear ballast.

• Integrated or self-ballasted CFL: These are created to replace incandescent and halogen lamps.

Literally, take out the incandescent or halogen bulb and put in a CFL bulb in the same socket.

In order for these CFLs to work in a regular medium base screw socket, a ballast has to be integrated into the CFL.

How it works?

• In a CFL, an electric current is driven through a tube containing argon and a small amount of mercury vapor. This generates invisible ultraviolet light that excites a fluorescent coating (called phosphor) on the inside of the tube, which then emits visible light.


• Efficiency.
• Savings.
• Pollution reduction.
• High quality light.
• Versatility