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How CFL Bulbs Work

Everyone knows that one of the biggest advantages of a Compact Fluorescent Lamp (CFL) is its low energy consumption. It also produces less heat, has a much higher life than incandescent or halogen lamps and produces pleasant light. Replacing incandescent lamps with CFLs results in cost savings in terms of electricity bills that together with its long life offset the higher purchase price of the lamp. How does a CFL bulb save energy? The answer to this question lies in the technology.

What is a CFL?
Fluorescent lamps and CFLs are very similar. In fact, a CFL is just a compact version of a fluorescent lamp that is smaller and easier to install. The glass tube is bent and both its ends are fixed onto a base that holds the ballast and can fit into standard incandescent bulb sockets. Therefore, there is no major difference between the working principle of a fluorescent lamp and a CFL.

Light without heat:
Traditionally, light is generated by heating something, whether it is a lighted candle or an incandescent lamp, something has to be heated to the point where it emits light. In an incandescent lamp, electricity is passed through a filament, which is usually made of tungsten. This in turn heats it to a point where it glows and produces light. To prevent the filament from burning, the whole setup is in a sealed vacuum bulb.

In incandescent lamps most of the energy is converted to heat and the light produced is just a byproduct of the whole process. It is not surprising then that only about 10 to 12% of the electrical energy consumed is converted to light and the rest is just wasted as heat. In physical terms, an incandescent or halogen lamp is very poor when it comes to lighting efficiency.

In fluorescent lamps, light is generated using a very different method without the need to heat anything. It consists of a sealed tube with a coating of fluorescent material on the insides and an electrode at each end. The tube contains mercury vapor.

When a voltage is applied across the electrodes, the gas inside the tube gets ionized, conducts electricity and in the process generates ultraviolet (UV) light. When the UV light hits the phosphor coating on the inside of the tube, the material glows to produce visible light.

When the lamp is switched on, a component called the ballast produces a high voltage between the electrodes, which is necessary for the initial ionization of the gas in the tube. Once the lamp starts operating, the current and light output can be maintained using a much lower voltage. Unlike incandescent lamps, the little heat produced in a fluorescent lamp is just a byproduct and most of the energy is converted into light.

Due to their much better efficiency in converting electricity to light, which is about 40 to 50%, a CFL that produces the same amount of light as an incandescent lamp consumes two-thirds less power and produces very less heat in comparison. How does all this translate into savings?

CFLs save energy in two ways:
The light output of a lamp is measured in lumens, which is related to the way the human eye perceives light intensity. A lamp’s efficacy is measured by the amount of lumens produced for each watt of electricity that is consumed. For CFLs, the efficacy is about 50 to 70 lumens per watt when compared to an incandescent lamp, which is just 10 to 17 lumens per watt.

To get the same amount of light, you can replace an incandescent with a CFL that has just one fourth its rated wattage. A 100 watts incandescent lamp can be replaced by a CFL of just 25 watts without any reduction in brightness.

In places with warm climatic conditions, there is another way in which CFLs indirectly save electricity. Incandescent lamps tend to heat the rooms in which they operate much more than CFL lamps. Using CFLs instead of incandescent lamps means lesser work for air-conditioning equipment and hence further power savings. This is very significant for offices and commercial establishments which are usually air-conditioned and brightly lit with a large number of lamps.

A CFL saves energy due to its higher efficiency, producing the same amount of light with much lower consumption of power while generating very little heat as a byproduct. This results in lower electricity consumption for lighting and cooling. Now that we know how a CFL lamp saves energy, it makes sense to replace incandescent and halogen lamps with CFLs. Their compact size and compatibility with existing lighting fixtures should make the change easy.