Today, fluorescent lamps and tubes are found in many homes and commercial buildings. These lamps are gas-discharge lamps that use electricity to excite mercury vapor. The excited mercury atoms produce short-wave UV light that causes phosphor in the lamp to fluoresce, thereby producing light.
Though these lamps are initially expensive, the energy saved brings down the overall usage cost, hence making these lamps a popular, money-saving option.
How a Fluorescent Light Works - Schematic Animation
Types of Fluorescent Lamps
There is a wide range of fluorescent lamps available on the market today. Some of the most common are listed below:
- Black lights
- Infrared lamps
- Bilirubin lamps
- Germicidal lamps
- Tanning lamps
- Glow lamps
- Electrodeless lamps
- Cold-cathode fluorescent lamps (CCFL)
Features of Fluorescent Lamps
Fluorescent lamps process several qualities that in certain situations make them preferable to conventional incandescent lights.
For example, florescent lamps are capable of converting more of the input power to visible light than incandescent lamps and have also been shown to last 10 to 20 times longer than an equivalent incandescent lamp when operated for several hours at a time. Fluorescent lamps also give out less heat than an equivalent installation of incandescent lamps.
Fluorescent lamps can be a physically larger light source than the incandescent lamp can provide more evenly distributed light without glare. Furthermore, fluorescent lamps can be designed in many shapes and sizes.
However, there are also drawbacks associated with florescent lamps, some of which are outlined below:
- When frequently switched on and off, fluorescent lamps tend to age rapidly
- Fluorescent lamps have to be handled with extra care and caution as they contain mercury. If the lamp breaks, the mercury can contaminate the surrounding environment
- Fluorescent lamps emit a small amount of UV light
Manufacturing Process of Fluorescent Lamps
Manufacturing CFLs is a lot more complex and expensive than incandescent bulbs.
The first step involves cutting of the straight glass shells. Then the shells are bent into a U shape. Next the tubes are washed in chemically purified water at 65-75°C (149-167°F).After the wash the tubes are dried for about 25 min at 80°C (176°F).
A coating of fluorescent powder is made using a binder, and purified water is then applied to the glass shells. The fluorescent powder comprises phosphor, which is a mixture containing calcium phosphate, aluminum oxide, polyethylene oxide and dispersion agents.The tubes are dried and placed in a baking machine that maintains the temperature at 550°C (1022°F).
After 3 min, the tubes are removed and a fluorescent-whitening agent is applied. The filament is then slipped inside the tubes. The ends of the glass tubes are cleaned and mounted on a sealing machine so that the filament can be fitted inside the tube. The tubes are vacuumed in an exhaust machine to enable mercury and argon to be supplied into the tubes while the cathodes are heated. The mercury can be in the form of pellets or liquid. The heated cathodes convert mercury into gas.
Finally the tubes are sealed using a tipping machine and the electrical components such as the ballast are soldered along with the tubes. The CFLs are closed with a plastic base and sent for quality check.
Applications of Fluorescent Lamps
The following are some of the uses of fluorescent lamps:
- Indoor and outdoor lighting
- Lamps for smart phones, iPads
- Decorative lighting
Environmental Impacts of Fluorescent Lamps
The main environmental concern regarding fluorescent lamps is that they contain mercury and phosphor, thus they are classified as hazardous waste when they have to be disposed. The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal.
Although manufacturers are trying to reduce the amount of mercury used in lighting, they are not yet able to eliminate the need for mercury. Hence the only option to safely discard these lamps is to recycle.
Recycling prevents the release of mercury into the environment. When thrown into the dumpster, trash can or compactor, or in a landfill or incinerator, these lamps will break causing the mercury to be released. In order prevent the release of mercury; these bulbs should be taken to a recycler before they break.
Fluorescent lamps reduce the need for power plants to burn fossil fuels in order to generate electricity, and hence helps reduce emissions including mercury, carbon dioxide and other pollutants that contribute to climate change.
Fluorescent bulbs should be taken carefully to recycling centers, so that the mercury can be safely removed. The other materials (such as glass, metal) in the bulbs can then be separated, cleaned and sold for reuse. Even the phosphor powder, can be separated and recycled. The recycled glass can be remanufactured into other glass products. The mercury can be recycled into new fluorescent lamps and other mercury-containing devices.
Applications of Recycled Fluorescent Lamps
Each component of the fluorescent lamp is reusable and recyclable. The metal components are recycled and sent as scrap to metal manufacturers. The recycled glass components are made into other glass products. Similarly, mercury is once again used to make lamps. Hence recycling helps to save cost and energy.