How have lighting fixtures that use electrical energy improved their luminous efficiency and lifespan, from incandescent bulbs to LEDs?

Lighting fixtures that use electrical energy, such as incandescent bulbs, fluorescent lamps, and LEDs, have steadily evolved to improve their luminous efficiency and lifespan. Incandescent bulbs suffered from heat inefficiency and short lifespans, while fluorescent bulbs improved upon this by using ultraviolet light and fluorescent materials. LEDs use semiconductor technology to provide low energy consumption, long life, and a wide range of colors of light, and are now the dominant lighting fixture.

 

Lighting fixtures that use electrical energy have been continuously improved since the invention of the incandescent bulb to increase luminous efficiency and extend the lifespan of the fixture. Luminous efficiency is the rate at which power consumed is converted into light. Light is a type of electromagnetic wave, and visible light is between infrared and ultraviolet light. Modern lighting fixtures are becoming more efficient and environmentally friendly, with a variety of technological innovations.
The incandescent light bulb is a simple structure consisting of a filament inside a round glass sphere filled with an inert gas. When a voltage is applied to the filament, some energy is released from the heated filament in the form of electromagnetic waves. These electromagnetic waves have a continuous spectrum of wavelengths, of which light is about 10% and the rest is infrared, which is heat. Since most of the power input to the bulb is dissipated as heat, the luminous efficiency is very low, and the filament heats up to a high temperature, making it easy to break, which is why incandescent bulbs have a short lifespan. Increasing the voltage applied to the bulb to increase the temperature of the filament increases the percentage of light, but shortens its lifespan. Because of these problems, incandescent bulbs are gradually being replaced by other high-efficiency lighting fixtures.
Fluorescent lamps consist of a cylindrical glass tube containing mercury and an inert gas, with a filament attached to each end. When the thermal electrons emitted by the filament strike the mercury particles, they produce ultraviolet light. When this UV light hits the fluorescent material applied to the inside of the fluorescent lamp, it turns into light. The color of the light varies depending on the type of fluorescent material, and the conversion efficiency of UV light to light varies, which affects the luminous efficiency of the fluorescent lamp. Since fluorescent lamps do not obtain light directly from the filament, the heating temperature can be lowered, allowing them to produce the same brightness of light with about 30% less power consumption than incandescent bulbs. They also emit less infrared light and last five to six times longer than incandescent bulbs. However, fluorescent bulbs also use mercury, which poses environmental and disposal safety concerns.
Light-emitting diodes (LEDs) are made by joining two types of semiconductors, p-type and n-type, and when a voltage is applied, a certain voltage difference occurs between the two semiconductors. When electrons move between them, they release energy equal to the voltage difference as light. Depending on the compounds that make up the two semiconductors, the amount of voltage required or the amount of energy released varies. The magnitude of this energy determines the wavelength of the emitted light, and the light from the light-emitting diode has a single color. LED lights are very popular because of their low energy consumption, long lifespan, and the ability to provide light in a variety of colors.
To use a light-emitting diode as a light-emitting element for lighting, it must be able to emit light in the full range of visible light. This is done by coating a monochromatic light emitter with a fluorescent material so that it emits light like a fluorescent lamp. However, light-emitting diodes don’t have a heating element like a filament, so they have a longer lifespan and lower energy loss than fluorescent lamps. Thanks to advances in LED technology, they are now the mainstream lighting fixtures replacing incandescent and fluorescent bulbs and are used in a wide range of applications.
The evolution of lighting fixtures that use electrical energy continues, with smart lighting systems emerging in recent years to further increase the efficiency and convenience of lighting fixtures. Smart lighting leverages IoT technology to allow users to control their lights remotely, and automated lighting adjustments can maximize energy savings. These technological advances are not only making lighting fixtures more efficient, but they are also helping to improve the quality of life for users.