Since the discovery of fire, man-made light has seen lots of evolution in giving humans the best in terms of convenience and energy.
Not until the invention of the electric incandescent light bulb which only came into being in the 19th century, the light had only been available for use in the form of flames licking the tips of torches, candles or oil lamps. Using electricity as a source of energy to produce light that can be used in a convenient form is perhaps one of man’s greatest inventions. This has greatly influenced the way businesses are run, houses are built and has doubled the activities and output of man’s work.
Through a series of various inventions from various scientists and Thomas Edison, the incandescent bulb came to become the platform on which modifications of lamps would take place. Today, lamps are generally classified under 3 factors: temperature, gas discharge and solid state.
Lamps under temperature include the incandescent and halogen lamps and the flood lights, technically known as reflector lamps. The light emitted from the incandescent lamp is produced by heating a filament wire with electric current until it glows. Various materials used as filaments have included carbon and platinum, and later the tungsten filament. Basic variables involved testing the filament and keeping the space within the lamp conducive by removing air to avoid oxidising the filament or replacing it with an inert gas, like halogen, to increase its efficiency. The lamp foot was also designed to be either screw (coded as E) or pin (coded as B). Today, the incandescent lamp come in many variations in shape and size, having lots of time since its invention to undergo different tests. However, only about 5 to 10% of the energy used by the conventional incandescent bulb is converted to visible light radiations; the other percentage is lost as heat. Demands on energy also grew with the increasing rate and spread of industrialisation and the human population, making it pertinent to create ways in which light could be used with as little energy as possible, and without compromising its luminous characteristics.
In the later years of the 19th and the beginning of the 20th centuries, alongside experimentations on the incandescent bulb, scientists discovered that light can be produced by passing electric discharge through an ionised gas in a tube whose insides are coated with powder. Some gases included neon, sodium and mercury, and powder, phosphorus. By the 1970s, fluorescent tubes were produced for residential purposes, and the compact fluorescent light (CFLs that go by the generic name energy saving bulbs) was designed (by Edward Hammer at GE) to lessen the bulkiness of the fluorescent tube.
Unlike the incandescent and fluorescent lamps which produce light with filaments and gases, solid state lighting refers to light produced by semiconductors which are either light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs) or polymer light-emitting diodes (PLEDs). Though the first practical LED component was developed in 1962 by Nick Holonyak at GE in the form of red diodes, and later yellow and green diodes, the invention of the blue diode in the 1990s led to the discovery that white light can be created by coating the blue diode with phosphor. Shortly after, it was also discovered that a combination of red, green and blue LEDs produced white light. Over time, researchers worked on how to develop the efficiency of the LED, and in 2009, an arm of Philips Lighting featured an LED replacement for a 60W incandescent bulb.
One of the most elusive things in purchasing lamps is the belief that higher wattages give brighter lights. The efficiency of a light bulb is a ratio of the measure of the light it emits (lumens) to the power it draws (wattage). A little calculation of how wattages are measured would help in the appreciation of LED lighting. The table below represents the typical luminous efficacy (lumens/watt, lm/W), i.e. how efficient a lamp is, of various types of bulbs.
The incandescent bulb, for example, has an average luminous efficacy of 15lm/W. This means it only emits 900 lumens by using 60W of power. On the average, it will take the fluorescent lamp to yield the same 900 lumens using 15W only. On the same scale, an LED would require only 8W to emit the same amount of light.
Not only do the LEDs save more energy, they have been reported to last between 25,000 to 100,000 hours, and are capable of operating between a voltage range of 50 to 2000volts. They also come in different shapes and sizes which include bulbs, tubes, recessed fittings and customised luminaires, and applications include use in home lighting, automobiles, traffic control lights, street lighting, camera flashes and advert screens.
Undoubtedly, LEDs are one way to solve the problem of high energy consumption in Nigeria. Replacing incandescent and fluorescent lamps by LEDs would save tonnes of energy and billions of cash for the country. In 2015, former Minister of Power, Prof Chinedu Nebo said that the use of low-emitting diode (LED) bulbs across the country would free 1,200 megawatts (MW) of electricity valued at ₦500billion for industrial and commercial use. This means that replacing incandescent and fluorescent lamps by LEDs would save tonnes of energy and millions of cash to invest for other purposes.
It took several millennia before the development of electrically generated light. But barely two hundred years after these inventions, one of man’s greatest ideas would usher in the use of the LED, and would make the incandescent bulb and fluorescent tube become as historical as oil lamps and candles.