21 June 2018

The Origin and Evolution of Electric Light Bulbs

Some claim that certain engravings found in the tombs of ancient Egypt suggest that the people of that time were able to generate electricity from batteries. and use it to energise a filament in order to provide illumination. Whether truth or fantasy, the devices we recognise today as light bulbs did not make their first appearance until several thousand years later. Contrary to popular opinion, however, Thomas Edison was not, technically, the individual responsible for their invention, and should rather be accredited with the development of the first commercial prototype.

Over 70 years before Edison filed his patent, Humphry Davy invented an electric battery and connected it to a piece of carbon which then produced an intensely bright light known as an electric arc. His success spurred contemporaries worldwide to develop a more practical version, experimenting with different filament materials and containment methods to produce functional and durable light bulbs. Carbonised paper, carbon rods, cotton threads, platinum coils, and carbonised bamboo were among the filament materials used, and were surrounded by nitrogen gas or a vacuum to increase their lifespan. In the end, it was Edison’s race, and in 1880, his bamboo filament vacuum combination with its 1 200-hour lifespan was the first to hit the market.

It was not until 1906, however, that engineers at America’s General Electric Company developed a method to produce the more durable, fine tungsten wire filaments that are still to be found in many of the cheaper incandescent light bulbs in use today. While cheap to produce, however, as the demand for electricity increased and the cost to consumers rose in parallel, it became apparent that, although bright enough and tough enough to provide a practical product, tungsten filaments convert less than 10% of the energy they consume into visible light, radiating the rest in the infra-red spectrum as heat. That their use persists is largely due to their low production costs and suitability for low-voltage use, as in battery-powered devices.

Environmental concerns, however, have prompted many countries to introduce legislation to gradually phase out the production and sale of tungsten filament light bulbs in favour of more energy-efficient and eco-friendly alternatives. One such alternative is the compact fluorescent light bulb or CFL. Designed either in the form of multiple loops or a spiral, although rather more expensive than a tungsten globe, they are also far more energy efficient and will definitely pay for themselves over time.

With no risk of hazardous waste, the tungsten halogen light bulb is another option whose versatility allows its use in applications as diverse as car headlights, projector light bulbs, stage lighting, and motion-sensing security systems. Under power, the halogen atmosphere promotes a reaction in which evaporated tungsten is re-deposited on the filament, thus extending the life of these light bulbs.

For economy, reliability, and longevity, though, the light emitting diode (LED) is a clear winner. Now widely used for ceiling-recessed downlights, to illuminate kitchen cabinets and work surfaces, and outdoor pathways, a recent US study suggests one LED could produce savings of over $100 dollars during its lifespan. Let Eurolux, leaders in this specialised field, recommend your best option.