The iconic, compact incandescent light bulb is dead: meet the next generation replacement of fluorescent light bulbs that are brighter, more efficient, longer-lasting, and mercury-free, as described recently by Tim Dawson
“Today fluorescent tubes are widely used for some domestic and much commercial and retail store lighting because of their durability and greatly improved efficiency compared with incandescent bulbs. Their energy-saving potential has now led to the widespread promotion of the use of domestic compact fluorescent lamps (CFLs). A considerable amount of electrical energy in standard incandescent light bulbs produces infrared radiation and heat, rather than visible light, and it was therefore desirable to find a more efficient and durable alternative. The present moves to replace this type of domestic lighting have been proposed against the background of ever-increasing energy costs and for the potential environmental benefits. Fluorescent lights are considerably more economical to run, but less aesthetically pleasing compared with the familiar tungsten light bulb. CFLs are self-contained for, unlike fluorescent tube lights, their start-up circuitry is built into the lamp base. Compared with incandescent lights, CFLs offer appreciable energy savings
as well as lasting considerably longer before failure. For example, it is usually suggested that a 12-watt CFL should replace a typical domestic 60-watt tungsten bulb, which it will far outlast. CFLs are also available as direct replacements for most other types of incandescent bulb, even for candle bulbs, with the exception of miniature and the more elaborately shaped ones. Most people are aware of general descriptions of fluorescent tube lights as ‘daylight’, ‘warm white’ or ‘cool white’, but these categories can be more precisely defined by the correlated colour temperature (CCT). The CCT is defined as calculated temperature of a black body radiator whose perceived colour most closely resembles that of the source being assessed, measured in degrees Kelvin (ºK). One disadvantage of CFLs lies in the fact that, although they switch on instantaneously, full brightness is not attained immediately, the full warm-up time (3–5 min) of these lights depending greatly on the ambient temperature. Unless more expensive special types are selected, their light output cannot be controlled using standard dimmer controls. In addition, there is a perceived potential environmental problem with their disposal as they still contain small amounts of mercury. There are also some reports that visually impaired people find that the light from CFLs gives less contrast to their field of view than tungsten lighting, leading to problems in reading small script. Improvements in tungsten filament bulbs have been achieved, in particular with the development of quartz tungsten halogen lamps in which the filament can be run at a higher temperature than
is practical for conventional bulbs… Despite the improved efficiency of halogen bulbs compared with normal tungsten bulbs, the EU intend that they too shall be phased out for domestic lighting by 2016. CFL lights may be the best option for domestic lighting at the moment, but it seems probable that solid-state devices will start to replace them in the next 10 years, in view of the rapid progress that is being made in their development and the greater efficiency and durability they could afford.” This is an extract of a review article, first published in issue 1, 2010 of Coloration Technology. To read the full article for free, visit: www.interscience.wiley.com/ journals/colorationtechnology. To subscribe to the journal, email: editorial@sdc.org.uk. A special issue on lighting is planned for 2011 (see p.2).
lighting focus
Energy efficient lighting
FACTS: ■ American Thomas Edison and Englishman Joseph Wilson Swan both obtained patents for the incandescent lamp between 1878 and 1879; while Swan successfully sued Edison over the invention, he later sold the rights to his patent to Edison ■ The traditional incandescent light bulb loses over 90 per cent of its energy in heat ■ If every incandescent light bulb in the world were replaced by a compact fluorescent lamp, we could reduce our annual energy consumption by 728 terawatt-hours and cut lighting’s energy footprint by 27% ■ Sept 2009 saw the multi-year EU phase-out of energy-inefficient light bulbs; they will be gone from the shelves altogether by 2012 Source: Greenbag.com (Sept, 2009)
Issue 2 | 2010
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