Energy Glossary

Fluorescent Lamp

Fluorescent lamps use the following mechanisms to produce light: Ultraviolett (= UV) radiation is produced by ionisation of mercury atoms under low pressure by means of a current flow through a near vacuum glass tube. The UV radiation is converted by an inner coating of the glass tube which absorbs the UV and emitts visible light at different wavelengths.

Main properties of fluorescent lamps

Fluorescent lamps are easily scalable between 1 W and roughly 100 Watt power demand. Their efficiency (best available models) is about 75 Lumens per Watt and hence 7 - 4 times better than standard incandescent lamps.

Starting with tube shaped "linear" lamps modern variations have folded or spiraled designs resulting in the so called compact fluorescent lamp which is available in many designs and sockets like the E27 or E14 standard screw in sockets. The modern designs lead to a 1:1 replacement for the standard incandescent lamps.

Light quality has been improved till the year 2000 - since than tiny variants like warmer color adjustment happened but the main problem has not been solved: Fluorescent lamps have a discrete spectrum with a minor continuous background. Emission maxima are congruent with the colors red, green blue and a orange-yellow emission range.

Flourescent lamps have - good production quality assumed - have enhanced lifetimes of up to 10 000 hours until the light output goes down to 50 % of the initial value. Compare that to the 1000 hours lifetime of standard incandescents, 2000 hours for high voltage halogene lamps and 4000 hours for low volt halogene lamps. The lifetime of standard products seems to be nearer to 5000 hours - meaning that modern low volt halogene lamps are competitive from that point of view.

Advantages and disadvantages of fluorescent tubes

Pros are the high efficiency and the larger area of light emission to provide soft and shadowless light.

Cons are the use of mercury which is toxic. The spectrum is just not similar to the continuous spectrum of the sun or incandescent lamps (including halogen lamps) - color rendition is not optimal except for special tubes with higher Ra values but lower efficiencies. Power up cycles are round about 10 000 for the best bread, but realistically a number of 3000 power up cycles is usual for cheaper product series. Fluorescent lamps are areal light sources and cannot be focused as well as the point like light sources like e.g. incandescent lamps or LEDs.

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