Electric lighting is performed by specialized sources, Figure 1 and is one of the mandatory elements of the engineering infrastructure of urbanized and rural areas. One of the challenges faced by a street lighting designer is choosing the type of lamp to be installed in it. Traditionally, mercury sources have performed this function.
The industry offers serial samples of LED lamps, which, in terms of their lighting characteristics, may well constitute an alternative to them, Figure 2. The experience of their successful mass use in indoor lighting systems becomes a serious argument in favor of their use. To make an appropriate decision, it remains only to check the fulfillment of the well-known provision that the best is the enemy of the good.
The principle of operation of a mercury and LED lamp
A mercury lamp is a gas-discharge arc source, the typical design of which is shown in Figure 3. The source of the luminous flux generated by it is the breakdown channel in mercury vapor in an enclosed space. To enhance light output, change in the desired direction of the spectrum and increase efficiency, the inner surface of the bulb can be additionally coated with a phosphor.
The LED lamp uses radiative recombination of charge carriers in the pn junction of semiconductor materials. To increase the luminous flux, obtain a given radiation pattern, etc. up to several hundred of these crystals are mounted in the lamp.
Both sources use similar methods of generating radiation, which do not involve heating any components with an electric current. As a result, the electrical efficiency of the sources is comparable, and the light output is approximately the same.
Other parameters of mercury and LED lamps
When mercury enters the body, a headache occurs, the gums begin to bleed, and in severe cases pneumonia develops. However, poisoning is possible only with a high concentration of vapors. In reality, it can be created only in a closed room, and even then, if several dozen lamps are broken in it at the same time.
The performance of a mercury lamp as a street source initially presupposes its increased mechanical strength, so it will be quite difficult to damage the bulb.
The reliability of the LED source does not correspond to typical outdoor conditions due to its low resistance to voltage surges typical for such networks.
Conclusion
As you can see, the lighting characteristics of street lighting systems based on mercury and LED lamps are approximately identical. At the same time, in terms of operational properties, the LED source is noticeably inferior to its analog. Therefore, most likely, after the end of a short period of enthusiasm for fashionable LED lighting systems, the desire for a widespread transition to a new type of emitter will end: With the current state of the art, LED lamps are significantly inferior in terms of a set of parameters to mercury lamps, i.e. LED street lighting is possible, but only in some niche areas.