- Comparison criteria.
- Incandescent lamps.
- Fluorescent lamps.
- LED lamps.
- Comparative summary.
- Typical use cases.
In recent years, existing technologies to light our homes have multiplied. The diversification of compact fluorescent bulbs and the arrival of LED bulbs offer us a wide choice of shapes and types of light... And it is not easy to make choices with such diversity. To compare the different lighting, it is possible to take several points of view: energy bill, impact on the environment, quality of light or even health. This week HandymanDuenchanche reviews these different sources of light so that everyone can then make his choices.
To better understand and compare lighting technologies, it is useful to clarify some concepts. For example, the perceived luminous quality is dependent on several physical factors: continuous appearance or not of the light spectrum, blinking or not of the lighting.
The light spectrum represents all the visible electromagnetic waves emitted by the lamp in the form of a graph with the abscissa frequency (or color) and the ordinate the power emitted. The more continuous a spectrum, the better the rendering of colors. However, since the human eye is made up of three types of color-sensitive receptors, it is possible to have a feeling of white with three precise sources corresponding to these receptors: red, green and blue. It is on this principle that televisions for example work, or multicolored LED lamps. In order to represent this information, a synthetic index exists: the IRC (Color Rendering Index).
In the same way, a light source can be constant, or vary in time. The retina of the eye has a certain persistence of the image, so it can discern a continuous light source from a flashing source only if the blinking is slow enough. Starting from this principle, if a light source flashes fast enough, it will be perceived as fixed by the eye. Despite this, we are not all equal to this phenomenon, and some are more sensitive than others to flashing. This results in increased visual fatigue for sensitive people.
Finally, the power consumption indicated on the packaging is often a misleading value. Indeed, for the same amount of energy supplied, two different lamps will not necessarily produce the same amount of light. This is why the concept of efficiency representing the efficiency of the conversion of electrical energy to light will be preferred in this article. It is also interesting to note that the output of the lamp is not the only one that matters. In the case of low voltage lighting, it will also be necessary to take into account the efficiency of the transformer to judge the energy performance of the whole.
This type of bulbs is historically the first to have been adopted massively for domestic use. To emit light, an incandescent bulb carries as its name indicates, a metallic filament bathed in an inert atmosphere at very high temperature. The metal then emits light with a spectrum that shifts from infrared to blue with increasing temperature. By increasing enough, we obtain a part of radiation emitted in the visible which is acceptable. In spite of this, a good part of the radiation emitted remains of the infrared, which implies a not negligible part of losses. A variant of conventional incandescent bulbs exists: halogen bulbs. The presence at their inner surface of an element of this chemical family makes it possible to recombine a portion of the metal atoms which have sublimated the filament during its heating on the surface of the latter. Therefore, it is possible to increase its temperature, and thus increase the portion of the visible spectrum emitted by the bulb, thus improving its performance.
These bulbs are ideal for visual comfort, with a CRI of 100. In addition, they do not fluctuate, because the filament has a certain thermal inertia which makes its temperature almost constant, even with an alternative power supply like that of the network. domestic electric. At the ecological level, the balance sheet is a little more mixed in the sense that their manufacturing energy cost is quite low, but their electricity consumption remains quite high. In cold weather, these losses will however be included in the heating bill, which limits the scope.
These lamps come historically from neon tubes, which they sometimes misuse the name in everyday language. Their operation is based on the principle that a gas excited by the passage of an electric current emits electromagnetic waves according to a discontinuous spectrum, or line spectrum that is specific to it. In the case of neon for example, much of the emission is in orange and red, so it is not used for home lighting. In order to overcome the problems due to the discontinuous appearance of the spectrum emitted by the excited gases, the solution generally adopted consists in using a fluorescent coating that will re-emit a portion of the light that it absorbs in lower wavelengths. Thus, the present tubes generally contain a mixture of gas rich in mercury vapor as a light emitter, with a fluorescent powder on the walls re-emitting the ultraviolet emitted by mercury in various ranges of the visible spectrum. Depending on the composition of the gas mixture, and phosphors deposited on the tube, these lamps have a CRI that can vary from good to poor. To operate, these tubes need a ballast, which is a device to limit the intensity of the current flowing through them in cruise mode, and to allow their ignition. The latter is external in the rectilinear tubes, and integrated in the base in the compact fluorescent lamps.
The efficiency of these lamps is good, but their overall ecological impact is questionable because of their complexity in manufacturing, and because of the toxicity of the materials composing it. Therefore, these lamps must be recycled by a specialized channel to minimize the release of these elements in nature. In addition, some points may be problematic health: a small portion of ultraviolet can pass the tube wall, which is not good for the eyes. Finally, depending on how it is designed, the ballast can emit a significant amount of waves, which can be embarrassing in sensitive subjects.
LED lamps, as their name implies, use light-emitting diodes to emit light. The acronym LED comes from the English "Light Emitting Diod", and it is sometimes Frenchified in LED. An LED is an electronic component generally based on a semiconductor crystal, one of which is positively doped, and the other negatively. During the passage of the current between these two portions of the component, part of the energy is dissipated in the form of wavelength light, and therefore of defined color. Therefore, a diode that is natively white is not feasible. Two options exist to obtain white: the use of three diodes, a red, a green and a blue in the same medium, or the use of one or more fluors that will complete the original spectrum. It is usually this second option that is used in commercially available lamps that are often made of blue diodes with a phosphor re-emitting in the yellow for the cold white, and a combination of phosphors for the blank models hot. The efficiency of these lamps is generally good, and is close to that of fluorescent lamps. Depending on the type of phosphors used, the CRI of these lamps varies from mediocre to good, so their lighting can be fixed or flashing depending on the way in which the electronics that compose them are designed. Finally, their ecological balance is average in the sense that their yield is good, but their ecological cost of manufacture is high. However, this last point can be offset by their longevity which is very high in the case of good quality lamps.
Typical use cases.
Given the number of parameters, it is therefore difficult to give specific use cases for a particular type of lamp. However, it is possible to come up with some great rules as to whether to use, or not to use, certain lamps. The rest will depend on the personal choices of each.
Thus, we avoid using LED lights that emit a lot of blue in the room of a small child whose retina is more sensitive than that of an adult (just as we avoid blue LEDs in general). In the same way, for people sensitive to radio frequencies, it is better not to use fluorescent lamps as a bedside lamp or as a desk lamp. Because of their heating time and sensitivity to repeated ignitions and shutdowns, they are also prohibited in places where lighting is short-lived: stairs, corridors, lighting on timer. Finally, for all uses where the lighting quality is more important than consumption, it is better to use incandescent lamps: photo or art exhibitions, makeup salon or clothing sales. In case of prolonged use, it is also possible to opt for specific fluorescent lamps with a high CRI (codes 930 or 940 for example).
More generally, in the case of energy-saving lighting (LED or fluorescent), it is interesting to focus on the lighting temperature and the power to determine its choices. Thus, a warm lighting (2700-3500K) and average power will be preferred in living rooms: living room, kitchen... On the other hand, higher lighting temperatures (4000-6500K) and higher power will be interesting in rooms intended for work or storage such as the office, attic or cellar.