In the last few years, sales of LED luminaires have increased in all world markets. Light emitting diodes made it possible to produce luminaires that could not be designed during the time of fluorescent lamps, mainly thin LED panels. Customers became very fond of this solution and LED panels began to appear as replacements for office grilles. But is that the only right solution?
In the search for artificial light sources, humanity gradually progressed from the beam through light bulbs to low-pressure discharge lamps. One of the sources belonging to this category are linear fluorescent lamps, which have proven to be suitable for interior lighting. To be fitted with these sources, the luminaires had to be prepared in such a way that they made ideal use of their luminous flux and luminosity distribution. The development of such luminaires took decades, and at the end of it, the luminaire with an aluminum parabolic grille remained the optimal solution for professional office lighting. The grille luminaire actually became a standard for the mentioned use in its time. The advantage of these optical systems has increased with the advent of personal computers, as the correct optical grating prevented light from reflecting off monitors. Today, however, in all fields it requires efficient, economically economical and environmentally friendly technical products and production processes. This trend has not escaped lighting technology either, so modern manufacturers are gradually installing their products with LED chips. These are now light sources with the best possible specific power in lumens per watt. The development of luminaires with LED chips has gone through several phases. One of the first was to equip classic fluorescent lamps with tubes equipped with LED chips. However, such a design is not entirely suitable because the fluorescent lamp has a different light distribution from the tubular LED source. The light characteristics are then different from what the luminaire designer intended. There are also often problems with heat dissipation from LED tubes, which shortens the life of the LED chips used. The current most suitable approach is to use a module of any length with LED chips in quantities as needed. The resulting thin and long module can be installed in the luminaire and the optics can be adapted to its light distribution. This construction is also used in very popular LED panels, where the LED module is oriented with the light part to the edge of the light guide plate, the so-called edge-light technology, which evenly illuminates the entire surface of the LED panel. The LED panel then resembles not only in appearance, but also in the distribution of luminosity a classic luminaire with an opal cover for four 18W fluorescent lamps (Fig. 1).
Figure 1 - Luminosity distribution of the MODUS Q LED panel
Figure 2 - Luminous intensity distribution of the luminaire with opal cover MODUS IKO418600EP
The luminaire with an opal cover was also used in the era of fluorescent lamps. Especially when the customer required luminaires with a homogeneous illuminating surface. Alternatively, they were suitable for areas requiring higher coverage of luminaires. However, the use of an opal cover is at the expense of the quality of the luminaire distribution. A larger area can be used to illuminate a larger area with a grille luminaire, while a luminaire with an opal cover directs a large part of the luminous flux directly under the luminaire. This also applies to LED panels. In Fig. 2 from the computer program WILS 7 it can be seen that the LED panel concentrates the power below itself and relatively illuminates even walls on which lighting is not required.
Figure 3 - Comparison of luminaires of the company MODUS, spol. s ro: LED grid luminaire IS (left) and LED panel Q at the same luminous flux of 3,900 lm
Looking at the technical solution of a classic grating luminaire, it is clear that the optical part is designed to use as much light as possible from the fluorescent lamp. It emits light throughout its surface, ie more than half of the light is oriented inside the luminaire, to which the reflectors are adapted, which return the light reflections back where it is needed.
The design of the LED grid luminaire is different in that the chip module is located at the bottom of the luminaire. The LED chips are oriented in the direction of the illuminated surface with their entire beam angle. The grid in the luminaire is designed mainly for light scattering and curve optimization, but there are no losses of reflections to the same extent as in conventional fluorescent luminaires. As a result, the advantageous light distribution is maintained, but due to the greater efficiency of the grid for LED luminaires, the source is better used (Fig. 3).
Figure 4 - Comparison of the luminosity distribution of the MODUS IS grille luminaire
Figure 5 - Comparison of the luminosity distribution MODUS I418AL600EP luminaire
Even from the point of view of minimizing glare, the so-called UGR factor, a luminaire with a grid construction is more advantageous than an LED panel, especially in softer illumination of the entire space achieved by the already described light scattering. With an LED panel, it is possible to achieve a similar effect, but only with a special prismatic diffuser plate, while, for example, the advantage of easy cleaning of the luminaire is lost. In addition, the prismatic covers have a lower transmittance, so the efficiency of the luminaire decreases and the light output is lower at the same wattage. When using better materials that compensate for this loss, the production cost of the LED panel increases.
However, grille luminaires do not only have to be built into plasterboard or grid ceilings. One of the similar classic types of interior lighting, but for installations on fixed ceilings, is a surface-mounted grid luminaire equipped with two fluorescent lamps with a power input of 36 or 58 W. A replacement for a planted luminaire in LED design can be manufactured using the same principles. In addition, thanks to a smaller light source located completely in the lower part of the luminaire, it is possible to make surface-mounted luminaires lower than conventional tubular luminaires.
For more representative spaces, it is possible to produce luminaires with a more elegant body, but with an identical optical part. In addition to a suitable luminosity distribution, it is also possible to meet the demanding taste of the customer with greater design requirements. Design luminaires with grilles are also very suitable for pendant mounting. For this installation, the luminaire can be supplemented with another light source, this time on the top of the luminaire - designed to illuminate the ceiling. The indirect component of the lighting softens the entire interior space and the user thus achieves a very pleasant and at the same time functional lighting.
After summarizing the advantages, it is certain that by implementing the grating as an optical system in the LED luminaire, the obtained product retains the advantages of a classic grating luminaire in the form of an optimal luminosity distribution. However, unlike conventional tubular luminaires, there are no losses in the reflections necessary to redistribute the light in the right direction.
At the same time, the benefits of LED sources remain in terms of savings and efficiency. Also, the light distribution is better than what can be obtained from LED panels.
The company MODUS, spol. s ro, a MODUS IS luminaire, which replaces classic grille luminaires with its output and dimensions. There are variants for built-in installation in grid or plasterboard ceilings. The MODUS FL luminaire is similar (Fig. 4), which can be added or built in using accessories.
With its power and dimensions, it replaces classic grille luminaires. There are variants for built-in installation in grid or plasterboard ceilings.
Luminaire that can be added or built in with accessories. The luminaire has a unique appearance compared to the classic-looking MODUS IS luminaire.
For surface mounting, which replaces the classic MODUS LLX grille luminaire. Dimensions and adequate performance have been retained for easier replacement in existing installations.
Compared to its predecessor, the luminaire is also 13 mm lower.
An alternative to MODUS LLL, reminiscent in appearance of a single-tube luminaire with a minimalist design.
The design, but at the same time functional luminaire is usually produced in gray for a more elegant look. Installation is possible by surface mounting, or hanging. For only suspended mounting, a variant with an indirect light part illuminating the ceiling above the luminaire is offered. Thanks to the two-circuit connection, it is possible to control the direct and indirect components separately.
The novelty, offered in white, is a luminaire with an asymmetrical luminosity distribution, which is suitable for illuminating school blackboards and other vertical surfaces.