Louvre LED luminaires make sense

In search for good artificial light sources, mankind spent lot of time development, starting from torches, via bulbs and finally to low-pressure discharge lamps. And one of the sources belonging to last category are linear fluorescent lamps, which have proven to be suitable for interior lighting. For the installation of these light sources were needed to prepare the luminaires to ideally utilize their lumen output and light distribution. The development of such luminaries took decades and in the end remained an ideal solution for professional office lighting - luminaire with aluminum parabolic louvre. At its times, louvre luminaire actually became something like the standard for office application. The advantage of these optical systems has increased with the advent of personal computers, using correct optical louvre for preventing light reflections from monitors.

However, the present time in all segments of market requires effective, economically efficient and environmentally friendly technology products and production processes. This trend did not avoid lighting technology, so manufacturers of modern luminaires fitted their products with LED chips. These are currently light sources with the best possible luminous efficacy in lumens per watt.

Development of luminaires with LED chips went through several phases. One of the first phase was equipping of conventional luminaires with the LED tubes. However, such solution is not very suitable, because the fluorescent tubes have a different distribution of light than the LED tube. This leads to great differences in light curves of this retro-fit, compare to original luminaire and original developer intentions. Also, we often encounter problems related to heat dissipation of LED tubes, which leads to a shorter life of the LED chips. Problem can also be with certification, when luminaires are certified for T8 sources, and this luminaire is equipped with LED tube, the original certificate loses its validity

Presently most suitable approach is to use a module of any length with number of LED chips by needs. Thus formed thin and long LED module can be fitted into luminaires and adjust optics for desired light distribution. This structure is used even for very popular LED panels, where the LED module is oriented by its light side into edge of light guiding plate (so-called edge-lid technology) that uniformly illuminates the whole surface of the LED panel. LED panel is comparable to classic luminaire with opal cover for 4 18W fluorescent lamps. Not only by its appearance, but also with very similar light distribution.

 

Luminaire with opal cover was of course used even during the times of fluorescent lights. Especially when the customer demanded luminaire with homogenously lighted surface. Or they were suitable for spaces with require of higher IP coverage. Using of luminaire with opal cover was at the price of lower quality of light distribution. Luminaire with louvre will evenly illuminate a larger area, while the luminaire with opal cover directs a great part of luminous flux directly below the luminaire. This also applies to the LED panels.

 

 

When we take a look on a technical solution of the classical louvre luminaires, it is apparent that the optical part is designed to use as much as possible light from fluorescent lamps. It emits light across its whole surface, and more than half of the light is directed into the interior of luminaire. This light is returned back by reflectors, which are precisely constructed to direct light output below luminaire, where illumination is needed.

Difference in structure of LED luminaire and classical luminaire is basically just in placement of LED module at the bottom of the luminaire. LED chips are oriented by whole lighting angle directly onto illuminated area. Louver for the LED luminaire is primarily designed just for optimization light distribution, but with smaller part of reflections, so with lower loss of light compare to luminaire for conventional fluorescent lamps. Due to this solution, we can get same quality of light distribution, but with greater efficiency than from classical luminaires.

 

Even when we want to minimalize glare (UGR factor) louver luminaire has advantage against LED panel - mainly for the softer light and greater illuminated space, which is achieved by mentioned light distribution. It is possible to achieve a similar effect also with LED panel, but only with special nano-prismatic diffusing cover (for price of losing the advantage of easy cleaning of luminaire). Nano-prismatic covers have lower light permeability, thus luminaire efficiency decreases and for the same wattage light output is lower. When we use better materials to compensate this loss, price for LED panel will be higher.

Louver luminaire may not just be recessed into the drywall and raster ceilings. One of the classic types for indoor lighting, but for installation on solid ceilings is surface-mounted louvre luminaire mounted with 2 lamps with an input of 36W or 58W. Surface-mounted luminaire using LED technology can be produce with the same principles. Moreover, thanks to the smaller light source located entirely in the lower part of the body we can produce surface-mounted luminaire lower than the classical luminaire for lamps.

For prestigious buildings can be used luminaires with a more elegant body, but with identical optical system. In addition to the appropriate light distribution can also satisfy the demanding tastes of customers with greater design requirements. Designed fixtures with louvre are well suited for suspended installation. For this installation is possible to add another LED module on top of the luminaire - intended to illuminate the ceiling. Indirect lighting softens the entire interior space and the users reaches a very pleasant and also functional lighting.

After a summary of benefits is certain that the usage of the louver as the optical system for the LED luminaires retains the advantages of classical luminaire in the form of optimum light distribution. Unlike conventional lamp luminaires we avoid losses by reflection, which is necessary for directing light into the right angle. And still we use benefits of LED technology in terms of savings and efficiency. Also, the light distribution is better than we can get from the LED panels.

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