When it is said that a product is highly efficient, we generally only consider it in terms of energy consumption. We do not usually refer to its effectiveness and whether it accomplishes the marked goal. But when we talk about emergency lighting and signage, it is the whole installation what should be efficient. Therefore, the following factors should be considered:
- The set of luminaires
- Their location
- The quantity of used luminaires.
If a luminaire has very low power consumption, but you need a high number of appliances to meet the minimum lighting requirements, the installation itself is not efficient anymore. Conversely, if you achieve to reduce the number of luminaires installed, but they still consume too much energy, the installation will not be efficient whatsoever. For this reason, the key is to achieve an optimal balance between the consumption of the luminaire and the area covered.
Correct projection of the light to avoid wasting it.
To improve the illuminated covered area, it is essential to control uniformity. Regulations require a minimum of 1 lux on evacuation routes and 0.5 lux of open area illumination. In both cases, the uniformity demanded in every spot must comply with the lux max /lux min < 40 relation. In other words, the maximum illumination level, at any given spot, must not be over 40 times higher than the minimum illumination level at any other spot.
Imagine a project where the highest value of an evacuation route is 39 lux at a certain point and the minimum 1. The relation lux max/lux min equals 39. Therefore, the calculations are valid. Nevertheless, at the point where the 39 lux are being projected you would only need 1 lux and, therefore, you would be wasting 38 lux. Ideally, we should project the light of the extra 38 lux to another point of the same evacuation route in order to increase the separation distance between two luminaires and reduce the number of luminaires in the installation. The same applies to open area illumination.
The correct way to optimize the lighting output used consists of designing the correct lens. By doing so, it is possible to distribute the light as required, so there is the exact amount of light needed in every spot and the rest can be used to cover other spots.