Daylight sensors in conjunction with well designed lighting system can maximize the qualities of daylight; prevent its drawbacks all the while using the whole system as efficiently possible without compromising user comfort.The highest efficieny can be reached in environments with ample daylight coming through windows. The function of the sensors is to measure the amount of daylight available and increase the illumination when there is bright sunlight, and reduce it when it is darker. This does not provide energy savings during the day when high brightness levels are needed, but the savings made by reduced energy consumption during the night are a strong motivating factor for retailers. This also ensures that people passing the shop are never glared by overly bright shop windows, as is often the case at night. The level of illumination during the darker hours is attracting, provocative and interesting without being too intense and visually disturbing. This visual comfort means that passers-by will not turnaway from glaring window displays but rather move closer to take a look.
The basic functionally of these two sensors is to ensure a determined level of illumination, although both operate on very different principles. Daylight sensors adjust the level of illumination according to the amount of daylight available within a space, whereas constant illuminance sensors ensure that a set level of illumination is delivered throughout the entire lifetime of a lighting system.
Similarly to presence detectors, these sensors can be used independently or as part of a complex control system. The advantage of these sensors is that they make sure light is only provided where and in the quantity needed, never more, never less. This opens up a huge potential for energy savings, especially in stores with access to a large amount of daylight.
There are two ways in which daylight sensors can be used : on the shop floor and in the shop window. Both uses guarantee energy savings as well as making the lighting far more visually comfortable for customers.
On the shop floor, daylight sensors are used to regulate the general lighting by reducing the amount of artificial light according to the daylight available. This is done by the system being set to provided a certain level of illumination, and if that is provided in part of in full by daylight, the artificial lighting can be dimmed or switched off. In many stores, there is in fact a great amount of daylight available, meaning that energy consumption can be reduced and significant savings made.
However, no matter what changes occur, accent lighting must remain at full illuminance to ensure that the attracting,contrasting and modelling effect is maintained at all times.In larger stores and supermarkets, where daylight cannot penetrate the full depth of the space, it is appropriate to use a cascade system. There are ways to calculate the general amounts of daylight to reach each point of a store from its source, be it a window or skylight, according to which particular dimmed levels of illumination can be sent in each group of luminaires. Alternatively, more sensors can be used to control each group precisely.
The highest efficieny can be reached in environments with ample daylight coming through windows. The function of the sensors is to measure the amount of daylight available and increase the illumination when there is bright sunlight, and reduce it when it is darker.
This does not provide energy savings during the day when high brightness levels are needed, but the savings made by reduced energy consumption during the night are a strong motivating factor for retailers. This also ensures that people passing the shop are never glared by overly bright shop windows, as is often the case at night. The level of illumination during the darker hours is attracting, provocative and interesting without being too intense and visually disturbing. This visual comfort means that passers-by will not turnaway from glaring window displays but rather move closer to take a look.
During the lifetime of a lighting system, it is natural that the level of illumination provided decreases. This is the case regardless of the type of light source used and due to the ageing and dirtying of optical parts and lamps. However, it is possible to incorporate into an LMS the constant illuminance function, which maintains a defined level of illumination throughout the entire lifetime of the system. This is achieved by over-dimensioning the system at the design stage, deliberately choosing luminaires that can provide higher than required levels of light. The sensors act to regulate the illumination, at the beginning of the system's life by reducing the amount of light emitted, the end of the system's life by increasing the illumination.
