The Lighting Laboratory of the School of ECE NTUA presents an Innovative Photosensor

Innovative photosensor with adaptive field of view in respect to its position, using a new methodology and mathematical functions which correlates LED’s light output with the power consumption.

Harvesting daylighting can significantly reduce the energy use especially in office buildings. Nevertheless, the daylight responsive systems are widely misunderstood and they have been characterized hastily as problematic systems. The lack of knowledge and comprehension of these systems is a great withdraw against their widespread use and a lost opportunity for energy savings. Scope of this research is to develop an automated photosensor for the optimal exploitation of daylighting aiming at greater energy savings within the installed lighting system in various types of buildings.

A new type of photosensor has been developed which is capable to adapt different fields of view in regard its position on the ceiling and used in experiments and real case rooms. In that way selecting the proper field of view of the photosensor in regard its position the ratio of the lighting levels between the working plane and the ceiling can remain relatively constant for various types of sky for the most time of use of the lighting system.

Figure 1. The designed photosensor with the variable field of view

A number of experiments are realized inside a scaled room. The developed photosensor is placed on the ceiling and a photometer on the working plane underneath the photosensor. The signal of the photosensor and the illuminance values on the working plane are been monitored and recorded constantly for many cases of fields of view and positions of the modified photosensor.

Part of the ongoing research is the development of a model for controlling the luminous flux in an artificial lighting system, the optimization of the spatial response of the new designed photosensor as well as its placement in the room.

Figure 2. An example from the set of the ongoing experiments

Figure 3. Flowchart of the proposed methodology

Furthermore, while the efficiency of the Lighting Emitting Diodes (LED) is increasing and new installations are being implemented, their control due to the adoption of daylight harvesting systems, have not been sufficiently examined yet, although this can reduce further energy consumption. A crucial parameter for improved performance is the proper matching of a dimming system with the luminaires used, since this can significantly affect energy savings not only among various luminaires with T5 tubular fluorescent lamps but also among various LED luminaires.

This research tries to quantify energy savings among different LED and T5 fluorescent luminaires that are commonly used with daylight harvesting systems in offices and investigate their impact on power quality. Measurements are performed estimating the mathematical function which correlates their light output with their associate power consumption. Using the measured data, a set of hourly annual simulations can be performed in combination with the new type of photosensor with adaptive field of view.

Figure 4. Relative consumed power versus light output ratio for LED luminaires

For more information please contact: Prof. Frangiskos Topalis, Tel. (+30) 2107723627

Lighting Laboratory website