Aris Τsangrassoulis is a professor of the Department of Architecture, University of Thessaly and director
of the Lab. of Sustainable Design of the Built Environment. His research activity focuses on the effect of
architectural design on building energy balance, daylighting, the development of techniques for achieving
lighting energy savings and the impact of building design and operation on thermal/visual comfort. The
Lab supports consultancy work in daylighting design and building low energy consumption techniques,
based on modelling and simulation.
Coupling between daylight and artificial lighting: Optimizing building's energy efficiency
The reduction of energy consumption for lighting is an important strategy for the overall reduction of
energy consumption and also for the reduction of peak loads. It is usually carried out by adopting a more
efficient technology, better design and of course with through the use of automation systems. One of
these systems is the Daylight control system (DCS) which is controlled by a photo-sensor and is capable
of adjusting the electric lighting level according to the quantity of daylighting impinging on the photo-
sensor. Their target is to maintain a constant illuminance level on the working surface although, quite
often, this cannot be realized as their placement is on the ceiling and their position does not coincide with
the working area they control. The energy savings derived from measurements in office buildings range
from 20% to 62.6% while those estimated from simulations range from 25% to 80%. This potential of
energy savings can improve considerably the energy performance certification class of the building.
The presentation discusses control algorithms, system calibration, the effect of sensor characteristics on
system performance, and energy savings calculation techniques used today. Additionally, the capabilities
of lighting control systems using CCD sensors will be analyzed as well as their ability to regulate human-
centered lighting systems.
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