Niko Gentile

Daylight harvesting control systems design recommendations based on a literature review

In indoor spaces, lighting control systems are highly effective to reduce electric lighting use. Daylight harvesting systems (DHS) promise to deliver the greatest energy savings. This article presents a review about DHS based on recent scientific and technical literature. The review shows that the energy saving potential of DHS lies between 20-60% in comparison with non-dimmed installations. However, many studies outline serious limitations of these systems such as e.g. limited user acceptance. The review suggests that, during the design and commissioning of a DHS, the following aspects deserve attention: technical robustness, architectural integration and human acceptance. The review concludes that, while further research in the technical area is still needed, the architectural and human aspects have been so far insufficiently studied. The review emphasizes that competent designers and installers, as well as post-commissioning are mandatory to ensure the success of DHS installations.

A field study of fluorescent and LED classroom lighting

Indoor lighting is facing a massive retrofit to LED lighting. Research is needed to assess whether LED-based lighting can promote energy efficiency, boost visual comfort and support biological functions. This field study considered the lighting of four identical classrooms in an upper secondary school in Helsingborg, Sweden. Two classrooms were fitted with state-of-the-art ceiling pendants containing T5 fluorescent tubes and that had a direct/indirect light distribution (the control rooms). The other two classrooms were fitted with an experimental LED indirect lighting system (the experimental rooms). In the classrooms, 72 students aged 17–18 years performed their usual educational activities over a whole academic year. The light environment, electricity consumption, and students’ mood, light perception and saliva cortisol concentration were monitored. The two lighting systems produced only marginal differences. Overall, the experimental rooms were slightly preferred but achieved only small energy savings due to high parasitic losses.

Lighting control systems in individual offices at high latitude: measurements of lighting conditions and electricity savings

This paper presents measurement results of electricity use and lighting conditions in individual office rooms located in Lund, Sweden. The aim is to demonstrate the energy saving potential by using different lighting systems and the satisfaction of users. The measurements are carried out in one empty reference room and four fully occupied test rooms equipped with different electric light control systems. The tested systems include: a presence detector (automatic switch on/off), a manual switch at the door combined with absence detector (automatic switch off), a photoelectric dimming combined with presence detector, and a switchable task light with no ambient lighting except daylight. The four rooms are fully occupied by test persons performing their normal computer-based tasks, and who make a subjective evaluation of lighting conditions in the room and control system once a week. The results for the first monitoring period show that the automatic switch on/off (presence) system is the one yielding the highest electricity use, which repeats earlier simulation results. The photoelectric dimming system which combines a presence detector yields very modest energy savings compared to the presence detector system, a result which contradicts earlier findings but which may be explained by malfunctions and poor sensor position. The room with the task lamp achieves the lowest energy use, which is mostly attributed to the low levels of illumination in the room, which is further confirmed by the test persons. The system with manual switch at the door combined with absence detector achieves the best results in terms of combined low energy use and user satisfaction, and the magnitude of the savings are generally greater than anticipated in earlier simulation studies achieved in the same context.