Lighting Control Systems to Save Energy in the non-Residential Sector : State-of-the-art, Field Studies, and Simulations

Abstract: This thesis examines the energy-saving potential for lighting when using traditional indoor LCSs in non-residential buildings. In the study, an overarching theoretical framework is used that distinguishes between energy efficiency and energy saving, as well as between energy use for lighting and functional illumination. This framework also includes the hypothesis that user acceptance is a determinant of energy saving for lighting, so an examination of the user role is included in the thesis.In the first part of the research, a literature review explores technical and non-technical issues relating to lighting control systems. The review concludes that the energy-saving potential of LCSs lies between 10-93% compared to no lighting control. In general, simulation studies overestimate the savings compared with field studies, possibly because of design, commissioning and installation issues in real-life scenarios. Properly working systems need some degree of manual control or override to improve acceptance, while malfunctioning systems lead to very low levels of acceptance and are apparently subject to sabotage. To overcome such issues, the literature review also proposes a design workflow for the specific case of daylight harvesting systems.The second part of the research includes field and case studies in real-life scenarios, which confirmed most of the literature review findings. The studies highlight that the overarching definition of ‘occupancy strategies’ may be misleading, whereas a clear semantic differentiation between ‘presence’ (automatic on-off) and ‘absence’ or ‘vacancy’ (automatic off) is needed, even in scientific publications. As an additional conclusion, the field studies showed a controversial role of auxiliary devices for advanced LCSs, since they may lead to high energy use for standby. In extreme cases, the standby may offset the gain from adoption of more efficient light sources. The issue of standby is addressed in the third and final part of the thesis, consisting of simulations based on real occupancy data in individual office rooms. The simulations show that, at growing efficiency of light source, the additional savings afforded by LCSs become smaller. In such a situation, the standby may account for over 30% of the total energy use for lighting. Standby can be reduced or eliminated by choosing the right LCS, integrating it in the Building Management System (BMS), and designing the electrical system so that the lighting system can be completely switched off.To secure savings from LCSs through a high degree of user acceptance, the thesis concludes that proper training of specialists of LCS designs is required. Such specialists should be involved from, preferably, the early design stage of the BMS. Finally, proper budgets for monitoring and verification activities should be allocated, as this would allow timely tackling of project issues and iteratively add knowledge in the field.