Alternative strategies for artificial lighting using electronic ballast

Antonio Almeida, A. Gomes Martins, Paulo Rodrigues, and Eliseu Ribeiro, Instituto de Engenharia de Sistemas e Computadores, Portugal

Keywords

Abstract

A secondary school in Portugal has been designed according to energy efficiency criteria. It incorporates several passive solar devices both for thermal comfort and daylighting, such as, for instance, thermal masses, natural cross-ventilation of classrooms, south windows provided with external and internal shading and reflective blades, skylights, light ducts. Besides, the main support systems have high efficiency, as the artificial lighting system. It has electronic ballasts and correspondingly adapted fluorescent tubes. A data acquisition and control system provides, among many other functions, automatic control of artificial lighting, according to occupancy of rooms and light availability, both internal and external. In the design, dimming has not been considered, though it seemed the "smarter" approach, namely owing to the potential good use of the computational system for this purpose. ?he paper presents the alternative between dimming and qualified on-off control, both from the economic and the visual comfort points of view. Both energy consumption estimates and subjective matters such as the roles of manual overriding for light control and the existence of discrete steps of luminous flux have been taken into consideration in the analysis. They are the basis for concluding for the advantage of the present implementation of light control in the building. Some remarks are made about the conditions to be verified for the validity of the conclusions in other cases.