Lighting engineers should aim to provide the appropriate quantity and quality of light in relation to the required visual task, in a way that is cost-effective throughout the life of the installation, energy efficient, and environmentally sound. The choice of lighting class for an installation should recognise that the visual task varies over time, so that different classes may be suitable at different times. Techniques to reduce luminaire outputs during specific periods include the use of multi-lamp systems, with variable numbers of lamps switched on, and dimming by reducing lamp current. Dimming can be applied to high-pressure sodium, metal halide, and fluorescent lamps. A new scheme is being introduced to the county of Lancashire, England, which will dim street and road lights between midnight and 6am. According to the extent of the scheme, it is predicted that annual energy consumption should be reduced by about 7% to 9%. In the fairly near future, the author hopes and expects to see: (1) general acceptance of the case for dynamic control of lighting levels; (2) efficient solid state HF equipment for all lamp types, with easy control of switching and dimming; (3) sophisticated control systems, using mains-borne or radio signals; and (4) direct links between lighting controls and traffic flow measurements.
Samenvatting