Lighting controls: Their current use and possible improvement

Abstract

The use of automatic lighting controls to modify artificial lighting consumption, either to implement the concepts of Permanent Supplementary Artificial Lighting or to save energy, has been previously proposed by several authors. However, since little quantitative evidence of likely benefits exists, implementation of the proposals has been rare. the increased cost of energy has renewed interest and recent studies at the Building Research Station have attempted to: (a) decide if the use of photoelectric controls would save energy; and (b) define the situations where this might be done cost effectively. A [broad brush] picture of likely waste was obtained by a survey of about 200 offices, visited on at least five occasions each, over the course of several months. the illuminance at desk positions and the prevailing switching conditions were noted, and an estimate of waste was calculated by comparing the data with the known design illuminance. More detailed information of lighting use and apparent waste was obtained by [time-lapse photography] in seven installations; three offices and four teaching areas of different depths and occupancy patterns. Here, waste associated with excessive use during daylight hours and use during unoccupied periods could be isolated and savings predicted for the use of automatic photoelectric controls and time switches. The available hardware for such control has been surveyed and its cost effectiveness investigated in general terms for several types of installation. Predicted savings have been calculated using a simple model of available daylight and it is expected that analysis of more recent meteorological data will provide more precise estimates. the validity of using [daylight factors] as an effective control parameter in these calculations is also being investigated. The results of the studies outlined above are being assessed by installing control equipment in several real working interiors, including three of those originally monitored by [time-lapse] cameras. Energy consumption and user acceptability are being monitored and preliminary results on both counts are promising.