Determination of Optimum Sector Size for Automatic Lighting Controls

Automatic lighting controls can significantly reduce operating costs in commercial buildings. However, the design of these dynamically operated lighting systems has not kept pace with advancements in equipment. This paper focuses on determining how many lights should be grouped into sectors and controlled as a unit in order to minimize the life-cycle cost of an automatically controlled lighting system. The analysis is based on occupant behavior patterns, the cost of the lighting controls, the energy costs, and a decision criterion based on life-cycle cost.

Occupant switching patterns in the morning and afternoon were experimentally determined at a lighting control demonstration at the World Trade Center (WTC) building in New York City. The experimental procedure used to estimate the occupancy probability distributions at the WTC site is described in section 2. Section 3 develops a general analytical model for determining how large to make independently controlled lighting sectors in order to most cost-effectively use the scheduling control strategy. In Section 4, the model is applied to the occupant behavior patterns measured at the WTC site. Section 5 discusses the significance of the results; the final section summarizes the study.