Energy-efficient control of solid-state lighting

Lighting control is in the midst of radical change. Presentday state-of-the-art lighting systems tend to be extremely complex. They exhibit very flexible actuation possibilities with many degrees of freedom that can be exploited to answer dynamiclighting needs. However, user interfaces to these systems are woefully lacking. They are frequently denigrated to a panel of buttons that select particular presets that are often cryptically defined, poorly labeled, and seldom desirable. Higher-end lighting systems can provide affordances such as a touch screen to select particular, graphically illustrated presets, but the straitjacketed assumptions that are made often lead to frustration. Most attempts to integrate sensor feedback into commercial systems exploit simple motion sensors that tend to activate all lighting in a space when one occupant moves. This is generally energy wasteful. The converse, turning off all lights when the occupant does not move for a while, may also be a wrong choice that can irritate the user. Today’s crude motion sensors represent a coarse attempt at leveraging limited information and simple context to reduce energy consumption. Balancing precise control and energy efficiency remains a goal in modern lighting systems,1–10 since lighting accounts for 22% of all electricity consumed in the United States.11 The inherent control flexibility implied by solid-state lighting—combined with a rich description of a user’s environment provided by emerging sensor networks—offers a chance to rethink our present modes of lighting control. It also requires us to consider the importance of color and efficacy.12–18 Building upon the inherently digital nature of this technology, we discuss our vision of lighting control and suggest several highly responsive schemes that are adept at meeting users’ needs while mitigating energy usage. Our research aims at minimizing the energy spent lighting while simultaneously maximizing the light source’s usefulness. Figure 1. The lighting network consists of LED light sources, optional incandescent and fluorescent sources, and ambient room conditions (daylight), that are measured by a single or a group of sensor nodes. The latter return intensity and color information to the control node (e.g., a computer) for processing. Here, the intensity is controlled by a link to the artificial-light sources that is bidirectional from either the sensor node or the LEDs.