Barriers to Using Photosensors

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Photosensor dimming of fluorescent lamps has been an available control option since the advent of electronic ballasts for fluorescent lamps in the early 1980s.

Despite popular enthusiasm for daylight and case studies documenting energy savings from dimming, photosensor products have not been widely installed by building professionals. The reasons for this lack of use include:

added cost of dimming systems in both materials and installation labor
risk of investing in a newer technology
belief that occupants dislike automatic lighting control
perception that automatic dimming controls are unreliable or just don't work properly

The LRC has recently completed the first phase of the Daylight Photosensor project that focused on the technological barriers to photosensor use. The LRC analyzed photosensor operation as a complete system, which includes room geometry and window location, electric lighting layout, ballast dimming response, and photosensor characteristics. A major part of the project was to establish a data base for photosensor performance data. The LRC established a testing method to characterize photosensor performance. Eight photosensors representing the majority of products available in the U.S. market were tested.

Results from the Daylight Photosensor project show that poor performance is a major barrier to the widespread use and acceptability of most photosensor products. Although researchers can describe the proper functioning of a daylight photosensor system, many manufacturers appear not to have incorporated the theoretical knowledge that has been published. At the outset of this study the LRC did not know which characteristics contributed to poor performance. The LRC found no standard performance or technical specifications, no standard test procedure, no standard commissioning procedure, and no detailed guidelines for commercial building illumination applications.