Development of computational algorithm for prediction of photosensor signals in daylight conditions Younju Yoon a, 1 , Ji-Hyun Lee b, 2 , Sooyoung Kim c, * a Samsung C&T Corporation, Construction Technology Center, Seoul, South Korea b Graduate School of Culture Technology, Korea Advanced Institute of Science and Technology, Daejeon, South Korea c Department of Interior Architecture & Built Environment, Yonsei University, Seoul, South Korea article info Article history: Received 7 January 2015 Received in revised form 22 February 2015 Accepted 24 February 2015 Available online 5 March 2015 Keywords: Photosensor signal Lighting control Daylight conditions Shielding abstract This study aims to develop and validate an annual photosensor performance simulation method (APPSM) to compute the photosensor signals for a lighting control system under various daylight conditions. A series of computer simulations using PSENS, which is a simulation program within Radiance software were conducted and field measurements were performed under various daylight conditions in order to validate the simulation results of APPSM. Results indicate that the photosensor signals predicted by PSENS and APPSM showed a strong linear correlation. Prediction results by APPSM generally consisted with the results field measurements, although slight differences between them existed under particular daylight conditions. The differences in photosensor signals between the prediction by APPSM and measurement effectively decreased as shielding conditions were applied to photosensors. A strong linear relationship existed between the photosensor signals obtained from prediction by APPSM and the field measurements. The prediction models for the photosensor shielding conditions were acceptable with a significance level of 0.01. The majority of percent differences between the measured and simulated photosensor signals were within 10% under clear and partly cloudy sky conditions. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction A daylight responsive dimming control system, which maintains a design level of illuminance at the task surface with the use of electric lighting, can significantly reduce the electric lighting use in spaces where daylight is a useful source of illumination [1e 7]. Daylight associated with electric light which is controlled by a daylight dimming system contributes to occupants' visual comfort, psychological satisfaction and work productivity [8e15]. Despite the energy saving potentials and occupants' satisfaction obtained from the daylight dimming control system, it has not been widely used in commercial buildings due to the difficulty in the calibration and optimization of the system performance and malfunction of control system devices [16e19]. For the daylight dimming system, the ideal location for a pho- tosensor would be on the workplane but this position is inappro- priate because the photosensor would likely be disturbed or shaded by activities in the room. Thus, the photosensor is mounted on the ceiling rather than the workplane to minimize interference from activities in the room. Controlling workplane illuminance with a sensor located on the ceiling complicates photosensor control [20e25]. The correlation of the illuminance levels between the workplane and ceiling is strongly influenced by the position and spatial response of the photosensors [4,20,23,26e28]. Therefore, a proper calibration of a photosensor is critical to ensure reliable operation of lighting control system and lighting energy savings. In order to achieve a target light level at the workplane, the calibration of the photosensor for a particular sensor position and orientation for optimum operation adjusts the control algorithm, which is based on sensor signal to ballast output relationship [29e31]. * Corresponding author. Tel.: þ82 2 2123 3142; fax: þ82 2 313 3139. E-mail addresses: younju.yoon@samsung.com (Y. Yoon), jihyunlee@kaist.ac.kr (J.-H. Lee), sooyoung@yonsei.ac.kr (S. Kim). 1 Tel.: þ82 10 9379 3371. 2 Tel.: þ82 42 350 2919. Contents lists available at ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv http://dx.doi.org/10.1016/j.buildenv.2015.02.030 0360-1323/© 2015 Elsevier Ltd. All rights reserved. Building and Environment 89 (2015) 229e243