Making the switch from task illumination to ambient illumination standards: Principles and practicalities, including energy implications

Abstract

It has been proposed that general lighting practice should switch from specifying indoor illumination standards in terms of task illuminance to ambient illumination specified in terms of mean room surface exitance. The reasons for this proposal are reexamined and the energy implications are assessed. To enable comparison of equivalent levels of illumination, it was first necessary to establish mean room surface exitance levels that equate to task illuminance levels as being typical for similar applications. A simulation was developed using AGi32 lighting design software to determine lighting power density levels for providing equivalent illumination by three luminaire luminous flux distributions for three room shapes with three surface reflectance combinations. As anticipated, the downlight distribution was found to be the most efficient way of satisfying task illuminance criteria, but also it was found that uplighting achieves similar lighting power density levels for the equivalent mean room surface exitance criteria if room surface reflectances are reasonably high, indicating that the switch could be made without departing from the lighting power density limiting values currently proposed for efficient use of lighting energy. However, to base lighting standards on low lighting power density levels would have the effect of severely restricting options in lighting practice. Accordingly, a range of lighting power density levels is proposed for lighting standards that would eliminate inefficient use of lighting energy while permitting reasonable levels of design flexibility in lighting practice.

Extending the lighting design objectives procedure for holistic lighting solutions

“…The Lighting Design Objectives (LiDOs) Procedure has been introduced through a series of LR&T papers. 1–4 It is briefly described in the Appendix 1 and a summary document (Supplemental Material 1) with a worked example of application and a bibliography. It is based on the notion that the prime purpose for providing indoor lighting is to generate a light flux field that will stimulate an intended human response, 1,5 and that practitioners may specify such a response in the form of a list of LiDOs, where each objective describes a lighting related response for a selected purpose.…”

“…If these selected target surfaces are to be the only surfaces to receive direct light, then the FRF from these surfaces is the sole source of ambient illuminance. 4,5 Consider a situation where a target surface tgt receives the entire direct flux and the surrounding room surfaces rs may be assumed to be of uniform reflectance ρ rs , then the maximum attainable level of TAIR…”

Light Source Layout Optimization Strategy Based on Improved Artificial Bee Colony Algorithm

“…e main purpose of this paper is to optimize the layout of indoor light sources, and the premise is to model and analyze the indoor LED lighting model. In the process of modeling, the commonly used energy-saving and environmentfriendly LED light source is selected, and many factors such as brightness, luminous intensity, illumination uniformity, and indoor glare value are comprehensively considered [20,21]. Based on the indoor lighting calculation theory [22], the point by point method is used to calculate the receiving plane illumination.…”

Investigating mean room surface exitance values for office lighting

“…Room brightness was classified by Cuttle as perceived brightness of illumination (PBI), 9 an assessment of how brightly lit the space appears. PBI is the same as spatial brightness, 10 the term used in the current study; however, mention is made to PBI in Cuttle's work at times.…”

“…Cuttle has proposed a new interior lighting design procedure, the lighting design objectives (LiDOs), 9 which uses PAI, PBI, MRSE and target ambient illuminance ratio (TAIR) as shown in Figure 1. This study focuses on ambient illumination, investigating PAI, spatial brightness and MRSE in a small office.…”