Reducing the energy consumed by lighting with gaze-dependent illumination

Initial computational simulations have been performed, as the first step of this project, to compare the energy consumption for two groups of simplified spaces, representing conventional lighting design and the implementation of gaze-dependent lighting strategies.

Conventional design strategies evenly illuminate entire spaces. Gaze-dependent strategies illuminate spaces partially without sacrificing occupants’ visual experience, as the illuminance and uniformity of task areas, as well as the luminance of the visible walls, remain comparable to uniform lighting.

Photometric files of 1500 products, collected from 13 light-emitting diode (LED) downlight suppliers, were categorised into 17 groups according to their beam angles. A square room was created in the Radiance software. Since the amount of light that eventually enters occupants’ eyes highly depends on the physical property of the surfaces of the room, the common reflectance values recommended by the Illuminating Engineering Society were adopted: 20% for floors, 50% for walls and 70% for ceilings.

Luminaires from each group were used in simulations to achieve an average illuminance of 320 lx at 0.7 m above the floor with a uniformity greater than 0.5 across the entire space, representing traditional lighting design. Simulations were then repeated to yield the same illuminance with a 0.7 uniformity only on the task areas, representing Gaze-dependent lighting design.

Simulation results show that gaze-dependent lighting using luminaires with beam angles greater than 60° can reduce lighting energy consumption by an average of 27.69 %, compared to conventional lighting design, and create a similar visual experience.

Further computational simulations are investigating the effects of the number of occupants, viewing direction, etc. on the energy consumption using gaze-dependent lighting. After simulations, psychophysical experiments will be conducted to evaluate the impact of the size of the illuminated field and background lighting on both occupants’ ability to navigate throughout spaces and their holistic, subjective impressions of the environment.

The outcomes of two psychophysical experiments will be compared with the simulation results to determine how gaze-dependent lighting systems could be developed that save the maximum amount of energy while maintaining a pleasant visual environment.

The results will also quantify the extent to which the energy consumed by lighting could be reduced as a function of a number of variables (e.g. size of illuminated field, background lighting, etc.). This understanding can guide the development of gaze-dependent lighting systems, the benefits of which may prove crucial in the coming decades.

The project is funded through the Australian Research Council (ARC) Discovery Project (DP) scheme under the number DP210102193.