Wireless Sensor and Actuator Networks for Lighting Energy ...

solid red horizontal lines and dashed cyan lines in the same plots represent the
occupant’s preferred lighting and the ±5% boundary respectively. As soon as any sensor
reading deviated from the occupant’s specified preference by 5%, new iterations of
lighting optimization were triggered to bring the light back within the ±5% range. It is
obvious that the closer the desks to the daylight simulating structure, the more
susceptible to the extraneous light the sensors would be. Nonetheless, the light was
maintained well within 5% of each occupant’s preferred lighting during the entire test.
The percentage of energy usage of the system during the test compared to the
original all-on/all-off lighting configuration is shown in Figure 9-24. Only 33.3% of
energy was used to deliver occupants’ preferred lighting before daylight was available.
The energy consumption reduced while harvesting daylight, and the minimum energy
usage of 28.9% was achieved when the light output from the daylight simulating
structure was at the brightest level.
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