Wireless Sensor and Actuator Networks for Lighting Energy ...

indicates that 15 fixtures and ballasts are sufficient to light the office under the
following assumptions:
a. The office is 15m in length, 10m in width and 3m in height, and features typical
ceiling/wall/floor reflectance of 80/50/20% [20]. The luminaire mounting
height, which is defined as the height from the worksurface to the fixture, is
1.65m.
b. Each luminaire is equipped with one 4-lamp electronic ballast and four 32W T8
fluorescent lamps.
c. The lamps are generic T8 fluorescent light tubes, such as those manufactured by
Philips [111] and GE [112] with 3500K color temperature and 2660 design
lumens.
d. The input power to each 4-lamp ballast is 98W, in accordance with a
representative electronic instant-start ballast manufactured by Advance
Transformer Co. [113].
e. The office was originally designed such that the worksurface illuminance is 500
lux, meeting the IES (Illuminating Engineering Society) recommendations for
visual tasks of medium contrast or small size [110].
f. The lights are on for 14 hours (from 7am to 9pm) per day, 5 days a week; in
other words, 260 days per year.
g. The office is considered a clean environment for calculating the light loss factor
(LLF).
The annual energy consumption under the original non-dimming groupcontrolled
ballasts is estimated at 5,350.8 kWh, as calculated in (9.1).
180