Every luminary
consisted of two fluorescent tubes (twin type) and two ballasts
with standard diffusers. Totally, forty open type luminaries were
installed. Each luminary consumed 72W and 20W for the lamps
and the conventional ballasts, respectively. The total lighting load
was 3680W including the power expended by the conventional
ballasts. The power density defined as the electrical power consumed
by lighting installations per unit floor area was about
22.3 W/m2 which is less than the maximum recommended value
of 25 W/m2 for educational institutions.