Civil Engineering Reference
In-Depth Information
Table 14.6
Worksheet for energy-saving evaluation in lighting
New
system
Reference
Technical data
a
Rated initial lumen per lamp
lm
b
Input electric power per lamp
W
c ¼a
/
b
Lamp efficiency
lm/W
d
Input electric power per
lamp + ballast (or dimmer)
W
e
¼
a
/
d
Lamps + ballast (or dimmer)
efficiency
lm/W
f
Coefficient of utilization—CU
%
g
Lamp depreciation factor
%
h
Dirt depreciation factor
%
i ¼e f gh
/10
6
Effective lumen per watt
lm/W
h
/10
6
l
¼
a
f
g
Effective lumen per lamp
lm
m
Average lux required
lx
m
2
n
Surface to be lighted
o¼mn
Total lumen required
lm
p¼o
/
l
Number of lamps
lamps
q
¼
o
/
i
¼
p
d
Total electric input power
W
W/m
2
KPI
¼q
/
n
Installed power per unit of surface
Capital cost
r
Luminaire cost
U
s
Auxiliary equipment cost
U
t
Installation cost
U
u¼ r
+
s
+
t
Total capital cost
U
Operating cost
v
Cost of replaced lamps
U/year
x
Cost for replacing
U/year
y
¼
v
+
x
Total annual operating cost
U/year
Energy saving
W
Working hours
h/year
EC
¼
W
q
/1,000
Annual energy consumption
kWh/year
ES
¼
EC(REF)
EC(NEW)
Annual energy saving
kWh/year
CA
Electric energy cost
U/kWh
CS
¼
ES
CA
Annual energy cost saving
U/year
The lighting system existing in the shopping center has 1,400 standard F96T12
lamps (input power 75 W per lamp) with two-lamp luminaires and standard ballasts
of 10 W per lamp. The input power for each luminaire is 170 W. An average
illuminance of 600 lx has been measured. The CU coefficient is 60 %.
The new lighting system includes two-lamp luminaires with HF 50W input power
per lamp and ballast input power of 6 W per lamp. The initial lamp efficiency is
100 lm/W; the lamp + ballast efficiency is 89.3 lm/W. The CU coefficient is still 60%.
