Answer
2
13
K1. Lux = 500 × = 1 725 lux
72
F 1× A
K2. N=
Lu× LLF ×CU
500 ×150
N=
3 000× 0.65 ×0.7
N = 55
K3. h = 3 – 0.6 = 2.4m
L+W
RCR = 5 × h ×
L×W
10+15
RCR = 5 × 2.4 ×
10× 15
RCR = 2
K4. RCR = 2;RC = 70% RW = 50%
From table: CU = 81%
K5. (B). False
K6. (B). False
K7. ( C ). High pressure sodium
K8. (A). True
K9. ∆kW = (800 ×
0.455 kW
lamp (
× 2lamps ¿− 800 ×
lamp )
0.465 kW
=356 kW
Power = 356kW × R50 × 12 mnths/yr = R213 600/yr
Energy = 356kW × 8 000hrs × R0.20/kWh = R569 600/yr
Total = R783 200/yr
,K10. = 1000 × 0.5 × 0.9/3
= 150 kWh
K11. ALR = (1000 × 3) × 4000/ 25 000
= 480
K12. GRI = 25 000 × 0. 000
= 4 375 yrs
= 52.5 months
K13. (b) Fluorescent
K14. (C ). As a group when they reach a chosen lumen depreciation level.
K15. A = highest
B = lowest
K16. Power = (100 ×(75 – 22)/1 000)kW × $4/kW × 12mnths/yr = $254.40/yr
Energy = 5.3kW × 4 680hrs × $0.08/kWh = $1 984.32/yr
Total = $2 238.72/yr
K17. Power = (360 × 188W) – (360 × 112W)
= 27.36 kW
= 27.36kW × $4/kW × 12
= $1 313
Energy =27.4kW × 3 640hrs/yr
= 99 590 kWh
= 99 590 kWh × $0.08/kWh
= $7 967.23
Total = $9 280
, K18. Power = 6 × 4 × 188W
= 4 512 kW
Energy savings = 4 512 × (2 600 – 1 820)
= 3 519.36 kWh
K19. (D). 20.7
30 × 192 + 10 × 100 + 20 × 75 = 8 260 W
W 8 260
2 = = 20.65
m 400
K20. (E). $3 240/yr
kWsaved = 196 × 0.285 – 140 × 0.185 = 30kw
30kW × 24hr/d × 200d/yr × 3.6MJ/kWh/0.8/1 000 = 648 GJ/yr
Added cost = 648 × $5 = $3 240/yr
kJ w 800 h 1 3 600 kJ 1 kW
K21. = 20 fixtures × (88 – 51) × × × ×
yr fixture yr 0.8 kWh 1 000 W
kJ
= 2 664 000kJ/yr
yr
K22. C). A T8 lighting system with dimmable electronic ballasts several lux sensors to read
lighting level at task location and a control system that adjusted the ballasts to provide a
measured total light level of 500 lux.
K23. ∆kw = 20 × (100W-75W)/1000 = 0.5kW
Power = 0.5kW × R10/kW/mo × 12 mo = R60
Energy = 0.5kW × 2 800h/yr × R0.09/kWh = R126
Total = R60 + R126 + = R186
(P/A,I,10) = R930/R186 = 5
= 15%
2
13
K1. Lux = 500 × = 1 725 lux
72
F 1× A
K2. N=
Lu× LLF ×CU
500 ×150
N=
3 000× 0.65 ×0.7
N = 55
K3. h = 3 – 0.6 = 2.4m
L+W
RCR = 5 × h ×
L×W
10+15
RCR = 5 × 2.4 ×
10× 15
RCR = 2
K4. RCR = 2;RC = 70% RW = 50%
From table: CU = 81%
K5. (B). False
K6. (B). False
K7. ( C ). High pressure sodium
K8. (A). True
K9. ∆kW = (800 ×
0.455 kW
lamp (
× 2lamps ¿− 800 ×
lamp )
0.465 kW
=356 kW
Power = 356kW × R50 × 12 mnths/yr = R213 600/yr
Energy = 356kW × 8 000hrs × R0.20/kWh = R569 600/yr
Total = R783 200/yr
,K10. = 1000 × 0.5 × 0.9/3
= 150 kWh
K11. ALR = (1000 × 3) × 4000/ 25 000
= 480
K12. GRI = 25 000 × 0. 000
= 4 375 yrs
= 52.5 months
K13. (b) Fluorescent
K14. (C ). As a group when they reach a chosen lumen depreciation level.
K15. A = highest
B = lowest
K16. Power = (100 ×(75 – 22)/1 000)kW × $4/kW × 12mnths/yr = $254.40/yr
Energy = 5.3kW × 4 680hrs × $0.08/kWh = $1 984.32/yr
Total = $2 238.72/yr
K17. Power = (360 × 188W) – (360 × 112W)
= 27.36 kW
= 27.36kW × $4/kW × 12
= $1 313
Energy =27.4kW × 3 640hrs/yr
= 99 590 kWh
= 99 590 kWh × $0.08/kWh
= $7 967.23
Total = $9 280
, K18. Power = 6 × 4 × 188W
= 4 512 kW
Energy savings = 4 512 × (2 600 – 1 820)
= 3 519.36 kWh
K19. (D). 20.7
30 × 192 + 10 × 100 + 20 × 75 = 8 260 W
W 8 260
2 = = 20.65
m 400
K20. (E). $3 240/yr
kWsaved = 196 × 0.285 – 140 × 0.185 = 30kw
30kW × 24hr/d × 200d/yr × 3.6MJ/kWh/0.8/1 000 = 648 GJ/yr
Added cost = 648 × $5 = $3 240/yr
kJ w 800 h 1 3 600 kJ 1 kW
K21. = 20 fixtures × (88 – 51) × × × ×
yr fixture yr 0.8 kWh 1 000 W
kJ
= 2 664 000kJ/yr
yr
K22. C). A T8 lighting system with dimmable electronic ballasts several lux sensors to read
lighting level at task location and a control system that adjusted the ballasts to provide a
measured total light level of 500 lux.
K23. ∆kw = 20 × (100W-75W)/1000 = 0.5kW
Power = 0.5kW × R10/kW/mo × 12 mo = R60
Energy = 0.5kW × 2 800h/yr × R0.09/kWh = R126
Total = R60 + R126 + = R186
(P/A,I,10) = R930/R186 = 5
= 15%
