What is Coefficient of Utilization (CU)? What factors affecting the CU value? Is it possible for a CU to be greater than 1.0? Why? (3 marks) A lobby (length: 6 m; width: 6 m; height: 3 m) uses a two-lamp fluorescent luminaire. The luminaire details are given in Figure Q3. The fluorescent lamp has an initial lumen of 2500 Im and a mean lumen of 2200 Im. The total light loss factor is 0.78. The reflectance of the ceiling, wall, and floor are 0.8, 0.5, and 0.2. The target illuminance is 550 lx. (i) What is the CIE classification of the luminaire, why? (2 marks) (ii) What is the total luminous flux from the luminaire? (2 marks) (iii) What is the luminaire efficiency of the luminaire? (4 marks) (iv) If a designer proposes to use 9 luminaires, what is your opinion? (4 marks) (v) If we use 9 luminaires, what is the average illuminance on the workplane due to the direct light? How about inter-reflection? (4 marks) (vi) If using a lighting simulation software to perform the design, we typically place a calculation grid on the workplane. Please briefly explain how the simulation software actually handles the simulation. (6 marks) COEFFICIENTS OF UTILIZATION - ZONAL CAVITY METHOD EFFECTIVE FLOOR CAVITY REFLECTANCE: 20% 30 10 0 70 50 RCC %: 80 RW %: 70 50 30 0 70 50 30 0 50 30 20 50 30 20 50 30 20 Q RCR: 0.84.84.84 .84 .79.79.79.46 .68 .68 .68 .59.59.59.50.50.50 .46 1.78.75.73.70 .73.71.68.41 .62 .60.59 .54.52.51 .46.45.45.41 2.72.67.63.59 .67.63.59.37 .55.53.50 .48.46.45 .42.40.39.36 3 .66.60.55.51 .62.56.52.32 .50 .46.43.44.41.39 .38.36.34 .32 4.61.54.48.44.57.50 .45.29 .45.41.38.39.36.34 .34.32.30 .28 5.57.48.42.38 .53.45.40.25 .40.36.33.36.33.30 .31.29.27.25 6.52.44.38.33 .49.41.36.23 .37.32.29 .33.29.27 .29.26.24 .22 7.49.40.34 .30 .45.37.32.21 .33.29.26 .30 .26.24 .26 .24.22.20 8.45.36.30.26 .42.34.29.19 .31.26.23 .27.24.21 9.42.33.27.24 .40 .31.26.17.28.24.21 .25.22.19.22.20.18.16 70-100 0-60 60-90 ZONAL LUMEN SUMMARY ZONE LUMENS % LAMP % LUMINAIRE 0-30 868.8 17.4% 1,394.7 27.9% 2,166.4 43.3% 2.6% 128.0 154.1 3.1% 10.39.30 .25.21 .37.29.24.16 .26.22.19.23.20.18 .21.18.16.15 90-120 726.2 14.5% Figure Q3 luminaire specification sheet .24.22.20 .18 0-40 22.5% 36.1% 56.1% 3.3% 4% 18.8%