To calculate the amount of illuminance received from different models, it is preferable to use a fixed simulation. Point-In-Time Grid-Based Simulation in the case study presents by Ladybug- Honeybee that compared in 4 pipe lengths of difference configurations. The simulation program for all pipes in equal conditions on one day and time was analysed. The exterior illuminance for the overcast sky condition on June 21 at 12:00 in Ankara is 18314 lux. In the first step, there are three variable parameters in this comparison (‘d’ length, the elbow modules and the connections) for elbow models. Then, as straight pipe and single elbowed pipe models are two variable parameters which are space’s height and pipe length. In double elbowed pipe models, the distance “k” is added to these variables. Maximum and average illuminance levels in the working plane, distribution of light on a heatmap, and perspective views of the models are in Fig. 6 for straight and single elbowed pipes and Fig. 7 for double elbowed pipes.
According to simulation results, in the overcast sky condition for different pipe length, the amount of maximum illuminance from straight pipes in room, reaches between 160 to 180 lux. This amount reaches between 95 to 115 lux for single elbowed pipe, 55 to 110 lux for 45° angled double elbowed pipe, 75 to 130 lux for 90° angled double elbowed pipe. The amount of illuminance received the working plane decreased as the pipe length increased. The P1 model provides the best illuminance levels and light distribution. In this context, the most inefficient light levels are achieved with the 5.20 m length 45°angled double elbowed pipe.
The light losses occurring according to the simulation outputs should be determined and the effect of the length difference or typology difference should be evaluated. he light losses between different lengths in the same pipe typology are given in the Table 3, and the light losses between different pipe typologies with the same length are given in the Table 4. For instance, when the pipe length is increased by 1.20 m, the illuminance levels decreased 3% at maximum and 21% at average in straight pipes. On the other hand, this ratio increased 21% at maximum and 38% at average in 90° angled double elbowed pipes.
As different pipes of the same length, for example 1.60 m pipe length, when a 45° elbow is added to a straight pipe, light loss is 36% at maximum and 33% at average. In the present case, as the length of elbowed pipe increases, more light loss is expected, while double elbowed pipes give different results. Light gains occurred when 45° elbow turned into 90° elbow (P9-P12, P10-P13, P11-P14 in Table 4). In this case, it is thought that the angle of the 𝓁2 pipe in the 45° pipe affects the efficiency of the system negatively.
Table 3
The light losses between different lengths in the same pipe typologies
Straight
|
Single elbowed
|
|
Double elbowed (45°)
|
Double elbowed (90°)
|
|
Max
|
Avr
|
|
Max
|
Avr
|
|
Max
|
Avr
|
|
Max
|
Avr
|
P1- P2
|
5 lx
%3
|
10 lx
%17
|
P5 - P6
|
7 lx
%6
|
6 lx
%15
|
P9 - P10
|
28 lx
%26
|
6 lx
%20
|
P12 - P13
|
27 lx
%21
|
9 lx
%35
|
P2 - P3
|
5 lx
%3
|
15 lx
%19
|
P6 - P7
|
4 lx
%4
|
6 lx
%19
|
P10 - P11
|
25 lx
%31
|
8 lx
%33
|
P13 - P14
|
21 lx
%21
|
7 lx
%41
|
P3 - P4
|
3 lx
%2
|
9 lx
%28
|
P7 - P8
|
6 lx
%6
|
8 lx
%30
|
Average
|
%29
|
%27
|
Average
|
%21
|
%38
|
Average
|
%3
|
%21
|
Average
|
%5
|
%21
|
|
|
|
|
|
|
Table 4
The light losses between different pipe typologies with the same length
1.60
|
2.80
|
|
4.00
|
5.20
|
|
Max
|
Avr
|
|
Max
|
Avr
|
|
Max
|
Avr
|
|
Max
|
Avr
|
P1- P5
|
66 lx
%36
|
19 lx
%33
|
P2 - P6
|
68 lx
%38
|
15 lx
%32
|
P3 – P7
|
67 lx
%39
|
6 lx
%19
|
P4 – P8
|
70 lx
%42
|
5 lx
%22
|
|
|
|
P6- P9
|
0
0
|
2 lx
%6
|
P7 – P10
|
24 lx
%23
|
2 lx
%7
|
P8 – P11
|
43 lx
%44
|
2 lx
%11
|
|
|
|
P9 – P12
|
+ 19 lx
+%17
|
4 lx
%13
|
P10 - P13
|
+ 20 lx
+%25
|
7 lx
%29
|
P11 - P14
|
+ 24 lx
+%44
|
6 lx
%38
|
|
|
|
P2 - P12
|
49 lx
%28
|
21 lx
%44
|
P3 – P10
|
71lx
%42
|
15 lx
%47
|
P4 – P14
|
89 lx
%53
|
13 lx
%57
|
When the amount of light in the exterior illuminance changes, the light received into the working plane can be calculated as an approximate value with daylight factor coefficient. Besides the fixed simulations, dynamic simulation is used to reach more general results about the system, regardless of time and weather conditions. The daylight autonomy values are calculated as the ratio of the minimum 100 lux illuminance required for the space on the working plane to the total usage hours for a year, when only daylight is received. The result obtained when Daylight Factor and Annual Daylight components of light pipe models are run on Honeybee are given in Table 5. In addition, comparison maximum and average DF and DA metrics for all pipes is seen Fig. 8. The DF and DA curves showed different trends. The highest DF values were achieved with the 1.60 m long straight pipe and the lowest DF values with the 5.20 m length 45° angled double elbow pipe. DF values remained below 1% for all pipe models.
The DA’100 on the working place decrease consecutively, when the length of pipe increases each 1.20 m. In the working plane, it reaches 100 lux light level during the year, between around 30–50% for straight and single pipes, 40–50% for 45° angled double elbowed pipes, 25% to %50 for 90° angled double elbowed pipes.
Table 5
Daylight factor (DF) and daylight autonomy (DA) value for all light pipes
Pipe Models
|
Straight
Pipe
|
Single Elbowed
Pipe
|
Double Elbowed Pipe (45°)
|
Double Elbowed Pipe (90°)
|
Metrics
|
P1
|
P2
|
P3
|
P4
|
P5
|
P6
|
P7
|
P8
|
P9
|
P10
|
P11
|
P12
|
P13
|
P14
|
DF
(%)
|
Max
|
0.98
|
0.95
|
0.93
|
0.91
|
0.62
|
0.58
|
0.56
|
0.52
|
0.58
|
0.43
|
0.29
|
0.68
|
0.54
|
0.43
|
Avr
|
0.31
|
0.25
|
0.17
|
0.12
|
0.20
|
0.17
|
0.14
|
0.09
|
0.16
|
0.13
|
0.08
|
0.14
|
0.09
|
0.06
|
DA
(%)
-t100
|
Max
|
49
|
47
|
46
|
29
|
46
|
39
|
36
|
32
|
49
|
41
|
39
|
49
|
44
|
25
|
Avr
|
27
|
21
|
13
|
5
|
26
|
21
|
17
|
13
|
15
|
14
|
14
|
20
|
14
|
3
|
Figure 8. Comparison of maximum and average daylight metrics among all light pipes (a) daylight factor (DF), (b) daylight autonomy (DA)
The analysis results of the P14 pipe with a length of 5.20 m and a diameter of 0.52 m under clear sky conditions with the same diameter and under clear and overcast sky conditions with a diameter of 0.60 m are shown in Fig. 9. In overcast sky conditions, when the pipe diameter increased by 0.08 m, 50% light gain at the maximum level and 80% at the average level occurred. The exterior illuminance for the clear sky condition on June 21 at 12:00 in Ankara is 96256 lux. In overcast sky conditions, when the pipe diameter increased by 0.08 m, 50% light gain at the maximum level and 80% at the average level occurred. This ratio is 51% at the maximum level and 63% at the average level in clear sky condition. The dimensions of the space were not changed to ensure that the analysis conditions were equal. It can be said that the rate change in the average level is since the pipe diffuser is located very close to the east facade of the room. For 0.52 m and 0.60 m pipe, the light level between the overcast and clear sky condition increased by approximately 5.3 times as close to each other. Looking at the Fig. 10, this ratio can be seen.