Table 5.
Results of sensitivity analysis.
| Parameter(s) | Unit | Minimum | Base case | Maximum | Interval | Number | Influential coefficient | Ranking |
|---|---|---|---|---|---|---|---|---|
| Building Load | ||||||||
| Annual mean dry bulb temperaturea | °C | 22.066 | 23.066 | 24.066 | 0.1 | 21 | 1.080 | 1 |
| Annual mean dew point temperaturea | °C | 17.907 | 18.907 | 19.907 | 0.1 | 21 | 0.460 | 4 |
| Annual mean global solar radiationa | W h/m2 | 192.907 | 292.907 | 392.907 | 10 | 21 | 0.124 | 11 |
| Occupant density (office) | m2/person | 5 | 8 | 20 | 1 | 15 | −0.104 | 14 |
| Occupant density (SA) | Person/floor | 35 | 42 | 45 | 1 | 10 | 0.0428 | 17 |
| Lighting load (office) | W/m2 | 10 | 20 | 30 | 1 | 20 | 0.113 | 13 |
| Lighting load (SA) | W/m2 | 10 | 20 | 30 | 1 | 20 | 0.0646 | 15 |
| Equipment load (office) | W/m2 | 10 | 25 | 40 | 1 | 30 | 0.148 | 9 |
| Equipment load (SA) | W/m2 | 10 | 12 | 40 | 1 | 30 | 0.0310 | 18 |
| AC operating hours (office)b | h | 17:00 | 19:00 | 22:00 | 0.25 | 20 | 0.627 | 3 |
| AC operating hours (SA) c | h | 24 | 24 | 24 | – | – | – | – |
| Annual mean occupancy rate (office)d | % (floor) | 50% (31) | 73.4% (47) | 100% (62) | 1 | 31 | 0.239 | 6 |
| Annual mean occupancy rate (SA)d | % (floor) | 50% (14) | 73.4% (21) | 100% (28) | 1 | 14 | 0.215 | 7 |
| Ventilation rate (office) | m3/s/person | 0.005 | 0.01 | 0.015 | 0.002 | 6 | 0.0243 | 19 |
| Ventilation rate (SA) | m3/s/person | 0.005 | 0.01 | 0.015 | 0.002 | 6 | 0.0199 | 20 |
| Infiltration rate (office) | ACH | 0.05 | 0.1 | 0.25 | 0.02 | 11 | −0.00113 | 22 |
| Infiltration rate (SA) | ACH | 0.05 | 0.1 | 0.25 | 0.02 | 11 | 0.00470 | 21 |
| System control and operation | ||||||||
| Supply air temperature (office) | °C | 10 | 14 | 18 | 0.1 | 80 | −0.116 | 12 |
| Supply air temperature (SA) | °C | 10 | 14 | 18 | 0.1 | 80 | −0.151 | 8 |
| Thermostat set point (office) | °C | 20 | 24 | 28 | 0.1 | 80 | −0.290 | 5 |
| Thermostat set point (SA) | °C | 20 | 24 | 28 | 0.1 | 80 | −0.131 | 10 |
| HVAC plant | ||||||||
| Chilled water supply (CHWS) temperature | °C | 4 | 6.7 | 9 | 0.1 | 50 | −0.0614 | 16 |
| Overall COP of chiller plant | – | 3 | 4.1365 | 5 | 0.1 | 21 | −0.864 | 2 |
This SA study focused on the importance of parameters affecting the energy use of a chiller plant. The seasonal variation in these weather variables, therefore, was not included. The annual mean temperature was taken as the average value of the daily mean air temperature throughout a year.
AC operating hours (office) involves two parameters, the AC start-up time and operating duration, would be adjusted. In this study, the AC start-up time, which is 8:00 am, remained unchanged and only the operating duration was changed.
AC operating hours (SA) was assumed to be unchanged as it is very unlikely for SA operators to reduce the operating hours.
The data on occupancy rate is in terms of the annual mean percentage. The occupancy rate was converted into the number of floors being fully occupied. Besides, it was assumed that a tenant rents the office floor in terms of a whole floor, instead of half-floor. Similarly, the SA operator will try to occupy the whole floor for minimising the operation costs.