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Equipment of the air-conditioning system was selected from a
local supplier (Alarko-Carrier). Net cooling capacity and electricity
consumption of the chiller unit selected are 111 kW and 47.4 kW
for Buildings A, B and C, 152 kW and 67 kW for the no insulation
building under nominal operating conditions (38 C condenser
temperature, 12 C evaporator inlet and 7 C outlet water temper-
ature), respectively. Total mass flow rates of the supply and return
fans in AHU for the no insulation building is 45,438 m3
/h. The sup-
ply and return fans have 22 kWand 18.5 kWpower consumptions,
respectively. Total mass flow rates and power consumptions of the
supply and return fans for Buildings A, B and C are 30,000 m3
/h,
15 kW and 11 kW, respectively.
4.2. Initial cost
Total initial costs of the air-conditioning system including the
chiller unit, AHU, duct and automation equipment costs are given
in Table 7. When building envelopes were insulated (Buildings A, B
and C), the initial cost of ACS for CAV and VAV systems were about
22% less than those of buildings without insulation.The Binmethod was used for calculation of energy consumption
of the chiller unit. This method is based on the calculation of the
energy consumption for different values of the outdoor tempera-
ture (Tout) and multiplying it by the corresponding number of
hours (Nbin) in the temperature bin centered on that temperature
[27]. The bin method, which has different forms today, has been
developed from the various degree-day methods available. For
many applications, the degree-day method should not be used,
even with the variable-base method, because the heat loss coeffi-
cient, the efficiency of the HVAC system, or the balance point tem-
perature may not be sufficiently constant. The efficiency of the
HVAC equipment, for example, varies strongly with outdoor tem-
perature. In such cases, a steady-state calculation can yield good
results for the annual energy consumption if different temperature
intervals and time periods are evaluated separately [27].
Monthly bin data with 3 C increments in 4-h periods between
9:00–20:00 h during cooling season for Adana are given in Table 8
[28]. The cooling period for Adana, which has a hot and humid cli-
mate during summers, covers 184 days between May and October
[7].
Operating costs of the air-conditioning systems during cooling
season for 9:00–12:00 h, 13:00–16:00 h and 17:00–20:00 h were
obtained using bin number. The minimum reducing ratio of the
variable-speed drive (VSD) used in VAV system in order to adjust
the operating speed of the fan was taken to be 30%.
Free cooling systems use outdoor air to reduce the cooling
requirement when outdoor air is cool enough to be used as a cool-
ing medium. In this study, the sample building is conditioned by
free cooling (outdoor air is directly supplied to the air-conditioned
space) when outdoor air temperature is least 8 C lower than in-
door temperature (Tout 6 18 C) [29]. By doing this, operating hours
of the chiller unit in ACS is reduced. Therefore, both electricity con-
sumption and environmental impact are reduced as well.
Total operating hours of the mechanic and free cooling systems
during cooling season for Adana are presented in Table 9. Free cool-
ing is possible only in May and October with the conditions
Tout 6 18. As shown in Table 9, the potential of free cooling is not
enough for the occupation period considered in this study (9:00–
20:00). However, an increase in the potential of free cooling for
Adana is noticeably observed in night time (20:00–08:00).
The main electricity-consuming units in the air-conditioning