for the change in external conditions (e.g. temperature, humidity)
which, in the real case, would affect the storage efficiency. This simplified
model is particularly suited for a preliminary technoeconomic
feasibility study in Singapore’s climate characterized by
almost steady ambient conditions along the day and across the year
(Fig. 6).
2.3.2. Cooling energy demand of the building
The assessment of the cooling energy demand of the building
is essential for the techno-economic analysis of a CTES. Table 5 shows
a list of parameters used to define the daily cooling energy demand
of the building. For each month, the daily average cooling energy
consumption of the building, the daily average COP (Daily AVG COP)
of the chillers, the daily AVG electricity consumption (Daily AVG Electricity
Consumption) and the monthly cooling energy consumption
(Monthly load) were calculated referring to the real load profiles,
obtained by monitoring the cooling system for four months. In order
to assess the effect of CTES on the performance of the cooling system,
the COP of the system was also calculated for three different periods
of the day: the Daily AVG COP, the Daily AVG COP between 07:00 and
18:00 and the Daily AVG COP between 19:00 and 23:00.
Table 5 also reports the “monthly surplus” and the “daily average
surplus” calculated from real acquired data. These values were calculated
in order to address Action 2 (yellow area in Fig. 4) in which
only the most efficient chiller (chiller C) is operated during peak
hours.
The “monthly surplus” represents the sum of all the “hourly
surplus” of a specific month. The “daily average surplus” is calculated
as the Monthly Surplus divided by the number of operative
days. The “hourly surplus” is defined as the difference between the
hourly energy demand and the rated capacity of chiller C (1050 kWc)
and it is calculated for the ith hour as