Page 582 - Sustainable Cities and Communities Design Handbook

550 Sustainable Cities and Communities Design Handbook

Using this information, we can determine the minimum size of the solar
PV required to meet the maximum energy demand. Polycrystalline KD
205GX-LP cells manufactured by Kyocera were the choice for PV modules.

They have a rated power of 205 W at a cell temperature of 25 Cand solar
irradiance of 1 kW/m2. The panels have dimensions of length 1.50 m and
width 0.99 m, with a quoted cell efficiency of approximately 16%.
The following equation is used to calculate the output of the PVarray [kW]
at a given time step:

G T
P PV ¼ Y PV f PV 1 þ a P T c T c;STC (27.1)
G T;STC
where Y PV is the rated capacity of the PV array [kW]; f PV is the derate factor
[%]; G T is the solar radiation incident on the PV array in the current time step
2
[kW/m ]; G T,STC is the incident radiation at standard test conditions [1 kW/
2

m ]; a P is the temperature coefficient of power [%/ C]; T c is the PV cell
temperature in the current time step [ C]; T c,STC is the PV cell temperature

under the standard test conditions [25 C].

The PV cell temperature, T c , is given as follows:
Eq. (27.1) holds true if the PV system is equipped with a maximum power
point tracker, which the modeled system does. A derate factor of 0.804 is
assumed for the system. The effect of temperature on the PV array was
neglected in this model.
The energy generated by the three PV arrays for hour t, E G(t) , and can be
expressed as follows:
3

X
E GðtÞ ¼ N PV E PVðtÞ (27.2)
i
i¼1
where E PV(t) is the energy by PV array i during time step t [kWh]; N PV is the
number of PV modules in PV array i.
The minimum solar PVarray size was calculated using the data in Table 27.5,
solar PV specifications outlined earlier, and assuming that the campus needs to
generate 8,000,000 kWh of energy each year. The results are summarized in
Table 27.7.

TABLE 27.7 Summary of Minimum Photovoltaic (PV) Array Size Required to
Generate 8,000,000 kWh of Energy
2
Time Period Minimum PV Array (MW) Minimum Area Required (m )
Annual 4.21 4210
Summer 3.34 3340
Winter 4.84 4840