Proposed model architecture:
The proposed Solar-Wind-Diesel Hybrid generation system needs the following components. A brief description is given below. A Block Diagram of the proposed system is given in Fig. 1 .
Solar PV:
Solar PV is a semiconductor device that produces DC current when solar irradiation is incident upon it. Solar cell is the basic unit of solar system. It is a p-n junction basically. When light (photon) is incident upon these cells electron is emitted from the p-n junction. The current generated from the solar cell is called Photocurrent, Iph. We do not use a single PV cell or module in practical life. We use Solar PV array that is an interconnection of PV modules. The equivalent circuit in ideal condition for a solar cell is defined as a current source and diode connected in parallel. Load is connected in parallel to solar cells. The relation between voltage and current for a solar cell in ideal condition [24] can be represented as:
(1)
Here,
IPV = Solar cell output current measured in Ampere.Iph = Photocurrent measured in Ampere.I0 = Diode current for Reverse saturation measured in Ampere.q = Electron’s charge =1.6×10-19 C.k = Constant (Boltzman Const.) = 1.38×10-23J/K.T = Temperature of the cell measured in Kelvin.
As we know P = VI, the power output of the solar cell can be defined as
PPV =VPV * IPV(2)
Here,
PPV = Output power of the solar cell (W)VPV = Operating voltage of the Solar cell (V)IPV = Solar cell output current (A)
The electrical energy generation from a photovoltaic system can be calculated from the following worldwide formulated equation [7] :
E= A × r × H × PR (3)
Where,
PR = Performance ratio, coefficient for losses (range between 0.5 and 0.9, preferred value = 0.75)E = Electrical Energy measured in kWh.A = Total area of solar module in m2.H = Annual std. global solar radiation on tilted panels.r = Solar module ratio (%)
In HOMER, for solar PV, it assumes that the output from PV module is linearly proportional to the input irradiation. But in real life the efficiency is not like that and is limited by several factors like temperature, dust, various losses etc. Keeping these things in mind HOMER has an input named ‘derating factor’ dedicated to compensate for the variation in ideal and real life efficiencies. For this in our study a derating factor of 80% is considered. The energy production by the solar PV array can be formulated as [8],
(4)
Here,
f pv = Factor of derating.Ypv = Total capacity of solar PV array installed.It = Total solar radiation on the array in kW/m2.Is = Incident radiation at std. test condition = 1 kW/m2.
In this study Generic flat plate PV is used. It has a rated capacity of 1 kW. Ground reflectance was considered 20%. Here we have considered 1 to 11 kW capacity solar PV modules for the system simulation. Some relevant data regarding Solar PV is provided in Table 3 . Here the costs considered in this work, lifetime for the solar PV considered etc. are summarized. Fig.4 shows the cost curve which shows graphically the relationship between the Quantity of PV modules and Cost.
Table III: Solar PV parameters.