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28PHYSICAL SCIENCES
EQUIVALENT CIRCUIT MODEL OF THE SOLAR CELL
Ismoilov U.,
Independent researcher Siddikova S. Teacher of physics Komilov M., Master student Eraliyev A., Bachelor student Andijan State University
Azimov S.,
Bachelor student
Sotvoldiyev O.,
Bachelor student Zulunova M. Bachelor student Andijan machine building institute
Abstract
One of the main methods in the study of solar cells is mathematical modeling. This article describes single diode model used in the study of various photoelectric parameters of solar cells.
Keywords: solar cell, model, single diode circuit, I-V characteristics
The diode model is widely used in the study and mathematical modeling of the solar cell [1]. Figure 1 shows a single diode equivalent circuit model. In this case, the current in the IL circuit, the current in the ID
diode, the current in the Ish shunt resistor, the Rsh shunt resistor, the RS-series resistor, the total current I and the photocurrent V [2]. There is a connection between these parameters.
ID
(D
vw
+
V
Figure 1. Equivalent circuit model of the solar cell
Ideally, the volt-ampere characteristic of a solar cell is as simple exponential as the volt-ampere characteristic of a diode [3].
/o(«P®-l) (1)
/ = /,
ph
qv+iRs\
nkT J
1:
V+Rsl Rsh
(2)
l = h
ph
Where: I - current, I0 - dark current, Iph - photo-current, q-charge, V - voltage, T - absolute temperature, k - Boltzmann constant.
If we also take into account the above series and shunt resistances, a more perfect equation emerges [4].
Where: Rs - series resistance, Rsh - shunt resistance, n - ideality coefficient.
The main photoelectric parameters of a solar cell are fill factor, maximum power, efficiency, salt voltage, short-circuit current and photocurrent [5].
The magnitude of a short circuit is directly related to the wavelength of the light. The external quantum efficiency can also be determined by the dependence of the short-circuit current on the wavelength [6]. It is easy
h
0
to use and explain Formula 3, 4, 5 and 6 to calculate the total short-circuit current.
(3)
(4)
he = f0° he WdA No = f0Ä° N(A)dA
nA = N(A)(1 - exp[-a(A)h])dA (5)
he = (W1 + W2)rjeollVAqNo
(6)
Where: I - wavelength, No - total photon number, N(I) - photons number in exactly I wavelength, h -thickness, Wi - width of p type, W2 - width of n type, a(I) - absorption coefficient, ncoll - collection factor, nA - photon absorption factor, q - charge.
One of the most important quantities in the mathematical modeling of the solar element is the amount of reverse current [7]. Depending on its value, the amount of salt operating voltage can be calculated. It is calculated using formula 7. In this case, statistics were used.
(7)
0 k n4 JU ex-l
Where: q- charge, Io - dark current, c - Stefan-Boltzmann constant, T -temperature, k - Boltzmann
constant, u = ^ Eg - bandgap energy.
The photocurrent is the current when the solar cell is illuminated. It's hard to turn it off because chargers have very little lifespan. Photocurrent can be calculated from the light spectrum [8]. This is because the current produced is directly related to the wavelength of the light [9]. To calculate it, the solar cell is integrated from the minimum energy to the maximum energy of the absorbing photon, as shown in formula 8 [10]. In this case, the spectrum of light was considered to have a certain function. If it does not obey a specific function, it is considered as a discrete sum.
Iph = q^*maxf(E)dE (8)
Where: q - charge, Iph - photocurrent, f(E) - spectral derivation of light, Emin va Emax - minimum and maximum energy of photons.
The fill factor is used to determine the quality of a solar cell and the quality of its illumination. The fill factor of normal solar elements is in the range of 70-85%. Formula 9 is used to calculate it.
FF =
Jmpp Um\ J s c^oc
(9)
Where: FF - fill factor, Jmpp - current density in maximum power point, Umpp - voltage in maximum power point, Jsc - short circuit current, Uoc - open circuit voltage.
In conclusion, a diode model can be used to determine the photoelectric parameters of solar cells. Because this model differs from the rest of the models by its simplicity and clarity.
References
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