knjiga solarna energija dobra

720 MEASUREMENT AND CHARACTERIZATION
(E 2 = E 1 ) and assuming no series resistance (R s = 0), the value of K that best translates
the I –V characteristics for temperature is determined.
Translation equations for I SC , V OC ,V max ,andI max as a function of E tot ,T c , absolute
air mass (AM a ), and angle of incidence (AOI) based on multiple regression analysis of
field data have been proposed by King [63]:
I SC (E, T c ,AM a , AOI ) = (E/E 0 )f 1 (AM a )f 2 (AOI )[I SC0 + α ISC (T c − T o )] (16.6)
E e = I SC (E, T c = T 0 ,AM a , AOI )/I SC0 (16.7)
I mp (E e ,T c ) = C 0 + E ec [C 1 + α Imp (T c − T 0 )] (16.8)
V OC (E e , i) = V OC0 + C 2 ln(E e ) + β VOC (T c − T 0 ) (16.9)
V mp (E e ,T c ) = V mp0 + C 3 ln(E e ) + C 4 [ln(E e )] 2 + β Vmp (T c − T 0 ) (16.10)
I SC0 = I SC (E = E 0 ,T c = T 0 ,AM a = 1.5, AOI = 0 ◦ ) (16.11)
V OC0 = V OC (E e = 1,T c = T 0 ) (16.12)
V mp0 = V mp (E e = 1,T c = T 0 ) (16.13)
f 2 =
E 0
I SC (AM a = 1.5,T c = T 0 ) − E diff
I SC0
, (16.14)
E dir cos(θ)
where E is the plane-of-array solar irradiance, E e is the effective irradiance in units of
suns, E 0 is the one-sun irradiance of 1000 Wm −2 , E diff is the diffuse irradiance in the
plane of the module, E dir is the direct-normal irradiance, and AOI is the solar angle
of incidence on the module; T c is the temperature of the cells inside the module, T 0
is the module reference temperature, and α ISC , α Imp , β VOC ,andβ Vmp are the temperature
coefficients of I SC , I mp , V OC ,andV mp , respectively. These temperature coefficients are in
absolute units so they will vary with the size of the PV device, the number of devices
in series, or the number of devices in parallel. The pressure-corrected relative optical air
mass AM a can be written as [64]
AM a = P P 0
[cos(θ) + 0.50572(96.07995 ◦ − θ) −1.6364 ] −1 , (16.15)
where P is the barometric pressure, P 0 is the pressure at sea level, and θ is the angle
between the sun and zenith in degrees. The function f 1 (AM a ) is empirically obtained
from the temperature- and irradiance-corrected I SC versus air mass and assumes that the
only spectral dependence is the zenith angle. Data are collected over a range of irradiances,
incident angles, air masses, and temperatures and a multiple regression analysis is
applied. These translation equations have been compared with simple linear translation
equations derived from simulator-based measurements for several modules using outdoor
data [49]. These translation equations give similar results to equation (16.3) when temperature,
maximum-power tracking, and spectral issues are considered [48]. Other translation
equations for current and voltage are possible [16, 65].