number of element are not equal

Hi all; I am trying to predict the output of solar module by using the code below:

% Va = module operating voltage (V)
% Ia = module operating current (A)

%-----MANUFACTURER'S DATA-----
VOC=21;     %open circuit voltage (V)
ISC=7.7;    %short circuit current (A)
VM1=16.9;   %reference voltage for maximum power
IM1=7.1;    %reference current for maximum power
T1=298;     %reference temperature (K)
G1=1000;    %reference irradiance (W/m^2)
NS=36;      %number of cells per module
AM0=0.974;  %area of one module (m^2)
mi=0.0025;  %temperature coefficient for short circuit current (A/K)

%-----CELL PARAMETERS-----
EG=1.124;           %energy gap (eV)
A=1.3;              %ideality factor
k=1.38*10^-23;      %Boltzmann's constant (J/K)
q=1.6*10^-19;       %charge of electron (C)
n=1.2;              % diode quality factor

h=VOC/1000;         %setting increment
Va=0:h:VOC;           %range of I with increment h

%-----------input variable-----------
TaC=input('Temprature (C): ');           % ambiant temperature (c)
G=input('Irradiance (W/m2): ');          % solar irradiance (W/m2)

TaK=273+TaC;                            % ambiant temperature Kelvin
IL_T1 = ISC * (G/G1);                   % Ecuacion (3)
IL = IL_T1 + mi*(TaK - T1);             % Ecuacion (2)
I0_T1=ISC/(exp(q*VOC/(n*k*T1))-1);      % reference saturation current
I0= I0_T1*(TaK/T1).^(3/n).*exp(-q*EG/(n*k).*((1./TaK)-(1/T1)));      % saturation current
Xv = I0_T1*q/(n*k*T1) * exp(q*VOC/(n*k*T1));                    % Ecuacion (8)
dVdI_Voc = - 1.15/NS / 2;            % dV / dI at Voc 
Rs = - dVdI_Voc - 1/Xv;                                         % Ecuacion (7)
VT = A * k * TaK / q;                                 % Thermal voltage (V)
Vc = Va/NS;                           % Cell voltage [Va is the output voltage]

N=length(Va);         %number of data points
Ia(N)=0;               %setting final value of V

for i=1:(N-1)
Ia(i) = Ia - (IL - Ia - I0.*( exp((Vc(i)+Ia.*Rs)./VT) -1))/(-1 - (I0.*( exp((Vc(i)+Ia.*Rs)./VT) -1)).*Rs./VT);
end

figure (1)
plot (Va,Ia), xlabel('Voltage (V)'), ylabel('Current (A)');

but I get this error:

??? In an assignment A(I) = B, the number of elements in B and I must be the same.

how to overcome this error ??? please advice.. thanks

[Walter Roberson]

Please read the guide to tags and add tags that have more useful meanings; see http://www.mathworks.co.uk/matlabcentral/answers/43073-a-guide-to-tags

Answer 1

[Azzi Abdelmalek]

use * instead of .* , the problem is in your last for loop

for i=1:(N-1)
Ia(i) = Ia - (IL - Ia - I0.*( exp((Vc(i)+Ia.*Rs)./VT) -1))/(-1 - (I0.*( exp((Vc(i)+Ia.*Rs)./VT) -1)).*Rs./VT);
end

also you set Ia(N), i=N-1:-1:1 was expected

corrected code

Ia(N)=0;
for i=N-1:-1:1
Ia(i) = Ia(i+1) - (IL - Ia(i+1) - I0*( exp((Vc(i)+Ia(i+1)*Rs)/VT) -1))/(-1 - (I0*( exp((Vc(i)+Ia(i+1)*Rs)/VT) -1))*Rs/VT);
end

[Samer Husam]

so do suggested to set : i = 1:N ?

[Samer Husam]

its really works... thanks