In [3]:

```
# Given data :
import math
T=27 +273 # temperature converted in kelvin
NV=1e22 # effective density of states in valence band in cm^(-3)
NA=1e19 # acceptor density in cm^(-3)
k=8.629*10**(-5) # boltzmann constant in eV/K
EFV=k*T*math.log(NV/NA) # closeness of fermi level i.e Ef-Ev
print "Closeness of fermi level with valence bond is",round(EFV,4),"eV"
```

In [20]:

```
# Given data :
E =2.42 # Band gap in eV
hc=1.24 # planck's constant * speed of light
# solution
Lambda=1.24/E # in micro-meter usinf eq 6.4
print "The optimum wavelength is ",round(Lambda,3)," micro meter"
```

In [22]:

```
# Given data :
Pout=1*735 # motor power output in W
Peffi=0.85 # motor efficiency
cellarea=9*4*125*125e-6 # area in m^2
Rad=1000 #incident radiation in kW/m^2
celleffi=0.12 # cell efficiency
# soln.
Pin=Pout/Peffi # power req by motor in W
N=Pin/(Rad*cellarea*celleffi) # number of modules
print round(N)," number of modules are required"
```

In [24]:

```
# given:
noMPPTpower=10*8 # power without MPPT in W from fig 6.25
MaxP=25*5 # maximum power by PV module in W from fig 6.25
effi=0.95 # efficiency of MPPT
MPPTcost=4000 # Cost in rupees
# Soln
Pact=MaxP*effi # actual power produced in W
Psurplus=Pact-noMPPTpower # Surplus power in W
t=MPPTcost/(3*Psurplus/1000) # time required in hours
print "time required is ",round(t,2),"hours"
```