Hi everyone welcome back to PV Solar energy course. 1
Today we are going to discuss two main parameters first one is the conversion efficiency. 2
This is the ratio between the power coming out of the solar cell or Pout and the light power of 3
photons on the solar cell or in other war going into the solar cell Pin 4
the conversion efficiencies of solar cell are defined in its maximum power point so that power output 5
equal to P maximum as discussed which equals to Imp times Vmp this product equal to the product 6
of short circuit current with open circuit voltage and the fill factor as a result of the energy conversion 7
efficiency can be expressed in external parameter of solar cell, the open circuit voltage and 8
short circuit current and fill factor as shown in this equation the efficiency equal to P output over 9
P input. the power output the output power is equal to the maximum power which equal Vmp times Imp 10
which are also equal to open circuit voltage times short circuit current times fill factor. To be able to compare 11
the efficiencies of different solar cell. 12
The so-called standard test condition have been introduced. 13
The standard test condition describes the condition for the Pin and the temperature of solar cell during 14
the IV measures the temperature of solar cells under Z standard. 15
test condition is determined to be 25 degrees celuis. the solar spectrum has the special 16
shape of AM 1.5 and a total irradiation of 1000 W/meter2 17
A typical solar spectrum with the shape of AM 1.5 is shown in the right figure on the left vertical 18
axis. 19
We show the power density the irradiance under the standard. 20
test condition has to be equal to 1000 watt/square meter and is given also right axis 21
the blue line represents irradiance and equal to the area under spectrum power density. 22
Up to the wave length lambda 23
as illustrated if we integrate over the entire spertial power density the Blue Line corresponding 24
to irradiance equal to 1000 watt/ square meter. 25
Note that 1000 watt /square meter is equal to . 26
100millions Watt per centimeter. 27
So don't be confused when you are reading in some books with the standard 28
Test irradiance of one hundred million watt per square centimeter. 29
The second thing we are going to talk about is the solar irradiance even so it is so so many technical advancement 30
are being made at the cell level to improve the efficiency. 31
As discussed there is is still a lot to be done and there PV system level to ensure the healthy. 32
PV yield. 33
Getting a good module in terms of efficiency and the output since 50s is way only a half of the battle but what's 34
matter is the yield of the power system. 35
So the question is what else can you do to increase the yield of your PV system at the system level. 36
Of course MPP tracking or MPPT as MPPT is a valuable tool to ensure the PV module always 37
operated as the MPP point. 38
On IV curve under a given set of irradiance and temperature. 39
But how do we improve the amount of light falling on the PV. 40
model at the system level the simplest way of doing that is by playing with the orientation and tilt 41
of the module. 42
What do we mean by orientation and tilt. 43
tilt is the degree of freedom that defines the elevation or the pitch of solar module with the respect to 44
the horizontal axis. 45
Of course this seems from a basic fact that in order to get maximum energy from the sun at any moment 46
the plane of solar panel or the plane of the array as sometimes called should be perpendicular to 47
the direct rays of the sun. 48
at this moment the amount of solar energy falling on the earth depend on some astronomical factors like 49
the tilt of the earth's axis and the near spherical shape of this earth. 50
But this is not our case. 51
So in general all as a parameter being unchanged higher in radians greater output power's generated. 52
So you need to change the tilt angle of the PV module as shown to get higher irradiance during the whole 53
year. 54
So you need to change the tilte angle of PV module to get higher energy during the whole year. 55
So this is the end today. 56
See you in the next block.