How do you read the data sheet for a solar panel ?

How do you read the data sheet for a solar panel ?


In this video, I want to walk you through
a data sheet of a solar, solar panel, and I’ve just picked
one of these solar panels randomly. So I’ve picked this Panda Series solar
panels which is sold by this company Yingli
Solar. It is one of the larger manufacturers of
crystalline and multi-crystalline based silicon solar panels.
And this solar panel is is made up of these single crystalline, or
mono-crystalline silicon. Okay, so, one thing I should point out is
that these data sheets typically are a couple of pages,
maybe two or three pages. and the first page is always filled with
this marketing information, which I should warn you, you should take it with a
grain of salt. So for example it talks about how much the
installation how much of capacity of modules, this
company has installed. And then it says that you know it can supply these aesthetically pleasing
black modules. I don’t know what, how, you know, making
this thing black instead of of white, would make it more aesthetically
appealing. But they do send to tell, they do tend to
sell like these these modules with, you can choose the color of this plastic
or these [UNKNOWN] sheet, and you can choose it to be either
white or black. The other information that this this data
sheet claims is that this module has the highest
PTC by STC ratio. So, there are two terms over here, one is
STC and PTC. And then there’s a ratio of these two
terms. Wo let me explain now what they, what they
mean. Let me go over here so I can write
some stuff down. So this PTC essentially what it means it corresponds to PVUSA Test Conditions.
And that particular test condition, it essentially corresponds, it
corresponds to having a intensity, having a solar spectrum with and intensity which is normalized
to 1000 watt per meter squared. And you use a AM 1.5G spectrum. And, then you assume that your ambient is essentially you have a temperature, of the
ambient, Is, essentially equal to 20 degrees
centigrade. You assume that there’s a certain, wind
blowing. And this wind is blowing at the rate of one meter per second, which is equal to
2.25 mph. And you know, this was what, this is what
corresponds to PTC. Note that there’s no specification given
on the temperature of the cell. So all you specify is the temperature of
the ambient. And this wind speed. And this wind is also, you know, something
which would, if you have a module like this, and you have a solar
panel placed over here, your wind is essentially, it’s going to be
more effective cooling the panel when it blows at the bottom of
this panel. Because note that this panel essentially
consists of this it, it’s, encapsulated with this glass at the top,
which has a very poor, poor conductivity. So it’s it’s very hard to get heat out or,
you know, convective flow of heat out from the top surface of your
of your of your panel. So I want to state again that there’s no
specification given on the temperature of the cell. So the temperature of the cell for sure would be higher than the temperature of
the ambient, because you have this light with the
intensity of, 1000 watt per meter square shining upon
this panel. And this glass is a poor, poor conductor
of heat, so there’s no way for this heat to escape
as well. Besides from the bottom, if there’s a
wind flowing. So this temperature would be definitely
higher than 20 C. And it would depend largely on these, on
how your module is designed, how efficient your
cell is, and so on. So this PTC rating, or this this power
rating under these PVUSA Test Conditions, it’s usually measured, measured by an
independent body. So for example for the state of California there’s this
California Energy Commission. And they have this website where they measure measure the efficiency of
different modules. Also they list out, they make a list of what are the manufacturer of these
modules, what is the module number, what is it what’s its description,
It is suitable for BIPV? Is it suitable for integration into a building while the building is
being constructed? That’s called BIPV. And then it specifies this PTC rating of
these, of these panels. And this list is updated quite frequently. And the panels which are given in this
list are suitable, you know, California will give you a subsidy if you
use the panels from this list. So let me search for Yingli over here. So Yingli. And then the panel number which I was
using was this 30b panel over here, so I see that it says that you know, it’s it’s made in
China. This is the panel number. Then it says you know, it’s a
Monocrystalline Silicon Module and then it has a PTC rating of 235 watts, so let me
write it down. So this panel. The PTC rating as, as specified by, by the California Energy Commission is,
is 235, 235 watts. Okay. So now what is this STC?
What is this STC over here. So this STC essentially it corresponds to, it corresponds to standard test
conditions. So this STC corresponds to standard
test conditions. And this essentially corresponds to having a
intensity of light. which is again 1000 watt per meter
square and the AM 1.5G spectrum which is
the same as what we used for PTC. But now we give a specification on the
cell temperature and we specify that, it’s, it is 25
degrees Centigrade. And this, this STC test is very often used when these cells are
being manufactured in a line. So one of the steps, that is performed is to generate this solar spectrum using a
solar simulator. And these, measures the efficiency of these cells, while holding their
temperature constant, or, you know, while holding
their temperature to be 25 C. So you know that whenever we operate the
cell, and if we operate it under this, PTC condition, the temperature of the cell will rise because you have this light
shining, and also the cell is, essentially it’s thermally sealed by this glass from the
top. So this efficiency of the cell will, will
decrease as I increase the temperature. So this efficiency will decrease in the
PTC test condition. So that’s why this PTC to STC ratio is
important. And it’s important to find out what is
this PTC to STC ratio. So this STC rating is often given in the
data sheet itself. So I’m going to just look into that. So it says that under standard test, test
conditions, wo the maximum power is for this panel is
270 watts. So, the PTC to STC ratio is essentially 235 divided by, 270.
So this is this is your [UNKNOWN] it’s you know, its let me see, it’s close
to 90% over here. Then it also says that, these, these,
effi-, these panels, they give a efficiency,
these cells which are used in this panel. They give a efficiency of 90 per, of 90%,
but that’s, you know, not relevant. The, what’s relevant is the module
efficiency. And that is given to be 16.5%. Again, the thing you should be asking
yourself is that under what what what kind of test conditions is
this efficiency measured? And so it has you know, some other, other
marketing information such as it uses anti-reflective coating,
that it specifies what kind of warranty is available on
these panels. And then what certification and these
what quality certifications it has passed. So for example to, to operate them in California a very important certification
is this CEC certification. Which is the California Energy Commission.
So now, the, let’s come to the second page of this data sheet.
And this is where most of the meat or most of the information which makes a
electrical engineer’s heart sing, or even a mechanical engineer’s heart sing,
lies over here. So, as soon as, you know, I look at some,
of these metrics, I recognize, some of the
terms that I have learned. That is, I recognize my efficiency over
here. I recognize my, power max point, my
current max, open circuit voltage, short circuit
current. So these are things, you know, I’m very
familiar with. And, again, I note over here that this are
specified in in for a, for two cases. One is a standard test condition.
And if you read the footnotes over here, they say again that, that standard test
condition had corresponds to 1000 watt per meter square with a cell held at a temperature of 125
C, and the AM 1.5 G spectrum. Another thing to notice is that there are these
different columns over here. And they have, you know, they have very similar similarly lettered names, but you
see over here that the efficiencies of these are
different and they’re varying by you know, varying from
all the way from 16.5 to 15.3. So what have what have been done over here
is that they all use the same cell. But the highest efficiency cells have been
binned over into this module which has the highest
efficiency of 16.5. And all the bad cells, you know all the
black sheep in the, in the manufacturing line, they have been binned
over into this particular module which has efficiencies of 15.3.
But, from a manufacturing process or from a cell perspective, they came out,
all from the same manufacturing line. Okay? So, another thing I notice is my open
circuit voltage and I notice that this is equal to 39
volt. And then the next thing I’ll check is how
many, how many cells I had. So let me count the number of cells, so 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
and then I have six, six columns of these ten cells.
So total number of cells I had was around, or not around
but exactly 60. So for 60 cells, I get a open circuit voltage of 39 volt, assuming all of them
are, all the cells in a panel are connected in
series. This corresponds to a Voc of each
individual cell to be approximately 39 by 60 or approximately 0.65 volt. That’s the Voc of my, one, one of these
silicon cells and that sounds approximately right
given that these are made out of silicon. So another thing to notice over here is
this these, some of these metrics are also reported for this nominal
operating cell temperature. So these the STC conditions, they
corresponds to a cell temperature of 25 C. But there’s this also, this nominal operating
cell temperature. Which essentially you know it’s similar to the PT, similar to
the PTC condition. But it uses it uses a irradiance of 800 watt per meter squared instead of 1000 watt per
meter squared. Again 20 degrees centigrade ambient, and one meter per, one meter per second
speed. So the cell will essentially rise up, in
temperature. Typically for these,
crystalline-silicon-based, based cells, it can, vary all the way from, you know, the
cell temperature for this particular ambient condition in this area, irradiance, It can
vary all the way from 40 degrees C to all the way up to 70 degrees C,
depending upon depending upon how good is your, how good is your module design to
carry away this heat. And also it depends upon what is your
irradiance level as well. So again, at some of these these nominal
operating test conditions so they spec, specify some of these metrics for these conditions
otherwise. And then another important metrics to is to
note is specified in this table over here, where it gives a temperature coefficient
of of my power, the temperature coefficient of my voltage,
the temperature coefficient of my current. So I notice that as I increase my temperature,
my Voc decreases as as I increase my temperature because my Voc has
a negative coefficient over temperature. So, it decreases by 0.31 percentage
points. So, these things are reported by
percentage points per degree centigrade. So if I increase my temperature by one
degree centigrade, this Voc will essentially decrease by 0.31%.
Similarly, if I increase my temperature, my short circuit current typically
increases. Because my bandgap of my solar cell decreases. So my short circuit current increases, so this has a positive temperature
coefficient. The overall power of my cell essentially
decreases, and you can see that my power decreases with this negative temperature
coefficient of 0.42%. Sometimes these, they also specify the nominal
operating test conditions. So they say that if you do operate the
cell at this irradiance level of 800 watt per meters square. And this is the temperature of the ambient
and the wind speed, the temperature of the cell is going to be
between 46 plus, minus 2 degree centigrade, so it’s going to operate
between 44 to 48 degree centigrade. So these are some of the things to keep in
mind. What we need, what we desire for is a good PTC
versus STC ratio. And also low cell operating temperature, because
the higher the temperature the cell will operate at, the more would be the efficiency
degradation.

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