I have some news to share.
So I've decided to invest in this utility scale for the vortex poweplant.
Which is coming up near near Phoenix in the state of Arizona.
So I've decided to throw caution in the verdant and ignore all
the people who say that utility scale for a vortex is not profitable.
And I've decided to make
this investment.
So, if you ever have lived in Arizona, or if you have visited
Arizona, especially between the month of April all the way to September.
I had the fortune or the misfortune of going there
in the middle of the summer in one of the years.
And if you have ever been there, you might already know that it gets really hot.
So especially during the summer months, from April to September.
The temperatures are you know everyday you get
temperatures higher than a higher than 100 degrees Fahrenheit.
And even the average temperatures, they reach they reach
higher than 100, especially in the peak of the summer.
So initially, my concern is that if I am going to install these
Photovoltaic panels over here.
They should you know, they should behave well when the temperature rises.
So I'm interested in finding out
the temperature coefficient for these different options.
Which can be essentially used for installing or which
could be used in this utility scale Photovoltaic Plant.
So I do a quick Google search.
You know the first
thing I will do is do a quick, Google search.
And, you know the very first thing I find is
that, all of these tin film based, solar cell companies.
They seem to be touting about, the low temperature coefficient.
So, they seem to be doubting about
the low temperature coefficient for their technologies.
So for example, over here I have, borrowed
this, chart, from, the website of, First Solar.
and, they are a manufacturer. Picture of CdTe based solar cell.
And they seem to be claiming, over here, that
they have, you know, collected a large amount of data.
So each of these point corresponds to a data point.
And this data seems to be suggesting that
this CdTe based module is from First Solar.
They have a temperature coefficient of this point,
minus 0.2% per degree Centigrade increase in the temperature.
So what that means in, in you know, more realistic term, is that
if I have a module and it's operating at at 25 degree Centigrade.
that temperature, it will essentially give 100% of it of it's name plate capacity.
Now if I increase the temperature let's say, to a 65 degree centigrade.
Then, this temperature quotient of minus, minus 0.20,
what it means is that I would have efficiency degradation of
minus 0.2, multiplied by the increase in the temperature.
So I am increasing the temperature from 25 to 65, so multiplied by 40.
Alright, I have a 8% decrease in the output,
in the power output of the panel. If I'm using this CdTe based
[INAUDIBLE]
here from First Solar.
What if I use a Crystalline
silicon or Multi-cristalline based silicon module, which
I can also use for making this making this utility scale Photovoltaic powerplant.
If I do that, then according to them, I get a temperature coefficient of I get a
temperature coefficient of minus 0.48. which are you know I
can take it approximately as minus 0.5
percent per degree increase in the temperature.
So again if I have that if I have that 40 degree Centigrade increase
in the temperature, I'll get an efficiency
degradation of this minus 0.5 multiplied 40.
Or I'll get a 20% degradation in the power output of my panel as you can see from
over here, versus if I was using the scatter based, module.
I'll only get a 8%, degradation.
So this seems to be, you know?
This seems to be strongly favoring these, CdTe based, modules, from, First Solar.
So I decided to dig a little deeper, and,
you know, look up at, some, some more literature.
And I find this, very good, paper.
Which was,
published, in the Photovoltaic conference. And this you know it, it, it
you know it makes my hear sings, because it lists out all the all
the different differing as well as crystalline silicon based technology.
So for these different technology such
as Crystalline silicon, CIGS, amorphous silicon,
CdTe
It lists out the temperature coefficient for
for the efficiencies for all these different technologies.
And, it's plotted in this chart over here.
And, interestingly, I see that most of my different technologies such as amorphous
silicon, CdTe, CIGS, they are much better as compared to crystalline silicon.
So crystalline
silicon if you look over here, the efficiency, it degrades by minus 0.45.
What if I compare it, say, of to, let's say, six?
It has a temperature coefficient, efficiency which is 2 3rd of that.
If I compare it to CdTe, it's less than, it's less than half of that.
And if I compare it to amorphous silicon, which seems to have
the best temperature coefficient of efficiency.
It's, efficiency it only degrades by, minus 0.13.
So, you can see, over here, that
if I increase the temperature, my efficiency degradation
of the, of my cell, or of my panel, it's the lead for amorphous silicon.
Followed by a CdTe, followed by CIGS, and followed
by crystalline silicon, which seems to be the worst.
Some most of this efficiency degradation or degradation
in the maximum portion created by the panel.
It it arises due to this degradation of the open circuit voltage.
So if I increase the temperature, I've
covered this in one of the previous videos.
My Voc typically decreases.
And my JSC increases.
But this, decrease in the open
circuit voltage is, the dominant, dominant, effect.
And, that leads to degradation in my, in my efficiency of my cell.
Now I'm very intrigued by why these, thin film based technologies.
They seem to have a better
temperature coefficient as compared to crystalline silicon.
So I look at this chart, I stared at it for
many hours, many days.
and I find that there seems to be a correlation between
these temperature coefficient of efficiency and
the band gap of these materials.
For example, crystalline silicon it has a band gap of let's say 1.1 EV.
CIGS has a band gap of close to 1.1, you know,
it depends upon the ratio of these elements, but between 1.2 to 1.4, EV.
CdTel, it has a band gap of 1.44 EV, and
amorphous silicon, it has a band gap of 1.8 EV.
So you see that, as the band gap is essentially
increasing from, crystalline silicon to CIGS to CdTe, to amorphous silicon.
Though my temperature quotient
of efficiency seems to be improving, or the, my efficiency degradation,
it, seems to be reducing. So, now, this is, very interesting,
and in one of the previous, in one of the previous videos
I discussed that the temperature coefficient of Voc is
essentially given by this formula. Where it is related to
the difference of between my band gap and
and it's given by essentially this formula.
Where it's related to the difference in the band gap and the Voc of my cell.
So again this doesn't seem to reflect you know, what what this band gap will do.
Because according to this formula these are the band gap is is
the increasing it should you know it should
both this if the band gap in is increasing.
Both this term and this term increases.
So what I'm interested is in finding you know how
does this Eg minus Voc looks for these different technologies.
So again I do a quick literature search and you know its
it's, it's a way likely that this was measured by other researchers.
So I am showing this plot from Dr. King from Spectrolab, and he
has he has plotted this Eg as well as Voc, as
the rest of parameter, I am interested in my Eg divided, minus
my Voc for this different technologies. So what he says is
that, if you increase your band gap, your Voc increases as well.
But this difference between my band gap and Voc, which is reflective
of these different mechanisms, different recombination
mechanisms which occur in my cell.
That essentially more or less remains a constant.
So, if I look at germanium, all the way from germanium,
to, you know, to let's say gallium arsenide, to all these other,
[INAUDIBLE]
material. So this Eg minus Voc remains, constant.
So if I, if I essentially look at, Eg minus Voc, divided by Voc,
which would be reflective of how my Voc changes as a percentage point.
So, thi, this term is essentially the numerator is a remaining constant.
While this Voc is increasing a lot and increasing
my band gap. So this is one you know, one at least one
point at which says that essentially my my Voc degradation.
It would be lower for these high band gaps cells.
And here's my efficiency degradation, would
be lower for these other different technologies.
Which typically have a bind gap, which is higher than what is what
is the case for this crystalline silicon.
But besides that you know there are, this is one of the factor
which can be explained easily by by the physics of the solar cells.
But there are you know other other trends I see in this data as well.
For example this amorphous silicon here.
It's efficiency, it seems to be
degrading non-linearly as a function for temperature.
And the reason
for that is that this amorphous silicon or
the amorphous materials, they suffer from this light-induced degradation.
And the effect for that is called a Staebler, Wronski effect.
So essentially the if these these says if you essentially expose them to
or you keep them at high temperatures for a long period of time.
There's some self
unhealing, or there's unhealing of this damage which takes
place if you increase the temperature of these cells.
So, essentially, it's efficiency, it degrades
non-linearly as a function of temperature.
Similarly, there are some other effects for CdTe, as well.
So, CdTe based solar cells, they, they
essentially suffer from this large contact resistance.
Which reveals from this back contact
for the CdTe based
[UNKNOWN].
And again, if you increase the temperature, the resistance
[INAUDIBLE]
which comes to this high contact, resistance,
it seems to seems to negate aswell.
Similarly we see ahead this there's a, there's a tandem
set over here which is essentially a combination of amorphous silicon.
Which has a band gap of 1.8, and
micro-crystalline silicon which has a lower band gap.
And we see that essentially the combination of these, it has a temperature
coefficient which is somewhere in between
in between crystalline silicon and amorphous silicon.
So there are other things which essentially also help
in giving lower temperature coefficients for these thin frame technologies.
But the bottom line is that most of these thin frame technologies,
have a much better temperature
coefficient, as compared crystalline silicon.
With amorphous silicon being the best, CdTe being quite impressive.
And 6, even 6 being better as compared to these as compared to crystalline silicon.