Hello, and welcome to the Physics World weekly
podcast. I'm Hamish Johnston.
Solar panels offer a way of mitigating
climate change
by generating
electricity with an extremely low carbon footprint.
Today,
India ranks fifth amongst nations
in terms of installed
solar energy capacity,
and increasing this is playing a crucial role
in the country's drive to reduce its greenhouse
gas emissions
by 45%
by 02/1930
when compared to 02/2005.
While much of India is blessed with abundant
sunshine,
the country is experiencing
a persistent
decline in incoming solar radiation
associated with aerosol pollution.
What is more, higher temperatures
associated with climate change
reduce the efficiency of solar cells,
and their performance
is also impacted
by other climate related phenomena.
To understand how a changing environment is affecting
solar energy in India,
I'm joined down the line from the Barcelona
Supercomputing
Center by Shashovan
Ghose.
He is formerly of the Center for Atmospheric
Sciences
at the Indian Institute of Technology,
Delhi,
where he coauthored a paper that looks at
India's future
photovoltaic
potential.
Hi, Shashovan.
Welcome to the podcast.
Thank you. Now, Shashovan, you begin your paper
by saying that the effects of climate
change are already creating significant
challenges to solar power generation
in India.
Why is that?
Yeah. You correctly mentioned this thing and pointed
out. So let me talk about,
basic understanding of, this climate change and the
solar renewable
energy nexus.
So you already know that climate change is
happening,
and the evidence are numerous.
Interestingly, the very solution
to tackle the climate change is to switch
to renewable energy.
However,
the renewable solar energy and other renewable energy
to harness
and also use the renewable energy is also
vulnerable to the climate change. So if you
ask me why, so let me give you
an example in the in the case of
solar photovoltaic.
So for solar photovoltaic,
surface solar radiation is the primary factor for
our solar generation.
But to harness that energy,
we need solar panel.
So this very technology
is also vulnerable
to the climate change consequence.
So here, two things are are are to
be mentioned.
The first one is the how much amount
of solar
radiation
is is is coming to the solar panel
to produce the solar energy. And the second
one is that when the solar panel
l is, is exposed to the, daylight sunshine,
how the climate change will impact that, technology
itself.
So there are three three factors
which is actually playing a role all to
the solar photovoltaic.
One is the solar radiation,
and then the sec second thing is that
the temperature
are and the wind speed, relative humidity, and
other meteorological
parameters. So if you look into the climate
change landscape,
then you see this all these factors, like
the solar radiation,
temperature,
wind speed, all these things are also going
to change. So to tackle climate change, we
need to switch to renewable energy, but at
the same time, we also take care of
that how the climate change will impact these,
primary variables,
to better harness the solar radiation.
So in coming to India, if you looked
into this,
we use the,
climate global climate models,
from the,
coupled model intercomparison
project phase,
six, which are actually an initiative by the
World Climate Research Program. And we also looked
into,
the future scenarios
or,
to to design in the, the input variables
for the solar photovoltaic. And what we found
that the the the the different solar energy
indicators
are going to decrease
is in this consequence. And from that, at
point of view, we are telling that the
solar energy
potential over Indian region and is expected to
decrease in the mid century.
So I just wanna make sure that I
understand,
the connection between a warming climate and the
performance of solar cells. Are you saying that
as the temperature increases, the ambient temperature,
then the efficiency
of a solar cell will drop?
Exactly.
You understood,
correctly.
So the solar panel material,
is,
is, is a is a subjected to
change by the climate change consequence. The meaning
is that the solar panel material,
one parameter is important.
We call this temperature coefficient of the solar
panel material. So in the in the market,
the the different type of solar panels, we
we we now get. One is monocrystalline,
then the multicrystalline,
and, now,
recently,
the, thin film, solar panels. So all these
type of solar panels have a different temperature
coefficient. Meaning is that,
the temperature coefficient indicates the percentage decrease in
efficiency
for every degree
degree Celsius rise in temperature
above a threshold temperature, which we call as
25 degree centigrade.
So for instance, if you can think of
a panel of temperature coefficient
of point four percentage,
that means that the temperature is if above
10 degree centigrade,
from this 25 degree,
the standard threshold, then there will be a
a possibility that 4% decrease in efficiency.
That means if a solar panel have a
efficiency of 2020%,
now it will work at 19.2.
So so so that is the case. So
for for to tackle this, high temperature,
we need to produce climate resilient,
solar panel. And for that, the thin film
solar panels are are better preferred, and,
and that will actually tackle this high temperature.
And, also, along with this, we need to
have a sufficient,
heat exchange,
methodology
to the, solar panel to better,
get the,
solar harnessing capability.
And and one of the key findings that
you found in your paper
is that,
future solar photovoltaic potential across India
in the period twenty forty one
to twenty fifty
will drop by about 3%
when compared
to nineteen eighty five twenty fourteen
baseline.
Is this is is all of that due
to,
temperature increase, or are there other factors involved?
Okay. Well,
like, in our paper,
we actually use a PV conceptual
model,
which actually
takes the input from
the different climate,
models output, like the solar radiation,
wind speed,
temperature, and other fact other variables
to the input, to this, PV conceptual model.
And and we get,
the output of different solar energy indicator from
that PV conceptual model. So one of the
indicator is,
PV potential,
which is a function of radiation,
temperature, and the surface wind speed. So let
me clarify that this PV potential,
has a three different,
type of variability,
with these three parameters.
So if you have high radiation,
then you get more PV potential. If you
have high surface wind, you get better heat
exchange from the solar panel, so you get
more or PV, potential.
But if you have higher temperature, then that
leads to a drop in PV potential. So
what we found in case of India,
is that the drop in PV potential
are in the mid,
century decades
is expected to due to
the drop in radiation
followed by the increasing temperature. However, the surface
wind and has a very minimal effect.
I see. And and India is a is
a huge country.
You know, you've got deserts,
in the Northwest.
You've got mountains.
You've got huge cities. You've got lots of
countryside.
In the South Of India,
I suppose you have a tropical climate.
Is this
3%,
is that something that is going to be
uniform across India, or are there gonna be
some parts of the country where it's more
than 3% and some parts that are less?
Yeah.
Well,
so,
the India is a first country, as you
mentioned, and it has a, like,
a, different,
if you go from north to south or
east to east to west,
there is a variability in the climates and
all these,
factors.
So, as you as you rightly mentioned, so
these the the input variables for this PP
conceptual model will vary from one parts of
Indian,
to the other parts of India. So what
we found is the drop in PV potential
is not uniform. As you mentioned that the,
PV potential, as I already talked about, that
is a, function of the radius and temperature
and the surface wind wind speed. So in
almost all part of the country,
what we found on is the drop in
PV potential, and this 3% is the national
average.
So
and this drop in PV potential is mainly
because of the increasing aerosol that is related
to the higher air pollution
and then the followed by the increasing temperature.
So what we found is that, most part
of the Indian nation having a drop in
PV potential except the Northeastern region and where
we are getting a increase in solar potential,
and that is due to the decrease in
cloud,
cover over those region. But interestingly, the Northwestern
Part of India where the Thought Desert is
there, which is,
inherently
inherently,
with the high aerosol load. But what we
found in future
are it is expected that the cloud cover
will increase and the aerosol load will decrease.
So over those region, we'll be more sensitive
to the cloud cover. So as you rightly
mentioned,
that,
the PV potential the drop in PV potential
has a regional pattern, and that is mainly
governed by the aerosols
and some part with the clouds and followed
by the increasing temperature.
Okay. And you you've just mentioned aerosols. Aerosol
pollution is a big problem,
in many parts of the world, and I
think particularly
in parts of India, for example, of Delhi.
How how does, aerosol pollution affect
the efficiency of solar panels?
Well, aerosol
are very common. Aerosol pollutions, particularly
particularly particulate matter pollutions are very common in
global South
and mainly over India,
China, and Bangladesh. And, these these are the
countries,
the aerosol pollutions are are are quite high
and always in the, in the global media,
mentions.
So so let me just talk about the
physics behind how aerosol will impact the solar
radiation.
So as you know that the aerosols,
float over the atmospheric
atmosphere,
and it based on its property, it either
scatter or absorb the incoming solar radiation reaching
to the, solar panel and reduces the solar
panel,
performance efficiency.
So what we found is that the most
part of the,
country, an increase in aerosol, loading is expected
in mid century and which, will lead to
the reduction of radiation and at the same
time to, to lead to the,
reduction
in on PV potential.
In in another paper,
which was published,
two years back where we quantified
that due to aerosol, India lost almost
one third of its solar resources in the
last two decades from 02/2001
to, 02/2019.
So, yeah, aerosol pollution,
is a big concern, for our solar photovoltaic
potential
in India. I see. And is it,
is it also a problem that,
I mean, I'm guessing that some of these
aerosols,
and other particulates
will settle on,
solar panels and,
you know, essentially make them dirty and not
as efficient. And you you'd have to people
will have to go out them and go
out there and and clean them
more often,
to to, to boost their efficiency. Is that
is that also a problem with, with pollution?
Exactly.
Like,
so so let me just tell you that,
what we found is that in
the last two years,
we are working on these things.
So,
what we found that there are two mechanism
in which aerosol is impacting the solar radiation
and followed, the, solar photovoltaic potential.
One is what we call this the atmospheric
attenuation effect where the aerosols are floating over
the atmosphere,
and they block the solar radiation reaching to
the solar panel. And the second, what we
called is the, settling of aerosol over the
solar panel, which we we we technically called
is a soiling loss. And we found that,
the soiling loss is, very, very,
severe in India,
for, the places where there are either dust
dominated
or, there are polluted,
from the other, aerosol species. So as you
rightly pointed out, there's these two factors are
actually impacting the, solar radiation
and and also the solar photovoltaic
generation.
I see. And that I mean, cleaning solar
cells is is an important,
issue on its own, isn't it? Because I
mean, I'm not sure exactly how they're cleaned,
but I suppose if you're if you're having
to clean them regularly with lots of water,
that could be a problem
in in parts of the world and and
parts of India where there isn't a lot
of water. You know, it could put a
strain on on local resources.
Yeah. It is a a very fantastic,
point you you mentioned. If you looked into
the most of the, solar parks are are
over the, desert region. So there is inherently,
they are, water stressed.
So if you do not have a proper,
like, cleaning,
cleaning, cleaning, requirement or maintenance, you you may
lead, to the water stress problem.
So so so so to
to avoid this problem, we we need to
focus on,
certain coating,
which are are, maybe,
euphoric to this particulate matter. So they will
not stick to the panel. And,
so so we we have to look into
that type of,
resilient,
technology
before the, solar panels.
I see. And and I would imagine in
in other parts of India where, you know,
let's say it's it's very wet,
you might have the opposite problem in the
sense that,
because you've got so much water
around, you're getting,
I don't know, things like moss and lichen
growing on the solar panels.
And, you know, you have to go out
and and clean that material off.
Yeah. Exactly. This atmospheric variable, if I correctly
understood your point that, the high humidity and
all these things can lead to algae and
other, things to grow over the, solar panels.
So, yeah, that that could be also a
factor. So so the all these things comes
under,
what we call the soiling of the, solar
panels.
So in in one of my future,
work is on that, lineup where we are
actually working on this, soiling sorts of, problem,
and, we are trying to provide some sorts
of,
periodic,
periodicity of the cleaning cycle, what should be
the proper, cleaning cycle period to to get
a better performance, to better assess the solar
energy,
generation.
And I suppose we've talked a a little
bit about how solar technologies can be made
resilient
to the effects of climate change in India
and elsewhere.
What what what are the main things that
that need to be done,
you know, when we're thinking about what types
of solar
panels we should use and how we should
maintain them? What are the big things that
we can do to,
make the systems resilient
to increasing temperatures?
Yeah.
So so there are, there are actually,
two, three things,
could be the main features to look into
the future solar,
technology in terms of climate resilient to make
it climate resilient.
One could be the,
temperature coefficient of the material,
which I already mentioned you. Like, we need
to think about, like, the material which has
a a less temperature coefficient. Meaning is that
every degree rise in temperature
from a threshold like 25 degree centigrade,
the,
drop in PV potential efficiency should be less.
So so for this,
there are three three, four,
type of solar panels,
material like monocrystalline,
multicrystalline,
and the thin film. And what we found
is that the thin film,
solar cells
have,
less temperature coefficient.
So meaning is that if there is high
temperature, or,
increment
from the threshold limit,
they will not get,
more efficiency drop. So so that efficiency drop
for high temperature will be less for the,
thin film
solar cell.
And the second thing is that,
to avert the,
solar,
soiling losses,
we need to thought thought about,
certain coating materials,
which are at the same time high heat
resistive,
and, also,
they will not allow to stick to the
stick to different,
particular matter,
if if there is. So so so do
these two, three things we need to think
about
one for to tackle the, climate change in
terms of temperature
and the, particulate matter pollution.
And and when you're looking at these different
technologies,
is there is it the case that there's
a trade off that if you want,
if you want to make a a solar
panel that's resilient
to increasing temperatures, then
it has to be more expensive than existing
technologies,
or perhaps it's not as efficient
as existing
technologies?
Or are you confident that you can come
up with,
with photovoltaic
photovoltaics
that are
both resilient and
efficient and low cost.
Yeah. Obviously,
when you have all these, things you incorporate
in one material, which you are, trying to
prepare,
that will comes with an, with a cost.
So so so so that needs to be,
like, we need to we need to thought
of, these,
these these things. But but what I what
I found from the studies
and from my, PhD thesis is that, like,
if you want,
to have
a better utilization
of solar,
potential,
we need,
two things. One is that we need to
clean our environment.
So the clean air should come
hand to hand with the clean energy.
So if you clean your environment,
then what will happen, you are coming up
with
less,
a particulate matter pollution.
So you get
more solar radiation impinge into the solar panel
to produce more solar energy.
But at the same time, if you also
look into
all the climate action, if you have a
strict climate action,
then what will happen? You will avoid the
temperature induced losses.
So the PV panel will work,
its rated efficiency
so you get better,
solar energy generation.
So so for me,
we need strict
air pollution,
mitigation.
And at the same time, we also need
strict climate action to better,
utilize
the PV potential
and to make a sustainable lesson.
I see.
Well, that's great. Thanks thanks so much for
coming on the podcast
and, and talking about this. It's a really
fascinating
subject.
Sushovan's
paper is called Future
Photovoltaic
Potential in India,
navigating the interplay between air pollution control and
climate change mitigation.
And you can find it in the journal
Environmental
Research Letters,
which is published by IOP Publishing,
which also brings you Physics
World. Thanks for coming on the podcast.
Thank you, doctor Hamish, for the opportunity.
I'm afraid that's all the time we have
for this week's podcast. Thanks to Shoshovan Ghos
for joining me today, and a special thanks
to our producer, Fred Isles.
We'll be back again next week, But in
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