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 the meantime, do check out the latest episode of the Physics World Stories podcast, which looks back a century to the birth of modern quantum theory. In 1925, the physicist Werner Heisenberg holidayed on the German island of Helgoland seeking respite from his pollen allergy.
There, he formulated matrix mechanics, which provided a mathematical framework for describing the curious observations of quantum physics. This June, physicists will gather on Helgoland for a six day workshop that will celebrate Heisenberg's historic breakthrough. The podcast features three physicists who are involved in the workshop.
They share their insights on the current state of quantum science and technology, discussing the latest developments in quantum sensing, quantum information, and quantum computing. They also reflect on the significance of attending a conference at a location that is so deeply ingrained in the story of quantum mechanics. Talks at the event will span the science and history of quantum theory, as well as the nature of scientific revolutions.
You can listen to that episode of the Stories podcast on the Physics World website or at your favorite podcast provider. It's called Helgoland, leading physicists to gather on the tiny island where quantum mechanics was born.