Solar energy, a sustainable and abundant energy resource, offers huge potential in driving the global shift to renewable energy. It has grown widely in recent years as a result of better affordability and reliability of technologies available to harness solar radiation and convert it to electricity or thermal energy. As you can see in the graphs below, solar energy still provides a small part of total electricity generated globally last year. However, together with wind, solar energy has the most added electricity generating capacity in the same year.
N.M. Haegel and S. R. Kurtz, IEEE J. Photovoltaics 11, 1335 (2021).
To explore the full potential of solar in driving global Energy Transition, along with the challenges that must be addressed to realise this, we invited Nancy Haegel from the United States National Renewable Energy Laboratory (NREL) to answer a few questions touching on the potential of solar photovoltaics (PV) in supporting the Energy Transition.
Nancy is Center Director of the Materials Science Center in the Materials, Chemical, and Computational Science Directorate at NREL. Prior to joining NREL in 2014, she was a Distinguished Professor of Physics at the Naval Postgraduate School. Previously, she held faculty positions at Fairfield University and UCLA.
In addition to the U.S. Department of Energy, her research has been supported by the National Science Foundation, the David and Lucile Packard Foundation, Research Corporation, NASA, the Office of Naval Research, and the Department of Homeland Security.
Read her insights below.
How huge is the potential of solar PV in driving (or accelerating) Energy Transition globally? How much of the global energy requirement can it supply by 2050? Please provide the latest numbers that could support the magnitude of its potential.
The potential for PV to drive or to enable that global Energy Transition is, to no one’s surprise, very large. Almost all the studies show that photovoltaic (PV) and wind, together, would be the majority energy sources around the globe in a sustainable energy system.
The sun ultimately is the source of most of our energy, with some amount from geothermal as there is also potential there. The sun was the source of fossil fuels that have brought us to this point, concentrated through living matter.
I think of it as transitioning to solar energy being converted for us in different ways, such as through PV directly to electricity. So, fossil fuels had concentrated that energy for us in a particular way. Now, the challenge for us is to transform that energy in a way that does not disturb the atmospheric and environmental balance that is so critical to the health of the planet. Luckily, we know how to do this. I think the world will benefit from the highly distributed nature of the PV resource, the ability to convert sunlight directly to electricity, and the tremendous progress we have achieved on that front.
Today, PV contributes only about three percent of global electricity. In terms of how much energy PV can supply by 2050, it is really driven by choices we make and how we couple to the larger energy system. Studies and systems are increasingly more sophisticated both in their time resolution and modelling, improving their ability to couple various sectors of the energy system. In general, we are seeing them converge and suggest that PV could be in the range of 40-80% of total energy by 2050.
Wind, offshore and onshore, will also play a key role but to varying degrees across countries. Certainly, the debate continues on the future of nuclear energy. Geothermal can be a contributor as well depending on location.
Overall, I think there is a growing consensus that PV will likely be the majority global energy source. This makes sense as the majority of the world's population lives in regions of pretty high insolation . And our ability to store that energy, whether as pumped hydro, batteries or coupling in sectors like transport and heating, will drive the degree to which we can fully utilise solar energy.
What drove its growth to its current levels? Is there still room for the same level of growth leading to the 2050 Net Zero target?
I would say growth has been driven by a combination of many factors, and I will identify three: decreasing cost, increasing performance, and increasing reliability and bankability. One important factor going forward is the development of sustainable industry, what people call the ‘circular economy’, at scale.
Familiarity with the technology has grown. As deployment grows, you get more information on operating PV systems and plants and how to do that more effectively. We also see increasingly reliable products as indicated by a recent study from NREL, surveying 100,000 PV systems in the US. This builds the confidence of investors.
Leading up to 2050, I still see decreasing costs and continuing learning curves. I also think that we will benefit in the future from manufacturing investments today. PV is not a static technology. Silicon PV technology is evolving. There are new styles of contacts that improve performance, increased thinking about tandems where you put two materials together to enhance efficiency of conversion of light to energy, among other innovations.
Important to note here is that cost will continue to be very important, but there is also a growing cost to not acting decisively. It is not like our current situation is cost-free, both in terms of the use of other fuels and in terms of the impact to the environment.
What are the challenges in achieving the full potential of solar in driving Energy Transition?
There are multiple challenges. The above factors --- decreasing cost, increasing performance, and increasing reliability and bankability -- would not have happened without effort and investment. So that investment must continue.
Certainly, continued work on grid integration from majority renewable or variable energy sources is also needed. We have to learn to operate these grids differently, and utilities, in the US and around the world, are making tremendous progress on that.
And then, optimizing the integration of PV with wind and other generation sources, whether that is geothermal or nuclear. We need flexibility and reliability. Treating this as competition is not the right way to think about it --- it is going to be ‘both-and’. So, integration of these renewables and integration with the broad energy sector, including transportation, and housing and industry.
The growth rate has been tremendous, but we need to install much more renewable energy in a short time frame. I think many governments, communities and major industries and commercial partners are moving fast. The important thing is to maintain that momentum and understand that we have to continue to scale up. It won’t be easy, but it will be well worth it.
What are the types of technologies that are or would be needed to maximise the potential of solar in driving Energy Transition?
PV will be critical and it has to continue to improve. Then, we will see other technologies be complementary for different types of applications: utility scale, commercial scale, residential, distributed PV. Different kinds of technologies may come into play there.
There’s also a lot of interest now in perovskite materials which can potentially result in high efficiency and low-cost PV that could be manufactured at very high rates. They could be used for utility scale PV, perhaps as tandem modules with silicon, and then in some environments where both lightweight and high efficiency PVs are important.
Storage is also critical. We have two good technologies now: pump hydro, which is very efficient, has been in existence for a long time and the majority form of grid level storage today; and utility or residential scale kind of batteries. Both will likely have to play a role going forward if we want to reach our global goals.
New power electronics technology is also going to be very important because we are going to have to manage and transmit very large quantities of electricity. If we electrify large segments of transportation or parts of industry, this will place huge demands on our ability to deliver electricity.
Lastly, technologies that will take electricity, PV or wind, to fuels, whether that is hydrogen at scale or other fuels.
With all these technologies coming together, we can create a future energy system that will meet our needs and be reliable while respecting the delicate balance in the environment required for a sustainable future.
TechnologyCatalogue.com’s Faces of the Energy Transition blog series aims to shed light on key issues surrounding the global transition to clean energy. We invite thought leaders, industry players and members of the academe to share their insights on topics that are related to the Energy Transition.
If you have suggestions on topics and/or resource persons, feel free to reach out via email at email@example.com.
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