Sustainable Solar Technologies with Meng Tao

June 17, 2021

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Dr. Meng Tao joined Arizona State University in 2011 as a professor in the School of Electrical, Computer and Energy Engineering. He came from China in 1992 with a Master degree in Materials Science and Engineering. He received his PhD in Materials Science and Engineering from the University of Illinois at Urbana-Champaign. His current research focuses on sustainable solar technologies. It covers from materials and devices to systems and applications. His book, “Terawatt Solar Photovoltaics – Roadblocks and Opportunities”, was published by Springer in 2014. He is an editor of the Electrochemical Society Journal of Solid State Science and Technology. He co-founded TG Companies LLC and serves as its CTO to commercialize innovative and sustainable solar technologies. He was awarded the Fulbright Distinguished Chair in Alternative Energy Technology, “one of the most respected Fulbright awards globally”, and was invited to the 2017 Nobel Award Ceremony in Stockholm.

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John: Welcome to another edition of the Impact Podcast. I’m John Shegerian. I’m so excited to have with us today, Dr. Meng Tao. He’s a distinguished professor of sustainability and innovation at Arizona State University. Welcome to the Impact Podcast.

Dr. Meng Tao: Thank you, John. Thank you for having me.

John: Well, it’s an honor to have you today. You’ve done so much hard work and research in this area of sustainability and innovation. Before we start talking about all your fascinating work with regards to solar technologies and other technologies, I’d love you to share your fascinating background of your journey, where you grew up, where you got educated, and how you came to this important work that you do.

Dr. Tao: Yes, sure. This is a long story. I came to this country in 1992. I spent the first half of my life in China and the second half of my life in the US. I got a bachelor’s degree and a master’s degree in China. I decided to pursue my Ph.D. here in the US. I still remember that when I boarded the flight from Shanghai to San Francisco, I had $60 in my pocket; that’s all the money I had. I had to borrow money to buy my ticket here. Of course, the first few years were pretty tough, the financial constraints, language, cultural barriers, and then also, [inaudible] on the school because all the classes were taught in a different languages. I was also working up to 40 hours a week, doing research in the lab, because I was financially supported by a research assistantship. That’s what it was like.

I guess, more importantly, there was this anxiety, this uncertainty about my future at that time. I wanted to stay, but could I find a job after my Ph.D.? If not, where would I go? This was an unsettling time of my life, but I’m so grateful that this country did provide me opportunities and I got my Ph.D. in 1998 from the University of Illinois at Urbana Champaign, under Professor Joel[?] Ivy. Actually, I noticed he’s still there today.

I got my first job as an assistant professor at Louisiana Tech University. Two years later, I moved to the University of Texas in Arlington. In 2011, I came to Arizona State University as a professor in the School of Electrical, Computer, and Energy Engineering. I have been here for 10 years now.

John: I always loved the immigrant origination story. My family, I’m a third-generation immigrant. To me, I always relate to every immigrant story; I feel that I’m part of it, it ties us together as a family. When you left Shanghai in 1992, were you the only family member in your family that came here, or did you already have family and friends here?

Dr. Tao: Yes. My sister came to the United States in 1987. When I said I borrowed money, I borrowed the money from my sister.

John: Okay. She was already here, your sister? She’s still alive and she’s still here in the United States?

Dr. Tao: Yes, they live in Minnesota.

John: Wonderful. It’s good you had your sister here.

Dr. Tao: Yes. Otherwise, it would be even more difficult.

John: Wow. Yes, I can imagine. Now, you’re at Arizona State University, I’m on your website.

For our listeners and viewers that want to see the important and great work that Dr. Tao is up to, you can go to

Can you talk a little bit about what specifically you work on at ASU and what your passion and your focuses are?

Dr. Tao: Yes, sure. My research focuses on sustainable solar technologies. Why did I put “sustainable” in front of solar technology? I think people may still have the misconception that “I have solar panels on my roof. Now, I have sustainable energy.” What’s wrong with that? In fact, we need 2 things, simultaneously, in order to have sustainable energy. The first thing, we need a sustainable energy source. Solar is certainly sustainable. The second thing, we also need a sustainable technology to utilize that energy source. This is an issue that has been largely overlooked in the past.

Just to give you one example, the end-of-life solar modules, all solar modules have a finite lifetime, typically 25 years. What do we do when they die? Today, most of them go to the landfill. We have to ask ourselves the question, “Are solar panels really green if they end up in the landfill?” That’s just one example. There are also other roadblocks to sustainable solar technology.

The reason is that the amount of energy we use is enormous. I could give you numbers. Right now, we use an average of 2 times 10 to the power of 13 joules of energy every second. That’s an enormous number. When we could price[?] solar technology, the technology that has to be deployed at an enormous scale is comparable to the scale of our demand to make a tangible impact on carbon emissions.

That translates into enormous amounts of resources to produce and deploy solar technology, things like electricity, water, chemicals, raw materials, transportation, storage, recycling, you name it. We have to ask ourselves the question, “Do we have enough of the resources on our planet to make all the solar panels that we have to make?” It turns out, in many cases, these resources are limited. That’s the focus of my research. My goal is to find a technical solution to these resource constraints and make solar technology sustainable.

John: Really, you’re at the forefront of taking solar technology, which was part of the linear economy, historically, and taking, now, solar technology into the circular economy, as well?

Dr. Tao: Yes, exactly, and the way we want solar technology to be sustainable, so we can use solar energy for many decades, long time to be here.

John: Doc, how far away are we from your goals? You’ve done lots of research, you’ve been cited more than 3,200 times in scientific writings, you’re very well esteemed around the world in all of your research. What does the road ahead look like? Are there lots of roadblocks? Are you more hopeful right now about breaking through than ever before?

Dr. Tao: Yes, there’s always hope. I think we, as humans, are smart enough to come up with a solution to the problem that we face. Now, certainly, that doesn’t mean that there will be no roadblocks, no barriers to achieve our goal. I think the end game is that by 2050, a significant portion of the energy we use must come from solar.

Now, we also have other renewable energy sources like wind, geothermal, biomass. We also have low carbon energy sources like nuclear energy, but solar has to play that leading role in solving our energy crisis. That means to deploy solar technology at a large enough, sufficient scale and roadblocks that we face, like raw materials, electricity, storage, recycling, all these, we need to work out a solution to these problems. I’m optimistic that when we put our concerted effort into the issue, these problems will be solved.

John: If today, the biggest roadblock to solar panel recycling is that the cost of recycling far exceeds the revenue from the recycling, how far away are we from developing these technologies to maximize that revenue and take a solar panel or solar panels, or solar farm to the circular economy?

Dr. Tao: Right now in the United States, I must say that the need to recycle solar panels is well recognized, but it is seldom done today. As you mentioned, the cost for recycling far exceeds the revenue from recycling by today’s technology, so it does not make a business sense, unless somebody walks in first view[?].

How far are we? Right now, I think maybe 10% of the end-of-life solar panels are recycled, and 90% actually end up in the landfill. Even if they are recycled, in my view, they are not properly recycled because there are a couple of issues. One of the issues that there is a toxic material in solar panels, lead. Each panel contains about half an ounce of lead and it’s a liability issue if it does get into water or soil. Today, technology does not allow us to get the lead out.

There are also encapsulated in solar panels, which is ethylene vinyl acetate, which is a polymer. This polymer reacts with water to form acetic acid, that’s vinegar we use at home. Acetic acid is what we use to dissolve lead. Lead, as an [inaudible] are really a bad combination in the module if you sent them to landfills. Then there are also other materials in solar panels like silver, copper, aluminum, silicon, glass, zinc. These materials are worth between $10 to $15 per panel. The technology we have today only allows us to exchange the aluminum and maybe also the copper for about $2 per panel. We are missing out almost 90% of the potential revenue here. That’s what we are focusing on now.

I work with my students to develop technologies for solar panel recycling. We have 2 main objectives. One is to maximize the revenue from solar panel recycling in order to offset the cost. The other is to extract 100% of the lead from modules and then we use that lead in new modules, because lead is used in assorted, new modules.

John: Are we getting closer? Are we getting closer to this dinging of the cost structure of recycling? Do you believe in the next 5, 10 years, we’re going to be able to achieve a program and a system-ology that allows us to responsibly recycle solar panels economically, efficiently?

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Dr. Tao: We have to. The projection is that by 2030, I know that’s a five-year part by the International Renewable Energy Agency, at that time, 2016, they projected that by 2030, we will see a larger quantity of end-of-life panels. Last week, I had a meeting with Evelyn Butler for our Solar Energy Industries Association. Now, the nearest projection is that by 2025 to 2027, we will see a large quantity of end-of-life modules. We have to be ready before that. I think on the technical side, we’re certainly making great progress, but we do need to move on to the next stage. That is to build a prototype to actually test this out, and then provide a service to anybody who wants to get their panels recycled.

John: For our listeners and our viewers that have just joined us, we’ve got Dr. Meng Tao, the very esteemed professor of Arizona State University. You can find Dr. Meng and his colleagues at ASU at We’re talking about solar panels, innovation, his important research, and the technological revolution involving solar panels to be able to be responsibly recycled in the future, instead of being landfilled, which then creates all sorts of hazardous waste, opportunities into our ecosystem, ground, water, animals, vegetation, and eventually, of course, back to human beings.

Dr. Tao, recently, you’re co-founding a company and you’re serving as a CTO for TG Technologies. What’s the goal of TG Technologies, and how is that different from the role that you play as a professor, researcher, and teacher?

Dr. Tao: Yes, that’s really a good question. Being an engineering professor, I guess my career goal is to solve maybe one practical problem for the society, that’s why I co-founded TG company. The company’s mission is to commercialize innovative and [inaudible] technologies for sustainable solar technology. Right now, it focuses on solar panel recycling technology. The federal government gave this on what they call an SBIR grant, Small Business Innovation Research Projects. The company received the post[?] phase one and phase two from the National Science Foundation, totaling being almost a million dollars.

We have come up with a circular chemistry to recycle solar panels. What does circular chemistry mean? Typically you process these panels then you generally have tons of chemical waste. We want solar panels to be circular, but can we have the recycling processes circular, as well? That’s how we got started with this. Now, we figured out a way to basically reuse the chemicals that we use for recycling.

The way we do it is that we first dissolve the solar panels in chemicals then we extract the metal from the chemicals. During the metal extraction, the chemicals get regenerated, and then we reuse the dissolved metal again. That’s how we can cut down chemical waste by 80% from the recycling process. We have, I believe, the best, the most environmentally benign recycling process with this company, with the support from our National Science Foundation.

John: It’s sort of a closed-loop recycling system?

Dr. Tao: Yes, exactly.

John: How long are you from commercializing that invention and those technologies? Are you a year away or five years away? What are your thoughts?

Dr. Tao: Now, we are actively talking with potential investors. Our next goal is to build up a small scale, maybe roughly 100 ton a year-type of facility, which is maybe 100,000 panels a year-type of capabilities to grow [inaudible] from bench top research actually is a feasible, reasonable scale than for that point[?]. That’s probably, I would say, maybe 2, 3 years away.

John: That will be an Arizona, that first plan?

Dr. Tao: That’s a good question. That is still being discussed. Arizona certainly takes care of Southern California, Nevada, Arizona, all those solar panels installed in this region. It could have been in some way in Texas, that also takes care of the Southern part of the United States, or even Georgia, which takes care of the Southeast of the United States. The exact location is still being discussed.

John: You are also a teacher of students and ASU is a wonderful learning institution, especially your Global Institute of Sustainability and Innovation has a world-known record. It’s world-known for the importance of what you teach in sustainability. You were early, your Global Institute of Sustainability and Innovation at ASU was early in teaching this. Are almost all the stars aligning now? Is everything coming together? It seems as though we can’t turn on CNBC, Bloomberg, or CNN, and another story is about sustainability, ESG, green innovation, infrastructure, President Biden’s infrastructure program is all about green innovation. Are your students now the rockstars of the future? Are they gonna make fortunes as we turn the linear economy into the circular economy over the next decade?

Dr. Tao: Yes, that’s certainly an important point. I have a couple of things to say to your point. One is that I spent a year in Sweden between 2017, 2018, as the Fullbright Distinguished Chair. I went to Sweden [inaudible] the United States. The ones I noticed is that the Europeans or Swedes are doing a better job in terms of the circular economy, than the United States.

I’ll give you one example, they recycle being there are 6 or 8 different boxes. One for colored glass, non-colored glass, metal, paper, cardboard. Every city does this sorting so the recycler doesn’t have this heavy burden of sorting different [inaudible]. That’s one thing. Let’s also get into your point of we need to educate them, our next generation, in that direction.

The other point I want to add to your comment is that I was educated in the 1980s, 1990s. At that time, we were so shocked by technical advances without considering all the environmental, social, societal consequences of new technologies that we’re developing. Circularity was not into the initial design or development of a new product. That attitude has to change. I’m glad that as you’re taking a leading position in doing that, we’re trying to convey the message of circularity of sustainability into everything we teach. We will have a new generation who are well knowledgeable and capable of pushing for a circular economy.

John: I wanna ask you a question, though. I want us to agree with my theory. I assume that you and I both love two great countries, China and the United States. We love them, but they’re very big land masses. If you go back to what you just said about Sweden, it’s been my theory all along that Sweden, Germany, Italy, France, UK, and then when we look to the other side, Japan, South Korea, these countries have been generationally ahead of us, as you pointed out, with regards to sustainability and circular economy behavior. Because they’ve been forced to, they have small geographies, they can’t go build more landfills.

You said, we were so interested in advancing our societies in China, in the US, we weren’t thinking in those terms, plus we also had the land mass to just say, “Just dig more landfills. Use it once, throw it out. Don’t worry about taking those resources and reusing them again.” Now, finally, both China, the United States, thank gosh, are getting on board with what the EU and what other smaller countries in Asia have been doing for at least two generations, historically. Is that along the lines of that how you see this, as well?

Dr. Tao: Yes. I definitely agree with you that in the United States, we have not really had lived tough times or lived on extremely limited resources. We tend to buy a bigger house if we can, or buy a bigger car if we can. If we just look at the cities that we have, they are so spread out. Phoenix, if you drive from East to West, that’s like 80 miles. In the city I stayed in, Gothenburg in Sweden, it probably has like on the order of maybe one million people, but the city is really concentrated. East to the West is no more than 50 miles.

Now, it’s probably difficult to have a public transportation system in such a sparsely populated region. In Sweden, it makes perfect sense. You don’t need a car to live in Sweden. They just hop on a bus or train, and it will take you almost anywhere. In the US, you can see that if I travel from the East side of Phoenix to the West side of Phoenix, I will go through 80 miles. It’s difficult to run a public transportation system in such a big city like here, so I agree with you.

Now, we probably need to rethink about these things and see how we can better design our cities to be more sustainable. If we continue to take this article[?], it will come back and bite us, for example, the price plus the waste that you know well. That’s the same attitude, “Oh, let’s just throw it out, nature will take care of it.” Eventually, it will come back and now, it’s a problem we have to deal with.

John: How about with solar panels? There’s so much debate that I always hear, Dr. Tao, over who should pay for the responsible recycling. Is it the manufacturer? Is it the State that they’re used in? Is it other stakeholders that use these in their homes or in their businesses? Who really is responsible? What are your thoughts on that? You’re such an expert in this area, I’d love to hear your thoughts on who should be paying for the responsible recycling of solar panels?

Dr. Tao: Okay, a really good question. In EU, the mandate, the manufacturer has to pay for recycling and offline[?] management. In the US, now, it’s largely left to the waste that you generate, and basically, the panel owners are responsible. There’s no mandate here, that’s why most solar panels end up in the landfill. I see the advantage of putting that responsibility on the manufacturer instead of the customers or the users. If you put this on the manufacturers, then they have to take recyclability into their design. If the customers are responsible, especially these manufacturers, largely they’re overseas, then also these panels last for 25, 30 years, 30 years later, that manufacturer may be out of business. You have nobody to go after.

Also, to be able to recycle these solar panels, we also need to have the basic information. What’s the structure? What type of materials are in there? What constitutes each material? Where do these materials stay inside the panel? This information is totally missing on panels. Some 25 years later, you gather these panels, you don’t know what’s inside these panels because each manufacturer may have a different structure, may have slightly different material, then the recyclers’ job becomes extremely difficult in that scenario. I hope that if we put this on the manufacturer’s shoulder, then they have to behave a little bit more responsible than they have been behaving up to this point.

John: Well, Doc, we’re at the end of this interview, but I always like for our guests to share some final thoughts and words. We have a lot of young viewers around the world that want to be the next generation of entrepreneurs, as well. I’ll leave it to you, and then I’ll say goodbye to both of us at the end. I’d like you to share your last thoughts before we have to sign off for today.

Dr. Tao: Yes, sure. For the young people out there, if you’re looking for the next big thing, or if you’re looking for the next Intel, Microsoft, Facebook, or Google, my path[?] is probably in energy and circular economy. Yes, simply because we use so much energy; we need to shift our energy from fossil fuels to something more sustainable.

John: Wonderful. Doc, I wish you continued success. I hope your company, TG Companies, LLC, becomes a huge success, and we get to create a circular economy of recycling solar panels. I hope you win that, that would be wonderful.

For our listeners and viewers who want to find Dr. Tao and his colleagues doing great work, they are at ASU at the Global Institute of Sustainability and Innovation. Please go to

John: Dr. Tao, you are truly making a great impact on this planet, making this world a better place. I’m so honored and grateful that you spent time with us today on the Impact Podcast.

Dr. Tao: Thank you so much, John. It’s a great opportunity for me, as well.

John: This edition of the Impact Podcast is brought to you by Trajectory Energy Partners. Trajectory Energy Partners brings together land owners, electricity users, and communities to develop solar energy projects with strong local support. For more information on how Trajectory is leading the solar revolution, please visit