Game-changing solar

Francis O’Sullivan: From MIT, this is the Energy Initiative and I’m Francis O’Sullivan. Welcome to today’s podcast, one of a series we’re carrying out focusing on game-changing energy technologies. We’re talking with colleagues from across MIT on the work they’re doing looking at defining the future of energy. Today we’re very fortunate to be joined by Professor Vladimir Bulović, the director of MIT.nano and co-director of the MITEI Solar Low-Carbon Energy Center. Vladimir, it’s an absolute pleasure to have you.

Vladimir Bulović: It’s a pleasure to be with you, Frank.

FO: Vladimir, we hear a lot about solar energy today. It has, obviously, come to prominence in the past five years, maybe over the past decade. We’ve seen dramatic reductions in the cost of panels and we’re seeing real deployment today. There’s a tremendous amount of excitement about solar energy really offering a pathway to very significant decarbonization of the electricity systems. With that said, some, including yourself, have begun to reflect on some of the inherent limitations that today’s crystalline silicon technologies have as we move from their current competitive envelope into the future, and we look at a broader electrification of the economy. I’d love to hear your reflections on that, on the journey that solar has made over the past 10, 20, 30 years. Where we are today and where we’re going to go from here, as we look to really build on the momentum that the low-carbon energy transition has.

VB: Frank, I think it’s really important to start by emphasizing that the solar technology of yesterday is nothing like the solar technology of today. Today it’s much dramatically improved, both in lifetime and efficiency, in the way that modules are being able to more economically be made. The next version of it really is driven by asking, what part of the solar cell is useful? Most of the solar cell materials are actually not functional besides providing mechanical stability to the functional parts. That is to say, you only need a few dozen microns of silicon and that is the part that will absorb all of the light you need to generate electricity. If you then go ahead and say, can I go ahead and use other materials beyond silicon? Could I make an even thinner version of the cell? The answer is absolutely yes. Silicon is not optimized for absorbing light. It’s an indirect bandgap semiconductor. You can do a lot better by direct bandgap semiconductors in many, many, many of the nanostructured solids in the forms of molecules or quantum dots, or more directly, lately, so-called perovskite crystals. These are the material sets that have direct bandgap and absorb light really, really strongly, and hence can get away with being extremely thin. Now why does that matter? Silicon needs to be supported by a thick piece of glass. Because if it’s not, the silicon wafer will crack. The moment it cracks, it oxidizes and stops operating efficiently or at all. The nanostructured solids are thin enough that even if you bend them, they do not crack. As a matter of fact, you can make them on top of flexible, lightweight, paper-like substrates, our latest demonstration showed. What does that open up? Today, two-thirds of the cost of an installation of a silicon module is going to be spent on the installation itself and one-third will be on the module itself. Which simply means if I can make my installation simpler, I can reduce the cost of solar technology by a factor of upwards of three. Solar today can be bought at five cents a kilowatt hour. Reduce that by a factor of three and you’re less than two cents a kilowatt hour. That’s remarkable. No other technology can, in a short run, imagine doing that. Solar can, but it requires a redefinition of what the solar cell is.

FO: I’ve reflected on this a little bit, Vladimir, over the years. The trajectory that solar has had. If we look at crystalline silicon as the ubiquitous silicon paradigm today, as you mentioned, we’ve seen very, very significant gains in the efficiency. We’ve seen tremendous—and perhaps the most profound—gains with respect to the cost of manufacturing. Wafers have gotten thinner, plants manufacturing them have gotten much larger, et cetera, et cetera. But something that strikes me is that, if you step back and you actually look at where record efficiency was achieved, or when record efficiency was last achieved for a crystalline silicon cell, it was certainly maybe ten years ago, maybe a little bit longer. It really feels to me that a lot of the progress that we’ve seen today has been in the transition from the lab into the market into the scaling and then ultimately into the deployment. What you and your team and many of our colleagues here at MIT—and, of course, in other institutions—are working on today feels to me that it’s back in that lab. You’re envisaging, concocting, that new formula that is going to allow us to utterly turn things around, utterly reimagine the deployment paradigm, open up a whole host of additional markets and opportunities. That’s exciting but, of course, we’re going to have to bridge from the lab to that market. We’re going to have to think about scaling, we’re going to have to think about how we actually make this compelling relative to the alternative. I’d like your thoughts on where we are today in terms of, perhaps, the academic or the science, but also where we are today in terms of how we take that progress and really get it deployed.

VB: I’m expecting that as the cost of the solar cells come down, as we make them thinner and installation simpler, it will start being obvious that what we should really do is not necessarily focus on the 30-year lifetime. A 10-year lifetime will be enough, costs will be low, and installation will be as simple as stapling things to the roof. Because with lightweight cells you would not need to reinforce your roof, and delivery of such cells to remote parts of the world that are longing for electrical power will be much easier to do than with the present silicon. The developing world market might be the perfect stepping stone to the broader introduction of solar in the developed world, this new type of solar. The metric of weight, again, becomes a very significant metric for the deployment of such technology. I would also say that there are novel modalities that will start coming through in the use of solar. Solar as a power source is brilliant, in that it harvests the sunlight. Sunlight gives us 10,000 times more energy than we consume in the matter of a year, but the challenge is collecting it all. If you can collect all the sunlight for one hour, we can power the planet for one year. The catch is for that one hour the entire planet Earth needs to be covered with solar cells, or at least the half of it facing the sun. Still, the challenge of such large area deployment is quite significant. Active surfaces of the present objects we build now, meaning to activate solar activity of any surface you touch, that might be another way of deploying solar energy. Except, since by design solar is meant to absorb all the light, a typical solar cell is very dark looking or maybe reflecting blue due to the AR [anti-reflective] coating that’s up on the top. Aesthetics of solar becomes an issue if you actually want to deploy it in the built environment. It’s silly to consider aesthetics except for the fact that in the built environment, we already do spend effort and energy building, so if we can come up with an inadvertently-introduced solar-gathering device within in that environment, that would be a very powerful method for covering large areas of the present world with solar cells. For that purpose, another technology that you could consider with solar is to make so-called invisible solar cells. Solar cells that do not absorb any visible light but do absorb infrared and ultraviolet light. In such a way these solar cells are never going to work as well as silicon or some of these dark-looking cells, because we’re purposefully throwing out a third of the available spectrum. Nevertheless, the Shockley-Queisser limit on these cells is on the order of 21% for a single junction versus 31% for silicon. Yet, when you make them, they look like absolutely nothing. They look like a piece of glass, you can think of it that way. They are transparent to visible radiation and consequently to what our eye catches. Any surface now can become solar active, providing you power in a format that is unobservable. Hence, incidental collection of power by your solar windows, or even your glasses. If you put a micron-thick coating on your glasses you can, today, generate 5-10 milliwatts of power. Place that power to your ear and run your hearing aids so you’ll never have to replace the batteries of those hearing aids. Or, indeed, if you have a Bluetooth radio, that’s another thing you might want to power in your ear. If you put it on top of your Kindle, such a transparent cell, you would never need to charge your Kindle again. Because even with a 1% efficient version of such a cell, you’ll collect enough power in the course of a few days to fully recharge the Kindle battery that lasts a couple of weeks. The point being that I think we can redefine the built environment by introduction of yet another version of these nanostructured solar technologies that are just coming around the corner. Although they might not be the most efficient things around, they might be even more easily deployable because they’ll be just a value-added, thin-film coating to existing surfaces that we’ve already built.

FO: I think this is such a compelling and exciting aspect of the work you’re doing. It’s really an expansion, as you said, of solar from a standalone “this is what a solar farm looks like” to a circumstance where it’s more deployable with flexible formats and so on. It’s easier, whereas less proprietary work is more flexible from a transportation point of view, et cetera. Right the way through to something that is inherently integrated into the world around us. Each step is making it more accessible, more flexible as a kind of method for powering the economy, opening up more opportunities for value-add and so on. You, with your work here at the MIT.nanocenter, are putting together a center, an element for the Institute that feels to me has many strong parallels to that particular story. Because it’s about helping broadly expand and enable the deployment of these new technologies across this wide spectrum of opportunities and helping the innovators to access the technologies and so on that they need to move through the development process in a way that hasn’t been available to date. Tell me a little bit about how in your own mind, from the solar side, and indeed, perhaps, from a more broader general sense, how this effort here at the Institute today with MIT.nano is becoming more and more relevant, more and more important as we face these big challenges for technology development.

VB: I would love to. It turns out that MIT.nano has been in the making for over a couple of decades. It has been in the forefront of our mind, recognizing that we are short on laboratory space given the desires for us, as a community, to invent the next and the next ideas. We built right in the middle of our campus, right next to the MIT dome, footsteps away from everyone, a central facility. It’s 100,000 square feet of shared laboratory space in a 200,000 square foot building that is shared between every single department of MIT. It doesn’t belong to a single school, it doesn’t belong to a single department. It unifies on the order of 2,000 researchers per year that will utilize it. As time goes on, it will likely grow to 3,000-4,000, meaning roughly half of MIT at some point will be stepping into MIT.nano. Right now, it’s about a quarter of MIT researchers will step into MIT.nano to get their work done. Now, what’s inside? Right now, a whole bunch of space is awaiting the installation of new equipment and installations of new ideas that faculty have.

FO: I like that, Vladimir. The installation of new ideas. That’s excellent.

VB: We started construction and design of MIT.nano six or seven years ago. If then we had everything figured out, the building would be old right now as we’re opening it. The flexibility and the growth continues. The evergreen nature of the space is really important and is built into the operation of MIT.nano. Inside it, right now, one of the first tools we’re going to be installing are sheet coating toolsets for sheet coating of thin, nanostructured films for the sake of developing either organic, polymeric, molecular, quantum dot, or perovskite thin films so they can be utilized as solar-active media. We have over the summer visited other facilities to understand the opportunity for wall-to-wall coating, the ability to do a large area, and the development of such ideas. All of that is doable, it really is just a question of finding the right kind of tools, or building new tools from scratch, as many of these technologies are at such nascency. Because they have been recently developed, they are performing amazingly well. Over 20% perovskite cells are now available in laboratories through spin counting. Not through doctor-blading or large-area gravure coating or such. What simply that means is that today’s technology is extremely promising but we haven’t yet shown the proper scalability of it. Except in very rare instances, but not as efficiently as what we are able to do, in the best of the best results. They’re just one-offs. The opportunity within MIT.nano is to ask, if you have a fantastic idea, go ahead, develop it in your private lab here somewhere at MIT. Then you want to figure out how to scale it. You can try building inside your lab a new system to do it. Typically there’s no space for something like that. MIT.nano, though, does have space. As long as you’re willing to engage others, generate a community of people around you, you’ll be able to locate the toolsets in MIT.nano to allow you hands to build a grand idea together. And then there are startups that provide quite a unique set of ideas, or call it take the quite unique set of ideas from the universities, and try to scale them up. The big challenge with startups is that, I was recently told that back 10 years ago, 30% of the venture capital went into hardware developments, like would be needed for solar development. Today less than 5% of the venture capital is invested in the development of hardware ideas, whereas 95% is invested in digital ideas. So money is sparse. If you actually want to launch a new technology from scratch using new materials and processes and they’ve never been scaled before, a typical number when it comes to how much money you will need, is about $50-$100 million dollars over the course of five to 10 years of scaling up the idea. That’s a lot of money and it’s non-existent. You can ask in the beginning of that journey of starting a new idea, how will you validate that you indeed have a great idea in your hand? Raise round A, and round A is typically $10 million, then you can go ahead and reduce the practice and consequently you’ll attract new capital. You’ll never raise round A, given the present situation. The question is my mind was, is there a way to utilize facilities like MIT.nano to dramatically reduce the amount of money you’ll need to generate the next set of ideas? Or at least validate them beyond just the initial stages that the universities typically work at? I believe the answer is yes. Looking at startups I had the privilege being a part of, we would generate a great new idea at a university, and the next thing we would do is step out of the university. Because universities are not for profit and if you start a for-profit entity, you need to do it off the campus. If that’s the case, the very first thing we need to do is reproduce the labs we just left. Refill them with equipment. Figure out how to deliver liquid nitrogen or figure out how to set up glove boxes. Huge amount of expense. I say a few million dollars in a year and a half just to get you to the place where you were when you left MIT. Why not shorten that journey and make it less expensive by simply saying, the day after you graduate, come back to MIT.nano as a visiting researcher or research scientist from outside. We have those. We have startups using MIT.nano and other facilities on campus as external users, to maximize utility of our toolsets. You do as well. And for a fraction of the cost. The day after you graduate, you can start the journey of validating that idea, so when you actually stand in front of venture capitalists, you have a much more baked idea in your hand. A couple of years after you graduated, let’s say. That also means that the journey from that moment to actual deployment of your technology to a million hands is also not going to take five to 10 years. Now it will take three to eight. Let’s call it five, to make things simpler. Making it much more amenable to being funded. I think MIT.nano can help us accelerate hardware technology development in ways that we could not have done before on this campus without the central facility that now we are opening up.

FO: It’s such a compelling idea. I think it really resonates with respect to the energy challenge. The fact that we need systems of solutions, we need communities of folks coming together and working together to deliver the innovation. I think it’s a very exciting new component for the MIT community. For the broader world, though, for the broader energy community, it also feels to me like this approach that you’re pioneering really has a tremendous amount of value and utility. That leads me to this issue of the game-changers concept in energy. You recently participated in an event in Washington, DC, reflecting on some potential game-changing technologies in the energy space, along with some of our colleagues from Stanford. At that event, a lot of really fantastic narratives about the potential out there were delivered. The point was that we wanted to bring those stories to DC and have policymakers understand this so that they can appreciate the need to support this work. Because of your prominence in this space, Vladimir, because of the thoughtfulness that you’ve brought to solar, but also more broadly to innovation—I’m curious on your reflections about where we are today, nationally—internationally potentially—in this arc of innovation and seizing the opportunities that we see from the work in the lab at least. Where are we and what do we need to do, more broadly from a policymaking point of view, maybe even from the societal point of view, in terms of giving us the opportunity to move those ideas forward?

VB: Frank, it’s a very deep question you’re asking. I would try to simplify it in ways that allow us a way to take a concrete action forward. Which is, the new type of solar is coming. If it’s not going to be the United States that will lead the way of developing two cents a kilowatt hour or one cent a kilowatt hour solar technology, someone else will. There is no question in my mind that there is a next generation of solar just around the corner. Meaning, in the next five years we’ll have more readily deployable, lighter, very inexpensive solar energy. That being said, if we are not the ones, as the United States, to lead that way, and some of our economic competitors might be, we will be in a dramatically reduced position where the big challenge we’ll have is that all our energy will be way more expensive than the energy utilized elsewhere to produce anything from food to everyday existence. As a result, we will be disadvantaged, just because we haven’t opened our eyes to the opportunity today, that we should indeed seize the moment and be the lead, as we are presently, in developing the next and the next set of ideas to give us this very, very inexpensive electricity.

FO: Vladimir, we have come to the end of our time. That’s always bad from my point of view because speaking to you is such a pleasure, such an inspiration, really. Both in terms of your vision and the work that you’re doing on the solar front, and the groundbreaking and game-changing potential there, but perhaps even more importantly, the work that you’re doing in trying to bridge the gap from the lab to deployment and understanding the real system opportunities and challenges and what it would really take to be game-changing for energy. Let me thank you so very much for your time.

VB: Frank, I have to just reciprocate in the following way, if I may. Thank you very, very much for engaging me in this journey. I cannot be thankful enough to the MIT Energy Initiative for having the vision to recognize that beyond our technical outputs, what is dominantly important is our perspective on where the future is heading and our appreciation of how to blend that perspective with the policies that are needed to translate those visions into actionable items that the world can benefit from. I just commend you on your ability to comprehend very complex systems, not just of technology. In some ways technology is the simplest. What is really important is asking those next steps. Now that we have it in our hand, how do we give it to the world? The work you’re doing, and through this podcast advocating, are the keys to our future success and benefit the planet.

FO: Vladimir, thank you for the kind words. I think it’s reasonable for us both to say it’s a team effort. We’re all trying to make a little bit of difference.

VB: I agree.

FO: Thank you so much. If you have any questions, comments, or feedback on this podcast, please tweet us @mitenergy. And of course, feel free to subscribe and review us where you get your podcasts. From MIT, I’m Francis O’Sullivan and thank you for listening.