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Engineering the Future: The Future of Energy

 


Podcast Host

Episode 1 Guests


Vijay Ramani

Professor



 

podcast

This is the first episode of Dean Aaron Bobick’s new podcast: Engineering the Future.

What are both the near term and mid-term futures of energy around the globe and what technological discoveries and innovation are taking place to help determine that future?

Transcript

Hello, everyone, and welcome to the first episode of this new show, Engineering the Future, from the School of Engineering and Applied Science at Washington University in St. Louis, otherwise known as WashU. I'm your host, Dean Aaron Bobick. In this podcast series, we'll explore some of the world's more daunting problems and discuss how engineers who, by the way, are some of the world's best scientists, are working to solve these problems through research, innovation, collaboration, and education. One of the great things about being an engineering dean is that I am continually amazed by the advances my engineering colleagues around the world are making that address some of the great challenges facing society. The domains range from energy and automation to the implications of nanoparticles in medicine and agriculture. My goal of this series is to take you, the listener, along for the ride as I learn about these remarkable developments.

Our first episode focuses on the future of energy. The recent humanitarian disasters that have ravaged the US, Mexico, and the Caribbean reminded us all of modern society's dependence on electricity and fuel for everything from refrigeration to transportation. To feed that dependence, our world is still relying on easy, cheap access to fossil fuels and technologies first developed more than a century ago. But over the last several decades, we've come to understand the environmental and health challenges posed by the extensive use of such combustion-based energy sources. Everyone has heard the discussions about the possible impact on climate caused by such use, but now the health and environmental effects of the fine particles produced by energy combustion have become an even clearer concern. How our energy sources and uses evolve will have dramatic impact on the quality of all of our lives.

What is the future of coal and other fossil fuels? The question I want to explore today is what are both the near-term and mid-term futures of energy around the globe, and what technological discoveries and innovation are taking place to help determine that future? To help answer these questions, I'm beginning my conversations with Professor Vijay Ramani, the Roma and Raymond Wittcoff chair professor here at WashU. He is also the director of our solar energy and energy storage center, and his own research focuses on grid-scale storage, a topic I suspect we'll be discussing shortly. So welcome, Vijay. You have the incredible good fortune to be the very first guest ever on Engineering the Future. Thanks for making the time.

I'm honored.

So let me start off with a pretty basic question. In the next 20 or, say, 30 years, can the world stop using fossil fuels?

No, it would not be possible for us to stop or divest completely from fossil fuels in that time frame or even in more extended time frames, even though that might be desirable to some. But practically, that's not possible to do so.

Why not?

The magnitude of the problem — or the magnitude of the energy landscape, it's massive, and replacing the distribution network available for fossil fuels as well as the availability of fossil fuels with alternate technologies, in toto, is simply something that cannot be done, even if economics was not a problem. But having said that, if you look at economic aspect of replacing fossil fuels, the word which comes to mind is stranded assets. So you already have invested a huge, huge amount of money into building this massive infrastructure which is entirely fossil driven, and to essentially divest away from that and reinvest an equal and/or larger amount of money to replace it with a completely renewable-based infrastructure — and this is not to say that we should make no efforts to replace fossils where we can with perhaps cleaner technologies but, at the same time, to aim for a complete replacement, I think, would be unrealistic.

What percentage of the world's current energy budget is fossil fuel, approximately?

If you take all the sectors together, it would be on the order of 80 to 90 percent.

Wow. So, basically, this is a challenge of just overwhelming scale. The magnitude of what needs to be replaced is so large that in some sense it's not physically possible to do it worldwide in 20 or 30 years. All right, well, let's talk just a little bit about the US. This last October, St. Louis, where we are now, joined I think it's 46 other cities across the US, committed to 100% clean energy by 2035, and the last time I checked, that's like 17 years from now. Can we get there?

If by clean energy they mean clean fossil fuels as well as renewables then there is some hope of meeting the target. But if by clean energy they mean 100% renewable-powered city of St. Louis in 17 years, I think that's probably a step too far. But the issue really is we need very good baseload power generation for our society to be able to function, and at this point, renewables simply do not provide baseload power generation. They are extremely intermittent. And so to have 100% of your energy needs met completely from renewables, you would need to have energy storage of the magnitude that would be economically challenging to achieve.

As opposed to saying we're going to get to X percentage of renewables by whatever date, let's assume that what we want to do is essentially move as effectively as possible to renewables. What are the biggest barriers to such large-scale conversion, not just the economics but also in terms of the technologies, in terms of where we are versus where we need to be?

From a technical perspective, renewable energy is very well advanced, and it's not very likely that you're going to get very much further in terms of efficiencies. The problem with solar, it's as simple as sun shines during the day and not at night, so it's extremely variable. And so if you need to have solar energy powering your entire city all through the time, 24/7, you just have to make sure that you have adequate storage capacity so that when the sun doesn't shine you still have electricity. Wind is even more intermittent. You could have variations on the order of seconds, minutes, and it's very difficult to predict what those variations will be. And so one of the main challenges with very large-scale implementation of intermittent renewables would be the storage challenge, so the question of how do you store these electrons for when the sun doesn't shine or the wind doesn't blow?

What are sort of the fundamental challenges that have to be overcome for that scale storage to really become viable?

There are multiple technical approaches to actually store the electricity. I mean, a very simple one to understand is pumped hydro. And if you have certain geographical features, you can essentially pump water up an incline when you have electricity available, and just run it down the incline when you need to make electricity out of a turbine. So pumped hydro is easy to understand but, of course, it's geographically limited. And some may argue not because you can always dig a hole and store water there and pump it up and down.

That doesn't sound very sophisticated or effective.

It isn't. It's reasonably effective except that, of course, you have to deal with the compressor efficiency, so either round-trip efficiency is going to be impacted by that.

I remember hearing that, in China, they were installing something called vanadium flow batteries as a way of handling grid-scale storage for renewables. So what are flow batteries, and are vanadium flow batteries the path forward for the future?

You are correct in that flow batteries are being extensively used for grid-scale storage, at least at a demonstration scale, these days. So a flow battery is like any other kind of battery, for example, a lithium battery, with the exception that the energy of the vanadium flow batteries is stored outside of it in a large tank or, rather, in two large tanks which store vanadium salts which are dissolved in acid. And the way the battery works is when you pump these solutions through the central battery itself, separated by a membrane, you actually allow electrons to be stored in and out, and the ions move through this membrane, back and forth, when you charge or discharge the battery, so it's a relatively elegant device.

Can we just use those to make renewables more reliable?

Well yeah, except that they are a bit expensive and that vanadium in itself is a very expensive component. And so if you use vanadium as your active medium to store the electricity then the technology becomes a bit too expensive to adopt, well past the cost targets set by the Department of Energy. And so the solution that we are proposing to that is we go to cheaper elements like iron and chromium. But when we do that we run into the issue of the membrane which really is key, because since you have two different components now, iron and chromium, the membrane would let them pass through and go to the other side, and they can't be recovered. And so we are actually working on a membrane that prevents these ions, iron, chromium, etc., the cheaper ions, from moving from one side to the other, and that's how we intend to make this technology cheaper and more affordable.

So the key to moving towards flow batteries being able to be adopted in a larger way and more affordable is to figure out how to make those membranes such that we can use less expensive materials in the medium and still have it be reliable.

Absolutely.

How far away do you think we are from having grid-scale storage flow battery technology that, if people want to deploy, is effective and affordable? And I guess I'll use the word resilient, right? They have to be reliable and they have to last for a while. How far away are we from having that?

There's a two-part answer to that question because the economics differs based on the location. If you look at a country like the United States, where the grid is pretty well established, you are competing against electricity coming out of the wall at 10 cents a kilowatt hour, which is probably what you pay here in Missouri. You're probably at least a decade away, minimum, because of the cost aspect of it. But if you go to southeast Asia or to India where you have issues where there are places, and many places, impacting tens of millions, maybe hundreds of millions of people, where the grid simply doesn't extend far enough, then the economics becomes a lot easier because now you're competing against the cost of extending the grid and not the cost of the power plant. And so in those, what I would call, weak grid sectors, the cost the people or the government would be willing to bear to introduce these technologies as part of distributed solution as opposed to a unified solution would be a lot higher than what the DOE predicts for what is required for the United States. So that $100 a kilowatt hour number was for the United States.

Before we move to talking about changing things so that using fossil fuels can be a cleaner operation. When I was a kid, we were sure that we were just going to have nuclear power plants everywhere, and that was going to save the world. And even when I was in college, just 100 years ago, you could demonstrate that nuclear had the ability to produce enough electricity. We had the resources for many hundreds of years in a way that was effective. And then, of course, a variety of events, Three Mile Island, Chernobyl happened and, from what I can tell, it just became politically untenable. Do you think the energy budget requirements, the needs, the availabilities are going to force us to go back to nuclear at some point whether we like it or not?

I don't think so. I don't think it's going to force us to go back to the nuclear. And if you look at the US, and if you want to review the facts, the last nuclear power plant was approved in the early '90s. And once you get approval, it takes about 10 to 12 years to build one of these online, so it's extremely slow process. And a nuclear power plant is a gigawatt at most, maybe 500 megawatts, a gigawatt at most, so if you're talking about using nuclear to replace legacy fossils, you need to be building or commissioning a new nuclear plant a week for the next 20 years. And to me, even if the political bid was there, which is probably not there in this country, nor is it there in Japan, nor is it there in Europe — it exists in abundance and places like India and China, and France is about 80% nuclear already. So there are some countries where, politically, it's acceptable. Some countries it's not. But even assuming the political go ahead is given to use nuclear as an option to perhaps replace the existing legacy fossil fuel network, it would just involve a tremendous investment of time and money, and it would be equivalent to opening a new plant every single week, maybe, for the next 10 years or 12 years. There are many countries which are pursuing nuclear, and for the smaller countries it adds up to a more appreciable fraction. But for the larger countries, it's going to be very difficult to have it replaced.

So basically, you're saying it's not inevitable to go nuclear based upon our energy needs, it's just potentially part of the portfolio.

Yes, it will be part of the portfolio. And there are some countries, Germany is one example, Japan is another, where it's becoming politically very, very unpopular to go nuclear, but neighboring France has absolutely no problem with it.

So let's take it as a given that we can't get to all renewables quickly. Then the question becomes is, what can we do to make fossil fuels in the US and in the world sort of less damaging, both in terms of immediate health challenges and potential environmental impact? What are some of the steps that we need to take that can help us get to a more effective and safer use of fossil fuels?

If you look at the primary sources which are used for electricity generation, you got coal, and you got natural gas, so ...

Not oil?

Well, for electricity generation, not as much. I mean, for transportation, quite a bit, of course. But for electricity generation, it's not as much. And so the absolute easiest thing you could do is switch from coal to natural gas. It's still fossil, it's still legacy, you have to retrofit, of course, and there's a cost associated with retrofitting an existing plant. And this country has actually moved in that way. I mean, if you look at why there are no more coal plants being built, well, that's the reason. It's just not economical for them to compete against natural gas at this point in time, but that could change. Again, if the natural gas prices rocket up, coal becomes economical again. So the coal versus non-coal is not is not a political issue; it's an economic issue. And remember, these plants are built and amortized over 30 years, and so it's very difficult to go to a coal plant and tell them you got to shut down, because they can't do it. They have to recover the sunk cost somehow, and so there are small amendments they can make to make it cleaner burning. They can add on attachments which essentially take out some of the more damning pollutants which come out. And I think a lot of that work is already in progress because there are regulations in place to make sure that what comes out of the coal plant today is actually a lot cleaner than what used to come back even 15 years ago. And that's in the US. Now, in a place like India, things have changed quite a bit. If you look at the coal sector, the thermal power sector, it's extremely distressed right now. Even the existing coal plants are running at 50% capacity or less, and this is not the only reason. The other reason has been that the cost of producing power through coal is actually greater in India today than the cost of producing power through renewables, solar and wind. It's a complicated calculation, but there are two approaches. One is you retrofit and go to natural gas. That's, again, not possible everywhere. The other option is you have to add on attachments which would essentially make it a cleaner burning coal plant.

We also have this problem that we have, I don't know — last time I checked there was somewhere in the order of 100 million cars driving around in the United States. They're currently burning fossil fuels. What are the technological things we need to start thinking about doing in order to make the burning of fossil fuel as least damaging to our health and environment as possible?

One option, and it's still not something which can be done overnight, is essentially to electrify the transportation sector, and that would involve essentially replacing internal combustion engines, or a sizable fraction of them, with batteries. Remember, the electrons that charge the battery are still produced on the legacy grid, which is essentially fossils, and that's fine, but now you have options of containing the emissions associated with generating the electricity at one point source or a series of large point sources as opposed to a distributed a hundred million tailpipes, and so that could be one approach that you could consciously move towards in terms of minimizing the emissions.

A lot of folks say, "Well, moving to electric vehicles doesn't really fix the problem because you're still going to burn stuff to make the electricity." But what you're saying is that if we create the electricity in a centralized location, you have the opportunity to control both the pollutants in the air and carbon or other things that you don't want to have go into the atmosphere. You can do it at that location, whereas you couldn't possibly do it as effectively on every tailpipe.

Exactly. And the engineering exists today to be able to control those particulates, at source, in large plants, and it's much harder to scale those techniques down and fit them on every individual tailpipe.

Somehow, coal is the evil fossil fuel and in some sense the most controversial. So here's a simple question to start with. We said the world could not easily, or maybe at all, stop burning fossil fuels in 20 or 30 years. Can the world stop burning coal in the next 20 or 30 years?

I would very much doubt it, to be honest, because again, it's a question of replacement. What do you replace it with? I mean, today, if you look at the amount of electricity generated from coal, it's still a very appreciable factor of all the electricity generated. And also, don't forget heating requirements too. I mean, in winter, houses need heat, and some of that is gas-fired, some of that oil-fired. But in other parts of the world, there's a lot of coal-based stoves used for cooking. So it's very, very difficult to completely divest from an established legacy technology. And I could give you a flippant answer and say, "Sure, if you can find enough natural gas and distribute it all around to replace all the coal," but it's very difficult to do so.

Vijay, thank you for joining us. I think you really helped to set the stage for what we need to do.

Thank you very much. Appreciate the opportunity.

After my conversation with Vijay, it was clear to me that for at least the next 20 or 30 years, we can't stop burning coal if we think about it in a global perspective. So then the question is can we burn coal more safely in terms of public health hazards and near-term environmental damage? And for fossil fuels in general, and coal in particular, what can we do to reduce the overall carbon impact? To find the answer to these questions and others regarding, well, basically burning stuff to produce energy, I reached out to Professor Richard Axelbaum who, not so coincidentally, is also in the energy, environmental and chemical engineering department here at WashU. Rich holds the Stifel and Quinette Jens Professor of Environmental Engineering Science chair. And if you think that's easy to read, you're mistaken. So, Rich, welcome.

Thank you.

Can you just say a little bit about your research, in general, over the long-term and specifics, more recently?

Sure. I've been involved in energy research for 27 years at Washington University and have been involved in a wide range of areas of energy, many of them being related to fossil fuels but actually more recently, in late 2008, began focusing a major part of my effort on addressing coal and how we can utilize coal in a environmentally sustainable way.

As I think you know, your colleague, Vijay Ramani, says we're going to be burning fossil fuels, including coal, in the world for quite a while. So I guess the first question is do you agree?

I do. Coal has the characteristics that, number one, it's pretty ubiquitous around the world. The major centers that require large amounts of energy, China, India, Germany, South Africa, the United States, have abundant coal reserves. That in itself is not a reason to utilize them, but it certainly is a benefit of having coal, in that, from a global perspective, a major challenge of energy is that we need it. It's our life blood, and we need to have sustainable quantities of it and reliable quantities of it, and having it distributed throughout the world is a means of ensuring that the world has access to coal. The world does not have wind resources worldwide, doesn't have solar resources worldwide, doesn't have oil, gas, or even nuclear resources that are available worldwide, so there is a uniqueness about coal in terms of being available. When it comes to actually storing coal, it also has a unique feature in that if I want to have a source of energy that is not at risk, I can take a field and pile coal on it, and that field can last me six months, and I know that it's going to be there for me. There's not another single source of energy in the world that can make that statement. So when we're talking about security, national security, to know we have a resource that we can just dump on the ground, and it's there to pick it up when we want it, is of enormous value.

So in some sense, it was able to drive this explosive growth in the consumption of energy because, frankly, the energy was just there. Is that a fair characterization?

That's right. It was there when we wanted it and where we wanted it.

There are lots of fossil fuels. There is petroleum-based, natural gas, even wood. Why is coal always singled out as the evil, worst possible fossil fuel?

I've pondered this myself quite a bit, and I can certainly give you my opinion. Number one, I think, historically, coal was not regulated until the '70s. So we have pictures and memories of polluted cities, we have pictures of China, Beijing and seeing polluted cities, and since we remember the pictures of pollution as being due to coal, then we project that those polluted cities must be due to coal. In China, right now, the new power plants are as clean as a natural gas-burning power plant in terms of criteria pollutants, the local emissions. Nonetheless, we consider the pollution in China being due to coal power plants. In fact, when coal is involved in pollution, it's due to coal for cooking stoves and for heating and not for power plants. So we have the ability to have clean skies with coal-burning power plants. We have that in St. Louis, with 80% of our energy from coal, and very clean skies. So intrinsically, coal doesn't have to have smoke coming out of the stacks, but we associate it with that. Its also, it looks dirty. It gets on your hands. A coal miner has the black on his cheeks. So we have this vision that goal is dirty from our memories, and it's hard to shake that.

So there's this question of, essentially, the particulate that coal produces and some of the chemicals that go right into the atmosphere that have immediate health effects. And having been to China multiple times in the last couple of years, there are times when, because of coal-burning plants generating heat, the atmosphere is very difficult to breath in. Is it economically plausible to just upgrade that so that they don't have that problem?

It is and they are. In other words, what they are doing right now is they are taking their older plants, their less efficient, polluting plants, and replacing them with highly-efficient, non-polluting plants.

As you know, the term clean coal is controversial, and my sense is that it's controversial because you can talk about clean coal when you're talking about those particulates and those chemicals but not about the carbon dioxide. So where are we in the ability to have less carbon dioxide emitted from fossil fuel plants? Both LNG, which produces, I presume, a reasonable amount of carbon dioxide as well. Where are we on our ability to do this effectively and not produce as much carbon dioxide into the atmosphere?

We've had a number of demonstration sites. We have two ongoing sites right now, one in Canada, the Boundary Dam facility, also one in Texas, the Petra Nova facility, that have demonstrated that we can capture CO2 from power plants and use it for enhanced oil recovery to be able to sequester it underground so it remains out of the atmosphere. So that technology has been demonstrated effectively. Now the challenge is to be able to do that better and do it at a larger scale. Right now, it's limited to specific applications, which is what you would want to have starting off with a technology, identify the most promising use of that technology and apply it to that case. But to really be effective at reducing the CO2 emissions, it has to be a much broader scale.

I know some folks are skeptical that the time frame is that we can get to that scale sooner than we can get to some other solution that provides energy by not burning things. What is the time frame by which you think it becomes economically viable to be able to burn fuels in a way that the carbon is not as problematic as it is now? And presumably, you know that politically viable is deeply, deeply tide to economically viable.

In terms of being able to expand the scale of these units, that is doable today. The challenge is really economics right now. We're at the beginning of these technologies. And just like the beginning of solar and wind, the cost of those technologies was very expensive. If we looked at those costs today, we would say, well, there's no way we're going to do that. So if you look at the cost of carbon capture today and we say we're not going to do that, then we're stuck. But if we realize that if we have large-scale implementation of this then, of course, the experience that we gain from that, the economies of scale will bring the price down. And of course, it even needs to be brought down more than that because, right now, we're talking about what we know in terms of technologies and just expanding the application of those. What we really want to be able to do is come up with radically improved technologies that actually bring that cost down.

So let's talk a little bit... this is supposed to be an engineering show. What is the mechanism, the method, generally the approach taken now, and what methods are being explored that you think might yield the most likely advances that would push this forward to the level that it has to get?

What you'd expect. The first generation technologies were saying we have a power plant, that power plant's emitting CO2, we have to stop that emission from leaving. So the approach to that is to have a chemical that can grab the CO2 out of the exhaust, capture it, and then take it off that chemical, and now you have a concentrated stream of CO2 that you can use for enhanced oil recovery or for sequestration. And that would be considered what I call a patch. If you think about it, a power plant's continuously patched. So they started off just producing power, and particulates, NOx and SOx, all the pollutants just came out of the stack. People were happy to have the power, not as worried about the environment. As our technology, our economies improved, we got more concerned about health effects. And so then we put a patch on the system to get rid of particulates, then a patch to get rid of the SOx.

SOx being?

I'm sorry, sulfur dioxide. Sulfur-based acid rain.

I was going to say, I grew up in New York, and I remember that the acid rain was a big deal. And then, eventually, acid rain went away because they stopped... they did something in the Midwest that made us all very happy.

That's right. They had new technologies, and they switched fuels, and that combination really eliminated the issue in terms of acid rain. And so now we actually have another patch. Now we have to remove the CO2 on the back end. But as you take a basic technology and just keep patching onto it, you end up just increasing the cost, and there's no intrinsic benefit to that. So what needs to happen now is there has to be an approach that recognizes our goal is not just to produce electricity. Our goal is to produce electricity and have zero emissions, meaning, we have to do something with the CO2. And the most promising approach is in utilizing it, for example, for enhanced oil recovery or sequestering it. So then the question is how do you take coal and make electricity but also be able to produce a stream of CO2 that you can sequester, and not from a patch but from a redesign of the concept?

So a redesign of how we burn coal?

That's right.

So for the naive, you stick coal in something that can hold the heat, you light it, you capture the gas, then the gas goes through some things that remove some of the particles that you don't want, some of the chemicals that you don't want, but you didn't fundamentally change the burning. You're talking about changing the actual way it's burned.

That's right. Yeah, in other words, when we started, we wanted to just produce electricity. Now, if you think about it, we have two products. One product is electricity, the other product is a stream of CO2 that we can either sell or dispose of. So then you think about the problem from that perspective and things change. For example, what we do when we sell CO2 for enhanced oil recovery or sequester it is we have to pressurize it. So the existing approach, for example the Petra Nova plant, is that they will capture the CO2, and then they put it in a compressor and compress it down to about 100 atmospheres — that's quite high pressure — and then they can stick it underground. However, what happens is, once you actually know you have to pressurize anyway, you can now pressurize the power plant. So existing power plants don't operate under pressure. Your car operates under pressure. The plane, it operates under pressure. Existing power plants don't operate under pressure, and that's just inherited from the past. But now, if we can operate the power plants under pressure, since we need to have pressure anyway, it doesn't cost us anything extra to have that pressure. In the past it would have, that's why we don't do it. But now when you have to have pressurized products, then you can do that at no additional cost. And then, all of a sudden, many benefits occur that allow you to redesign the power plant that can actually capture the CO2, produce electricity, at an efficiency comparable to what a plant would do when it was really just producing electricity.

I only recently learned that we actually have... I guess we have these domes that capture CO2 that's coming up from the earth. And they enter in these pipelines, and we pipe the CO2 around in order to then use it for various types of oil exploration and oil extraction. So I guess what you're talking about is that you could now capture the CO2 stream and, instead of having these domes and pipelines, etc., which I didn't know we had for CO2, you would be able to produce that directly, so there's now intrinsic value of the CO2 itself.

Exactly right. Yeah, they're actually paying for that CO2 right now, so they could pay the power plant for that CO2.

So is this going to happen?

I believe so. My crystal ball is this challenge associated with the intermittency of wind and solar is going to become very evident to society. Right now, we're somehow believing the problem's going to go away, but it will not go away. Reliability is the fundamental point, and if we don't address reliability then we're going to miss it. And so, ultimately, you have to match supply and demand. It will become impossible for us to really be able to do that with intermittent sources. And so once that reality occurs... it's occurred in Germany. It will occur in the United States, and at that point, we have to have technologies available and they have to be reliable technologies that are low-carbon solutions. So we see it as we don't know when. We do know it will occur, and we need to have those solutions available when it does.

Rich, thanks so much for coming in and sharing with us. It's one of these topics that is tremendously politically charged. I think, from an engineering perspective, our goal is to make sure the world has as many options as possible, and then we leave it to the folks who control economy and political world to make those decisions, but our goal is to give them all the levers that we can. So thanks for the work you do, and thanks for coming in.

Thank you very much, Aaron.

So what have we learned today? Well, frankly, the first few things are a tad depressing. One is that the world, including the US, is not going to stop burning fossil fuels anytime soon. The energy requirements are just too large, the deployed infrastructure too expensive to replace quickly, and there are still real challenges to renewables being able to provide the reliable, resilient, 24/7 energy needed at scale. And if we consider the world and not just the US, coal is going to be an important energy source for many years as well, and these situations will exist regardless of consequence. But we also learned about some technical insights and innovations that are going to potentially help overcome these challenges. We learned that flow batteries are being worked on in a way that could make them more affordable and work at grid-scale and that, in fact, if you think about carbon burning a little bit differently, if you're not just producing electricity but also producing carbon dioxide which is, in turn, used for other systems, the way we leverage coal might in fact be environmentally possible, so it's a very interesting set of opportunities. Well, that's it for today. This is Aaron Bobick, Dean of Engineering at WashU, and you've been listening to Engineering the Future. I look forward to chatting with you again.


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