header

f

The Terawatt Challenge

From finding new catalysts for fuel cells to better understanding wind energy’s wake, Hopkins researchers are stepping up to meet the global need for energy that’s abundant, cheap … and clean.

By Mike Field

plugsIn the final years before his untimely death from cancer at the age of 62, Nobel Prize winning chemist Richard Smalley had a set speech that he gave over and over, to any audience he could find. Using PowerPoint, chalkboard, whiteboard, or whatever was at hand, he would list the 10 top problems facing the world today: energy, water, food, environment, poverty, terrorism and war, disease, education, democracy, population. This list of challenges, he would remark, seems insurmountable.

But to Smalley, there was one key that could unlock the entire puzzle. In the 21st century what the world needs most, he said, is abundant, low-cost, clean energy-a resource that can raise living standards, desalinate seawater (for crop irrigation and human health), increase food production, restore the environment, and promote global peace, health, and cooperation.

By the time of Smalley's death in 2005, the world was consuming the energy equivalent of 220 million barrels of oil per day, or in electricity terms, about 14.5 million megawatts-or 14.5 terawatts-of electricity. Looking into the future, Smalley estimated that it would probably take a staggering 60 terawatts to provide a comfortable first-world lifestyle to all the planet's 10 billion or so inhabitants expected to be around in the year 2050. That is a tall order by any measure, and Smalley was hardly alone in recognizing the scope of the problem.

"I'd been scratching my head for a couple of years about what we can do on energy," recalls Whiting School dean Nick Jones. Part of his job, after all, is to look forward to the next great engineering challenge and try to position the school with the necessary resources in place to address it. But Hopkins academic departments tend to be small by design, narrowly focused, and nimble. Energy is such a large problem that Jones found himself wondering if the Hopkins approach could contribute in any meaningful way.

Not only must the world effectively quadruple its energy production, but it also must confront an enormous engineering stumbling block: These new energy sources cannot add to atmospheric carbon dioxide, which is generally accepted to be a cause of global warming. In the years before his death, Smalley often challenged his audiences to "imagine the world where that problem was solved, just totally solved." He recognized that learning to produce abundant, cheap, clean energy is the great science and engineering opportunity of the 21st century. Smalley dubbed this global problem "The Terawatt Challenge."

For Jones, the enormity of this challenge arrayed against the comparatively small scale of Whiting School resources provoked a David-and-Goliath kind of conundrum: If you can only throw a few small stones at the problem, they had better be very, very carefully chosen stones. "Because of our size we can't be all things to all people," he says, "but it was unclear what approach we should take and where we would find compatible expertise." Then, last May, Jones was asked to chair a panel of Hopkins experts making a presentation in Denver on global sustainability as part of the Knowledge for the World Campaign Tour. The group included Liberty Media chairman and Whiting School alumnus John C. Malone (MS '64, PhD '69), chair of the Colorado chapter of The Nature Conservancy, and faculty members from the schools of Public Health, Arts and Sciences, and Advanced International Studies at Hopkins. That meeting, says Jones, was a revelation. "That's when I realized we do have the people at work on this and what we need to do is find ways of bringing them together." And, as gas prices peaked in the months following, there was suddenly a new sense of urgency surrounding the issue.

 

You can’t predict. There might be an advance in photovoltaics [for solar cells], but there might be entirely new technologies that are transformative. We just don’t know.”
Ben Hobbs professor, Geography and Environmental Engineering

Here in the United States, where 5 percent of the world's population consumes one quarter of its energy, there is an accelerating sense that the current oil-coal-natural gas energy economy will need to rapidly evolve into a system that creates less pollution (especially climate-warming carbon dioxide) and relies far less on foreign sources, particularly petroleum from the Middle East. President-elect Barack Obama's campaign platform called for a $150 billion investment over 10 years to "build a clean energy future" and pledged that 25 percent of American electricity will come from renewable resources by 2025. Meanwhile, former vice president Al Gore-who received the 2007 Nobel Peace Prize for his work on climate change-has called for a "moon shot" approach to renewable energy, challenging the nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years.

Ten percent or 100 percent ... both figures represent an order of magnitude increase in the amount of electricity now generated in America from renewable energy. Wind and solar currently account for less than 1 percent of U.S. electricity generation (compared to 7 percent for hydroelectric and 19 percent for nuclear power). Add to that the extra burden of at least partially powering the nation's fleet of 244 million registered motor vehicles by electricity, hydrogen, or some other clean energy source, and the enormous scale of the challenge becomes evident. In October, Dean Jones asked four Hopkins faculty members whose research relates specifically to the Terawatt Challenge to make a presentation before the Whiting School's National Advisory Council. Jones is increasingly convinced that Johns Hopkins has an important role to play in our energy future. "Our traditional strength is to be able to pull faculty together from disparate disciplines and set them loose on a big, nasty problem," he says. "And this is the big, nasty problem for the 21st century."

Finding New Catalysts for Fuel Cells

“I always try to remember what Moore’s Law meant to electronics,” says Engineering’s Benjamin Hobbs, professor of geography and environmental engineering. Hobbs has spent more than two decades applying his mathematics, economics, and engineering expertise to find optimal ways of efficiently distributing energy to large markets. He believes that Intel Corporation co-founder Gordon Moore’s famous observation in 1965 that the number of transistors that could be fit on an integrated circuit was doubling every two years or so correlates to what we will soon see in the field of new energy development. Just as advances in microelectronic design brought about a revolution in computing, communications, and culture, so could similar advances in generating, storing, transmitting, and using electricity radically change how we work, play, and live our lives. “In 10 or 15 years things could be really different,” says Hobbs of today’s energy markets. But he cautions that neither he nor any of his fellow energy market analysts at this point has a clear idea of what that future will look like. “I’ve been doing this stuff since the 1970s and I’m always blindsided. You can’t predict. There might be an advance in photovoltaics [for solar cells], but there might be entirely new technologies that are transformative. We just don’t know.”

This much seems evident: The Terawatt Challenge will require not just new powergenerating plants, but entirely new ways of producing energy. And for that, there will need to be plenty of groundbreaking work in basic research. Jonah Erlebacher is a surface physicist interested in crystal growth and catalysis. An associate professor in the Department of Materials Science and Engineering, Erlebacher is finding fundamentally new ways to improve an old technology—the fuel cell, an electrochemical conversion device in which a fuel is combined with an oxidant in the presence of an electrolyte to produce electricity. “Most people don’t realize that the fuel cell was invented in 1839,” he says, referring to British physicist William Grove’s early experiment using hydrogen and oxygen to generate electricity on platinum electrodes. “But it is only in the last 15 years or so that innovations have allowed fuel cells to be used more widely.” Advances in materials engineering focusing on the catalyst have increased the efficiency, improved the affordability, and extended the longevity of today’s hydrogen fuel cells. Specially built buses in Reykjavik, Iceland, are powered this way, for example, and both the Russian and German navies have submarines that can run silently for weeks below the surface on fuel cells, making them virtually undetectable. What has yet to be developed, however, is a relatively inexpensive fuel cell design that could be mass manufactured to power the millions of cars and trucks on the road today. “For now,” says Erlebacher, “this is still a specialty application technology.”

Because fuel cells convert chemical energy directly into electrical energy, they are inherently high-efficiency energy devices. Compare this, for instance, to a conventional coal-fired power plant, which burns coal to create heat to produce steam to drive a turbine to generate electricity. The simpler process and greater efficiency of fuel cells means less fuel and a smaller storage container are required for a fixed energy requirement. Plus, fuel cells can be easily scaled to fit whatever application is required. Imagined uses for affordable fuel cells range from a belt-clip-size device meant for charging cell phones and other portable electronics, to a washing machine-size contraption that would sit quietly in your basement fulfilling all your home’s electrical needs (and selling excess electricity generated back to the grid). This flexibility is one reason why they are so often mentioned as the ideal clean automotive engines of the future. Fuel cells can convert fuel to useful energy at efficiencies as high as 60 percent, whereas the internal-combustion engine is limited to efficiencies of less than 40 percent. And when hydrogen is catalyzed with oxygen, the only byproducts are electricity, excess heat, and pure water. Fuel cells do not pollute.

“It is only in the last 15 years or so that innovations have allowed fuel cells to be used more widely.”
— Jonah Erlebacher, associate professor, Materials Science and Engineering

But one persistent problem has always constrained the financial viability of fuel cells: Those platinum electrodes are tremendously expensive to produce, relying as they do on an element that is 30 times rarer than gold. Says Erlebacher, “If we could make them without platinum we could have them everywhere.” In his lab Erlebacher is trying to invent new catalysts more efficient (and much cheaper) than simple platinum by building porous micro layers of precious and nonprecious metals. “The architecture of the materials used is key to this problem,” he says. Recently, Erlebacher was named the first L. Gordon Croft Investment Management Faculty Scholar in recognition of his exceptional achievement in nanostructured materials and their application to energy generation and other uses. His lab has been instrumental in unlocking the secrets of nanoporous materials, including the notable co-discovery of mathematical equations describing how porous gold evolves. These are precisely the kinds of advances that are expected to lead to the next big breakthrough in affordable fuel cell design.

The invention of a new composite catalyst at the U.S. National Laboratory in Los Alamos improved current fuel cell power by a factor of 10. Basic advances in materials design might further improve efficiencies and reduce cost. “These kinds of advances have been part serendipity and part informed inspiration,” Erlebacher says. Musing on the short-term need for a small, inexpensive and powerful fuel cell to excite more people about the possibilities of hydrogen power, he says: “A fuel cell–powered lawn mower would be a killer app.”

The Right Chemistry for Solar Power

terawatt_solarBut there is a great challenge facing this “hydrogen economy”—the oft-discussed but still imaginary future in which hydrogen is the universal energy carrier (as opposed to an energy source) that would power all kinds of fuel cell vehicles. Fundamental to a hydrogen economy is the need for inexpensive plentiful hydrogen. Although hydrogen makes up three-quarters of the known universe, most of the hydrogen on Earth is locked in more complex compounds, primarily water. Currently, almost all hydrogenproduced and used around the globe comesfrom hydrocarbons such as methane and natural gas, but breaking out the hydrogen from these compounds creates carbon dioxide, thus amplifying global warming. Hydrogen can be removed from water by electrolysis leaving pure

oxygen, but this is a fairly energy-intensive process, requiring about 50 kilowatt-hours of electricity for every kilogram of hydrogen produced. The critical need will be to find a carbon-free way of generating ample electricity to power electrolysis and provide plentiful hydrogen. If that electricity comes from a power plant burning coal, oil, or gas, the carbon dioxide and other pollutants produced in the process effectively eliminate hydrogen’s environmental advantages.

“Of all the things we have confronted as a society, I think carbon is going to be one of the toughest,” says Kenneth DeFontes, a member of the Whiting School’s National Advisors Council and the university’s Presidential Task Force for Climate Change. He knows the scope of the challenge firsthand. DeFontes is president and CEO of Baltimore Gas & Electric Company (BGE), which provides electricity to more than 1.2 million business and residential customers in Central Maryland. He says it is important not to underestimate the scale of the problem confronting us: “We are so dependent on fossil sources that it is really a very fundamental change that is needed. But you have to recognize we cannot solve our problems of energy in any single way.”

One widely anticipated component of future clean energy production is photovoltaics, the production of electricity by sunlight. It’s another old technology that is new again. The first solar cell was produced by American inventor Charles Fritts in 1883. His version used selenium and gold to generate electricity from sunlight, and produced a sunlight-to-electricity conversion efficiency of only about 1 percent, rendering the pricey technology commercially worthless. Even then, however, visionaries imagined the seemingly limitless possibilities of electricity from the sun and rhapsodized about “the total extinction of steam engines, and the utter repression of smoke.” However, it was not until 1954, when Bell Laboratories scientists discovered that silicon wafers could be made sensitive to sunlight, that the first practical solar cells were created, realizing a conversion efficiency of about 6 percent. Today commercially available silicon solar cells typically realize efficiencies of about 15 percent, and solar energy is now the fastest growing source of electricity, expanding at an annual rate of 35 percent overthe past few years.

“Last year the planet used about 14 terawatts of electricity, and the United States was responsible for roughly a quarter of that [usage],” says Gerald Meyer, a professor of chemistry in the Krieger School of Arts and Sciences. “Depending on how you count, greater than 95 percent of that power was generated from nonrenewable resources such as coal, oil, and natural gas. So we are clearly using up a finite resource.” Five years ago Meyer was asked by the National Science Foundation to organize a workshop on sustainability, and in particular, what chemistry could do to help promote sustainable development and energy use. He brought together 22 scientists from around the country to consider the issue. Their conclusion, published just last year: “Energy stood out to everybody as the critical need for finding sustainable solutions,” Meyer says. It just so happens that has been his focus for many years now. “My research group makes molecules that absorb light and then enable us to take the energy that is stored and convert it to electricity.”

“The solar profile of our country is quite good, and my hope is that we can...optimize solar harvesting.”
— Gerald Meyer, professor, Chemistry

But photovoltaics still account for only a small percentage of the electricity generated in America, and will probably continue to do so until manufacturing costs can be significantly reduced. Meyer and his team have been conducting research into a new generation of “thin film” solar cells that are cheaper and easier to produce. “The solar profile of our country is quite good, and my hope is that we can create applications that will allow us to optimize solar harvesting,” says Meyer. “But to do so we have to reduce cost.” Although silicon is the second most abundant element on the planet, it is normally bound in silica sand. Processing it to produce the pure silicon needed for solar cells is a high-temperature, high-energy operation that produces considerable carbon dioxide. At current efficiencies it takes more than two years for a solar cell to generate the amount of energy that was used to make the silicon it contains.

Thin-film solar cells attempt to overcome this problem by using only a fraction of the silicon found in conventional cells, but they are considerably less efficient as a result. Meyer is working on a novel alternative technology pioneered by scientists Michael Grätzel and Brian O’Regan at the École Polytechnique Fédérale de Lausanne in 1991. The dye-sensitized solar cell, or DSSc (also known as the Grätzel cell), is made of low-cost materials, is not brittle like conventional silicon wafer solar cells, and should be relatively easy to mass manufacture. Meyer has been experimenting with high surface area nanocrystalline films and titanium dioxide (a common paint pigment) to create Grätzel cells in his lab. “We can make cells routinely in the 5 percent range of efficiency, and our champion cells have been in the 10 percent range. If we can get it to the 15 percent range, then this technology is practical,” he says.

In addition to lower costs, dye-sensitized solar cells (because of their different chemical nature) can generate electricity at low-light levels, such as a cloudy day or in indirect sunlight. They also can be manufactured in flexible sheets, are considerably more resilient, and can achieve better operational efficiency at higher temperatures than conventional glass-covered solar panels. “There is now a robust market for photovoltaics, but the likelihood of a solarpowered future really comes down to an economic issue,” Meyer says. “Right now the cost per watt just doesn’t line up with fossil fuels. It’s just too expensive. But the gap is closing. What  we are looking for is a leap-frog or fundamental discovery to move it along.”

Wind Energy's Wake

While sunlight and hydrogen remain largely energy sources of some future day, modern windmill technology has begun to contribute a significant and growing portion of world energy production. Denmark now generates about a fifth of its electricity needs by wind power. Today’s electricity-generating windmills can reach the height of the Washington Monument, with blade circumference of 100 meters. These mammoth machines are rated at up to 5 megawatts generating capacity, enough to supply 100 homes each with truly green energy. Their technology is proven, their reliability is sound, and in the last few years, they have been popping up wherever there is steadyand reliable wind. Last April, Rock Port, Missouri (population 1,395), became the first city in the U.S. to get all its electricity from wind power with the opening of a 5 megawatt, four turbine wind farm there that is expected to provide more electricity to the local power grid than the town’s annual consumption. By the end of 2007, U.S. wind power capacity had exceeded 18,000 megawatts, enough to serve 4.5 million average households; it accounted for nearly a third of all new power-producing capacity added during the year.

“The average life expectancy of wind turbines is expected to be about 20 years, and their energy pay-back period [to generate the amount of energy needed to manufacture the units] is only a matter of months,” says Charles Meneveau, the Louis M. Sardella Professor in Mechanical Engineering and director of the Center for Environmental and Applied Fluid Mechanics. “It’s very clear that wind energy is on a really steep growth path globally.” But Meneveau notes that despite this enormous increase in wind energy, some of the basic scientific understanding of how wind turbines interact with and affect the local environment is still lacking. Since wind turbines are generally built together in “farms,” what is the best way to arrange the structures—paralleled or staggered? What is the optimal number of towers that can be erected within a certain space? And does the action of the wind turbine’s blades affect the local climate?

Meneveau is an internationally recognized expert in fluid mechanics, including the behavior of air in contact with today’s massive wind turbines, which are the largest rotating machines ever built. Using a wind tunnel, smoke, scale model turbines, and a sophisticated laser photography system, Meneveau has been carefully measuring the fluid dynamics of airflow around wind turbines with the intent of creating a computer model for optimizing the placement and design of wind turbine farms. The National Science Foundation recently awarded his team a three-year, $321,000 grant to support the project.

“It’s very clear that wind energy is on a really steep growth path globally.”
— Charles Meneveau, director, Center for Environmental and Applied Fluid Mechanics

“Because of their effect of enhancing the turbulence downstream, there is some implication of changed wind patterns and maybe increased evaporation,” says Meneveau of his wind tunnel work to date. In theory, at least, dense clusters of wind turbines could affect nearby temperature and humidity levels, in turn leading to changes in local weather conditions. One fact that Meneveau does note is that to generate the current national electricity usage in the U.S. entirely by today’s wind turbines would require wind farms covering approximately 750,000 square miles—or roughly the size of Texas, California, Montana, and Florida combined. Considered from that perspective, the potential weather effects of wind turbines seem considerably more significant. With more and more large-scale wind projects planned, such as the 4,000 megawatt, 400,000-acre wind farm proposed for the Texas panhandle by oilman T. Boone Pickens, Meneveau’s research offers a first glimpse of the likely impact of a new global reality. “We need to develop the tools to predict what effect these arrays will have,” he says. “We currently have a pretty good idea of what happens when you put one wind turbine in a clean, nonturbulent wind stream. But when you put many of them together, and they receive realworld uncertain airflow, then it’s much less clear what will happen.”

In 1997 United Nations member states adopted the Kyoto Protocol to reduce carbon dioxide and other greenhouse gases to approximately 5 percent below 1990 levels. Achieving that goal—or even coming close—while meeting the planet’s increasing demands for moreenergy may be the greatest challenge of this generation. “We want a healthy environment but [we still want] cold beer and warm showers,” is how Hobbs describes it. “The only way to do that is to learn to produce energy in new ways.” And that may be the essence of the Terawatt Challenge: learning to perform familiar tasks in entirely new and different ways. “I’m not necessarily a fan of big science done in big labs,” says Hobbs, pointing instead to the need for many smaller solutions instead of one big answer. “Hopkins has people here who are fundamentally good scientists. And that’s what we need. That’s where we will find the answers.”

“Global energy is a big challenge, just likegoing to the moon in 1961 was a big challenge,” says Jones. “But I believe our nation will get it done in the same way as we did then—by pulling together a lot of folks from many different disciplines and setting goals. If you’d asked me this summer I would have been very confident that with oil at $150 a barrel, you had a lot of people’s attention. Now, at a third that cost, we’ve come back a bit from that assessment. But there is a change in Washington and the issue is on the table. I’m optimistic that a switch has been thrown. This is the future and Hopkins will be there.”




print this story »

Bookmark and Share




Responses to "The Terawatt Challenge"

konnor aiden says:
August 27, 2009
I want to disconnect from "the grid" and generate my own power on a continuous basis using propane for fuel. Most commercially available fuel cells for electrical generation are for back-up power only and require pure hydrogen to operate. I don't know why the industry isn't interested in the home market, but there seems to be no effort spent on this. If you know of any company that is working on this or currently has such a fuel cell, please provide details. hho cars

Brent says:
December 07, 2009
I don't think there is a single answer to this problem. It is going to take wind power, solar, and nuclear to provide the energy we want and keep greenhouse gases to a minimum. More importantly, it's going to take a bigger dose of willingness. Residential Wind Power

Leave a Reply:

* Name:

* Email:

* Comment:

* required

Remember my personal information
Notify me of follow-up comments?

Please enter the word you see in the image below:


sdf
Learn More