Toward a Sustainable Society

The Dow Sustainability Innovation Student Challenge Award (SISCA) at Caltech honors students and scientists who have made significant contributions to finding sustainable solutions to the world's most pressing social, economic, and environmental problems. The award was established in 2009 by the Dow Chemical Company with the goal of promoting "forward thinking in social and environmental responsibility," according to the SISCA website. This year, graduate students Trevor Del Castillo and Niklas Thompson shared the $10,000 grand prize for their research developing a sustainable catalyst for nitrogen fixation.

Nitrogen is an abundant element crucial to many fertilizers and other chemicals produced on a large scale, but it must first be "fixed" from its inert gaseous state (N2) into usable reactive forms such as ammonia (NH3). The current leading process for synthesizing ammonia, the Haber-Bosch process, is expensive and energy-intense, requiring extreme temperatures and pressures (about 700 degrees Fahrenheit and 200 bars of pressure).

"From a human health perspective, fertilizer production is arguably the most important industrial chemical process that we practice," says Del Castillo. "We currently conduct this chemistry on a tremendous scale in order to feed approximately half of the global population. However, the current technology for fertilizer production is underpinned by high inputs and is hence typically practiced where fossil fuel sources are readily available and inexpensive. In addition to these energy constraints, current modes of agricultural fertilizer use are environmentally harmful and can be impractical in the developing world, where the demand for fertilizer will continue to increase moving forward."

New catalyst technologies have the potential to address this challenge. Del Castillo and Thompson—both graduate students in the laboratory of Jonas Peters, the Bren Professor of Chemistry and director of the Resnick Sustainability Institute—have studied a recently discovered catalyst system to drive nitrogen fixation, resulting in improved performance and furnishing mechanistic insights. Inspired by a family of enzymes that performs biological nitrogen fixation at room temperatures and pressures, the Peters lab has demonstrated that a simple iron compound can catalyze the fixation of nitrogen gas into ammonia at very low temperature and atmospheric pressure.

"This is a field where new technology and innovation has the potential to impact global social equity and sustainable food security while reducing environmental impact," Thompson says. "Our team's work is a small step in this context, but we ultimately hope our fundamental science discoveries will inspire more practical, sustainable technologies. In principle, nitrogen fixing catalysts can be coupled to artificial photosynthesis technologies, potentially opening the door to modular, accessible, and carbon-neutral fertilizer production."

The runners-up for the SISCA prize are Cody Finke, a graduate student, and Justin Jasper, a Resnick Sustainability Institute Prize Postdoctoral Scholar. Both work in the research group of Michael Hoffmann, the James Irvine Professor of Environmental Science, and together they have improved upon a design for a solar-powered wastewater treatment system created for toilets in the developing and developed world. Their process combines ultraviolet (UV) irradiation and electrochemical treatment to produce water suitable for reuse in agriculture and ecosystem services.

"We proposed a hybrid electrochemical-UV system that could be used to provide efficient wastewater treatment in places where water and sewer infrastructure are not available, such as parts of the developing world," Jasper says. "We were particularly excited about our research since it suggested that adding a UV step to the process significantly accelerated treatment and limited formation of disinfection byproducts that can be detrimental to human health.  Therefore, with further work, our system may be able to provide not only wastewater treatment, but also a water source for applications such as irrigation or household cleaning."

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Where Is Solar Energy Headed?

In a new paper in ScienceNate Lewis, the George L. Argyros Professor of Chemistry at Caltech, reviews recent developments in solar-energy utilization and looks at some of the challenges and opportunities that lie ahead in the research and development of solar-electricity, solar-thermal, and solar-fuels technologies. Read the full paper.

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Toward Liquid Fuels from Carbon Dioxide

In the quest for sustainable alternative energy and fuel sources, one viable solution may be the conversion of the greenhouse gas carbon dioxide (CO2) into liquid fuels.

Through photosynthesis, plants convert sunlight, water, and CO2 into sugars, multicarbon molecules that fuel cellular processes. CO2 is thus both the precursor to the fossil fuels that are central to modern life as well as the by-product of burning those fuels. The ability to generate synthetic liquid fuels from stable, oxygenated carbon precursors such as CO2 and carbon monoxide (CO) is reminiscent of photosynthesis in nature and is a transformation that is desirable in artificial systems. For about a century, a chemical method known as the Fischer-Tropsch process has been utilized to convert hydrogen gas (H2) and CO to liquid fuels. However, its mechanism is not well understood and, in contrast to photosynthesis, the process requires high pressures (from 1 to 100 times atmospheric pressure) and temperatures (100–300 degrees Celsius).

More recently, alternative conversion chemistries for the generation of liquid fuels from oxygenated carbon precursors have been reported. Using copper electrocatalysts, CO and CO2 can be converted to multicarbon products. The process proceeds under mild conditions, but how it takes place remains a mystery.

Now, Caltech chemistry professor Theo Agapie and his graduate student Joshua Buss have developed a model system to demonstrate what the initial steps of a process for the conversion of CO to hydrocarbons might look like.

The findings, published as an advanced online publication for the journal Nature on December 21, 2015 (and appearing in print on January 7, 2016), provide a foundation for the development of technologies that may one day help neutralize the negative effects of atmospheric accumulation of the greenhouse gas CO2 by converting it back into fuel. Although methods exist to transform CO2 into CO, a crucial next step, the deoxygenation of CO molecules and their coupling to form C–C bonds, is more difficult.

In their study, Agapie and Buss synthesized a new transition metal complex—a metal atom, in this case molybdenum, bound by one or more supporting molecules known as ligands—that can facilitate the activation and cleavage of a CO molecule. Incremental reduction of the molecule leads to substantial weakening of the C–O bonds of CO. Once weakened, the bond is broken entirely by introducing silyl electrophiles, a class of silicon-containing reagents that can be used as surrogates for protons.

This cleavage results in the formation of a terminal carbide—a single carbon atom bound to a metal center—that subsequently makes a bond with the second CO molecule coordinated to the metal. Although a carbide is commonly proposed as an intermediate in CO reductive coupling, this is the first direct demonstration of its role in this type of chemistry, the researchers say. Upon C–C bond formation, the metal center releases the C2 product. Overall, this process converts the two CO units to an ethynol derivative and proceeds easily even at temperatures lower than room temperature.

"To our knowledge, this is the first example of a well-defined reaction that can take two carbon monoxide molecules and convert them into a metal-free ethynol derivative, a molecule related to ethanol; the fact that we can release the C2 product from the metal is important," Agapie says.

While the generated ethynol derivative is not useful as a fuel, it represents a step toward being able to generate synthetic multicarbon fuels from carbon dioxide. The researchers are now applying the knowledge gained in this initial study to improve the process. "Ideally, our insight will facilitate the development of practical catalytic systems," Buss says.

The scientists are also working on a way to cleave the C–O bond using protons instead of silyl electrophiles. "Ultimately, we'd like to use protons from water and electron equivalents derived from sunlight," Agapie says. "But protons are very reactive, and right now we can't control that chemistry."

The research in the paper, "Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site," was funded by Caltech and the National Science Foundation.

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Caltech researchers gain insight into carbon monoxide coupling, one carbon atom at a time

The Interface of Earth and Atmosphere: An Interview with Christian Frankenberg

Plants are an important mediator between the earth and the atmosphere. In order to grow, they breathe in carbon dioxide—one of the major greenhouse gases. Caltech associate professor Christian Frankenberg is interested in this relationship and how the biosphere reacts to climate change.

A native of Germany, Frankenberg earned a Diploma degree at the University of Bayreuth and a PhD at Ruprecht-Karls-University in Heidelberg. He spent the past five years as a research scientist at JPL and joined the Caltech faculty this fall. We recently spoke with Frankenberg about remote sensing, the biosphere, and life in Pasadena.

What do you do?

I use remote sensing tools—based on spectrometers in space and the air—to gain a deeper understanding of the carbon cycle. This means making measurements of atmospheric greenhouse gases like carbon dioxide and methane as well as measuring plant activity by sensing solar-induced chlorophyll fluorescence from space. Chlorophyll fluorescence happens when plants take in sunlight. A tiny fraction of that sunlight gets emitted at a slightly longer wavelength. We can see this glow from space, and it is a good proxy of the photosynthetic uptake of CO2 by plants.

One of my goals is to combine the atmospheric measurements and the fluorescence measurements to gain a deeper understanding of when, where, and why the carbon cycle changes. I work with the Orbiting Carbon Observatory 2 (OCO-2) at JPL, and also with a Japanese project called the Greenhouse Gases Observing Satellite (GOSAT).

Why is it important to understand the carbon cycle?

Many people are familiar with the famous Keeling Curve—a ground-based measurement of atmospheric carbon dioxide that has been ongoing since 1958. This curve shows a continual increase in CO2 abundances from year to year, but it also shows a strong seasonal cycle—abundances go up in winter and down in summer. This is because in the Northern Hemisphere summer, plants are growing and removing CO2 from the atmosphere; in winter, plants are releasing CO2.

If we count all the barrels of oil and everything else that we burn to release CO2, only about one-half of it remains in the atmosphere. One-fourth goes into the oceans, and the rest is taken up by vegetation. The biosphere is doing us a big favor in taking up a lot of what we're emitting, but we don't know exactly where on Earth that vegetation is absorbing the most or if will it persist in the future.

What can we do to improve our relationship with the biosphere?

There's always talk about reducing CO2 emissions, which is great, but often actions are pound-foolish and penny-wise. I think energy efficiency is a big factor in improving our relationship with the biosphere. This means probably not having single-pane windows, and it definitely means not running the air conditioning and the heater at the same time, which I've seen (too often)! I do see a great opportunity for clean solar power in California—there's so much sun!

How did you get interested in biogeosciences?

At school I liked natural sciences, like math and chemistry, but I didn't want to focus on just one of them. During my undergraduate education, I studied geoecology, which gives a broad background of all the natural sciences. But I found out pretty quickly that I liked the more quantitative stuff, so I focused on the physics, math, and chemistry aspects, and did my PhD in environmental physics. That's where I started working on remote sensing. I really liked it; the combination of working with the biosphere but also doing more technical work suited me. Now it seems I'm making a full turn again with my plant-based research. It's like going back to my geoecology roots.

What brought you to Caltech?

I've always been interested in Caltech, but after a postdoc in the Netherlands, I got a job offer from JPL—five and a half years ago. I knew that in the long term, I wanted to be in academia doing more basic research and having academic freedom.

How does your job as a professor differ from your previous appointment as a research scientist?

I still retain the title of research scientist at JPL, and I spend one day a week there. For me, it's an ideal situation to be at Caltech but still have the relationship with JPL, where so many things are happening in my field.

But now that I am on the Caltech faculty, I'll be expanding from pure remote sensing to ground-based and laboratory measurements of fluorescence and carbon exchange. We are studying the part of plants that are more relevant for the global carbon cycle, connecting the leaf scale to the global scale. Additionally, I will start teaching courses in the next academic year, which will probably be the biggest change.

What do you like about being in Southern California?

I like the mountains a lot. Pasadena is a nice combination of having a small-town feeling next to the foothills but also having a big city nearby if you want it. It's a sweet spot. What I miss most from Europe is the ability to just bike everywhere you need to go. There is no way to get around without a car here in the L.A. area.

What do you do outside of work?

I try to let the weekend be a weekend and not let it be too busy. I like getting outdoors, hiking and running, playing some soccer or squash. And, of course, spending time with my family and son is also a full-time sort of job.

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The Interface of Earth and Atmosphere
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An interview with Christian Frankenberg, an atmospheric and biogeoscientist and one of the most recent additions to the Caltech faculty.

When Harry Met Arnold

A Milestone in Chemistry

On November 12 and 13, the Beckman Institute at Caltech hosted a symposium on "The Shared Legacy of Arnold Beckman and Harry Gray." The two began a close working relationship in the late 1960s, when Gray arrived at Caltech. In this interview, Gray provides some background.

How did you come to Caltech?

I grew up in southern Kentucky. I got my BS in chemistry in 1957, and my professors told me to go to grad school at Northwestern University in Evanston, Illinois, to continue my studies in synthetic organic chemistry. They didn't give me a choice. Western Kentucky College had physical chemistry, analytical chemistry, organic chemistry, and that was it.

When I got to Northwestern I met Fred Basolo, who became my mentor. He did inorganic chemistry, which I was very surprised to discover even existed as a research field. I was so excited by his work, which was studying the mechanisms of inorganic reactions, that I decided to switch fields and do what he did. I got my PhD in 1960 from work on the syntheses and reaction mechanisms of platinum, rhodium, palladium, and nickel complexes. A complex has a metal atom sitting in the middle of as many as six ions or molecules called ligands. The metal has empty orbitals that it wants to fill with paired-up electrons, and the ligands have electron pairs they aren't using, so the metal and its ligands form stable bonds.

I had gotten into chemistry in the first place because I'd always been interested in colors. Even when I was a little kid, colors fascinated me. I really wanted to understand them, and many complexes have brilliant, beautiful colors. At Northwestern I heard about crystal-field theory, which was the first attempt to explain how metal complexes got their colors. All the crystal-field theory's big shots were in Copenhagen, so I decided to go there as a postdoc. Which I did.

I soon found out that crystal-field theory didn't go far enough. It only explained the colors of a limited set of metal ions in solution, and it couldn't explain charge transfers and a lot of other things. All the atoms were treated as point charges, with no provision for the bonds between the metal and the ligands. There weren't any bonds. So I helped develop a new theory, called ligand-field theory, which put the bonds back in the complexes. Carl Ballhausen, a professor at the University of Copenhagen, and I wrote a paper on a "metal-oxo" complex in which an oxygen atom was triple-bonded to a vanadium ion. The triple bond in our theory was required to account for the blue color of the vanadium-oxo complex. We also could explain charge transfers in other oxo complexes. Bonds were back in metal complexes!

Metal-oxo bonds are very important in biology. They are crucial in a lot of reactions, such as the oxygen-producing side of photosynthesis; the metabolism of drugs by cytochrome P-450, which often leads to toxic interactions with other drugs; and respiration. When we breathe in O2, our respiratory system splits the O=O bond, forming a metal-oxo complex as a reactive intermediate on the way to the product, which is water.

My work on bonding in metal oxo complexes got me a job as an assistant professor at Columbia University in 1961. By '65 I was a full professor and getting offers from many places, including Caltech. I loved Columbia, and I would have stayed there, but the chemistry department was very small. I knew it would be hard to build inorganic chemistry in a small department that concentrated on organic and physical chemistry.

There weren't any inorganic chemists at Caltech, either, but division chair Jack Roberts encouraged me to build the field up to five or six faculty members. I came to Caltech in 1966, and we now have a very strong inorganic chemistry group.

When I got here, I started work in two new areas at the interface of inorganic chemistry and biology. I'm best known for my work showing how electrons flow through proteins in respiration and photosynthesis. I won the Wolf Prize and the Welch Prize and the National Medal of Science for this work.

I also got into inorganic photochemistry—solar-energy research. That work started well before the first energy crisis in 1973, and continued until oil became cheap again in the early 1980s and solar-energy research was no longer supported. In the late '90s, I restarted the work. Now I'm leading an NSF Center for Chemical Innovation in Solar Fuels, which has an outreach activity I proudly call the Solar Army.

And how's that going?

The Solar Army keeps growing. We now have at least 60 brigades at high schools across the U.S., and 10 more abroad. I'd say that about 1,000 students have been through the program since 2008. We're getting young scientists involved in research that could have a profound effect on the world they're going to inherit. They're helping us look for light absorbers and catalysts to turn water into hydrogen fuel, using nothing but sunlight. The solar materials need to be sturdy metal oxides that are abundant and dirt cheap. But there are many metals in the periodic table. When you start combining them in twos and threes in varying amounts, there are literally millions of possibilities to be tested. We already have found several very good water oxidation and reduction catalysts, and since the National Science Foundation has just renewed our CCI Solar Fuels grant, we expect to make great progress in the coming years in understanding how they work.

Let's shift gears and talk about the Beckman Institute. How did you first meet Arnold Beckman [PhD '28, inventor of the pH meter, founder of Beckman Instruments, and a Life Trustee of Caltech]?

I gave a talk back in 1967, probably on Alumni Day. Arnold was the chair of Caltech's Board of Trustees at the time, and he and his wife, Mabel, were seated in the second row. When the talk was over, they came down and introduced themselves. Mabel said—and I remember this very well—she said, "Arnold, I didn't understand much of what this young man said, but I really liked the way he said it." Arnold gave me the thumbs up, and that started our relationship.

When I became chairman of the Division of Chemistry and Chemical Engineering in 1978, I asked him to be on my advisory committee. I didn't ask him for money, but I asked him for advice, and we became quite close. He said he wanted to do something for us. That led to his gift for the Arnold and Mabel Beckman Laboratory of Chemical Synthesis, as well as a gift for instrumentation.

He liked it that we raised money to match his instrument gift. He told me that he wanted to do something bigger, so we started thinking about building the Beckman Institute. [Caltech President] Murph Goldberger and I would go down to Orange County about every week with a new plan. He rejected the first four or five until we came up with the idea of developing technology to support chemistry and biology—methods and instruments for fundamental research—and creating resource centers to house them.

Once we agreed on what the building should house, we started planning the building itself. But when we showed Arnold our design, which was four stories plus a basement, he said, "That's not big enough. You need another floor for growth." So we added a subbasement that was quickly occupied by a resource center for magnetic-resonance imaging and optical imaging that has been heavily used by biologists, chemists, and other investigators.

The Beckman Institute has done a lot over the last 25 years. But it develops technology for general research use, so it doesn't often make the headlines itself. Are you OK with that?

Many advances in science and technology have been made in the Beckman Institute over the last 25 years. The methods and instruments that have been developed in BI resource centers have made enormous impacts at the frontiers of chemistry and biology. Solar-fuels science and human biology are just two examples of areas where work in the Beckman Institute has made a big difference. And there are many more. Am I proud? You bet I am!

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Douglas Smith
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When Harry Met Arnold
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Caltech celebrates the 25th year of the Beckman Institute and the 80th birthday of Harry Gray, the Beckman Professor of Chemistry and the founding director of the institute.

Peters Named New Director of Resnick Sustainability Institute

Jonas C. Peters, the Bren Professor of Chemistry, has been appointed director of the Resnick Sustainability Institute. Launched in 2009 with an investment from philanthropists Stewart and Lynda Resnick and located in the Jorgenson Laboratory on the Caltech campus, the Resnick Institute concentrates on transformational breakthroughs that will contribute to the planet's sustainability over the long term.

The Resnick Sustainability Institute, which involves both the Chemistry and Chemical Engineering and Engineering and Applied Science divisions, serves as a prime example of the multidisciplinary approach prized by Caltech.

"Some of the most important challenges in sustainability are also among the most complex," says Peters, who has been a member of the Caltech faculty since 1999. "We are committed to working on problems that are uniquely suited to the Caltech environment. This means starting with fundamentals and leveraging the cross-catalysis of ideas and creativity of this campus to come up with ways to have substantial impact."

Because the world's natural resources are dwindling, Peters wants to continue focusing the Resnick Institute's efforts on efficient energy generation, storage, and use. Some current projects include development of advanced photovoltaics, photoelectrochemical solar fuels and cellulosic biofuels; energy conversion work on batteries and fuel cells; and efficiency in industrial catalysis and advanced research on electrical grid control and distribution.

In addition, the Resnick Institute is exploring new opportunities in the area of water sustainability. In September, the institute hosted a workshop entitled "Water Resilience and Sustainability: Can We Make LA Water Self-Sufficient?" The workshop examined the long-term potential for sustainable water use in urban environments, using the Los Angeles area as a case study.

"The Resnick Sustainability Institute is continuing to build one of the great centers for sustainability research," says Peters. "We are doing this by supporting the most talented young scientists and engineers committed to tackling the fascinating, critical, and yet very difficult challenges of this field."

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Jonas C. Peters has been appointed director of the Resnick Sustainability Institute.

Toward a Smarter Grid

Steven Low, professor of computer science and electrical engineering at Caltech, says we are on the cusp of a historic transformation—a restructuring of the energy system similar to the reimagining and revamping that the communication and computer networks experienced over the last two decades, making them layered, with distributed and interconnected intelligence everywhere.

The power network of the future—aka the smart grid—will have to be much more dynamic and responsive than the current electric grid, handling tremendous loads while incorporating intermittent energy production from renewable resources such as wind and solar, all while ensuring that when you or I flip a switch at home or work, the power still comes on without fail.

The smart grid will also be much more distributed than the current network, which controls a relatively small number of generators to provide power to millions of passive endpoints—the computers, machines, buildings, and more that simply consume energy. In the future, thanks to inexpensive sensors and computers, many of those endpoints will become active and intelligent loads like smart devices, or distributed generators such as solar panels and wind turbines. These endpoints will be able to generate, sense, communicate, compute, and respond.

Given these trends, Low says, it is only reasonable to conclude that in the coming decades, the electrical system is likely to become "the largest and most complex cyberphysical system ever seen." And that presents both a risk and an opportunity. On the one hand, if the larger, more active system is not controlled correctly, blackouts could be much more frequent. On the other hand, if properly managed, it could greatly improve efficiency, security, robustness, and sustainability.

At Caltech, Low and an interdisciplinary group of engineers, economists, mathematicians, and computer scientists pulled together by the Resnick Sustainability Institute, along with partners like Southern California Edison and the Department of Energy, are working to develop the devices, systems, theories, and algorithms to help guide this historic transformation and make sure that it is properly managed.

In 2012, the Resnick Sustainability Institute issued a report titled Grid 2020: Towards a Policy of Renewable and Distributed Energy Resources, which focused on some of the major engineering, economic, and policy issues of the smart grid. That report led to a discussion series and working sessions that in turn led to the publication in 2014 of another report called More Than Smart: A Framework to Make the Distribution Grid More Open, Efficient and Resilient.

"One thing that makes the smart grid problem particularly appealing for us is that you can't solve it just as an engineer, just as a computer scientist, just as a control theorist, or just as an economist," says Adam Wierman, professor of computer science and Executive Officer for the Computing and Mathematical Sciences Department. "You actually have to bring to bear tools from all of these areas to solve the problem."

For example, he says, consider the problem of determining how much power various parts of the grid should generate at a particular time. This requires generating an amount of power that matches or closely approximates the amount of electricity demanded by customers. Currently this involves predicting electricity demand a day in advance, updating that prediction several hours before it is needed, and then figuring out how much nuclear power, natural gas, or coal will be produced to meet the demand. That determination is made through markets. In California, the California Independent System Operator runs a day-ahead electricity market in which utility companies and power plants buy and sell power generation for the following day. Then any small errors in the prediction are fixed at the last minute by engineers in a control office, with markets completely out of the picture.

"So you have a balance between the robustness and certainty provided by engineered control and the efficiency provided by markets and economic control," says Wierman. "But when renewable energy comes onto the table, all of a sudden the predictions of energy production are much less accurate, so the interaction between the markets and the engineering is up in the air, and no one knows how to handle this well." This, he says, is the type of problem the Caltech team, with its interdisciplinary approach, is uniquely equipped to address.

Indeed, the Caltech smart grid team is working on projects on the engineering side, projects on the markets side, and projects at the interface.

On the engineering side, a major project has revolved around a complex mathematical problem called optimal power flow that underlies many questions dealing with power system operations and planning. "Optimal power flow can tell you when things should be on or conserving energy, how to stabilize the voltage in the network as solar or wind generation fluctuates, or how to set your thermostat so that you maintain comfort in your building while stabilizing the voltage on the grid," explains Mani Chandy, the Simon Ramo Professor of Computer Science, Emeritus. "The problem has been around for 50 years but is extremely difficult to solve."

Chandy worked with Low; John Doyle, the Jean-Lou Chameau Professor of Control and Dynamical Systems, Electrical Engineering, and Bioengineering; and a number of Caltech students to devise a clever way to solve the problem, allowing them, for the first time, to compute a solution and then check whether that solution is globally optimal.

"We said, let's relax the constraints and optimize the cost over a bigger set that we can design to be solvable," explains Low. For example, if a customer is consuming electricity at a single location, the problem might ask how much electricity that individual is actually consuming; a relaxation would say that that person is consuming no more than a certain amount—it is a way of adding flexibility to a problem with tight constraints. "Almost magically, it turns out that if I design my physical set in a clever way, the solution for this larger simple set turns out to be the same as it would be for the original set."

The new approach produces a feasible solution for almost all distribution systems—the low-voltage networks that take power from larger substations and ultimately deliver it to the houses, buildings, street lights, and so on in a region. "That's important because many of the innovations in the energy sector in the coming decade will happen on distribution systems," says Low.

Another Caltech project attempts to predict how many home and business owners are likely to adopt rooftop solar panels over the next 5, 10, 20, or 30 years. In Southern California, the number of solar installations has increased steadily for several years. For planning purposes, utility companies need to anticipate whether that growth will continue and at what pace. For example, Low says, if the network is eventually going to comprise 15 or 20 percent renewables, then the current grid is robust enough. "But if we are going to have 50 or 80 percent renewables," he says, "then the grid will need huge changes in terms of both engineering and market design."

Working with Chandy, graduate students Desmond Cai and Anish Agarwal (BS '13, MS '15) developed a new model for predicting how many homes and businesses will install rooftop solar panels. The model has proven highly accurate. Researchers believe that whether or not people "go solar" depends largely on two factors: how much money they will save and their confidence in the new technology. The Caltech model, completed in 2012, indicates that the amount of money that people can save by installing rooftop solar has a huge influence on whether they will adopt the technology. Based on their research, the team has also developed a web-based tool that predicts how many people will install solar panels using a utility company's data. Southern California Edison's planning department is actively using the tool.

On the markets side, Caltech researchers are doing theoretical work looking at the smart grid and the network of markets it will produce. Electricity markets can be both complicated and interesting to study because unlike a traditional market—a single place where people go to buy and sell something—the electricity "market" actually consists of many networked marketplaces interacting in complicated ways.

One potential problem with this system and the introduction of more renewables, Wierman says, is that it opens the door for firms to manipulate prices by turning off generators. Whereas the operational status of a normal generator can be monitored, with solar and wind power, it is nearly impossible to verify how much power should have been produced because it is difficult to know whether it was windy or sunny at a certain time. "For example, you can significantly impact prices by pushing—or not pushing—solar energy from your solar farm," Wierman says. "There are huge opportunities for strongly manipulating market structure and prices in these environments. We are beginning to look at how to redesign markets so that this isn't as powerful or as dangerous."

An area of smart grid research where the Caltech team takes full advantage of its multidisciplinary nature is at the interface of engineering and markets. One example is a concept known as demand response, in which a mismatch between energy supply and demand can be addressed from the demand side (that is, by involving consumers), rather than from the power-generation side.

As an example of demand response, some utilities have started programs where participants, who have smart thermostats installed in their homes in exchange for some monetary reward, allow the company to turn off their air conditioners for a short period of time when it is necessary to reduce the demand on the grid. In that way, household air conditioners become "shock absorbers" for the system.

"But the economist says wait a minute, that's really inefficient. You might be turning the AC off for people who desperately want it on and leaving it on for people who couldn't care less," says John Ledyard, the Allen and Lenabelle Davis Professor of Economics and Social Sciences. A counter proposal is called Prices to Devices, where the utility sends price signals to devices, like thermostats, in homes and offices, and customers decide if they want to pay for power at those prices. Ledyard says while that is efficient rationing in equilibrium, it introduces a delay between the consumer and the utility, creating an instability in the dynamics of the system.

The Caltech team has devised an intermediate proposal that removes the delay in the system. Rather than sending a price and having consumers react to it, their program has consumers enter their sensitivity to various prices ahead of time, right on their smart devices. This can be done with a single number. Then those devices deliver that information to the algorithm that operates the network. For example, a consumer might program his or her smart thermostat, to effectively say, "If a kilowatt of power costs $1 and the temperature outside is 90 degrees, I want you to keep the air conditioner on; if the price is $5 and the temperature outside is 80 degrees, go ahead and turn it off."

"The consumer's response is handled by the algorithm, so there's no lag," says Ledyard.

Currently, the Caltech smart grid team is working closely with Southern California Edison to set up a pilot test in Orange County involving several thousand households. The homes will be equipped with various distributed energy resources including rooftop solar panels, electric vehicles, smart thermostats for air conditioners, and pool pumps. The team's new approach to the optimal power flow problem and demand response will be tested to see whether it can keep stable a miniature version of the future smart grid.

Such experiments are crucial for preparing for the major changes to the electrical system that are certainly coming down the road, Low says. "The stakes are high. In the face of this historic transformation, we need to do all that we can to minimize the risk and make sure that we realize the full potential."

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The Caltech Y—100 Years Young

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The Caltech Y Turns 100
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Caltech students hiking in the Sierras
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The Caltech Y's annual autumn hike in the Sierras offers a spectacular start to the academic year. Like all of the Y's activities, the hike is planned and led by and for the students themselves.

The Caltech "little t"
Credit: Caltech Y

The Caltech Y began publishing an unofficial freshman handbook, called the little t, in the 1920s. (The name is a nod to Caltech's yearbook, the Big T.)

Frosh Camp in the early 1950s
Credit: Caltech Y

The off-campus orientation weekend known as Frosh Camp was established early in the Y's history. Here, Wes Hershey, the Y's executive director, addresses an incoming class in the early 1950s.

The Rev. Martin Luther King, Jr. visits Caltech in 1958
Credit: Caltech Y

The Leaders of America Series was established in 1951 to bring in thought-provoking speakers such as Martin Luther King Jr., seen here in Caltech's Winnett Lounge in 1958. Such speakers promoted awareness of global issues and challenged the Caltech community to create ways to address them.

Senator Eugene McCarthy at Caltech in 1968
Credit: Caltech Y

Senator Eugene McCarthy (D-Minnesota) visited Caltech during his presidential bid in 1968. McCarthy opposed the war in Vietnam, and his strong showing in the early primaries forced President Lyndon B. Johnson to withdraw from the race. 

Archbishop Desmond Tutu at Caltech in 1990
Credit: Caltech Y

Archbishop Desmond Tutu, winner of the 1984 Nobel Peace Prize, visited Caltech in 1990 as part of the Social Activism Speaker Series, the contemporary version of Leaders of America. 

Caltech student volunteers at a Habitat for Humanity project.
Credit: Caltech Y

The Y established the Alternative Spring Break community service program in 1996. Here Caltech students volunteer on a Habitat for Humanity project in San Francisco.

Caltech Y students volunteering in Costa Rica on Alternative Spring Break
Credit: Caltech Y

The annual International Service Learning Immersion Program to Costa Rica was launched in 2005 as part of Alternative Spring Break.

Caltech undergraduates on the Caltech Y's annual Science Policy Trip to Washington, DC
Credit: Caltech Y

Established in 2006, the Caltech Y's annual Washington, D.C., Science Policy Trip takes place over the winter break and explores the intersection of public policy, science, and technology. As part of the program, students meet with D.C.-area alumni who have entered that arena.

Faculty and students at the Indian Institute of Technology, Gandhinagar.
Credit: Caltech Y

The Y also leads an annual cultural and educational exchange trip to India, where students participate in workshops with faculty and students at the Indian Institute of Technology, Gandhinagar.

Caltech undergraduates tutor local students in math and science.
Credit: Caltech Y

The Rise program matches Caltech students with Pasadena-area middle- and high-schoolers for math and science tutoring

WorldFest at Caltech
Credit: Caltech Y

Organized in collaboration with Caltech's International Offices and various student clubs and associations, World Fest celebrates the Caltech community's cultural diversity

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Founded in the 1915–16 academic year as a branch of the international Young Men's Christian Association, today's Caltech Y is a coed, nonsectarian, student-led freestanding organization dedicated to bringing students out of their academic cocoons so that they emerge as engaged citizens of the world.

"Caltech graduates are capable of having a global impact," says Y staff member Greg Fletcher, the student activities and community service director. "We're hoping to challenge them to make a difference."

The Y has emphasized community service since its founding, providing snacks to soldiers drilling on campus during the First World War. Today, volunteer opportunities include Rise, a math and science tutoring program; Make-a-Difference Day, devoted to cleaning local beaches, visiting the elderly, planting trees, and the like; and Alternative Spring Break, which is the same idea writ large. The Y also brings the outside world to campus, hosting events such as The Ghetto and the City conference in 1968 as well as such notable speakers as Walter Reuther, who unionized Detroit in the 1930s; Supreme Court Justice William O. Douglas; and Maharishi Mahesh Yogi, guru to the Beach Boys and the Beatles and the founder of transcendental meditation. The Reverend Martin Luther King Jr. "came for two days in 1958," says Caltech Y director Athena Castro, "and spent full days in the student houses having dinners, giving talks."

"Community service" also includes the Caltech community. In the 1920s and '30s, the Y created student-support programs—including new-student orientation, counseling services, off-campus room-and-board listings, student loans, and assistance for foreign students—that have long since become part of the Office of Student Affairs. But the Y continually reinvents itself to stay relevant, and new programs arise such as the Studenski Award. Endowed in 1974 in memory of a young alumnus who died in an accident on a cross-country road trip, the grant provides the time and money for a journey of self-discovery. As a result, some Studenski alumni have found their bliss in such nontraditional—for Techers—careers as singing opera at the Met or making award-winning feature-length films.

The Y's programs are structured around what Castro calls the "five pillars" of leadership, adventure, service, civic engagement, and perspective. "Leadership and perspective are the bookends," she says. "That's what we want our students to gain." 

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Getting the Lead Out

Caltech geochemist Clair Patterson (1922–1995) helped galvanize the environmental movement 50 years ago when he announced that highly toxic lead could be found essentially everywhere on Earth, including in our own bodies—and that very little of it was due to natural causes.

In a paper published in the September 1965 issue of Archives of Environmental Health, Patterson challenged the prevailing belief that industrial and natural sources contributed roughly equal amounts of ingestible lead, and that the aggregate level we absorbed was safe. Instead, he wrote, "A new approach to this matter suggests that the average resident of the United States is being subjected to severe chronic lead insult." He estimated that our "lead burden" was as much as 100 times that of our preindustrial ancestors—often to just below the threshold of acute toxicity.

Lead poisoning was known to the ancients. Vitruvius, designer of aqueducts for Julius Caesar, wrote in Book VIII of De Architectura that "water is much more wholesome from earthenware pipes than from lead pipes . . . [water] seems to be made injurious by lead." Lead accumulates in the body, where it can have profound effects on the central nervous system. Children exposed to high lead levels often acquire permanent learning disabilities and behavioral disorders.

When Patterson arrived at Caltech as a research fellow in geochemistry in 1952, he was looking not to save the world but to figure out how old it was. Doing so required him to measure the precise amounts of various isotopes of uranium and lead. (Isotopes are atoms of the same element that contain different numbers of neutrons in their nuclei.) Uranium-238 decays very, very slowly into lead-206, while uranium-235 decays less slowly into lead-207. Both rates are well known, so measuring the ratios of lead atoms to uranium ones shows how much uranium has disappeared and allows the sample's age to be calculated.

Patterson presumed that the inner solar system's rocky planets and meteorites had all coalesced at the same time, and that the meteorites had survived essentially unchanged ever since. Using an instrument called a mass spectrometer and working in a clean room he had designed and built himself, Patterson counted the individual lead atoms in a meteorite sample recovered from Canyon Diablo near Meteor Crater, Arizona. In a landmark paper published in 1956, he established Earth's age as 4.55 billion years.

However, there are four common isotopes of lead, and Patterson had to take them all into account in his calculations. He had announced his findings at a conference in 1955, and he had continued to refine his results as the paper worked its way through the review process. But there he hit a snag—his analytical skills had become so finely honed that he was finding lead everywhere. He needed to know the source of this contamination in order to eliminate it, and he took it on himself to find out.

Patterson's 1965 Environmental Health paper summarized that work. With M. Tatsumoto of the U.S. Geological Survey, he found that the ocean off of southern California was lead-laden at the surface but that the contamination disappeared rapidly with depth. They concluded that the likely culprit was tetraethyl lead, a widespread gasoline additive that emerged from the tailpipe of automobiles as very fine lead particles. Patterson and research fellow T. J. Chow crisscrossed the Pacific aboard research vessels run by the Scripps Institution of Oceanography at UC San Diego and found the same profile of lead levels versus depth. Then, in the winter of 1962–63, Patterson and Tatsumoto collected snow at an altitude of 7,000 feet on Mount Lassen in northern California. The lead contamination there was 10 to 100 times worse than at sea. Patterson concluded that it had fallen from the skies. Its isotopic fingerprint was a perfect match for air samples from Los Angeles—located 500 miles to the south. It also matched gasoline samples obtained by Chow in San Diego. Furthermore, the isotope fingerprint was different from that of lead found in prehistoric sediments off the California coast.

"The atmosphere of the northern hemisphere contains about 1,000 times more than natural amounts of lead," Patterson wrote, and he called for the "elimination of some of the most serious sources of lead pollution such as lead alkyls [i.e., tetraethyl lead], insecticides, food can solder, water service pipes, kitchenware glazes, and paints; and a reevaluation by persons in positions of responsibility in the field of public health of their role in the matter."

Patterson's paper was his first shot in the war against lead pollution, bureaucratic inertia, and big business that he would wage for the rest of his life. He won: the Clean Air Act of 1970 authorized the development of national air-quality standards, including emission controls on cars. In 1976, the Environmental Protection Agency reported that more than 100,000 tons of lead went into gasoline every month; by 1980 that figure would be less than 50,000 tons, and the concentration of lead in the average American's blood would drop by nearly 50 percent as well. The Consumer Product Safety Commission would ban lead-based indoor house paints in 1977 (flakes containing brightly colored lead pigments often found their way into children's mouths). And in 1986, the EPA prohibited tetraethyl lead in gasoline.

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Getting the Lead Out
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Artificial Leaf Harnesses Sunlight for Efficient Fuel Production

Generating and storing renewable energy, such as solar or wind power, is a key barrier to a clean-energy economy. When the Joint Center for Artificial Photosynthesis (JCAP) was established at Caltech and its partnering institutions in 2010, the U.S. Department of Energy (DOE) Energy Innovation Hub had one main goal: a cost-effective method of producing fuels using only sunlight, water, and carbon dioxide, mimicking the natural process of photosynthesis in plants and storing energy in the form of chemical fuels for use on demand. Over the past five years, researchers at JCAP have made major advances toward this goal, and they now report the development of the first complete, efficient, safe, integrated solar-driven system for splitting water to create hydrogen fuels.

"This result was a stretch project milestone for the entire five years of JCAP as a whole, and not only have we achieved this goal, we also achieved it on time and on budget," says Caltech's Nate Lewis, George L. Argyros Professor and professor of chemistry, and the JCAP scientific director.

The new solar fuel generation system, or artificial leaf, is described in the August 27 online issue of the journal Energy and Environmental Science. The work was done by researchers in the laboratories of Lewis and Harry Atwater, director of JCAP and Howard Hughes Professor of Applied Physics and Materials Science.

"This accomplishment drew on the knowledge, insights and capabilities of JCAP, which illustrates what can be achieved in a Hub-scale effort by an integrated team," Atwater says. "The device reported here grew out of a multi-year, large-scale effort to define the design and materials components needed for an integrated solar fuels generator."


Solar Fuels Prototype in Operation
A fully integrated photoelectrochemical device performing unassisted solar water splitting for the production of hydrogen fuel. Credit: Erik Verlage and Chengxiang Xiang/Caltech

The new system consists of three main components: two electrodes—one photoanode and one photocathode—and a membrane. The photoanode uses sunlight to oxidize water molecules, generating protons and electrons as well as oxygen gas. The photocathode recombines the protons and electrons to form hydrogen gas. A key part of the JCAP design is the plastic membrane, which keeps the oxygen and hydrogen gases separate. If the two gases are allowed to mix and are accidentally ignited, an explosion can occur; the membrane lets the hydrogen fuel be separately collected under pressure and safely pushed into a pipeline.

Semiconductors such as silicon or gallium arsenide absorb light efficiently and are therefore used in solar panels. However, these materials also oxidize (or rust) on the surface when exposed to water, so cannot be used to directly generate fuel. A major advance that allowed the integrated system to be developed was previous work in Lewis's laboratory, which showed that adding a nanometers-thick layer of titanium dioxide (TiO2)—a material found in white paint and many toothpastes and sunscreens—onto the electrodes could prevent them from corroding while still allowing light and electrons to pass through. The new complete solar fuel generation system developed by Lewis and colleagues uses such a 62.5-nanometer-thick TiO2 layer to effectively prevent corrosion and improve the stability of a gallium arsenide–based photoelectrode.

Another key advance is the use of active, inexpensive catalysts for fuel production. The photoanode requires a catalyst to drive the essential water-splitting reaction. Rare and expensive metals such as platinum can serve as effective catalysts, but in its work the team discovered that it could create a much cheaper, active catalyst by adding a 2-nanometer-thick layer of nickel to the surface of the TiO2. This catalyst is among the most active known catalysts for splitting water molecules into oxygen, protons, and electrons and is a key to the high efficiency displayed by the device.

The photoanode was grown onto a photocathode, which also contains a highly active, inexpensive, nickel-molybdenum catalyst, to create a fully integrated single material that serves as a complete solar-driven water-splitting system.

A critical component that contributes to the efficiency and safety of the new system is the special plastic membrane that separates the gases and prevents the possibility of an explosion, while still allowing the ions to flow seamlessly to complete the electrical circuit in the cell. All of the components are stable under the same conditions and work together to produce a high-performance, fully integrated system. The demonstration system is approximately one square centimeter in area, converts 10 percent of the energy in sunlight into stored energy in the chemical fuel, and can operate for more than 40 hours continuously.

"This new system shatters all of the combined safety, performance, and stability records for artificial leaf technology by factors of 5 to 10 or more ," Lewis says.

"Our work shows that it is indeed possible to produce fuels from sunlight safely and efficiently in an integrated system with inexpensive components," Lewis adds, "Of course, we still have work to do to extend the lifetime of the system and to develop methods for cost-effectively manufacturing full systems, both of which are in progress."

Because the work assembled various components that were developed by multiple teams within JCAP, coauthor Chengxiang Xiang, who is co-leader of the JCAP prototyping and scale-up project, says that the successful end result was a collaborative effort. "JCAP's research and development in device design, simulation, and materials discovery and integration all funneled into the demonstration of this new device," Xiang says.

These results are published in a paper titled "A monolithically integrated, intrinsically safe, 10% efficient, solar-driven water-splitting system based on active, stable earth-abundant electrocatalysts in conjunction with tandem III-V light absorbers protected by amorphous TiO2 films." In addition to Lewis, Atwater, and Xiang, other Caltech coauthors include graduate student Erik Verlage, postdoctoral scholars Shu Hu and Ke Sun, material processing and integration research engineer Rui Liu, and JCAP mechanical engineer Ryan Jones. Funding was provided by the Office of Science at the U.S. Department of Energy, and the Gordon and Betty Moore Foundation.

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