Greening Caltech's Bottom Line

You can see signs of Caltech's commitment to sustainability everywhere you look on campus: there are recycling centers, LEED-certified buildings, and arrays of solar panels, not to mention landscaping that uses drought-tolerant plants, and dining rooms that feature compostable utensils.

But some of the campus's most impressive efforts are also its least visible ones. Caltech's efforts to finance urgently needed energy-efficiency upgrades—and to do so in ways that give back to the Institute—have been recognized by the Sustainable Endowments Institute in its recently released report, Greening the Bottom Line: The Trend toward Green Revolving Funds on Campus.

Green revolving funds are monies set aside to finance needed upgrades that will increase the efficiency of energy use; these projects are funded based on their likelihood to return the capital spent on them—plus some—once the reductions in energy use or operating expenses are realized. And it's that return on capital that allows the funds to revolve—to be used for yet another energy-saving project.

Caltech's own green revolving fund—the Caltech Energy Conservation Investment Program (CECIP)—was initiated in 2009, and it manages $8 million within an existing endowment created to finance capital projects.

"CECIP allows Caltech to effectively deploy capital to realize energy and cost savings from energy-conservation measures that would otherwise be unfunded," says John Onderdonk, Caltech's manager for sustainability programs. "It's a perfect example of Caltech's sustainability vision in that it reduces the campus's environmental footprint while enhancing the Institute's core mission."

The projects' impact has been nothing if not impressive. According to the Sustainability Research Institute, the efficiency measures funded by Caltech's CECIP has allowed an average return on investment of 33 percent, and had—by August 2010—reduced the Institute's energy bills by $1.5 million.

What's perhaps more impressive is that these projects aren't the high-visibility, easy-to-get funded initiatives like rooftop solar panels. "A lot of the work done through CECIP is behind the scenes," Onderdonk says.

Among the projects that CECIP has funded in the past two years are heating, ventilation, and air-conditioning upgrades at the Broad Center; the installation of auto-closing flume hoods in the Schlinger Laboratory; an LED lighting upgrade in the South Wilson Parking Structure; and lighting upgrades at South Mudd, North Mudd, the Beckman Institute, and the Keck Laboratories.

Any member of the Caltech community is welcome to submit a project proposal, says Onderdonk; projects will be approved if they have a 15 percent return on investment or a simple payback period of less than six years.

For more information on the efforts being made to reduce Caltech's environmental impact and promote stewardship within the Caltech community, visit Sustainability at Caltech.

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Lori Oliwenstein
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Solar Decathlon Back on the Mall

Thanks to a campaign led by a joint team of students from Caltech and the Southern California Institute of Architecture (SCI-Arc), the 2011 Solar Decathlon is back on the National Mall in Washington, D.C. The announcement made last week reverses an earlier decision by the U.S. Department of the Interior (DOI) to relocate the event.

The two-week competition, taking place in the fall, will now be held in West Potomac Park, on a swath of land between the Lincoln and Jefferson Memorials. "Everyone's relieved and happy that we're back on the Mall," says Caltech's Fei Yang, a senior majoring in mechanical engineering, and one of the leaders of the SCI-Arc/Caltech team.

The biennial competition, sponsored by the U.S. Department of Energy (DOE), invites 20 teams from around the world and challenges them to build the most energy-efficient, affordable, and attractive house they can. All four previous competitions have taken place on the National Mall—between the Capitol and the Washington Monument—providing a high-profile venue to inspire policymakers, industry leaders, and the public to pursue a sustainable future with state-of-the-art design and technology.

But in January, the DOI, with the approval of the DOE, decided that the event could no longer be held on the Mall, citing the need to protect and preserve the grounds. "It came as a shock," Yang says.

A statement posted January 11 on the DOE Solar Decathlon website noted that the decision to change locations was made "in support of the historic effort underway to protect, improve, and restore the National Mall." The DOI is embarking on a $600 million plan to renovate the grounds and areas around the monuments. But this justification didn't make sense, says Elisabeth Neigert, a recent SCI-Arc graduate and one of the project managers for the SCI-Arc/Caltech team; a clause in each team's contract already makes them financially responsible for any damage.

Furthermore, Neigert says, this sudden change in venue was made three-quarters of the way through the competition, after design, engineering, and logistical decisions had been made based on the expectation that the house would be built on the Mall. And the promise of high-profile exposure was crucial in securing sponsors. "This late in the game, it left us in a really difficult position," she says.

"They tore the heart out of the Solar Decathlon," says Cole Hershkowitz, also a Caltech senior in mechanical engineering and another leader of the team. "One of the reasons why the competition is so prestigious is because the government supported it and it's in arguably the most prominent place in our country, right there between the Capitol and the Washington Monument." There's no monetary prize for the winner, so the prestige and the opportunity to showcase their innovations are the teams' rewards. "If we had known that it would not be on the National Mall, I think only half of us would've applied," Hershkowitz says.  

What followed was a concerted effort led by Neigert and the SCI-Arc/Caltech team to appeal the DOI's decision. Working with the other 19 Solar Decathlon teams, the group of architecture and engineering students suddenly found themselves in the middle of a political campaign. After much lobbying, they received support from organizations such as the National Coalition to Save Our Mall. They also got official backing from more than a dozen senators and other congressional leaders, including California senator Barbara Boxer and Massachusetts representative Edward Markey, ranking member of the Natural Resources Committee.

Then, the Washington Post stepped in to cover the debate, and Neigert and Eric Owen Moss, director of SCI-Arc, penned opinion columns for the Huffington Post. Two days after the op-eds appeared—and after six weeks of relentless campaigning—the DOI reversed its ruling. "I was filled with disbelief, but I was also absolutely elated," Neigert says. "I was pretty speechless, which doesn't happen very often." Even though the event would no longer be right in front of the Capitol steps, the team is satisfied. "It was probably the best outcome we could've gotten, given the circumstances," she says.

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The full-sized model of the SCI-Arc/Caltech house with its soft, insulating exterior.

Now, the team can refocus on building their house, which is computerized to control and monitor energy usage to maximize efficiency. Every house in the competition is required to be net-zero—that is, to use only as much energy as its solar panels can generate. But perhaps what's most striking about the SCI-Arc/Caltech design is its soft, insulating exterior, which gives the building the appearance of a giant pillow. The house is also the only two-story structure in the competition.

With the Solar Decathlon back on the Mall, the team hopes their design will attract plenty of eyes. After all, from historic moments like Martin Luther King's "I Have a Dream" speech to the numerous festivals that attract hundreds of thousands of visitors, the National Mall is a place where things happen and are noticed, Hershkowitz says. "What makes the National Mall so iconic is not how green the grass is, but the quality of events."

The SCI-Arc/Caltech team will hold a groundbreaking event on April 2 at the SCI-Arc campus in Los Angeles.

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Marcus Woo
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Sustaining the Next Generation of Energy Scientists

Training the next generation of scientists capable of creating startling and transformational advances in sustainable energy research is a critical component of the mission of Caltech's Resnick Institute.

And although the institute is not yet two years old—it was created in June of 2009 by a gift from Stewart and Lynda Resnick and began operating the following April—it has already begun to fulfill that mission, thanks to the newly developed Resnick Fellowship program.

The first two Resnick Fellows began their work in the fall of 2010. Last week, the institute put out a call for applications for the next set of two-year awards, which provide tuition plus a $30,000-per-year stipend for graduate students from any discipline who are seeking to explore unusual and creative sustainable-energy research projects on campus.

"The Resnick Fellowships are unique because they provide an opportunity for Caltech students to think outside the box and take a chance on potentially groundbreaking new work in areas that might not otherwise get explored," says Neil Fromer, the institute's executive director. "Caltech has always been a place where creative individuals can have a big impact. With these fellowships, we are similarly enabling students to chart new paths."

As part of his Resnick Fellowship, Matt Smith, a graduate student in bioengineering working in the laboratory of Frances Arnold, is looking for better ways to create second-generation biofuels—biofuels made from cellulose, hemicellulose, or lignin, all of which are components of plant cell walls. Specifically, he's using new protein recombination techniques to try to create active, stable forms of the enzyme beta glucosidase, which is used to cut small-length cellulose chains into individual glucose molecules.

"It's a more unusual, riskier project," Smith says. "When I started talking about it, Frances suggested I apply for a Resnick Fellowship. She felt it was in the spirit of the institute—a project on energy and sustainability that's a bit 'out there.'"

Smith's fellow Fellow, David Abrecht, is working with both Brent Fultz and Theo Agapie on a stationary hydrogen-storage project using ionic liquids. "Hydrogen gas is uneconomical to store," Abrecht explains. But in order to develop hydrogen as a fuel, hydrogen needs to be stored cheaply, at room temperature and pressure, and it needs to be able to release quickly.

The answer, Abrecht says, may lie in liquid storage. "I'd been thinking about liquid-state storage systems for a while," he explains. "Liquid-state storage might allow you to use hydrogen as a buffer to prevent supply spikes in the electrical-generation grid, to fill in the gaps."

Abrecht is looking at what are known as ionic liquids—which are salts in a liquid state—that would be able to bind with hydrogen at more-or-less normal temperatures and pressures. "Trying to find funding for this kind of project from typical sources would have been very difficult," he says. "I would not have been able to do this project without this fellowship."

Smith and Abrecht are looking forward to the next generation of Resnick Fellows. "The more Fellows there are, the more opportunity we'll have for interaction," Smith says. "I'm looking forward to that, to creating a small community of students working toward similar goals."

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Caltech Geobiologists Uncover Links between Ancient Climate Change and Mass Extinction

PASADENA, Calif.—About 450 million years ago, Earth suffered the second-largest mass extinction in its history—the Late Ordovician mass extinction, during which more than 75 percent of marine species died. Exactly what caused this tremendous loss in biodiversity remains a mystery, but now a team led by researchers at the California Institute of Technology (Caltech) has discovered new details supporting the idea that the mass extinction was linked to a cooling climate.

"While it’s been known for a long time that the mass extinction is intimately tied to climate change, the precise mechanism is unclear," says Seth Finnegan, a postdoctoral researcher at Caltech and the first author of the paper published online in Science on January 27. The mass extinction coincided with a glacial period, during which global temperatures cooled and the planet saw a marked increase in glaciers. At this time, North America was on the equator, while most of the other continents formed a supercontinent known as Gondwana that stretched from the equator to the South Pole.

By using a new method to measure ancient temperatures, the researchers have uncovered clues about the timing and magnitude of the glaciation and how it affected ocean temperatures near the equator. "Our observations imply a climate system distinct from anything we know about over the last 100 million years," says Woodward Fischer, assistant professor of geobiology at Caltech and a coauthor.

The fact that the extinction struck during a glacial period, when huge ice sheets covered much of what's now Africa and South America, makes it especially difficult to evaluate the role of climate. "One of the biggest sources of uncertainty in studying the paleoclimate record is that it’s very hard to differentiate between changes in temperature and changes in the size of continental ice sheets," Finnegan says. Both factors could have played a role in causing the mass extinction: with more water frozen in ice sheets, the world’s sea levels would have been lower, reducing the availability of shallow water as a marine habitat. But differentiating between the two effects is a challenge because until now, the best method for measuring ancient temperatures has also been affected by the size of ice sheets.

The conventional method for determining ancient temperature requires measuring the ratios of oxygen isotopes in minerals precipitated from seawater. The ratios depend on both temperature and the concentration of isotopes in the ocean, so the ratios reveal the temperature only if the isotopic concentration of seawater is known. But ice sheets preferentially lock up one isotope, which reduces its concentration in the ocean. Since no one knows how big the ice sheets were, and these ancient oceans are no longer available for scientists to analyze, it's hard to determine this isotopic concentration. As a result of this "ice-volume effect," there hasn’t been a reliable way to know exactly how warm or cold it was during these glacial periods.

Rock strata on Anticosti Island, Quebec, Canada, one of the sites from which the researchers collected fossils.

But by using a new type of paleothermometer developed in the laboratory of John Eiler, Sharp Professor of Geology and professor of geochemistry at Caltech, the researchers have determined the average temperatures during the Late Ordovician—marking the first time scientists have been able to overcome the ice-volume effect for a glacial episode that happened hundreds of millions of years ago. To make their measurements, the researchers analyzed the chemistry of fossilized marine animal shells collected from Quebec, Canada, and from the midwestern United States.

The Eiler lab’s method, which does not rely on the isotopic concentration of the oceans, measures temperature by looking at the "clumpiness" of heavy isotopes found in fossils. Higher temperatures cause the isotopes to bond in a more random fashion, while low temperatures lead to more clumping.

"By providing independent information on ocean temperature, this new method allows us to know the isotopic composition of 450-million-year-old seawater," Finnegan says. "Using that information, we can estimate the size of continental ice sheets through this glaciation." And with a clearer idea of how much ice there was, the researchers can learn more about what Ordovician climate was like—and how it might have stressed marine ecosystems and led to the extinction.

"We have found that elevated rates of climate change coincided with the mass extinction," says Aradhna Tripati, a coauthor from UCLA and visiting researcher in geochemistry at Caltech.

The team discovered that even though tropical ocean temperatures were higher than they are now, moderately sized glaciers still existed near the poles before and after the mass extinction. But during the extinction intervals, glaciation peaked. Tropical surface waters cooled by five degrees, and the ice sheets on Gondwana grew to be as large as 150 million cubic kilometers—bigger than the glaciers that covered Antarctica and most of the Northern Hemisphere during the modern era’s last ice age 20,000 years ago.

"Our study strengthens the case for a direct link between climate change and extinction," Finnegan says. "Although polar glaciers existed for several million years, they only caused cooling of the tropical oceans during the short interval that coincides with the main pulse of mass extinction."

In addition to Finnegan, Eiler, Tripati, and Fischer, the other authors on the Science paper, "The magnitude and duration of Late Ordovician-Early Silurian glaciation magnitude," are Kristin Bergmann, a graduate student at Caltech; David Jones of Amherst College; David Fike of Washington University in St. Louis; Ian Eisenman, a postdoctoral scholar at Caltech and the University of Washington; and Nigel Hughes of the University of California, Riverside.

This research was funded by the Agouron Institute and the National Science Foundation.
 

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Obama Touts Caltech Research

In last night's State of the Union Address, President Obama said, "We're issuing a challenge. We're telling America's scientists and engineers that if they assemble teams of the best minds in their fields, and focus on the hardest problems in clean energy, we'll fund the Apollo projects of our time. At the California Institute of Technology, they're developing a way to turn sunlight and water into fuel for our cars. At Oak Ridge National Laboratory, they're using supercomputers to get a lot more power out of our nuclear facilities. With more research and incentives, we can break our dependence on oil with biofuels, and become the first country to have a million electric vehicles on the road by 2015." Watch video of the speech.

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Allison Benter
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New Reactor Paves the Way for Efficiently Producing Fuel from Sunlight

PASADENA, Calif.—Using a common metal most famously found in self-cleaning ovens, Sossina Haile hopes to change our energy future. The metal is cerium oxide—or ceria—and it is the centerpiece of a promising new technology developed by Haile and her colleagues that concentrates solar energy and uses it to efficiently convert carbon dioxide and water into fuels.

Solar energy has long been touted as the solution to our energy woes, but while it is plentiful and free, it can't be bottled up and transported from sunny locations to the drearier—but more energy-hungry—parts of the world. The process developed by Haile—a professor of materials science and chemical engineering at the California Institute of Technology (Caltech)—and her colleagues could make that possible. 

The researchers designed and built a two-foot-tall prototype reactor that has a quartz window and a cavity that absorbs concentrated sunlight. The concentrator works "like the magnifying glass you used as a kid" to focus the sun's rays, says Haile.

At the heart of the reactor is a cylindrical lining of ceria. Ceria—a metal oxide that is commonly embedded in the walls of self-cleaning ovens, where it catalyzes reactions that decompose food and other stuck-on gunk—propels the solar-driven reactions. The reactor takes advantage of ceria's ability to "exhale" oxygen from its crystalline framework at very high temperatures and then "inhale" oxygen back in at lower temperatures.

"What is special about the material is that it doesn't release all of the oxygen. That helps to leave the framework of the material intact as oxygen leaves," Haile explains. "When we cool it back down, the material's thermodynamically preferred state is to pull oxygen back into the structure."

The ETH-Caltech solar reactor for producing H2 and CO from H2O and CO2 via the two-step thermochemical cycle with ceria redox reactions.

Specifically, the inhaled oxygen is stripped off of carbon dioxide (CO2) and/or water (H2O) gas molecules that are pumped into the reactor, producing carbon monoxide (CO) and/or hydrogen gas (H2). H2 can be used to fuel hydrogen fuel cells; CO, combined with H2, can be used to create synthetic gas, or "syngas," which is the precursor to liquid hydrocarbon fuels. Adding other catalysts to the gas mixture, meanwhile, produces methane. And once the ceria is oxygenated to full capacity, it can be heated back up again, and the cycle can begin anew.

For all of this to work, the temperatures in the reactor have to be very high—nearly 3,000 degrees Fahrenheit. At Caltech, Haile and her students achieved such temperatures using electrical furnaces. But for a real-world test, she says, "we needed to use photons, so we went to Switzerland." At the Paul Scherrer Institute's High-Flux Solar Simulator, the researchers and their collaborators—led by Aldo Steinfeld of the institute's Solar Technology Laboratory—installed the reactor on a large solar simulator capable of delivering the heat of 1,500 suns.

In experiments conducted last spring, Haile and her colleagues achieved the best rates for CO2 dissociation ever achieved, "by orders of magnitude," she says. The efficiency of the reactor was uncommonly high for CO2 splitting, in part, she says, "because we're using the whole solar spectrum, and not just particular wavelengths." And unlike in electrolysis, the rate is not limited by the low solubility of CO2 in water. Furthermore, Haile says, the high operating temperatures of the reactor mean that fast catalysis is possible, without the need for expensive and rare metal catalysts (cerium, in fact, is the most common of the rare earth metals—about as abundant as copper).

In the short term, Haile and her colleagues plan to tinker with the ceria formulation so that the reaction temperature can be lowered, and to re-engineer the reactor, to improve its efficiency. Currently, the system harnesses less than 1% of the solar energy it receives, with most of the energy lost as heat through the reactor's walls or by re-radiation through the quartz window. "When we designed the reactor, we didn't do much to control these losses," says Haile. Thermodynamic modeling by lead author and former Caltech graduate student William Chueh suggests that efficiencies of 15% or higher are possible.

Ultimately, Haile says, the process could be adopted in large-scale energy plants, allowing solar-derived power to be reliably available during the day and night. The CO2 emitted by vehicles could be collected and converted to fuel, "but that is difficult," she says. A more realistic scenario might be to take the CO2 emissions from coal-powered electric plants and convert them to transportation fuels. "You'd effectively be using the carbon twice," Haile explains. Alternatively, she says, the reactor could be used in a "zero CO2 emissions" cycle: H2O and CO2 would be converted to methane, would fuel electricity-producing power plants that generate more CO2 and H2O, to keep the process going.

A paper about the work, "High-Flux Solar-Driven Thermochemical Dissociation of CO2 and H2O Using Nonstoichiometric Ceria," was published in the December 23 issue of Science. The work was funded by the National Science Foundation, the State of Minnesota Initiative for Renewable Energy and the Environment, and the Swiss National Science Foundation.

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Kathy Svitil
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Caltech and the Clean-Energy "Sputnik Moment"

The quest for clean energy, and our country's competitiveness both now and in the future is, according to Secretary of Energy Steven Chu (seen here in a photo from Caltech's 2009 Commencement ceremonies), our "Sputnik Moment."

"From wind power to nuclear reactors to high-speed rail," Chu noted in a speech to the National Press Club on Monday, November 29, "China and other countries are moving aggressively to capture the lead. Given that challenge, and given the enormous economic opportunities in clean energy, it's time for America to do what we do best: innovate."

Where to find that innovation? At Caltech, of course. More specifically—as Chu pointed out in his descriptions of some of the top technological innovators in the United States—at the Joint Center for Artificial Photosynthesis. JCAP, a DOE Energy Innovation Hub headed by Caltech's Nate Lewis and his Lawrence Berkeley National Lab counterpart, Peidong Yang, is focused on producing a fully artificial version of photosynthesis with no living components or wires.

In his speech, Chu spoke of JCAP as "a program that will produce abundant domestic fuel directly from sunlight."

Look at the way a plant makes chemical energy. It takes sunlight, it takes water, and it uses sunlight and energy to split the water into hydrogen and oxygen. And it takes carbon dioxide, and reduces the carbon dioxide and builds a carbohydrate that we can then turn into a sugar that can turn into a fuel.
And so the question is, can we design, using nanotechnology, something that begins to replicate what a plant does? But we have an advantage. We have access to materials that the wet biological world doesn't have access to, therefore, we can in principle design something better… We decided that in the last couple of years there's been enough advances in science and nanotechnology that we have a shot. In maybe five, ten years, this can really happen in a cost-effective way. And so an Energy Innovation Hub has been started to fund that type of research.

Secretary Chu's speech can be viewed in its entirety on the National Press Club's website.

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Lori Oliwenstein
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Alternative Transportation Programs Honored

Five years ago, Caltech's transportation office had one vanpool and just 150 participants in its Bike-to-Work and Walk-to-Work programs. Today, the university boasts 13 vanpools, 150 carpoolers, and nearly 1100 Bike- and Walk-to-Work participants—along with a wide array of other commuter services, including transit subsidies, telework and flextime options, Zipcar rentals, secure bike-storage facilities, and more. Caltech's commuter- and environmentally friendly programs haven't gone without notice. Indeed, the university recently was singled out for a corporate Blue Diamond Award by the Los Angeles County Metropolitan Transportation Authority. The award is given annually to a company that has proven itself a leader in ridesharing, with an active and visible presence in the commuter transportation field.

"Ridesharing has a number of benefits for Caltech employees, including reduced commuting costs, more commuting options, increased personal time, decreased stress, better health, and the chance to make new friends," says Kristina Valenzuela, Caltech's employee transportation coordinator, who accepted the Blue Diamond Award on behalf of the university at a ceremony in September. "Caltech as a whole benefits by retaining employees, increasing employee productivity, reducing congestion, and improving air quality around the campus," she says.

Valenzuela—who is herself in a commuter vanpool ("I do practice what I preach," she says)—continues to explore innovative alternative transportation options. In September, for example, the Rideshare office instituted a folding bike loaner program on campus. For a $20 refundable deposit, Caltech students, faculty, and staff can rent one of two folding bikes from the Parking office at 515 S. Wilson, plus a helmet and lock, "to do errands, go to meetings or just enjoy a bike ride," she says.

Not content to rest on her success, Valenzuela plans to soon expand the bikeshare program and also hopes to install a one-stop bicycle parking area and service facility on campus. "I've applied for a grant to put a Bikestation here on campus," she says. "If the grant is approved, this will be a stand-alone secure bicycle parking facility. The facility will be fully self-contained with a solar electrical system and will offer bicycle commuters service amenities such as lockers and work bench area for small repairs, a free air station, and a hand washing area."

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Kathy Svitil
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Caltech/JPL Experiments Improve Accuracy of Ozone Predictions in Air-Quality Models

Team says current models may underestimate ozone levels; findings made by characterizing rates of key chemical reactions

PASADENA, Calif.—A team of scientists led by researchers from the California Institute of Technology (Caltech) and NASA's Jet Propulsion Laboratory (JPL) have fully characterized a key chemical reaction that affects the formation of pollutants in smoggy air. The findings suggest that in the most polluted parts of Los Angeles—and on the most polluted days in those areas—current models are underestimating ozone levels, by between 5 to 10 percent.

The results—published in this week's issue of the journal Science—are likely to have "a small but significant impact on the predictions of computer models used to assess air quality, regulate emissions, and estimate the health impact of air pollution, " says Mitchio Okumura, professor of chemical physics at Caltech and one of the principal investigators on the research.

“This work demonstrates how important accurate laboratory measurements are to our understanding of the atmosphere,” added JPL Senior Research Scientist Stanley P. Sander, who led that team's effort.

The key reaction in question in this research is the reaction between nitrogen dioxide, NO2, and the hydroxyl radical, OH. In the presence of sunlight, these two, along with volatile organic compounds (VOCs), play important roles in the chemical reactions that form ozone.

Until the last decade or so, it was thought that NO2 and OH combine only to make nitric acid, HONO2, a fairly stable molecule with a long lifespan in the atmosphere. "HONO2, or nitric acid, dissolves in rainwater, so that the molecules get washed away," Okumura explains. "It's basically a sink for these radicals, taking them out of the ozone equation and thus slowing down the rate of ozone formation."

Chemists had suspected, however, that a second reaction might occur as well: one that creates a compound called HOONO (pronounced WHO-no), otherwise known as peroxynitrous acid. HOONO is much less stable in the atmosphere, falling apart quickly after being created, and thus releasing the OH and NO2 back for use in the ozone-creation cycle.

But what was not known with any reasonable certainty—until now—is how fast these reactions occur, and how much HONO2 is created relative to the amount of HOONO created. Those relative amounts are known as the branching ratio, so called because OH and NO2 can chemically transform, or branch, into either HONO2 or HOONO.

Enter the Caltech and JPL teams. The JPL team took the lead on measuring the rate at which the OH + NO2 reaction produces both HONO2 and HOONO. They did this using "an advanced chemical reactor built at JPL that was designed to measure reaction rates with very high accuracy," says Sander.

Once the scientists had determined the combined reaction rate for the two possible products—coming up with rates that are on the higher rather than the lower end of the scale of previous estimates—the Caltech group took the lead to try to uncover the branching ratio, or the ratio of the rates of the two separate processes.

Using a powerful laser measurement technique called cavity ringdown spectroscopy, the team was able to detect both products being created in the lab in real time, says Okumura. "We could start the reaction and watch, within microseconds, the products being formed," he says. "That allowed us to measure the species immediately after they were formed, and before they got lost in other side reactions. That is what allowed us to figure out the branching ratio."

Because HOONO was not a well-studied molecule, another key was using state-of-the-art theoretical calculations; for this, the authors enlisted Anne McCoy, professor of chemistry at The Ohio State University. “Solving this atmospheric chemistry problem required us to use many tools from modern chemical physics,” says Okumura.

"This work was the synthesis of two very different and difficult experiments," adds Andrew Mollner, the Science paper's first author and a former Caltech graduate student who is now at the Aerospace Corporation. "While neither experiment in isolation provided definitive results, by combining the two data sets, the parameters needed for air-quality models could be precisely determined."

In the end, what they found was that the loss of OH and NO2 is slower than what was previously thought—although the reactions are fast, fewer of the radicals are going into the nitric acid sink than had been supposed, and more of it is ending up as HOONO. "This means less of the OH and NO2 go away, leading to proportionately more ozone, mostly in polluted areas," Okumura says.

Just how much more? To try to get a handle on how their results might affect predictions of ozone levels, they turned to Robert Harley, professor of environmental engineering at the University of California, Berkeley, and William Carter, a research chemist at the University of California, Riverside—both experts in atmospheric modeling—to look at the ratio's impact on predictions of ozone concentrations in various parts of Los Angeles during the summer of 2010.

The result: "In the most polluted areas of L.A.," says Okumura, "they calculated up to 10 percent more ozone production when they used the new rate for nitric acid formation."

Okumura adds that this strong effect would only occur during the times of the year when it's most polluted, not all year long. Still, he says, considering the significant health hazards ozone can have—recent research has reported that a 10 part-per-billion increase in ozone concentration may lead to a four percent increase in deaths from respiratory causes—any increase in expected ozone levels will be important to "people who regulate emissions and evaluate health risks." The precision of these results reduces the uncertainty in the models—an important step in the ongoing effort to improve the accuracy of the models used by those policymakers.

Okumura believes that this work will cause other scientists to reevaluate recommendations made to modelers as to the best parameters to use. For the team, however, the next step is to start looking at "a wider range of atmospheric conditions where this reaction may also be very important."

Sander agrees. "The present work focused on atmospheric conditions related to urban smog—i.e., relatively warm temperatures and high atmospheric pressure," he says. "But the OH + NO2 reaction is important at many other altitudes. Future work by the two groups will focus on the parts of the atmosphere affected by long-range transport of pollution by high-altitude winds (the middle and upper troposphere) and where ozone depletion from man-made substances is important (the stratosphere)."

In addition to Okumura, Sander, Mollner, McCoy, Harley, and Carter, the other authors on the Science paper, "Rate of Gas Phase Association of Hydroxyl Radical and Nitrogen Dioxide," are postdoctoral fellow Lin Feng and graduate student Matthew Sprague, both from Caltech; former JPL postdoctoral researchers Sivakumaran Valluvadasan, William Bloss, and Daniel Milligan; and postdoctoral fellow Philip Martien from the University of California, Berkeley.

Their work was supported by grants from NASA, the California Air Resources Board, and the National Science Foundation, and by a NASA Earth Systems Science Fellowship and a Department of Defense National Defense Science and Engineering Graduate Fellowship.

JPL is a federally funded research and development facility managed by Caltech for NASA.

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Lori Oliwenstein
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Capturing the Sun

With a prestigious Truman Fellowship at the Sandia National Laboratories, a Caltech graduate student continues his quest to create solar fuel.

William Chueh has traveled thousands of miles throughout the United States to pursue his passion of nature photography, often hiking deep into remote canyons to snap the perfect picture. But when it came time to choose a graduate school, he decided to stay put at his undergraduate alma mater, Caltech, summoning his love of nature and concern for the environment as a guide.

In 2005, Chueh, then a Caltech senior, applied to graduate school in the Institute's Division of Engineering and Applied Science, and in his application, he recalled an event that would inform his research path. Two years earlier, he wrote, he had made a trip to the iconic Yosemite Valley. He was anticipating pristine views, but what he found instead was a curtain of smog thrown up by thousands of cars and buses passing through. His goal as a graduate student, Chueh wrote, was to help fix that problem. Today, he's made significant progress toward that goal.

This month, after five years in the lab of Professor of Materials Science and Chemical Engineering Sossina Haile, Chueh wrapped up his doctoral research—work that included developing a novel method of using solar energy to generate fuel. That breakthrough recently earned him a prestigious Truman Fellowship at the Sandia National Laboratories in Livermore, California. Chueh is the first Caltecher to receive the three-year, $800,000 fellowship, which will give him the freedom and funding to pursue a line of research that may lead to crucial advances in the production of abundant, clean energy.

Chueh started his freshman year at Caltech shortly after 9/11, amid considerable discussion about America's critical need to wean itself off fossil fuels. One of the recommended areas of research concerned ways to improve energy conversion and storage, and Chueh got hooked on the subject.

"If you throw fuel and oxygen in an engine, it burns in an inefficient and dirty way," Chueh says. "But if you use electrochemistry and do it in a more controlled manner, then you will have better efficiency and lower emissions." During his senior year, he assisted in a research project led by Haile, who had been studying ways of improving fuel cells, which convert fuel into electricity through a chemical reaction.

One of the problems with many fuel cells concerns temperature.  Some can only operate at such high temperatures that they must be encased in expensive ceramic materials to withstand the heat, while those that can operate at close to room temperature need precious, scarce metals such as platinum to work. Another problem is that they need fuel—typically hydrogen derived from fossil fuels—to generate electricity.

Chueh holds three samples of metalized, thin-film cerium oxide, which he and Haile used to study the fundamental chemistry for generating fuel from the sun's heat.

Tackling the first problem, Haile had been investigating materials that would also allow fuel cells to work at lower temperatures. One of them, cerium oxide (CeO2), is derived from the element cerium—which is classified as a rare earth metal, but is actually as common as copper. Cerium oxide plays an important role in a car's catalytic converter, helping to turn smog-causing molecules into carbon dioxide.

Shortly after Chueh joined Haile's lab as a graduate student, he and Haile started talking about whether CeO2 could also play a role in using the heat of the sun to convert a chemical "cocktail," consisting primarily of carbon dioxide (CO2) and steam, into a gas mixture of carbon monoxide and hydrogen known as "synthesis gas." This "syngas," as it's commonly called, can then be converted into liquid fuels through a decades-old process involving a series of chemical reactions.

"I was pessimistic at first," Chueh says. For a while he held off on testing the idea, but at Haile's urging, he decided to run the necessary experiments during winter break in 2007, when everyone else in the lab was on vacation. "It worked right off the bat," Chueh says. "I'm very cautious, though, so I repeated it before I told her about it. We were all very excited by the results."

Currently, says Chueh, "I'm working on experiments to demonstrate that this is not just a laboratory curiosity, but a solution that could potentially work on a larger scale." The process could also be used in a variety of applications, including the production of fuel for transportation and for running factories.

Chueh took this photograph of the sensational fall colors in Yosemite Valley in 2006.

"William is a truly remarkable researcher, combining exceptional experimental talent with deep theoretical insight," says Haile. "This has allowed him to transform a loosely defined idea from a few sketches on a piece of paper to a meaningful scientific and technological breakthrough. I look forward to learning of his latest discoveries as he moves on to the next stage of his career."

At Sandia, a government-owned facility that develops technologies that support national security, Chueh will continue to study the cerium oxide–reaction to try to determine exactly what is happening at the molecular level while the catalyst is working. "Once we have a more detailed picture of that, we will be able to better understand why it works," he says, and possibly come up with ways to improve it.

Chueh says that he's "convinced that in the years to come, we'll see scaled-up plants that are actually producing a good amount of fuel from this kind of process. This system would work best in the desert, where there's lots of sun."

While Chueh acknowledges that there are numerous other solar research projects that could prove to be as beneficial as the cerium process, he says,  "Every system has its advantages and drawbacks. In the end, a solution to the energy problem will not come from a single technology but from a wide range of technologies. This gives consumers and policy makers one additional option."

As for the nature photography that started it all, Chueh didn't have much time for his hobby during graduate school, but he's looking forward to taking it up again.

"I'm hoping to go to the eastern Sierra in the fall when all the aspens turn yellow and then orange," he says. "In nature photography, I love finding order in chaos, and that's what we essentially do in science.

"Deep down, I have a great appreciation for the environment," Chueh says. "When I saw that smog-filled Yosemite Valley, that's when I thought, 'I've got to do something before all this gets wiped out.'"

Writer: 
Mike Rogers
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