Inventing a greener future

Sobering new reports from global climate experts paint an increasingly grim picture.

"Current choices regarding carbon dioxide emissions will have legacies that irreversibly change the planet," says Susan Solomon, lead author of a 2009 National Oceanic and Atmospheric Administration (NOAA) study on rising CO2 levels.

Former vice president and climate change activist Al Gore is cautiously optimistic that we can still successfully address climate change if we take immediate and decisive action. "It is retrievable and solvable-if we start now on a bold program," said Gore.

UCSC scientists are helping to meet the challenge by pioneering innovative alternatives to fossil fuels-from super-thin solar energy materials to renewable hydrogen. And because humans won't stop burning oil and gas anytime soon, research teams are also exploring ways to make fossil fuels cleaner and more efficient. Many of these advances draw on UCSC's leadership in nanotechnology, which provides a treasure chest of new tools to address tough energy challenges. And the campus's longstanding partnerships with Silicon Valley are helping to put much-needed new technologies into practical use.

However, warns UCSC's Ali Shakouri, professor of electrical engineering, "Engineering solutions alone won't be enough to address the world's environmental and energy problems. We also need to make societal changes in the ways we use energy, and that will be far more difficult."

Getting more sun

Solar energy is widely seen as the cornerstone of a green revolution that can revitalize the U.S. economy while saving the planet. Unfortunately, the solar industry's reliance on traditional silicon panels (the ones we see on rooftops) greatly limits its potential. The problem is that refining silicon is expensive, energy intensive, and fairly toxic-plus the cells and panels themselves are difficult to mass produce.

"We need a paradigm shift-a complete change in the way we manufacture photovoltaics," said UCSC's Sue Carter, professor of physics and a leading solar energy researcher. "Silicon-based solar panels are relatively efficient at generating electricity, but there is no way we can produce enough of them in the near term to put a dent in fossil fuel plants."

Carter's research team is creating the next generation of solar energy-liquid materials that can be applied in very thin layers much like printing a newspaper. Carter's approach is cheaper because it uses far less material and energy to produce than do silicon panels. It is also safer and can be applied to just about anything, including flexible materials like thin plastic and fabric.

"With print-based manufacturing, all of a sudden you can produce large areas of solar-generating material quite cheaply," added Carter.

Carter's research is already having an impact on the industrial landscape. She proudly lists former graduate students who play key roles at innovative solar startups, and Carter herself is a technical adviser to a number of leading-edge firms.

With Glenn Alers, UCSC adjunct professor of physics, Carter has also initiated

the Laboratory for Solar Energy and Renewable Fuels (SERF). SERF is part of the Advanced Studies Laboratories, a technology incubator located at the NASA Ames Research Center and sponsored by UCSC's Silicon Valley Initiatives (UCSC recently announced a partnership with NASA.). "We can offer the experimental expertise needed to help study new materials and incorporate emerging technologies into commercial products more effectively," said Carter.

Fill 'er up - on water and sunshine

The so-called hydrogen economy is a compelling vision. Hydrogen is a very clean fuel, and there's definitely a lot of it around--mostly linked with oxygen in the form of water. And while it's not complicated to separate out the hydrogen, the process requires a fair amount of energy.

UCSC chemistry professor Jin Zhang is working toward what he calls the "holy grail" of carbon-negative hydrogen--hydrogen produced without using fossil fuel. His ultimate goal is a device that will turn water into hydrogen using only solar energy. "We need to overcome some technical problems," said Zhang, "but the potential of this research is enormous."

Zhang's work is attracting a lot of interest, including major research funding from the U.S. Department of Energy. "The theory works," said Zhang. "We can actually do it, but we can't yet generate hydrogen efficiently enough for it to be practical. We need to make it competitive with gas for people to actually use it."

Zhang and his research team are developing and testing new nanomaterials for a two-part integrated system that splits water into hydrogen and oxygen using sunlight.

"In theory," said Zhang, "you could have this device on one side of your car, with perhaps solar collectors on the roof, and just refuel with your garden hose."

Realistically, he added, we might first see a hybrid vehicle that runs on its own solar-generated hydrogen when the sun is out-and on another fuel at night or on cloudy days.

New heat wave

UCSC's Ali Shakouri made news in 2001 when his research team developed a "refrigerator on a chip." The tiny device--about the width of a human hair--uses engineered nanomaterials with just the right electrical and thermal properties to cool hot spots in microprocessors.

Now Shakouri is turning that breakthrough on its head, developing similar materials to turn waste heat from cars and power plants into electricity. His work, like Zhang's, relies on designing new materials at the nanoscale. "Our task is to engineer materials that don't exist in nature," said Shakouri.

Put simply, when materials of differing temperatures come in contact, the more active electrons on the warmer side tend to flow to the cooler side, thereby generating electrical current. Shakouri's new materials are making the process more efficient, in effect "herding" electrons and heat where he wants them to go.

Shakouri heads the Thermionic Energy Conversion (TEC) Center, a major national initiative that brings together top materials scientists, engineers, and physicists from seven universities to attack various aspects of the waste heat problem. Supported by a multimillion-dollar investment from the Office of Naval Research and the Defense Advanced Projects Agency, partners in TEC include UC Santa Barbara, UC Berkeley, Purdue University, University of Delaware, Harvard University, MIT, and BSST Inc.

Shakouri is optimistic that TEC's heat-capturing technology will be able to increase fuel efficiency by as much as 15 percent. It isn't ready to install in vehicles yet, he adds, but we can expect to see a test model within the next four to five years.

Going carbon negative

Escalating CO2 in the atmosphere not only contributes to global warming but is also rapidly making the world's oceans more acidic as they absorb all that excess CO2. According to Gregory Rau, a senior researcher at UCSC's Institute of Marine Sciences, this change in ocean pH is already linked to declines in coral and other marine organisms.

"We need to implement sustainable energy sources immediately," said Rau, "but no matter how quickly we can gear up, fossil fuels will still be with us for the foreseeable future."

At UCSC's Long Marine Laboratory, Rau is testing an ingenious method of removing excess CO2 that takes its cue from nature. "We're simply accelerating the natural process of limestone weathering," he explained, "which is one of the ways nature consumes excess atmospheric CO2 and neutralizes ocean acidity." Unfortunately, Rau adds, in nature that process takes many thousands of years.

Rau's process borrows a technique from saltwater aquarium hobbyists, who use a comparable reaction to maintain the proper pH in tanks of coral and shellfish. Rau mixes limestone particles with seawater and pumps simulated power plant exhaust through the mix. His test reactor balances seawater chemistry while successfully removing up to 95 percent of incoming CO2.

Scaled-up reactors could potentially absorb the CO2 emitted by power plants, while benefiting ocean ecosystems. Rau is also working on a "supercharged" version of the technology designed to scrub CO2 from the general atmosphere, not just waste streams. The trick is making the process faster and more efficient by adding a jolt of electricity-from renewable sources.

"This could be done on a large scale," said Rau. "For example, we might see fleets of barges on the open ocean, loaded with limestone and covered with wind turbines, solar panels, or wave energy converters to power the reaction." An added benefit of the process is the production of hydrogen gas, a carbon-free alternative to fossil fuels.