Futuristic Fuels
By Marc Airhart. Illustrations by Galina Nelyubova
Some of the most revolutionary ideas for powering our increasingly energy-hungry society sound a bit like science fiction, requiring only abundantly available and affordable resources. Yet University of Texas at Austin scientists are taking steps in the direction of that future even now. They are looking to harness the extreme conditions inside the sun and the immense energy stored in atoms for new sources of energy. They’re exploring exotic quasiparticles to turn water and sunlight into hydrogen fuel. And they’re examining the genetics and microbial keys to what some would call a weed with the potential to become the best-ever biofuel. Here are four leading ideas about the future of energy and Texas scientists’ assessments of how close we are to switching them on.
FUSION WITH MAGNETS
Vision: In one approach to fusion energy, powerful magnets contain a plasma that’s several times hotter than the center of the sun while hydrogen atoms fuse and release energy. One gram of fuel could supply as much energy as 2,400 gallons of oil, with very little waste or climate-warming emissions.
State of play: Dozens of startup companies around the world are aiming to resolve the known technical challenges within the decade, each hoping to have the first small prototype fusion power plant. Larger national and international projects are also in development that will complement and support the private efforts.
Challenges: Among the challenges remaining to solve, the large electric current required with this approach to create a strong magnetic field can cause the plasma to whip around like a gushing garden hose when it slips from your hand. This “kink instability” can accelerate electrons up to high speed, causing them to smash into and damage the reactor walls.
Solutions: UT research professor François Waelbroeck is part of the Department of Physics’ Institute for Fusion Studies, where he and other researchers help design “magnetic bottles.” These systems can contain the intense heat and radiation of a plasma in a way that is controllable and stable. One possible solution to kink instabilities is to inject noble gases into the plasma to sap the energy of these energetic electrons. Another is to adjust the electric currents that create the magnetic confinement field to steer the electrons away from the walls until they lose energy.
The scientist’s summary: “Energy is needed for food, transportation, housing and health care. As the world’s need for energy is becoming ever more pressing, IFS scientists are excited to be overcoming obstacles to the construction of fusion reactors that can produce limitless, clean and affordable energy to improve people’s lives.”
Our goal: “limitless, clean and affordable energy to improve people’s lives.”
LASER-DRIVEN FUSION
Vision: In this version of fusion energy, also called inertial confinement, a high-intensity laser first compresses a fuel pellet containing hydrogen isotopes to a density that is high enough to support a fusion reaction. Then a laser (either the same one or a second laser) ignites the fuel.
State of play: In 2022, researchers at the National Ignition Facility (NIF) made a major breakthrough, releasing more energy than was put into a fusion reactor. But it’s taken decades of hard work to reach this milestone, and commercial viability remains a distant possibility.
Challenges: As scientists scale lasers up to the energies needed for a commercial reactor, the plasma surrounding the fuel tends to become unstable. Waves ripple through it, causing plasma to be wiggly like Jell-O, making it harder for the laser to compress the fuel to the high densities that are necessary.
Solutions: Lasers typically narrowly focus on one frequency, or color. Theoretical physicists have proposed that a laser with a broad range of frequencies, more like a rainbow, could overcome these instabilities and “confuse the Jell-O,” in the words of Todd Ditmire, director of UT’s Center for High-Energy Density Science. He’s starting experiments to test this at the Texas Petawatt Laser in Austin and with a new, even more powerful laser that he’s helping to build overseas.
The scientist’s summary: “It dawned on me that I have one of the broadest-band high-energy lasers in the world at UT. Could we use this to study the plasma physics and see if this bandwidth does indeed make some of these instabilities go away?”
FUEL FROM WATER
Vision: In the 1970s, researchers in Japan discovered that a naturally occurring mineral, titanium dioxide (TiO2), when combined with water and sunlight, produces hydrogen. That sparked the dream of a truly green way to power transportation and industrial processes with hydrogen fuel built from abundant, safe raw materials and zero pollution.
State of play: Unfortunately, titanium dioxide – used in a wide range of consumer products, from paint to toothpaste to sunscreen – is too inefficient for large-scale commercial use as a photocatalyst. The amount of energy you get out is a small fraction of that put in. So for decades, materials scientists have been looking for ways to either tweak the material or design entirely new, more efficient materials.
Challenges: Standing in the way of TiO2’s potential as a photocatalyst is getting enough electrons to the surface quickly enough to react with water molecules and sunlight.
Solutions: Theorists believe quasi-particles called polarons shuttle electrons to the surface, and physics professor Feliciano Giustino and his team member Zhenbang Dai recently developed a new, high-resolution computer simulation that sheds light on the phenomenon. Giustino’s team is now searching for a more complete picture of how photocatalysts like TiO2 split water and how properties of materials might be tweaked to boost electron transport.
The scientist’s summary: “So far, the limitation has been that we don’t really understand the basic mechanism of photocatalysis itself, so it’s still all trial and error to find better materials. If we can discover the right descriptors, we can identify other materials that can do this in a more efficient way.” – Feliciano Giustino
FUEL FROM PLANTS
Vision: In aviation, trucking and shipping, where batteries lack the ability to meet current energy demands, biofuels will be crucial for the nation’s energy and environmental security, according to the Department of Energy (DOE). Switchgrass, a hardy plant found across the U.S., is an attractive option for biofuel feedstock because it can grow on marginal land that’s not great for growing crops and is capable of storing carbon underground.
State of play: For commercial production of switchgrass for biofuels, there will need to be breeding programs to develop varieties that can grow in a wide range of conditions. A team led by professor of integrative biology Tom Juenger is conducting research aimed at making bioenergy feedstock crops more productive and resilient.
Challenges: It can take time, perhaps a decade, to develop all of the needed traits for these biofuels: high yield, freeze tolerance, drought tolerance, improved carbon storage in roots and low silica (basically sand that can occur in leaves and cause problems in industrial processing).
Solutions: Juenger and his team have already uncovered switchgrass genes that influence many of these desirable traits. They’re also studying how the microbes that live on and around the plants impact their biology. Now his work is shifting toward the more applied side of manipulating plant genetics and microbiomes to see if their hypotheses improve real-world performance.
The scientist’s summary: “I feel like we’ve learned a ton and now we could pick and choose a variety of different strategies to improve general agronomic performance, industrial processing or sustainability.”