|Photos by Max S. Gerber|
AS OUR ATMOSPHERE CHOKES on greenhouse gases and the planet’s thermostat inches up toward the danger zone, it sounds at first like a horrible idea: What if, in addition to the fossil-fuel combustors in our cars, we also put them in our computers and in all our other digital devices, from cell phones and PDAs to cameras and pagers? A hydrocarbon generator on every desktop and in every briefcase — that is the vision of a small coterie of engineers and materials scientists who believe that within the next decade we will begin to see this dream materialize. And they do mean dream, not nightmare. For despite hydrocarbons’ bad rap, they are a brilliant source of power and could potentially solve one of the major problems of our increasingly digital lifestyles without endangering the environment.
One recent morning I saw this bizarre coupling of the chemical and the electronic in action when Zongping Shao, a young Chinese scientist at Caltech, hooked up his MP3 player to a tiny generator running on propane. At 3 a.m. that morning, Shao had finally gotten the device working and, along with his supervising professor, Dr. Sossina Haile, I was the first to witness this radical new technology at work.
Almost unbelievably simple in appearance, Shao’s experimental apparatus was enclosed in the tip of a test tube with tiny plastic hoses running in and out to ferry the air and propane in and to release the exhaust fumes. But there the similarity to any conventional generator ceased. For a start, there were no moving parts and hence no mechanical noise. At the heart of Shao’s setup was a disc the size of a penny made of an amazing new material he has developed. By catalyzing a chemical reaction, this material will take the energy stored in a hydrocarbon — like propane or octane — and convert it into electricity. What he has made, in effect, is an exotic kind of fuel cell, of the solid oxide variety, that is far more powerful and practical than the hydrogen-based fuel cells we have been hearing so much about from George W. Bush and our own Governator.
After showing me the disc itself — a pale-gray wafer that looked not unlike a piece of asbestos — Shao sealed it within the test tube and hooked up the propane hoses. Minutes later he attached the MP3 player to the wires trailing out the bottom and handed me the earphones so I could hear the future for myself. Let it be known that the first sounds ever to be micropowered by fossil fuel were a selection of syrupy Chinese pop songs.
Haile, a professor in Caltech’s Department of Materials Science and Chemical Engineering, believes that within a decade we could begin to see small-scale generators powered by hydrocarbon fuels providing the energy for our laptop computers — thereby replacing the heavy and limiting batteries we currently rely on. Dr. Paul Ronney of the University of Southern California is working on another approach to micropower generation, using tiny combustion chambers. Eventually, he says, even our tiniest electronic devices could be powered by hydrocarbons. Though there
are a lot of technical hurdles to be overcome in terms of miniaturizing this technology, Ronney’s lab at USC’s Department of Aerospace and Mechanical Engineering is already working on a device just 3 millimeters across. Fuel would be provided in the form of cartridges, much like those in a Bic lighter, that you’d simply plug into the side of any electronic equipment.
USC’s Paul Ronney, below, is
building combustion engines the
size of a dime. Here, he holds a
plastic version under development.
But aren’t we supposed to be moving away from fossil fuels? The U.S. has still not signed the Kyoto Protocol, making us the only major holdout, while the rest of the world is taking global warming seriously. So what’s with this push to make even more hydrocarbon burners? Actually, says Ronney, this is not another case of belligerent American exceptionalism — digital devices require so little power that even if all our electronic helpers were powered by fossil fuels, the total amount of greenhouse gas produced would be utterly insignificant compared to what we generate by driving our cars and by heating and air-conditioning our homes and offices.
As anyone knows who has ever experienced their cell phone running out of juice at a crucial moment, batteries have a limited lifetime before they must be recharged. Moreover, they are heavy, typically accounting for around a quarter of the weight of a laptop. Imagine, then, the battery hell of the average U.S. soldier, who is now freighted down with a GPS locator, laser-guided gun sights, electronic night-vision goggles and an ever-expanding array of battery-dependent paraphernalia.
Warfare is not going away anytime soon; thus the Army clearly needs a better way of providing the soldier of the future with power. Looking ahead, the Defense Advanced Research Projects Agency (DARPA) announced in 1998 a major initiative in micropower research. The agency has spent $20 million to $30 million on its micropower program so far, and around the nation there are half a dozen teams working on the problem, including a group at MIT that is leading an effort to build a microscale gas turbine engine, and a team at UC Berkeley that is trying to make a tiny Wankel rotary engine — a scaled-down version of the one used in the Mazda RX-7 and RX-8. Ronney and Haile, however, are taking a radically different approach: Rather than scaling down existing technologies, they are trying to develop a whole new micropower system.
RECENTLY, I VISITED RONNEY in his cluttered USC office. On top of a bookshelf was a picture of him in an astronaut suit. As an expert on “flame balls,” enigmatic spheres of fire that form in a microgravity environment, Ronney has had experiments conducted on the space shuttle, and in 1997 he was a backup crew member for two shuttle missions on the ill-fated Columbia. Much of his work is conducted at USC’s Combustion Physics Laboratory, a place where grown-ups get to set things on fire and study what happens. Along with flame balls, his list of research interests includes such poetically evocative topics as “flame propagation in confined geometries” and “pre-mixed flame ignition by pulsed corona discharges.” He is also an authority on internal-combustion engines.
Pound for pound, Ronney says, hydrocarbons are a fantastically compact source of energy. The energy densities of propane, methane, gasoline and diesel are at least 50 to 100 times greater than the best lithium-ion batteries. “A gallon of gas is the equivalent to about 500 pounds of batteries,” Ronney notes — which is precisely why we have become so dependent on the stuff, and why all-battery cars have proved so elusive.
No one doubts the theory of hydrocarbon power generation on a microscale; the problem is putting it into practice. “It’s not so easy to shrink things down,” Ronney tells me. “There are good reasons why you don’t have people who are 1 inch tall.” Likewise, there are good reasons why no one has built microscale combustors before. In particular, as things get smaller, they tend to lose heat more rapidly, making it increasingly difficult to achieve the high internal temperatures needed for hydrocarbon combustion. Until recently, many engineers thought that indeed microcombustion would never work.
But Ronney has found an ingenious solution in a construction known as the “Swiss roll.” The basic idea is exceedingly simple: Just take the intake and outtake pipes and roll them up in a tightly coiled double spiral with the combustion chamber in the center. Now, as the hot exhaust is evacuated, a good portion of the heat remains circulating in the interior, thereby maintaining temperatures of 500 to 700 degrees Celsius at the center, where the fuel needs to burn.
In his lab, Ronney shows me one of his very first Swiss rolls. I had expected something circular, but it’s actually shaped like a cube, a little more than half an inch on each side. It’s milled out of a tungsten carbide–cobalt alloy. The top surface is open, and inside I can see the double spiral of the intake and outtake vents, with a tiny chamber at the center not much more than a millimeter across. Fuel and air are fed in through tiny pipes connected at one edge. The whole thing is like some dollhouse toy.
To make it even more heat-efficient, Ronney has taken six wedge-shaped Swiss rolls and joined them up in a circle. In this variation each wedge is fed simultaneously by its own little pipe, while all of the wedges are connected in a tiny plumbing network. Obviously assembled by hand, the whole thing is a marvel of miniature fabrication. The man responsible, Ewald Schuster, is a former Hollywood model maker the USC engineering department has hired as a research technician. “We couldn’t pay him what Hollywood can,” Ronney says, “but we figured we could give him a regular paycheck.” In his workshop, Schuster is also maaking the world’s smallest jet engine (see sidebar).
Lately, Ronney has been building his Swiss rolls out of a material called Vespel, a polymide plastic developed by Dupont that can withstand temperatures up to 500 C. These are the world’s first all-plastic combustion engines, he says. They are incredibly easy to machine, plus they have the added advantage “that you can kick them across the room and they won’t break.”
AT THIS POINT, Ronney ignites the fuel at the center of his rolls with a heated platinum wire. But another approach he is looking into is to use Haile and Shao’s fuel cells instead. Over the past year, both Governor Schwarzenegger and President Bush have touted fuel cells as a future alternative to gasoline. A car running on traditional hydrogen fuel cells would emit only a small amount of water. But there is no such thing as a free ride, and it is far from clear that hydrogen will ever be a practically viable fuel.
Hydrocarbons, however, also contain large amounts of precious hydrogen, and many of them are far easier to work with. Twenty years ago, a group of Japanese researchers discovered another type of fuel cell that could run directly off hydrocarbons — solid-oxide fuel cells — but until now nobody had thought that they could be made to work on small scales. Again, the critical issue was heat, for these devices will only operate at around 500 C. When Shao showed me his fuel cell, he had to pre-heat it in a small furnace to get the reaction started. That is where Ronney’s Swiss rolls come in.
The other breakthrough, Haile says, is the fact that Shao is a genius with the esoteric materials that make up these cells — weird combinations of metals such as barium, cobalt, cerium and samarium. Recently he has perfected a version that has incredible performance specs. Quite apart from micropower generation, Haile notes that this material could make an enormous impact on “the stationary power” industry, stand-alone generators for homes and offices in remote locations, and in facilities like hospitals that need backup in case of power failures from the grid.
Having proved the principles of micropower generation, Haile and Ronney now say that the hurdles they face are purely technical. Can this technology be made cheaply and is it mass-producible? One of the major problems they will have to address is their plumbing. At the moment, fuel and air must be pumped in mechanically, but tiny mechanical parts are hard to manufacture and they break easily. Eventually, Ronney would like to make the whole system with no mechanical parts at all, and in theory it is possible to have a non-mechanical pump. The trick is to have the right kind of material, and the quixotic substances known as aerogels happen to have just the required properties — microscopic pores through which the air and fuel can be sucked. “The moral of the story,” Ronney says, “is that with the right materials, you can do anything.”
Whereas the 19th century was the age of machines and the 20th century the age of computers, much of the technological development of the present century is going to be driven by innovations in materials science. Nothing could suggest this more vividly than the potential marriage of hydrocarbons and silicon brokered by the high-tech alchemy of solid-oxide fuel cells and aerogels. Here, elements from across the periodic table will work in concert to realize technologies unimaginable even a decade ago.
Jet's Sons: Former Hollywood SFX man Ewald Schuster gets real small
There are model-plane fanciers, and there are model-plane fanatics, people for whom miniature aircraft are not merely a hobby but, to crib from Richard Meltzer’s eloquent description of record collecting, “the designated essentials” without which “the universe would topple.” Ewald Schuster is definitively in this latter category. “When I was 9 years old,” Schuster says, “I saw a Harrier at an air show, and I realized that I had to have one myself.” For those of you who, like me, tend to think of black hawks and hornets as members of the animal kingdom, the Harrier is an airplane in a class of its own — it is the only jet plane that can hover. Designed by the British company Hawker Siddeley, the Harrier is the result of an insanely complex feat of engineering that overcomes a mass of instabilities to enable a fixed-wing craft to hover in the air like a dragonfly.
For the past decade, Schuster, who is a research technician in the engineering department at USC, has been building his own Harrier from the ground up, every part individually designed and fabricated by hand. At one-sixth scale, it has a 92-inch fuselage and a 60-inch wingspan. So far Schuster has flown it as a conventional jet, but the real challenge is to make it hover, something he hopes to achieve this coming year.
Schuster’s skill with eccentric machinery was honed by his years as a special-effects model maker for Hollywood — he designed the mechanisms for the irascible little fighters in Toy Soldiers and the mechanical tentacles for the aliens in Galaxy Quest. But frankly, he says, working in Hollywood was a bit unsatisfying: “They want everything too fast, and you never get to make things properly.” A few years ago, after an innocent inquiry to the USC Department of Aeronautical Engineering about the specifics of hovering aircraft, he found himself being offered a job. “I like it here,” Schuster says, “because they let you do things properly and I can do my own research.”
In addition to the Harrier, Schuster has fabricated the world’s smallest jet engines. The Harrier itself has a relatively large engine, 4 1/2 inches in diameter and 8 inches long. But Schuster has already made one half that size — 2 1/4 inches by 5 inches — which currently rates as the tiniest documented jet, and he is now working on one half as small again. In his workshop, he lets me hold it in my hand — it’s just 1 1/4 inches in diameter and 2 1/2 inches long. Although it hasn’t been flown yet, Schuster has tested it in the laboratory. At full throttle, the tiny turbine spins at 500,000 revs per minute, a rate that even the bearings’ manufacturers find hard to believe.
Apart from their novelty value, Schuster notes that miniature jets could be extremely useful for surveillance, when you need “something that can fly in very fast, take pictures, then fly out very fast.” The U.S. military has actually been looking for such devices, and Schuster hopes his jets might fit their bill. Moreover, microjets would be a perfect power source for certain applications because jets are intrinsically more fuel-efficient than internal-combustion engines.
True love is never a cheap affair: Schuster reckons that to date he has spent $50,000 on the Harrier alone, plus around 20,000 hours of his time. Each of the smaller jets has cost thousands more. Though USC has provided him with a workshop, the jets are his personal hobby project, and he bears the cost himself. Fortunately, the students find it fascinating, and he now has several merit scholars assisting him with the development of his hovering controls. Surrounded by his beloved planes, Schuster says he has no regrets about leaving the glitter of Hollywood, though he confesses that he would like to work on just one more film — something that would involve a miniature Harrier. “It would be cool to see it in a movie,” he says.