Shooting for the Sun  

Posted by Big Gav in , , ,

The Atlantic has an article on an interesting form of concentrating solar power that uses a fuel cell like technique to generate electricity - Shooting for the Sun.

In March 2003, the independent inventor Lonnie Johnson faced a roomful of high-level military scientists at the Office of Naval Research in Arlington, Virginia. Johnson had traveled there from his home in Atlanta, seeking research funding for an advanced heat engine he calls the Johnson Thermoelectric Energy Converter, or JTEC (pronounced “jay-tek”). At the time, the JTEC was only a set of mathematical equations and the beginnings of a prototype, but Johnson had made the tantalizing claim that his device would be able to turn solar heat into electricity with twice the efficiency of a photovoltaic cell, and the Office of Naval Research wanted to hear more.

Projected onto the wall was a PowerPoint collage summing up some highlights of Johnson’s career: risk assessment he’d done for the space shuttle Atlantis; work on the nuclear power source for NASA’s Galileo spacecraft; engineering help on the tests that led to the first flight of the B-2 stealth bomber; the development of an energy-dense ceramic battery; and the invention of a remarkable, game-changing weapon that had made him millions of dollars—a weapon that at least one of the men in the room, the father of two small children, recognized immediately as the Super Soaker squirt gun.

Mild-mannered and bespectacled, Johnson opened his presentation by describing the idea behind the JTEC. The device, he explained, would split hydrogen atoms into protons and electrons, and in so doing would convert heat into electricity. Most radically, it would do so without the help of any moving parts. Johnson planned to tell his audience that the JTEC could produce electricity so efficiently that it might make solar power competitive with coal, and perhaps at last fulfill the promise of renewable solar energy. But before he reached that part of his presentation, Richard Carlin, then the head of the Office of Naval Research’s mechanics and energy conversion division, rose from his chair and dismissed Johnson’s brainchild outright. The whole premise for the device relied on a concept that had proven impractical, Carlin claimed, citing a 1981 report co-written by his mentor, the highly regarded electrochemist Robert Osteryoung. Go read the Osteryoung report, Carlin said, and you will see.

End of meeting.

Concerned about what he might have missed in the literature, Johnson returned home and read the inch-thick report, concluding that it addressed an approach quite different from his own. Carlin, it seems, had rejected the concept before fully comprehending it. (When I reached Carlin by phone recently, he said he did not remember the meeting, but he is familiar with the JTEC concept and now thinks that the “principles are fine.”) Nor was Carlin alone at the time. Wherever Johnson pitched the JTEC, the reaction seemed to be the same: no engine could convert heat to electricity at such high efficiency rates without the use of moving parts.

Johnson believed otherwise. He felt that what had doomed his presentation to the Office of Naval Research—and others as well—was a collective failure of imagination. It didn’t help that he was best known as a toy inventor, nor that he was working outside the usual channels of the scientific establishment. Johnson was stuck in a Catch-22: to prove his idea would work, he needed a more robust prototype, one able to withstand the extreme heat of concentrated sunlight. But he couldn’t build such a prototype without research funding. What he needed was a new pitch. Instead of presenting the JTEC as an engine, he would frame it as a high-temperature hydrogen fuel cell, a device that produces electricity chemically rather than mechanically, by stripping hydrogen atoms of their electrons. The description was only partially apt: though both devices use similar components, fuel cells require a constant supply of hydrogen; the JTEC, by contrast, contains a fixed amount of hydrogen sealed in a chamber, and needs only heat to operate. Still, in the fuel-cell context, the device’s lack of moving parts would no longer be a conceptual stumbling block.

Indeed, Johnson had begun trying out this new pitch two months before his naval presentation, in a written proposal he submitted to the Air Force Research Laboratory’s peer-review panel. The reaction, when it came that May, couldn’t have been more different. “Funded just like that,” he told me, snapping his fingers, “because they understood fuel cells—the technology, the references, the literature. The others couldn’t get past this new engine concept.” The Air Force gave Johnson $100,000 for membrane research, and in August 2003 sent a program manager to Johnson’s Atlanta laboratory. “We make a presentation about the JTEC, and he says”—here Johnson, who is black, puts on a Bill-Cosby-doing-a-white-guy voice—“‘Wow, this is exciting!’” A year later, after Johnson had proved he could make a ceramic membrane capable of withstanding temperatures above 400 degrees Celsius, the Air Force gave him an additional $750,000 in funding.

The key to the JTEC is the second law of thermodynamics. Simply put, the law says that temperature differences tend to even out—for instance, when a hot mug of coffee disperses its heat into the cool air of a room. As the heat levels of the mug and the room come into balance, there is a transfer of energy.

Work can be extracted from that transfer. The most common way of doing this is with some form of heat engine. A steam engine, for example, converts heat into electricity by using steam to spin a turbine. Steam engines—powered predominantly by coal, but also by natural gas, nuclear materials, and other fuels—generate 90 percent of all U.S. electricity. But though they have been refined over the centuries, most are still clanking, hissing, exhaust-spewing machines that rely on moving parts, and so are relatively inefficient and prone to mechanical breakdown.

Johnson’s latest JTEC prototype, which looks like a desktop model for a next-generation moonshine still, features two fuel-cell-like stacks, or chambers, filled with hydrogen gas and connected by steel tubes with round pressure gauges. Where a steam engine uses the heat generated by burning coal to create steam pressure and move mechanical elements, the JTEC uses heat (from the sun, for instance) to expand hydrogen atoms in one stack. The expanding atoms, each made up of a proton and an electron, split apart, and the freed electrons travel through an external circuit as electric current, charging a battery or performing some other useful work. Meanwhile the positively charged protons, also known as ions, squeeze through a specially designed proton-exchange membrane (one of the JTEC elements borrowed from fuel cells) and combine with the electrons on the other side, reconstituting the hydrogen, which is compressed and pumped back into the hot stack. As long as heat is supplied, the cycle continues indefinitely.
Click here to find out more!

“Lonnie’s using temperature differences to create pressure gradients,” says Paul Werbos, an energy expert and program director of the National Science Foundation. “Only instead of using those pressure gradients to move an axle or a wheel, he’s forcing ions through a membrane.” Werbos, who spent months vetting the JTEC and eventually awarded Johnson’s team a $75,000 research grant in 2006, describes the JTEC as “a fundamentally new way, a fundamentally well-grounded way, to convert heat to electricity.” Regarding its potential to revolutionize energy production on a global scale, he says, “It has a darn good chance of being the best thing on Earth.” ...

Commercial photovoltaic solar cells convert approximately 20 percent of received solar energy into electricity. The best solar-energy systems today—thermal-power plants that concentrate the sun’s heat to drive turbines—operate at a rate of about 30 percent efficiency. The JTEC, Johnson claims, could double that figure, cutting the cost of producing solar power in half from its current average of 25 cents per kilowatt-hour, and making it competitive with coal.

“There’s a lot of debate in Washington about carbon emissions and energy,” Paul Werbos says—“about coal, nuclear power, and oil, what I call the three horsemen of the apocalypse. If we can cut the cost of solar energy in half, it becomes possible to escape from the three horsemen. The importance of this is just unbelievable.”


I would really like to see more detail on this.
There is an animation at the website.

Although a slightly different mechanism, I wonder if this is a bio inspired idea [see:proton pump AND light driven proton pump]

Thanks for the links SP - its an intriguing idea - hopefully it gores somewhere.

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