Posted on behalf of Richard A. Lovett
Rather than using nuclear, wind, or fossil fuel power, homes of the future might be powered by leaves – artificial ones, that is, designed to mimic the process by which plants draw energy from the sun.
The latest breakthrough comes from Daniel Nocera (pictured), a chemist at the Massachusetts Institute of Technology, Cambridge, Massachusetts, who has unveiled a prototype solar-powered device the size of a playing card that can break water down into hydrogen and oxygen – valuable fuels for producing electricity via fuel cells.
Previously Nocera had developed a catalyst that could do so with the low-voltage output from a solar cell, a major breakthrough in and of itself, since normally electrolysis (the process of breaking water into hydrogen and oxygen with electricity) requires higher voltage than can easily be produced with solar cells. But Nocera’s new “artificial leaf” combines the a the solar cell and the electrolysis unit into one piece by chemically painting the catalyst onto a solar cell and immersing it in water.
“We could put it in a bottle of water, hold it up to the sun, and you would start seeing hydrogen and oxygen bubbles coming off,” Nocera said at a press conference today at a meeting of the American Chemical Society, in Anaheim, California.
The chemistry is complex but is similar “from a systems engineering sense” to the manner in which leaves generate energy from sunlight. In plants, the energy of incoming sunlight is first used to produce electrons and positive charges within the leaf. These are then used to split water into oxygen and hydrogen (the latter being trapped as carbohydrates, rather than released into the air). “Whether you realize it or not, leaves are buzzing with electricity,” Nocera says. “They just don’t’ have any wires.”
In his artificial leaf, a silicon chip, similar to those used in conventional solar cells, produces electrons and positively charged holes. Then catalysts on the chip use this low-voltage current to produce oxygen and hydrogen – one gas on each side of the chip.
It’s not a new concept. The first such device was made in 1998 by John Turner, of the U.S. National Renewable Energy Laboratory in Boulder, Colorado. “But it used “really expensive materials,” Nocera says. “Things like NASA would use.”
His new device, on the other hand, uses abundant cheap materials, “The word here is practical,” he says.
But it’s still a few years from commercialization. “There’s got to be some tricky engineering to collect the gases as they’re coming off the silicon,” he says. “We don’t know how to do that yet.”
Meanwhile, however, his catalyst is under development as a way to power third world houses with fuel cells, fed by conventional solar panels. “By the end of 2011, we’re going to have prototypes of that on the ground, probably in India.” Nocera is reported to have struck a deal with India’s sprawling Tata group which is interested in the technology, though the details have not been disclosed.
The latest version of Nocera’s technology is of commercial interest because, by integrating the catalyst with the chips, it dispenses with the need for traditional solar panels. That, he says, will cut costs considerably, by eliminating wires, etc. “The price of the silicon of a solar panel isn’t much,” he says. “A lot of the cost is the wiring. What this does is get rid of all that.”
“The real goal here,” he adds, “is giving energy to the poor” – especially, he notes, in rural Africa, India, and China.
Even better, he adds, the device doesn’t need ultrapure water. “You can use nature water sources, which is a big deal in parts of the world where it’s costly to have to use pure water.”
Turner agrees. If the process works, he says, it’s a good candidate for meeting the U.S. Department of Energy’s ‘SunShot’ initiative for developing solar power at investment costs of $1 per watt or less. And they may also be a “path forward” toward a carbon-free hydrogen economy, he says.