The U.S. Department of Energy has awarded the University of Colorado at Boulder $1.2 million over four years for a novel proposal to produce clean hydrogen fuel by using concentrated sunlight to split water.
The process will include using an array of large mirrors to concentrate the sun's rays and create temperatures approaching 3,600 degrees Fahrenheit, much like sunlight is concentrated with a child's magnifying glass, said Professor Alan Weimer of CU-Boulder's chemical and biological engineering department. The process contains three steps, each involving reactions with manganese, to split the water into its two gaseous components, hydrogen and oxygen.
Although hydrogen is thought to make up about 90 percent of the universe by mass, it is most commonly found on Earth in its oxide form, water. The most common way of splitting water is through electrolysis, where an electrical current is passed through it to generate separate bubble streams of hydrogen and oxygen.
Weimer proposes to concentrate sunlight onto a small reactor tube made of heat-resistant material, through which a powder form of manganese oxide will be dissociated, reformed and then recycled during a continuous process of secondary reactions. The process ultimately will produce hydrogen gas ready to be captured and used as fuel, as well as oxygen.
Currently, the cheapest way of making hydrogen is by reforming it from natural gas, primarily methane. The most common method of producing hydrogen fuel today is steam-methane reforming, a process undertaken primarily over vast deposits of coal and that releases significant amounts of carbon dioxide, a major greenhouse gas, into the atmosphere.
"Both sunlight and water are renewable resources," said Weimer. "The challenge is to produce hydrogen economically without generating greenhouse gases." Weimer said the American Southwest, with a plethora of sunny days, would be best suited for such thermo-chemical, hydrogen-producing reactors.
Producing hydrogen thermo-chemically potentially is much more efficient than producing hydrogen via electrolysis on a commercial scale, he said. The thermo-chemical method takes the sun's energy directly to the reaction process, while the electrolysis method requires sunlight to first be converted to electricity.
As part of the winning DOE proposal, Weimer is collaborating with a research group at the Swiss Federal Research Institute in Zurich headed by Professor Aldo Steinfeld. Weimer and Steinfeld met several years ago at an international solar energy conference.
Three CU-Boulder doctoral students and roughly 30 undergraduates from the College of Engineering and Applied Science will be involved in the hydrogen project, said Weimer. The effort will require significant travel between Colorado and Switzerland, where the initial hydrogen reactor will be built.
"There is irrefutable scientific evidence that carbon emissions are negatively impacting the global environment, and the Bush administration has acknowledged that global warming is real," said Weimer. He believes that lawsuits in the United States against large, greenhouse-gas producing industries will become more prevalent in the coming years, much like lawsuits that have battered the tobacco industry.
"There are people having significant health problems in large cities like Los Angeles with severe air pollution as a result of greenhouse gases that have been pumped into the atmosphere," he said. "I think it's just a matter of time before we begin to see litigation against big polluters."
He envisions the owners of hydrogen and other clean power technologies having the ability to sell "carbon credits" to polluting industries in the future. The Kyoto Protocol -- in which participating countries have agreed to reduce carbon dioxide emissions -- has set in motion a global system of carbon emissions trading.
Carbon trading markets have been set up in Europe that allow polluting industries, primarily in power generation and industrial production, to buy carbon credits from companies polluting less than their allotted limits. During the first week of October, 670,000 tons of carbon emissions were traded in Europe.