Fuel of Possibilities
From hydrogen to biofuels, researchers seek out powerful ideas for energizing tomorrow.
During the hardship of last summer's soaring gas prices, the joke was that SUV stood for "suddenly unaffordable vehicle." While prices have come down in recent months, concerns over petroleum supply and demand remain. What are the options beyond petroleum? That's the $70 a barrel question.
"Most likely there will not be one single energy source to solve our problems, but several used in conjunction," says P. V. Ramachandran, associate professor of chemistry. "We don't know which alternative sources will be the solutions. We must pursue them all."
Purdue scientists tackling these challenges join researchers from other disciplines through the Purdue Energy Center at Discovery Park, which spans 12 disciplines throughout the university.
Hydrogen heats up"We must create efficient and safe methods to store and transport the hydrogen; this is the challenge. The U.S. Department of Energy refers to it as the 'Grand Challenge' and has issued a call to scientists across the nation," he says.
Ramachandran, who leads the hydrogen research initiative at Purdue's Energy Center, has developed a way to store hydrogen in compounds of boron and hydrogen, called boranes, creating a safe and stable material. Currently, he and his team are working with ammonium borate, which shows great promise for hydrogen fuel cells and is easily recyclable. "Recycling the end product back into the original borane is the challenge that limits its ability to be used as an energy source," he says.
"We are currently working to develop fuel cell batteries for U.S. soldiers' equipment," Ramachandran says. "The standard batteries they carry are 30 pounds. The batteries we are developing offer the same amount of power but weigh less than seven pounds."
Alternative energy sources ultimately depend on bench science, says Daniel Raftery, professor of chemistry and leader of the advanced electrochemical systems at the Energy Center.
"It boils down to basic research problems," he says. "We must make investments in such research, and then sometimes wonderful, life-changing things will happen."
While hydrogen may be a viable future fuel, its transport can be problematic, says P. V. Ramachandran, professor of chemistry. Instead of transporting pure hydrogen, Ramanchandran is working with ammonium borate, which can be transported safely in a solid state, and can be turned back into its elements, including hydrogen, through a chemical reaction once it reaches its destination. In his lab, Ramachandran makes ammonium borate, which resembles powdered sugar.
Raftery and his team are developing ways to convert solar energy directly to hydrogen by splitting water. They develop nanoparticle materials that absorb large amounts of sunlight and can be painted on conducting glass. The painted glass is then used as an electrode to split water into hydrogen and oxygen in the presence of sunlight.
"In the long run, everyone agrees we need to harness the power of the sun," he says. "As a fuel, it is incredibly clean. We also will need a cheap source of hydrogen because of its many applications as a renewable energy source. The Department of Energy suggests that 10 percent of the solar energy captured must convert to hydrogen in order to be a viable energy source," he says. "It also must be stable enough to last 20 years and be inexpensive."
Raftery's team chose to work with metaloxides because of their stability and found titanium dioxide, a common ingredient in sunscreen, to be a good candidate.
"Titanium dioxide is a known semiconductor, like silicon, but it absorbs ultraviolet light. This light makes up only a small percent of the full spectrum of light, which makes titanium dioxide very inefficient for energy purposes. We are working to enhance its absorption properties and efficiency by adding other materials to it."
The team has created a one-centimetersquare system that generates about one milliamp of energy. Although labor intensive, the system is relatively inexpensive and could be easily scaled up, Raftery says. The team plans to test a 100-centimeter-square system this summer.
"There is limited space on the roof of a car to paint this energy-absorbing material, so it would not be useful for powering transportation, but it could be used as a clean way to power the processing of another fuel, such as ethanol," Raftery says.