Managing a Changing Climate
 Uday Pal & Srikanth Gopolan: Climate Friendly Solutions
Boston University engineering professors Uday Pal and Srikanth Gopalan have taken up Kaufmann’s challenge and are designing hydrogen fuel cells—a technology that may someday replace fossil-fuel-burning engines. Pal, who worked as a steel manufacturing researcher, an engineer at Westinghouse, and an MIT faculty
member before coming to Boston University, also has an interest in reducing the costs associated with the manufacturing industry, which accounts for an estimated 25% of the world’s energy use.
Gopalan, who began his career as an engineer at Siemens-Westinghouse before coming to Boston University, says that the
promises of hydrogen cell technology are significant; yet, so are the challenges. One obstacle in using hydrogen as a replacement for fossil fuels is building the infrastructure to produce large quantities of pure hydrogen gas. The current methods—electrolysis and steam methane reformation—are both costly and energy intensive. The other challenge, he says, is manufacturing alternative fuel technology inexpensively enough to warrant investment from the private sector.
Pal and Gopalan have worked together since 2001 designing solid oxide fuel cells (SOFCs) that may someday overcome these barriers. These are essentially like batteries that generate electricity from a reaction between air and fossil fuels. SOFCs, say Pal and Gopalan, are highly efficient and emit negligible levels of the pollutants emitted by gasoline engines.
Though the chemistry involved in SOFCs is relatively simple, the manufacturing methods currently used to produce them are not. The different parts of the battery—cathode, anode, and electrolyte— must be produced at different temperatures and, therefore, require three separate manufacturing phases. Parts must be reheated, then cooled, requiring large energy inputs; these “extra steps,” say Pal and Gopalan, result in high production costs.
Pal and Gopalan are looking to cut these manufacturing costs by more than half by developing a process that will allow the components to be fired at a single temperature, reducing the manufacturing process to a single step. “Our process would allow a huge reduction in the manufacturing complexity and cost,” says Gopalan. Small prototypes produced by the team have been promising and perform comparably to cells produced by traditional means. “The important thing is that it’s simplification without a sacrifice in performance.” Pal and Gopalan envision a wide range of applications for their SOFCs—from car engines and residential furnaces, all the way up to megawatt-generating power plants.
 Pal and Gopalan say their other project, to produce hydrogen using a composite material known as an oxide membrane, also holds great promise. Oxide membranes are designed to generate large quantities of pure hydrogen from steam. They work when one side of the oxygen-permeable membrane is exposed to steam and the other side to hydrocarbon gasses. The oxygen from the steam passes through the membrane and reacts with the hydrocarbon gasses on the other side of the membrane—leaving ultra pure hydrogen on the “steam side” of the membrane. “The hydrogen produced with oxide membranes could be available at ‘hydrogen filling stations’ for fuel-cell-powered vehicles,” says Pal. Their novel design is being produced in partnership with private-sector companies.
Most importantly, perhaps, is the reduction in greenhouse emissions that these cells represent. According to Pal, fuel cells are more than twice as efficient as the typical gas turbine engine—meaning that for the same amount of energy, less than half the amount of carbon dioxide is emitted. And, since the energy-generating reactions occur in sealed spaces away from air, production of nitrogen and sulfur oxides—major components of smog—is negligible.
 The two researchers are also looking to overcome another major drawback of hydrogen: the difficulty of transport and storage. Currently hydrogen gas must be compressed into heavy containers that are difficult to transport and susceptible to rupture. A possible solution, according to Pal, is contained in the bottles of grey sludge lined up on the shelves of his laboratory. He explains that they hold magnesium hydride slurry, a liquid in which hydrogen gas can be temporarily “locked up.” The advantage, says Pal, is that hydrogen gas can be stored in a slurry at standard temperature and atmospheric conditions, then released merely by adding water.
Yet, the method has one major hurdle: it produces huge amounts of magnesium hydroxide—or milk of magnesia—as a by-product. The solution, says Pal, lies in devising a cost-effective method to convert the waste back to the initial compounds. Faced with the prospect of lakes of milk of magnesia, Pal smiles, “This problem will keep us busy for the next ten years at least.”
— by Jeremy Miller |
