In his State of the Union address last year, President Bush proclaimed, “our scientists and engineers will overcome obstacles to taking these cars from laboratory to showroom so that the first car driven by a child born today could be powered by hydrogen, and pollution-free.” Stepping up to that challenge are researchers at Sandia National Laboratories in California, which has been selected by the U.S. Department of Energy to lead a virtual Center of Excellence for the development of reversible metal hydrides materials.
A key Sandia objective will be to develop a class of materials capable of storing hydrogen safely and economically on board a vehicle that can be operated for at least 300 miles before refueling.
Sandia’s winning proposal is part of a “Grand Challenge” offered by the DOE last year. As part of the award, Sandia will manage $30 million of work in reversible metal hydrides research and development over the next five years. The virtual Center consists of eight universities, four other national laboratories, and three industrial companies, with Sandia serving as laboratory lead and coordinator of all R&D efforts.
The study of complex metal hydrides is a key stepping stone in clearing the hydrogen storage riddle, said Jay Keller, hydrogen program manager at Sandia. Storage is widely considered one of the most important hurdles for the commercial success of hydrogen as a clean fuel, especially for use in vehicles because of weight, volume, and cost constraints. Currently, no material exists that can be used to construct a fuel tank that can safely and efficiently store hydrogen fuel.
Hydrides are metallic alloys that can absorb and then release hydrogen. Sandia researchers have developed a promising new class of hydrides called complex metal hydrides, which operate at pressures and temperatures that are close to ambient conditions, making them highly promising for developing future onboard hydrogen storage systems.
Jim Wang, manager of Sandia’s analytical materials science department, said the laboratory’s 40 years of hydrogen science and engineering expertise leave the group well positioned to lead the hydrides research effort. Wang will serve as the Director of the Metal Hydride virtual Center of Excellence when it is established this October.
“Our approach will be to focus on achieving or exceeding the DOE’s hydrogen storage targets through novel materials development, supported by our strengths in fundamental and applied materials science,” said Wang.
Reversible metal hydrides have long been a strong suit of Sandia’s materials research efforts. Its researchers have studied complex hydrides with high capacities, including sodium-alanates, magnesium-alanates, and borohydrides. In addition, Sandia consultant Karl Gross tested the hydrogen absorption properties of a new sodium alanate material last year and termed its performance “astonishing.” Sandia scientists continue to study it as a model system for developing future hydrogen storage systems.
Just recently, Sandia researchers improved the operating conditions of lithium imides for hydrogen storage by partial substitution of lithium with magnesium. This new class of materials absorbs hydrogen reversibly in two steps, providing a total theoretical capacity of 10.8 wt percent. Current test results demonstrated 4.7 wt percent reversible hydrogen storage at about 30 atm and 200C from the first step reaction alone. A patent application has been filed on the synthesis of the materials.
Wang said his team is exploring further improvements on lithium amide/imide or other similar materials for hydrogen storage capacity and operation conditions towards the DOE FreedomCAR goal.
Sandia’s storage work with the DOE’s hydrogen program dates back 10 years and has included storage system design and fabrication, fundamental modeling, and fuel cell and storage integration. In 1997, Sandia initiated a collaborative alanate development DOE program with the University of Hawaii. Other current partnerships include those with the University of Geneva, University of Alaska-Fairbanks, and others. Wang says that collaborative efforts will expand substantially with the virtual Center of Excellence.
“Our plan is to coordinate, support, stimulate, and focus complementary expertise in chemistry, materials sciences, modeling, and synthesis and characterization with other national lab partners, universities, and industries to achieve the DOE’s hydrogen storage goals.”
The FreedomCAR initiative announced by Secretary of Energy Spencer Abraham in 2001 seeks to promote the use of hydrogen as a primary fuel, and targets initial hydrogen storage in a vehicle at about 6 wt percent of the storage system. Given the tradeoffs between weight and volume, that goal accommodates roughly a 300-mile driving range per fill-up.
“No material provides that yet,” says Wang. “Our research for the past few years has been on the leading edge of hydride development,” however, and has identified the class of material that appears to come the closest to that goal.
Hydrogen’s advantages over fossil fuels include its lack of polluting emissions and the fact that it can be produced anywhere from renewable energy resources such as solar electricity or biomass. Proponents of an energy economy that emphasizes hydrogen point to the potential to improve urban air quality, decrease greenhouse gases (released by burning fossil fuels) that contribute to global warming, and gain independence from foreign oil.
Meanwhile, Sandia researchers in the laboratory’s Combustion Research Facility (CRF) have also been building on Sandia’s long-standing strengths in the study of metal-hydrogen interactions and engine studies to explore hydrogen use for electrical production by stationary power sources — turbines in particular.
CRF researchers are also involved in the International Energy Agency’s efforts to create next-generation models for turbines that can burn hydrogen. The CRF is also seeking funding to demonstrate use of hydrogen fuel, with its near-zero emissions of NOx (smog-producing oxides of nitrogen), in an internal combustion engine.
Although one of the biggest impacts of switching to hydrogen from fossil fuel will be seen in transportation, its use in stationary power generation will also help to develop an infrastructure for its distribution and use.
The Center, said Wang, will bring together scientists and institutions with strong and focused capabilities in several research areas. The core philosophy of the Center will be to provide a collaborative teaming environment that offers full support of each member to solve interlinking problems through a coordinated effort. This, said Wang, will allow members to focus on specific tasks while also serving as a resource to others through their own individual areas of expertise.