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Imagine being able to drive a forty-mile round-trip commute every day without ever going near a gas pump. As the United States moves towards an energy economy with reduced dependence on foreign oil and fewer carbon emissions, development of alternative fuel sources and transmission of the energy they provide is only part of the equation. An increase in energy generated from intermittent renewable sources and the growing need for mobile energy will require new, efficient means of storing it, and technological advancements will be necessary to support the nation’s future energy storage needs.
A change toward alternative transportation – hydrogen fuel-cell vehicles, hybrid electric vehicles, plug-in hybrid-electric vehicles and electric vehicles – is essential for reducing oil dependency. Brookhaven National Laboratory conducts leading-edge research into two of the most promising technologies to move us closer to making such vehicles feasible, affordable and safe: solid-state hydrogen storage and lithium batteries.
Brookhaven scientists are conducting basic electrochemical research to significantly improve the efficiency and reliability of fuel cells and batteries. They have launched a concerted effort of basic and applied research for the development of improved energy-storage materials and systems with high energy densities, fast cycling rates and long cycling lifetimes in efficient, economical and safe media. The overall goal is to establish a comprehensive, cross-disciplinary energy-storage program that includes basic and applied experimental and theoretical efforts on energy storage for mobile and stationary applications. Brookhaven aims to establish a continuum of scientific expertise capable of bridging gaps between synthesis of new energy materials, the preparation and testing of new materials, characterization, and finally, developing models and identifying structure-property relationships.
The Center for Functional Nanomaterials (CFN) and the National Synchrotron Light Source (NSLS), and its successor, NSLS-II, are crucial Lab assets and a major component of its energy storage effort. Brookhaven has the tools to become a world leader in energy storage through its capacity to develop synchrotron-based and microscopy-based capabilities to study energy-storage materials, specifically lithium electrodes, electrolytes and metal hydrides. Using the Lab’s unique facilities, researchers will develop energy storage programs in lithium batteries, electrochemical capacitors, metal hydrides, and chemical hydrogen carriers.
Storage is one of the more challenging technological barriers to the development of hydrogen-fueled vehicles. Since hydrogen is a gas at ambient pressure and temperature, it has an extremely low volumetric density. On an energy basis, one kilogram of hydrogen is equivalent to about one gallon of gasoline. So if we use hydrogen as our energy carrier, the fuel weight would be only about one-third of gasoline. However, even a few kilograms of hydrogen onboard would occupy a volume much greater than the car. We need a way of storing the hydrogen in a lightweight and compact package. Existing storage technologies such as compressed gas and cryogenic storage have limited capacities, are too expensive and will not meet the targets established by the Department of Energy (DOE).
An example of a “tunable” hydrogen storage material developed by Brookhaven researchers. By controlling the ratio of different alkali metal ions (yellow and green balls), scientists can tailor the pressure and temperature at which hydrogen is released from the material.
Solid-state hydrogen storage has the greatest potential for meeting the requirements for onboard storage that will be needed to make fuel cell-powered vehicles a reality. Brookhaven has two programs on solid-state hydrogen storage. The first, funded by DOE ’s Basic Energy Sciences under the Hydrogen Fuel Initiative, investigates the process of hydrogen uptake and release in complex hydrides and is trying to identify how atoms and molecules move around during the charge and discharge process. The second program, funded through the DOE’s Office of Energy Efficiency and Renewable Energy under the Metal Hydrogen Center of Excellence, is developing hydrogen-storage materials for automotive fuel-cell applications.
Brookhaven researchers are developing new solid-state hydrogen-storage materials — metal hydrides and chemical hydrides — that have the potential to meet the requirements for onboard storage. In solid-state storage, atomic hydrogen is stored among the atoms of a host material. The complex hydrides, such as sodium aluminum hydride, can store around five percent hydrogen by weight, and are just one class of materials being investigated at Brookhaven. Other materials of interest at Brookhaven include aluminum hydride, which is a fine powder composed of more than 10 percent hydrogen. The unique feature of this material is that it is completely stable at room temperature, but will rapidly release hydrogen upon heating to around 80°C. The challenge is that once the hydrogen is released, it is difficult to get it back in, and extremely high pressures are necessary to “recharge” the material with hydrogen. Brookhaven scientists are working to develop alternative, low-cost methods to regenerate aluminum hydride under moderate pressure and temperature conditions.
Researchers are also developing new materials with higher hydrogen capacities that release hydrogen at lower temperatures and are tailored to an automotive fuel-cell system. They are also interested in using Brookhaven’s NSLS and CFN to study catalysts in these materials. These results will be used to develop new metal hydrides and catalysts with improved properties.
Last Modified: April 27, 2012