Hydrogen Storage and Its Limitations

The Electrochemical Society Interface • Fall 2004 ydrogen storage is a crucial step for providing a ready supply of hydrogen fuel to an end use, such as a car, as it is considered by many to be the most technically challenging aspect of achieving a hydrogen-based economy. Current hydrogen storage materials or systems are still far short of meeting target goals set for either 2010 or 2015. Two kinds of storage functions with very different requirements are needed for effective storage and delivery of hydrogen. Hydrogen storage systems used for such stationary applications as residential heating and airconditioning, neighborhood electrical generation, and many industrial applications can occupy a large area, employ multistep chemical charging/recharging cycles that operate at high temperature and pressure, and compensate for slow kinetics with extra capacity. In contrast, hydrogen storage for transportation must operate within minimum volume and weight specifications, supply enough hydrogen to enable a 480 km (300 mile) driving range, charge/recharge near room temperature, and provide hydrogen at rates fast enough for fuel cell locomotion of cars, trucks, and buses. Two-thirds of U.S. oil consumption is used to meet transportation energy needs. Therefore, this sector presents not only the most difficult challenges, but it also provides the most intense drive for the hydrogen economy. Developing effective hydrogen storage for transportation is a central challenge for basic research and a key factor in enabling the success of the hydrogen economy. The operating requirements for effective hydrogen storage for transportation include appropriate thermodynamics, fast kinetics, high storage capacity, effective heat transfer, high gravimetric and volumetric densities, long cycle lifetime for hydrogen absorption/desorption, high mechaniHydrogen Storage and Its Limitations