PERFORMANCE OF A METAL HYDRIDE HYDROGEN STORAGE SYSTEM

Introduction Hydrogen is considered to be the ultimate fuel for the future, not only because of its renewable and nonpolluting nature, but also because water is the only byproduct during combustion. However, there are many roadblocks to the implementation of the hydrogen economy, such as the lack of refueling and storage infrastructures. Hence, a considerable effort is being put fourth worldwide to alleviate some of these roadblocks. For example, the Savannah River Technology Center (SRTC) has developed a novel metal hydride hydrogen storage container for niche transportation applications. In fact, despite their low gravimetric density, metal hydrides as a means to store hydrogen have been under consideration for many years because they have the ability to store hydrogen reversibly in the solid state at relatively low pressures and ambient temperature. However, a metal hydride hydrogen storage container can be complicated and may contain heat transfer tubes as well as a heat transfer medium to overcome the enthalpic effects during charge and discharge. The SRTC container is an excellent example. It contains aluminum foam and a u-tube heat exchanger for heat transfer, it is only three-fourths filled with metal hydride powder to compensate for expansion during hydrogenation, and the sintered metal feed tube runs axially along the top of the container to ensure a uniform flux of hydrogen into the vessel. These complications present quite a challenge to the development of a mathematical model that can be used for design and optimization. To this end, experimental data are needed over a wide range of hydrogen charge and discharge conditions to calibrate and/or validate such a mathematical model. Therefore, the objective of this paper is to present some of the results from a simple two level fractional factorial design study that reveals the effect of seven factors on the discharge performance of the SRTC hydrogen storage container from only sixteen different experimental runs. These results are used to further test the models developed previously under diverse operating conditions. Select experimental and modeling results are presented to show how a relatively simple model is able to capture the dynamic discharge behavior of a complex hydrogen storage container.