A concept has been developed for the generation of hydrogen by reacting selected alkali metal hydrides with water. Hydrogen is consumed in a Proton Exchange Membrane (PEM) fuel cell to generate DC power for operation of a Left Ventricular Assist Device (LVAD and Total artificial heart (TAH). Generator and fuel cell operate safely and reliably at about atmospheric pressure producing potable water and electric power. The Hydride - PEM fuel cell power source operates like a battery but provides 2-3 times the energy density of advanced secondary batteries. Life cycle costs will be significantly lower. Lithium aluminum hydride is used for hydrogen generation. Water insoluble and chemically benign lithium meta aluminate is formed in the reaction. The generator operates in a passive and load responsive mode. Reactants are fully utilized. This is accomplished by the use of a corrugated, perforated sheet metal structure for support and distribution of hydride particles. Wicking is relied upon for distribution of water. Layers of wicking material placed adjacent to the metal structure preform this function. Water is stored in a bladder. From there it is forced through a hydrophilic microporous membrane into the generator until the pressure is high enough to force excess water back into the bladder. Hydrogen is kept from entering the bladder by virtue of the membrane bubble pressure.
The combination of a hydride based hydrogen generator and an oxygen or air breathing PEM fuel cell offers significantly higher energy densities than conventional rechargeable batteries in man-portable applications.
| Adlhart, O J; Rohonyi, P; Modroukas, D et al. (1997) A small portable proton exchange membrane fuel cell and hydrogen generator for medical applications. ASAIO J 43:214-9 |
