Compact Fuel Cell Power Supplies with Safe Fuel Storage

摘要

A compact, lightweight hydrogen-production system was developed for fuel-cell-based power supplies. Anhydrous ammonia is decomposed thermocatalytically in a microreactor to produce a fuel-cell feed gas. For an electrical energy capacity of 1250 W-h, this system has an energy density of 500 W-h/kg, which is roughly twice that of state-of-the-art batteries. Despite its energy-density advantage, this ammonia-based power supply will not likely be deployed in military or commercial markets unless safety concerns related to the possible rapid release of ammonia are resolved. Semi-permeable, high-void- fraction materials were developed to address the issue of ammonia safety. Liquefied ammonia is loaded into a monolithic block of safe-storage material, which is installed in a suitable lightweight tank. In the event of tank puncture or leakage from another system component, the release of toxic/flammable gas to the surroundings is restricted by the safe-storage material. Gas release from the safe-storage material is on the order of 1 g/min, which is sufficiently slow to avoid rapid formation of dangerous ammonia concentrations in an enclosed space. These safe-storage materials can also be used for storage of liquefied hydrocarbons such as propane and butane.