Low Pressure Cold Pack Fuel Cell Storage

Low Pressure Cold Pack Fuel Cell Storage

Much of the current research for the replacement of the internal combustion engine is focused on hydrogen fuel cells. Fuel cells use hydrogen and oxygen to create power in an electrochemical process. Before a "hydrogen economy" can be implemented, however, there are several practical problems that must be overcome. For example, despite being the far most abundant element in the universe, hydrogen is surprisingly difficult to produce. Several competing methods must be analyzed to determine how to supply hydrogen to the entire world.

The problem we are examining is storage. Hydrogen is a gas at room temperature, but storing it in pressurized cylinders in automobiles could be dangerous. It could also be converted to a liquid form, although that would require extremely low temperatures. Both of these approaches could also be hazardous since hydrogen is very flammable.

One of the more promising techniques is storage of hydrogen in metal hydrides. Below is a diagram of our "low pressure cold pack fuel cell storage" system, followed by a summary of our proposal.

Mission Area: New/Emerging technology and devices - Energy Storage
Proposal Title: Low Pressure Cold Pack Fuel Storage Module based on Nanoparticle Gas Absorption at Liquid Nitrogen Temperate

Operational Capability
• Hydrogen is stored at higher than liquid densities at pressures of 1 atmosphere.
• Operational period of cell 10 days.
• System does not require power to release hydrogen.
• Danger of explosion greatly reduced because overall system pressure is low.
• In case of accident, a ruptured cold pack will release hydrogen at a much slower rate than a pressurized system.
• Percent weight of hydrogen is higher than gas stored at 200 bar.
• Percent weight of hydrogen can be 50% more dense than liquid hydrogen at 20 K or solid hydrogen at 4.2 K.

Proposed Technical Approach
• Nanoparticles of some metals absorb hydrogen via the reversible reaction M + (X/2) → H₂N + heat. They absorb hydrogen into their molecular matrix giving off heat and desorb the hydrogen when heated.
• The particles absorb and expel hydrogen gas at a predictable rate under known conditions.
• Some metals store large amounts of hydrogen at liquid nitrogen temperature at atmospheric pressure. By allowing the fuel cell to warm up naturally using the heat within the environment, hydrogen is released for use. If higher rates of hydrogen are required, a small heater or heat “short” from the environment is applied to the core cell.
• The core cell is contained in high vacuum, super-insulated shell which will require approximately 10 days of storage.