Millennium Cell is leading a team comprising Dow Chemical Company, EWI, and NextEnergy to focus on developing critical manufacturing technologies that will reduce the overall process and product costs of hydrogen storage technology for near-term implementation in portable power applications.

Under the agreement, EWI is tasked with the development of joining technologies for key fuel storage vessels within the fuel cartridges.

The sodium borohydride process.

Millenium Cell uses a sodium borohydride-based technology. A sodium borohydride fuel solution is stored in a fuel tank and converted into hydrogen when required in a miniature reactor.

Sodium borohydride (short for sodium tetrahydridoborate: NaBH₄) is a compound with very high hydrogen content. When NaBH₄ is suspended in an aqueous solution and then passed over a catalyst, the reaction produces a large amount of hydrogen, along with a benign byproduct—sodium metaborate—that can be recycled back into sodium borohydride.

Hydrogen production is controlled by controlling contact between the fuel solution and the catalyst within the reactor. Hydrogen gas is subsequently separated from the liquid metaborate byproduct. The hydrogen stream is fully humidified because the heat of reaction converts some liquid water to vapor.

Hydrogen gas is generated during operation in direct proportion to the rate at which the borohydride solution is pumped into the reactor. When hydrogen is required, fuel is pumped into the reactor.

Fuel solutions of appropriate concentration are stored pre-mixed, generated onsite at the point of use (by adding water to a dry fuel mixture), or generated within the system by on-the-fly mixing of solid or concentrated fuel solutions with water.

Portable devices is Millenium Cell’s principle area of focus for commercializing its technology. Transportation is an area of future interest.