The equilibrium voltage of an electric storage battery is relatively stable over a wide range of temperatures. Metal hydride equilibrium pressure is much more sensitive to temperature changes. If a metal hydride has an equilibrium pressure of 5 atmospheres at 20 Celcius, the pressure will fall to half of that (2.5 atmospheres) at about 5 Celcius and rise to about 10 atmospheres at 35 Celcius. The equilibrium pressure of a typical hydride doubles or halves in about 15-20 degrees Celcius of temperature increase or decrease near room temperature.
Rechargeable Metal Hydride Containers
Storing and recovering hydrogen from a metal hydride container at specific rates requires a delicate balance of pressure and temperature management. Frank Lynch, Founder and President of HCI, is the pioneer of that technology. In the 1970s, he did experimental studies of absorption and desorption rates of hydrogen in cylinders containing metal hydrides at controlled pressures and external temperatures. The data from these studies resulted in an analysis tool called HAWK (Hydride Analysis With Kinetics) in the early1980s.
HAWK is a nodal finite analysis heat transfer model with chemical kinetics within each finite node. For large containers, HAWK is purely a heat transfer model. Chemical kinetics are very fast, relative to heat transfer, in large containers (several cm).
Choice of Hydride Alloys for Containers
HCI offers 4 different hydride alloys for its line of SOLID-H TM products: Alloys A, L, M and H. To view the pressure-temperature-composition characteristics of these alloys click Alloy A or Alloys L,M,H . We can also make special alloys to customer specifications in small quantities (a few kg). For large quantities, HCI works with a number of foundries to make tons of special alloys.