Ergenics

Solid State Hydrogen Energy Solutions

How Hydrides Work (continued)

The plateau pressure moves up with an increase in temperature and down with a temperature decrease.  Figure 2 shows several PTC plots for the same alloy at several different temperatures.

Hydride alloys can be engineered to operate at different temperatures and pressures by modifying alloy composition and production techniques.

Before hydriding, an alloy is usually crushed to coarse particles and activated. The activation step eliminates surface barriers for hydrogen penetration. Activation prepares the alloy for repeated use to rapidly take up and release hydrogen. Should the hydrides be exposed to critical levels of contaminants (e.g. CO2, CO, O2, H2O) during H2 cycling, they can be restored by reactivation with pure hydrogen.

Hydride absorption is accompanied by a heat of formation which is exothermic.  In order to continuously absorb hydrogen to an alloy's maximum capacity, heat must be removed from an alloy bed. The rate at which a hydride alloy can absorb or release hydrogen is dependent upon the rate at which heat can be transferred into or out of the alloy.  Increasing the heat transfer rate allows the processing of higher flow rates.

What It All Means

The Company's hydriding alloys absorb hydrogen when they are cold and then release that hydrogen at higher pressure when they are warm. This allows their use in thermal hydrogen compressors that are driven solely by thermal energy, as well as in temperature sensors and sensor-actuators.  Likewise, when releasing hydrogen, the alloys cool off and vice versa.  Using the cooling and heating properties of hydrides, Ergenics has built and patented air conditioners that are powered by waste heat and rapid heating devices, such as the Cold Start Heater for catalytic converters.

Ergenics' metal hydride expertise forms the backbone of solid state, hydrogen storage units for fuel cells and other devices that need a portable source of clean, low pressure hydrogen.  The Company's patented innovations enhance the ability of its metal hydride / hydrogen storage reservoirs to withstand impure gas streams (100% humidity) and deliver high flow rates, with quicker thermodynamics and increased vessel cycle life.  Ergenics' technologies have established it as the world's leading supplier of metal hydride devices.

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Figure 2 - Equilibrium Pressure increases with increasing temperature, as shown in these PTC Isotherms for Hy-Stor 207 hydride alloy.