Technology

Efficient and Safe Hydrogen Storage

pouring slurry

Efficient and safe storage and delivery of hydrogen is the major technical challenge of utilizing hydrogen as an alternative energy carrier.

Compressed and liquid hydrogen tanks often don't store sufficient volumes and pose safety risks. But Safe Hydrogen's metal hydride based chemical hydride and rechargeable hydride technologies offer storage efficiency and storage safety while providing the cost saving advantage of being able to use the existing fossil fuel infrastructure to deliver and store a pumpable and non-explosive hydride slurry as future "hydrogen fuels."

Superior storage efficiency:
Gravimetric: (fuel only)   Volumetric: (fuel only)
Chemical:11%.127 kgH2/L of slurry
Rechargeable:5.4%.064 kgH2/L of slurry

Because chemical slurry generates hydrogen from both the slurry and the water during the chemical reaction, one unit of chemical slurry carries the potential of generating twice as much volume of hydrogen (at about the same weight ) as one unit of cryogenically cooled liquid hydrogen. One unit of rechargeable slurry will release about the same volume as one unit of cooled liquid hydrogen.

Low cost and safe storage:

Cryogenically cooling hydrogen into a liquid state is a well established technology and considered the comparative benchmark for storing hydrogen. But the technology requires substantial energy to liquefy the hydrogen, includes continual "boil off" of hydrogen during storage and requires very costly storage tanks and handling.

Slurries, on the other hand, are stored at normal temperature and pressure, can use existing low-cost “fossil fuel” tanks and pipe lines and because they are not explosive and are flame resistant, they do not require any specialized and costly handling procedures.

flame test

A comparison of the currently available storage technologies is shown below: The red areas indicate problems for the alternatives.

AVAILABLE HYDROGEN STORAGE TECHNOLOGIES AND THEIR KEY ISSUES
  storage
safety
storage
capacity
storage
weight
heating/
cooling
material
safety
H2 generation
complexity
storage
cost
infrastructure
change cost
compressed                
liquid                
solid metal hydride                
other hydrides                
SH slurry excellent = to liquid some   none simple low minimal
The Hydrogen storage and release process used by Safe Hydrogen slurries:

Safe Hydrogen slurries can utilize any and all hydrogen sources and are designed to enable efficient, low cost and safe transportation and storage of hydrogen to a broad based hydrogen market. Slurries sharply reduce the significant costs of storing and transporting hydrogen. Rechargeable slurries provide cost efficiencies making them superior for most applications.

Today’s existing technologies of using compressed or cryogenically cooled hydrogen multiply the original production cost of hydrogen by a factor of 6 to 10 before the hydrogen reaches the market place.

S + W Testing Station
S+W Testing Station
Chemical Technology:

The hydrogen storing ingredient of the Safe Hydrogen chemical hydride slurry is a metal which had been converted to a metal hydride in the hydrogen “storing process.” The metal hydride releases it’s hydrogen, when required, in a managed reaction with water. The reaction, besides producing hydrogen, generates some heat and converts the slurry metal from a metal hydride to a metal hydroxide. This “metal hydroxide” slurry is then totally recycled including the conversion of the metal hydroxide back to a metal hydride. The recycling and conversion is achieved in a very large scale specialized process before the slurry can be used again.

The hydrogen storage and release reactions take place in specialized proprietary devices developed and designed by Safe Hydrogen and scaled to the appropriate process. The slurries and devices are patent protected.

S + W Diagram
Rechargeable Technology:

The hydrogen storing ingredient of the Safe Hydrogen rechargeable hydride slurry is a certain metal which had been converted to a metal hydride in the hydrogen “storing process.” The metal hydride releases it’s hydrogen, when required, in a managed application of heat. As the hydrogen is released from the slurry the metal hydride is converted back to the starting metal. This “metal” slurry can then be again “charged” with hydrogen. The charge/discharge process can be repeated hundreds of times.

The hydrogen storage and release procedures take place in specialized proprietary devices developed and designed by Safe Hydrogen and scaled to the appropriate process. The slurries and devices are patent (applied) protected.

S + H Diagram

Other Cost and Energy Efficiencies

No material waste or disposal

All materials, constituting the slurry are reclaimed and or chemically reconstituted into their original state and may be used over and over again.

Core Materials are safe to use and widely available

The initial development and demonstration of the concept utilized lithium hydride. Safe Hydrogen developed the technology using magnesium hydride. Magnesium hydride offers superior cost, efficiency and safety benefits. Safe Hydrogen expect to explore other metal hydrides as well.

No Need for a New Distribution Infrastructure

While slurry must be transported to the market and returned from the market, the slurry's exceptional hydrogen storage efficiency makes it a cost efficient hydrogen fuel that - unlike other options- can meet near term DOE hydrogen cost targets.

A major cost advantage of this technology is based on the characteristics of the slurry. Slurry is a nonexplosive, noncorrosive, environmentally safe, pumpable "hydrogen fuel". Slurry can be stored, transported and pumped with existing tanks, pumps and pipelines and can therefore distribute hydrogen to the market utilizing the existing fossil fuel infrastructure. The only difference from existing fuel delivery systems is that the delivery devices such as trucks or rail tankers don't return empty. They are fully loaded in both directions. They return from delivery runs, loaded with depleted slurry that needs to be recycled.

Technology Demonstration

test truckThe first demonstration of the technology (using lithium hydride slurry) confirmed the ability to produce a very reliable, controllable and dependable flow of hydrogen. The test included fueling a Ford Ranger truck. The truck had a normal internal combustion engine modified to operate on hydrogen. [view demonstration (1.3MB mpeg)]. (Note: the noise in the background is a shop compressor not associated with the demonstration.)

The demonstration technology is described in our report [1.8MB PDF] prepared for the Proceedings of the year 2000 U.S. Department of Energy Hydrogen Program Review.