Researchers at Sandia National Laboratories have successfully designed and demonstrated key features of a hydrogen storage system that utilizes a complex metal hydride material—sodium alanate. The system, developed through a multiyear project funded by General Motors Corp., stores 3 kilograms of hydrogen and is large enough to evaluate control strategies suitable for use in vehicle applications. (Earlier post.)
Sandia researchers point out that the system was not meant to fit on board a vehicle, and that sodium alanate will not be the material of choice for onboard storage of hydrogen. But, although it is indeed larger and heavier than a viable automotive storage system requires, the system’s engineered elements address many of the thermal management issues that are necessary for successful vehicular storage of hydrogen.
The design tools developed by Sandia researchers now provide GM with a workable template for future designs, which is expected to significantly save the company costs and time when developing hydrogen storage systems for onboard vehicular applications.
For GM, the enduring value of this project can be found in the design concepts, computational tools, and control strategies that Sandia developed. With this new body of knowledge and information, we will be able to quickly design viable systems as new storage materials emerge.—Jim Spearot, GM lead executive for hydrogen storage
|“We’ve shown that we can engineer vehicle-scale energy storage systems to meet a variety of operating requirements and driving cycles, and our design methods have been validated for relevant materials.”|
In addition to its size and storage capacity, the unique features of the Sandia system include an advanced heating system whereby a fraction of the stored hydrogen is used to provide heat to release the remaining hydrogen. This method—the catalytic combustion of hydrogen—is not new, Sandia engineer Terry Johnson said, but is unique to this particular application and the first to be successfully demonstrated. “We chose not to use resistive (electrically driven) heating, because it would have necessarily resulted in a larger and heavier system,” he said.
After considering a number of thermal management options, Sandia selected a “shell and tube” heat exchanger, a heating technique common in many industrial processes. The “SmartBed”—a term coined by Sandia that refers to the method for controlling a modular storage system—consists of four identical modules, each of which contains a shell and tube heat exchanger. The sodium alanate used to store the hydrogen resides within the tubes, which essentially serve as a high-pressure storage vessel. Inside the shell, a heating fluid circulates to transfer heat to and from the sodium alanate.
The modular design of the system means that only a minimum amount of the storage material needs to be heated at any one time. The design also aids in the packaging of the system to fit on board a vehicle.
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the US Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.