Metal hydrides store faster with graphite
Many metal alloys can reversibly bind large amounts of hydrogen, forming metal hydrides. The chemical reaction releases large amounts of heat. Metal hydrides are therefore suitable not only for hydrogen storage but also as thermochemical heat storage. Metal hydride storages achieve extremely high charging and discharging
performances by a combination of metal hydrides with thermally
conductive graphite in a composite material.
|Project status||Project completed|
|Typical system size Energy [MWh]||0.1|
|Typical system size Output [MW]||1|
|Volumetric energy density [Wh/l]||2,145|
|Gravimetric energy density [Wh/kg]||600 to 1,800|
|Storage loss [1/d]||none|
|Efficiency AC/VNH2||80 %|
|Cycle durability (80% discharge level)||> 1,000|
|Typical discharge time||few minutes|
|Typical period between storage and withdrawal||few minutes|
|Example application areas||thermo-booster, hydrogen storage|
|Type of storage||Reversible chemical reactions, Hydrogenation of metal alloys, storage material, storage construction (stainless steel tank), Components for charching and discharching (integrated heat exchanger), auxiliary equipment (valves, sensor technology)|
|Project duration||July 2012 until December 2015|
Future high dynamic hydrogen storage technologies, which allow a fast loading and unloading within a few minutes, rely on the ongoing improvement of the currently available storage materials. The targeted property improvements are not only beneficial towards reducing charging times of a hydrogen tank, but also facilitate the usage of suchlike materials for high dynamic thermo-chemical energy storage applications, such as high-temperatur process heat storage, thermo-booster or vibration-free and noiseless hydrogen compressor units.
Graphite increases thermal conductivity and hydrogen absorption
In order to achieve a suitable technical performance of the hydride-based hydrogen storage, it is enevitable to ensure sufficient long-term stable heat and gas transfer through the hydride bed. Hence, the project focuses the promising approach to prepare hydride-graphite composite materials. Their improved property portfolio is demonstrated in a technical realistic lab environment. In this respect graphite offers the possibility to control the hydrogen permeation as well as to increase the effective thermal conductivity from about 1 W/mK of pure hydrides up to 80 W/mK of the hydride-graphite composites. The project is divided into the sub-projects "Material synthesis and charecterization" and "Testing and Storage Tank".