Powdered metal hydride during the filling of a reactor
Investigation of coupled metal hydride reactors for thermochemical preheating of components in mobile applications
Hydrogen storage at low pressures in magnesium hydroxide: To optimize thermal management, the reaction is coupled with the thermochemical reaction in magnesium hydroxide to form an adiabatic overall system.
Quasi-continuously operating metal hydride reactors for converting unused potential energy between a pressure tank and a fuel cell into a cooling or heating effect.
3D printing processes are used for the further development of reactors.
Preheating in seconds with metal hydride
For an efficient and environmentally friendly vehicle of tomorrow, DLR is investigating both safe hydrogen storage and heating/air conditioning from surplus energy based on metal hydrides.
Metal hydrides are formed when gaseous hydrogen combines with metals. Through this heat-tinted process, which can be repeated as often as required, hydrogen is safely stored and heat or cold can be generated. In order to make these effects usable for storage or air-conditioning, thermochemical high-performance reactors are required, which enable rapid gas supply and very good heat transfer.
The safe storage of gaseous hydrogen is very important for both stationary and mobile applications. Important advantages of the technology compared to pressure tank applications are the small required storage volume and low working pressures of < 30 bar. A challenge is the heat management, which can be realized for example by coupling with a fuel cell or by combining with a heat storage material.
Heat or cold can be stored without loss in these thermochemical energy storage units and released at the push of a button. The pressure level at which the hydrogen is provided allows the temperature level of the heat/cold generation to be controlled. This pressure energy in the hydrogen tank is available anyway and has not been used so far. By integration into the hydrogen infrastructure of fuel cell vehicles, such air conditioning components can make an important contribution to efficient thermal management for electric vehicles (FC and battery).
For the chemical storage of hydrogen, reversible reactions between a solid (metal alloy) and gaseous hydrogen are used. The storage of hydrogen (hydride formation) is an exothermic process in which the heat generated must be dissipated. The back reaction, on the other hand, is endothermic, i.e. hydrogen is only released if sufficient heat can be supplied. This leads to an inherently safe inclusion of the hydrogen gas in the hydride compound.
Another important characteristic of this reaction is a direct relationship between reaction temperature and pressure. In an existing H2 infrastructure, such as in a fuel cell vehicle, this effect can be used for an innovative pressure reducer: At the inlet pressure level, heat is released, while a cooling effect is achieved at a low outlet pressure level.
The development of reactors with high specific performance at low reactor weight is of particular importance for the application. For thermal management, reactors have to be developed which convert the rapid heat release of the reaction very well into the desired benefit.
Fields of application