INTEGRATED SYSTEM WITH
ADVANCED CONTROL FOR THERMAL MANAGEMENT
AND ANTI-FREEZE MODULE
What are the main functions of the thermal cooling system?
During the reaction in the fuel cell stack not only electricity, but also heat is produced. The fuel cell stack, however, has to be kept in a narrow temperature range as it is closely connected with water management. Too high operating temperatures may lead to a dry out whereas too low temperatures may lead to a flooding of the cells. Furthermore, accurate thermal management is necessary to avoid excessive degradation and to achieve a reasonable lifetime of the fuel cell stack.
The thermal management is thus regulated by an adapted cooling system. Due to the thermal requirements of the fuel cell stack, the cooling system must ensure solid temperature control. Also, in terms of total heat rejection, the cooling system of a fuel cell vehicle has to meet higher demands than a comparable conventional system using a combustion engine. This is true even though the efficiency of a fuel cell is much higher than the efficiency of a combustion engine.
Two factors are responsible for this phenomenon: the operating temperature of a fuel cell is much lower than the operating temperature of a combustion engine, which leads to a lower temperature difference to the ambience, and the waste gas of the fuel cell – actually only water and air – is much colder than the waste gas of the combustion engine. In addition, several power electronic devices, which also need low temperature cooling, are utilized in a fuel cell vehicle.
Another important task of the thermal system is to support the cold start of the fuel cell. Cold start at freeze conditions is a sensitive issue, as the fuel cell produces water during operation, but the formation of ice might inhibit the transport of reactants. The cold start procedure involves therefore the cathode module and the control system. The thermal system supports cold start concerning the rapid heating of the stack.
What are the development goals for the integrated thermal management system?
The objectives are to enhance the conventional cooling circuit and to enable the cold start of fuel cell vehicles with minimum heat capacity. The INN-BALANCE partner propose a new method based on the injection of an electrochemical active antifreeze fluid into the stack that will enable an unsupervised cold start at much lower temperatures down to -40°C. This will significantly increase the reliability of fuel cells vehicles.
Alongside the cost-reduction of the thermal management components, another key target is the reduction of their weight and volume since installation space in fuel cell vehicles is very limited.