Robust and efficient measurements of 248 different cell voltages #
The fast measuring and visualization of individual cell voltages in a fuel cell is the basis for optimum and energy efficient load control of the fuel cell and allows deeper insight into the condition of the cells. In this way, the load of the fuel cell can be adapted to the operating state as much as possible, e.g., for achieving the optimal power at different temperature conditions while simultaneously protecting of the fuel cell.
The challenge with the present system is that the measurement of 248 different cell voltages for each of the two fuel cells is required, in the range between 0,4 and 1,0 Volts, reliably and within a few milliseconds, and although each of these voltages has its own reference potential. Using a conventional construction this would either require a specific potential-free AD-converter or a very complex circuit design to compensate the reference potentials, both being cost- and time-intensive.
The solution developed by the Fraunhofer IMM is based on a commercially available standard component allowing the detection of eight voltages from 0-10 Volts with one single common reference potential. In order to save development time and cost and to get to industrial implementation as fast as possible, only industrially tested and cost-efficient standard components were used, supplemented by specially programmed software. The required components are assembled and inherently meet both the usual industry standards as well as the demand for an easy integration into a process control system or a PLC. This significantly simplifies the installation process and as well improves the measuring accuracy. A special hardware design with corresponding tests is completely unnecessary. Since in this way always all eight voltages with a common reference potential are measured and processed, the number of potential separations required can be reduced by a factor of eight.
- Easy transfer of data from the point of acquisition directly at the fuel cell to the analysis system via an internationally standardized, manufacturer-neutral bus system
- Use of the powerful process control hardware allows the required calculation and evaluation of the individual values via software directly in the process control unit at no additional cost
- Extremely short processing times of 3 ms for a total of 496 values
- Dynamic limit value calculations and averaging are already integrated in the special software module
- Flexible design of the evaluation software, so that a scalable, component-by-component evaluation of the cell voltages is performed and a problem-free use with a different number of cells is possible
In summary, a system was developed that offers a stable solution for the operation of fuel cell systems in small series that is suitable for industrial use and at the same time cost-efficient.