IAV is an acknowledged development partner to the automotive industry when it comes to technology for testing engines, batteries and high-voltage components. The test facilities are being extended by a test station for fuel cells, a further potential component of the powertrain. The start of testing in the fourth quarter of 2016 will provide IAV’s customers a broad range of capabilities for testing the components of the fuel cell drive. The test station is prepared to solve questions coming out of the core avtivities for volume production but it is also ready for all matters of advanced engineering and research.
Fuel cells are a promising option for reaching the targets set for reducing CO2. In particular, the higher cruising range and short refueling time let consumers feel the technology’s benefits over battery driven vehicles.
Some manufacturers already have a limited number of series production vehicles available for customers or are working on introducing them in volume production. Besides the tests needed for developing them to the point of manufacturing readiness, the current engineering focus is mainly on reducing costs, improving lifetime and simplifying the system in the vehicle. The test station at Gifhorn is ideally equipped for these tasks. It can be used for simulating dynamic driving cycles as well as for accelerated life cycles to verify endurance in the vehicle. It uses state of the art measurement and testing technology.
Pooling available expertise already during planning the test station
The wealth of experience available at IAV from using the existing test facilities went into the process even while the test station was being planned. The demands on the test station were formulated in consultation with the experts from the various divisions. In conjunction with the knowledge already in existence from projects on all aspects of the fuel cell stack and the fuel cell system, this means that the knowledge was available from the start.
“The test station itself is designed for tomorrow’s demanding customers. To operate a fuel cell stack under realistic vehicle operating conditions, the relevant parameters, such as humidity, flow velocity, temperature and pressure, can be varied in a highly dynamic manner. In addition, hydrogen concentration can be varied in order to simulate the accumulation of nitrogen occurring in the vehicle from various effects”, says Ralf Wascheck, head of the High-Voltage and Fuel Cell Systems department at IAV.
Focussing on dynamic behavior
In particular, the demand on the dynamic controllability of operating parameters was a central challenge in calibrating the test equipment. Comparing the gas volumes in the fuel cell vehicle and test station, the gas volumes inside the vehicle are smaller and because of that the behavior of the gases inside these volumes is very dynamic.
This time-consuming process of optimizing the test station layout has paid its dividends because steady-state investigations, such as the recording of U/I curves under varying parameters, only permit a limited characterization of the fuel cell stack.
To obtain detailed findings on the operating behavior and state of the fuel cell stack, the extensive range of measuring equipment available also provides the capability of recording the voltage in individual cells. “In addition, electrochemical impedance spectroscopy can be used to draw conclusions regarding the various processes taking place in the fuel cell stack. As a result, the state of the test object can also be compared at the start of measurements and after completing them”, Wascheck explains.
Following on from proven development methods
The test station was designed to provide an interface for connecting it to existing systems and processes at IAV as a way of implementing the familiar operations for reducing testing times on this test station too.
One option, for example, is to apply Design of Experiments (DoE) methods. On base of IAV's EasyDoe software suitable measuring points are calculated and then measured automatically with the test station control system.
Subsequent modeling and optimization allow the optimum map parameters to be found quickly and the maps no longer have to be laboriously generated by measuring every possible parameter combination. This significantly shortens the time taken to test a fuel cell system and the results can undergo initial analysis during the test process.
Combining procedures familiar from productionlevel testing and knowledge about the operating behavior of the fuel cell stack and system provides the customer the maximum level of IAV’s expertise for testing in this field.