With the concept of energy saving, environmental protection and high efficiency, new energy vehicles have become a major direction of future automobile development. In the eyes of the public, pure electric vehicles are still a new thing, and many car manufacturers in Japan, the United States, and Europe have already started the development planning of hydrogen fuel cell vehicles. In my country, the subsidy for pure electric and plug-in hybrid electric vehicles will decline sharply in the future, but the subsidy amount for fuel cell vehicles will remain unchanged and higher than that of electric vehicles. Such policy incentives have spawned the rapid rise of fuel cell vehicles.
Figure 1. Fuel cell stack (also known as fuel cell engine)
A hydrogen fuel cell is a power generation device that utilizes the direct conversion of chemical energy stored in hydrogen and oxygen into electrical energy with high efficiency and without pollution. Proton exchange membrane (PEM) fuel cells are the fifth generation fuel cells developed after alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells and solid oxide fuel cells. The advantages of high height and small size have become the preferred technology in the field of global fuel cell vehicles. This also requires that PEM fuel cells can withstand the harsh tests of various environments and working conditions in the use of automobiles. The fuel cell generates water during the power generation process, and the water is prone to freezing in a low temperature environment, resulting in the battery not being able to start or being forced to shut down after a short time of operation. Repeated start-up will damage the internal structure of the fuel cell. Taking the low-temperature start-up test of a 6kW stack as an example, after 9 low-temperature starts, due to repeated freezing and thawing, cracks and perforations occurred on the proton exchange membrane, and the performance of the stack declined significantly. my country has a vast territory, and low-temperature startup below 0°C is an important operating condition that cannot be avoided for fuel cell vehicles. Therefore, scientific and accurate tests are required for the startup method and auxiliary startup method of PEM fuel cell stacks to reduce actual use. Lifespan declines.
Figure 2. Stack polarization curve
The national standard GB/T 31035-2014 test method for low temperature characteristics of proton exchange membrane fuel cell stack specifies the test methods for its storage, start-up and working performance under low temperature (below 0 ℃). In the low temperature start-up test, the main test equipment includes DC power supply, DC Electronic load, temperature and humidity sensor and measuring equipment for fuel and oxidant. ITECH’s broad DC power supply and DC load product line can provide high-efficiency and high-performance test equipment for PEM fuel cell testing.
Figure 3. Low temperature start-up experimental device of fuel cell stack
Control the starting current of the DC power supply, start the fuel cell stack with a current density of 0mA/cm2-1000mA/cm2, control the input of hydrogen and air, and record the start-up time and power consumption when the temperature of the fuel cell stack reaches zero. After the stack is started, the output power of the stack is gradually increased, and the load is pulled by the electronic load to test the time and power consumption from the output power to the idle state, and the idle state to the rated power. After running at rated power for 10 minutes, shut down. Repeat the low temperature start-up test until at least two successful starts. By comparing the gas leakage rate, startup time and energy consumption, shutdown time and energy consumption, purging time and energy consumption, external energy consumption and other parameters of the fuel cell stack before and after the test, the low temperature startup characteristics of the PEM fuel cell were obtained. .
ITECH IT8900 series high-performance and high-power DC electronic loads support three voltage ranges of 150V/600V/1200V, and the power can be extended to 600 kW, especially suitable for the test of fuel cell buses and passenger car stacks. It has ultra-high voltage and current resolution, up to 1mV and 1 mA, and voltage/current measurement speed up to 50Hz. Using the host computer software, it can perform complex load settings and long-term data storage.
ITECH IT6500 series wide-range programmable high-power DC power supply can provide a wide output range from 800W to 30kW, and up to 1000V, 1200A for stacks of different power specifications, and the CC&CV priority function realizes fast curve change without overshoot , with high-precision, high-reliability setting functions and safety features. The IT6500C series DC power supply can be equipped with a power dissipator to achieve an integrated load function of up to 90 kW, simplifying the wiring and control requirements of the bidirectional control switch in the national standard.
Compared with the battery, the hydrogen fuel cell test includes the control of the fuel and oxidant input and the linkage of the output power, as well as the test of the complex output polarization curve. The use of ITECH DC power supply and DC electronic load can form high-speed and high-speed Programmable performance test solution that simplifies the engineer’s work and has complete protection functions and high reliability