End Plate Effects on the Performance of PEMFCs During Cold Start Process

The efficient, fast, and reliable cold start of polymer electrolyte membrane fuel cells is one of the major challenges for their commercialization. In this paper a segmented single cell is used to simulate the end plate effects of the stack and to investigate how the effects work. The results demonstrate that the end cells in the stack have the lowest performance, the reasons for which include the lowest temperature of the cells themselves, and probably also ice blocking in part an area inside the MEA, or in the channels, or in both together. In order to mitigate or even eliminate the influence of ice formation in the end cells, the temperature of the end plates should be increased to -10℃ or above when liquid water is generated. A high inlet gas flow rate facilitates the discharge of supercooled water and is conducive to successful cold start.

Modelling of the air pollutants’ cold-start emissions depending on average vehicles’ speed

The aim of the study is to present the results of mathematically modeled influence of the average speed on the pollutant released in the air during the cold-start process. There were taken into consideration the emission from the passenger cars (PCs) for the different fuel types, vehicles’ segments (including hybrid), and the Euro standard. In the article the simulations was performed using the COPERT software, as well as WLTP-based research. The modelling results there are presented show that the change in average speed has a significant effect on air pollutant (CO2, NOx, NMVOC, CO) emissions released in cold-start process. Furthermore, the results show that pollutants’ emissions are sensitive to average speed fluctuations.

VSC-HVDC and Its Applications for Black Start Restoration Processes

System reliability is a measure of an electric grid system’s ability to deliver uninterrupted service at the proper voltage and frequency. This property of the electric system is commonly affected by critical processes, such as a total blackout. The electric system restoration is a complex process which consists of returning generators, transmission system elements, and restoring load following an outage of the electric system. However, the absence of a generator or unit of black start capabilities may worsen the duration and effects of blackouts, having severe consequences. Black start capability is important as it can reduce the interruption time, decrease the economic loss, and restart the power supply fast and efficiently. In recent years, several works have reported advances about the High Voltage Direct Current (HVDC) technology based on the Voltage-Source Converter (VSC) as an attractive and promising technology to increase black start capability. This paper is a review of the current studies of VSC-HVDC as black start power and discusses the advantages and limitations of recent methods. The major points addressed in this paper are as follows: the current theoretical approach of the black start process and the used HVDC technologies, the advantages of VSC-HVDC as black start power, a compressive review of the literature about the black start capabilities using VSC-HVDC technologies, and a description of the main methods recently used to provide an enhancement for restoration processes. Finally, this paper discusses new challenges and perspectives for VSC-HVDC links in order to provide an enhancement for restoration processes.

BESS Assisted Frequency Management for Black Start Process of Microgrid

This paper proposes a method for restoring the nominal frequency and improving the system recovery time using battery energy storage system (BESS) for an islanded microgrid (MG) which is operated by a black start unit (BSU). The frequency stability is controlled by varying the apparent power (MVA) rating of the BESS after simultaneously connecting with the BSU during the post fault scenarios. Simulations are performed on the IEEE Std. 399-1997 test MG using DIgSILENT PowerFactory. Results show that the nominal frequency of the system can be retained by connecting the BESS during the transient period and increasing the MVA rating up to a maximum value. Simulation results also show that with a higher distributed connection of the BESS units over the system, the frequency recovery time can be reduced.