Abstract
Hyundai Motor Company (HMC) has exported hundreds of ix35 fuel cell electric vehicles (FCEVs) to 15 countries since they, for the first time in the world, began to be manufactured on a commercial-production basis in February 2013. Moreover, the ix35 fuel cell system (FCS) was awarded as the 2015 Ward’s 10 best engines, which was the first instance the FCS itself was chosen. Consumers have been satisfied with the zero-emission FCEVs with excellent drive abilities and great utilities. However, critical challenges such as lack of hydrogen infrastructures and high manufacturing cost should be addressed. Furthermore, the enhanced durability, down-sizing of the FCS and the price reduction of FCEVs are needed to grade up with conventional cars and more popular green cars. To fulfill these requirements, HMC has developed a next-generation FCS for FCEVs.
As compared to the previous HMC’s FCS, the automobile assembly productivity was highly improved by integrating a motor-driven system into the FCS, and the mounting arrangement of the FCS and the structure of a fuel cell stack were optimized to safeguard the stack against low-speed collisions, motor vibrations, and damages from driving surfaces. Moreover, the combined fuel cell stack and balance of plant (BoP), e.g. interfaces for coolant and reactive gases, significantly increased the volume power densities of the FCS.
For the marketability of FCEVs, it is crucial that the volume of the stack and the loading quantity of expensive noble-metal catalysts on electrodes should be greatly reduced. Therefore, HMC has enhanced the performance of membrane-electrode assembly (MEA) and modified gas flow channels of bipolar plates, which remarkably improved the volume power densities of the fuel cell stack and considerably decreased the loading amount of Pt catalyst. In particular, a novel flow field substituted for a traditional, straight channel-type path contributed to increasing the gas diffusion on cathode.
As for the air supply system, in order to boost the performance of fuel cells under harsh operating conditions such as a continuous up-hill driving mode, HMC has developed a new system which can withstand a higher-revolving environment compared to the air compressor of ix35 FCEVs. It enabled to supply the required quantity of gas flow and stoichiometric ratio to the fuel cell stack, minimizing power consumption to raise the efficiency of FCSs. Thermal management system also includes a newly-developed electric water pump which ensures durability for the fuel cell stack under various operating conditions. Furthermore, it was designed to control the coolant flow rate by a new cooling loop to enhance the cooling performances under severe operating conditions.
A hydrogen system is composed of various systems for the supply/recirculation, charge/discharge, and storage of hydrogen. The main design goals of the hydrogen system include safety assurance and cost reduction; the strengthened safety standards were applied to the new system to satisfy the global technical regulation (GTR 13) which is more strict regulation than the EU environmental legislation (EC79/406). Moreover, the components of internal-combustion engines were employed without modification, and the number of parts was minimized through the omission and combination of them, thereby facilitating the manufacturing cost competitiveness improvement.
KEYWORDS : Fuel Cell Electric Vehicle, Fuel Cell Stack, Air Supply System, Thermal Management System, Hydrogen System