Current Status and Future Outlook of Fuel Cell Vehicle Development in Toyota

Abstract

Fuel Cell Vehicle (FCV) offers one of solutions to the issues in energy and climate change. It is well known that FCV is zero-emission and hydrogen can be made from a variety of energy resources. FCV has such environmental friendly features but the recent FCV also has useful features in cruising range of more than 500km, startability under subzero condition and about 3 minutes refueling time. Furthermore, it shows attractive drivability in excellent response under lower vehicle speed cruising; another feature is that it can be used as emergency power supply, that roughly estimated to supply a household for one week by FCV, and a shelter for several hundred people for about five days by Fuel Cell Bus (FC bus) with fully fueled condition. It is considered that FC system is applicable to from small vehicle to large bus since it has longer cruising range and shorter refueling time compared to EV which is more popular than FCV now. However, both FCV and EV need years before these vehicles will be widespread because of higher cost and lack of infrastructures. For the moment, HV or Plug-in HV are considered to be major vehicle in next generation because of advantages in cost reduction and infrastructure development. FCV will increase gradually in the market according to progress of its development. Toyota started the development of FCV in 1992. After several model changes and market experiences with limited market introduction in 2002, the model “FCHV-adv” in 2008 shows excellent performances in drivability under subzero condition, cruising range and durability. These performances are reaching the levels of gasoline vehicle. Toyota announced to start selling commercial FCV “MIRAI” in December 2014 in Japan. The system uses Toyota-developed components including the Toyota FC Stack, FC boost converter, and high-pressure hydrogen tanks. Toyota FC Stack The new Toyota FC Stack achieves a maximum output of 114 kW. Electricity generation efficiency has been enhanced through the use of 3D fine mesh flow channels, which ensure uniform generation of electricity on cell surfaces, providing compact size and a high level of performance, and a power output density of 3.1 kW/L. The amount of water on fuel cell electrolyte membranes has a substantial influence on electricity generation efficiency. Control of the amount of water is carried out using an internal circulation system for circulating the water created when generating electricity, meaning the Toyota FC Stack is a system that, unlike systems used in all other previous Toyota fuel cell vehicles, does not require the use of a humidifier. FC Boost Converter A new compact, high-efficiency, high-capacity converter has been developed to boost power generated in the Toyota FC Stack to 650 volts. Increasing the voltage has made it possible to reduce the size of the electric motor and the number of Toyota FC Stack fuel cells, leading to a smaller, higher-performance Toyota Fuel Cell System, thereby reducing system costs. High-pressure Hydrogen Tanks Tanks with a three-layer structure made of carbon fiber-reinforced plastic and other materials are used to store hydrogen at a very high pressure of 70 MPa (70 megapascals, or approximately 700 bars). Compared to the high pressure hydrogen tanks used in the Toyota FCHV-adv model, tank storage has been increased by approximately 20 percent while both weight and size have been reduced to achieve a world-leading 5.7 wt%.