Toyota's fuel cell car employs carbon fiber extensively

Toyota's first commercial fuel cell vehicle employs various carbon fiber solutions for lightweighting and safety. The Mirai will debut in December this year.

Toray Industries, Inc. (Tokyo) has supplied a carbon fiber reinforced thermoplastic (CFRTP) for structural components, high strength carbon fiber for a high pressure hydrogen tank, and carbon paper for electrode substrates of the fuel cell stack.

The CFRTP is used in a component called the fuel cell stack frame, which forms part of the vehicle floor. Toray, together with Toyota, developed a CFRTP which achieves a short press molding cycle time suitable for mass production. Toray says that this is the first time in the world that CF

TP has been used in a structural part for a mass production vehicle. Toyota plans to build 700 vehicles for global sales during 2015.

The Mirai's high pressure hydrogen tank adopts a three-layer structure of a plastic barrier layer, a carbon fiber-reinforced plastic structural layer that employs high-strength carbon fiber oriented helically and in hoops to reduce carbon fiber usage by 40% and achieve wall thickness down to 25 mm, and glass fiber reinforced plastic outer layer to protect the tank surface. This design satisfies the safety, strength and light weight requirements of such tanks, of which there are two in the vehicle: a 60.0-liter front tank and a 62.4-liter rear tank that store hydrogen at 70 MPa (700 bar). The tanks store 5.7 weight% of hydrogen gas, or approximately 5.0 kg in total. Filling time is around 3 minutes.

Further, carbon paper was adopted for the electrode substrates of fuel cell stack, which is the heart of a fuel cell vehicle. This carbon paper meets prescribed properties such as gas diffusion and durability and contributes to improvement of the fuel cell stack performance and space saving.

Since the vehicle does not emit heated gases, the floor can be fully covered. Air resistance is thereby reduced to boost fuel efficiency. Further, by connecting a DC/AC converter to the vehicle's DC power outlet, the Mirai can function as a domestic electricity source and supply power to a household (up to 60 kWh).

The Mirai can accelerate from zero to 60 mph in 9.6 seconds. Maximum driving range is estimated at 700 km (438 miles).

The Mirai will sell for approximately $63,000 in Japan and $57,500 in the US before local market incentives. For those that can wait, the next generation of the vehicle could cost considerably less. Toyota engineers are reportedly targeting a four-fold cost reduction for the fuel cell system employed in the next model, which might debut around the time of the Tokyo Olympics in 2020.